{"id":5,"date":"2023-05-23T17:08:05","date_gmt":"2023-05-23T21:08:05","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/?p=5"},"modified":"2026-02-20T22:12:06","modified_gmt":"2026-02-21T03:12:06","slug":"introduction-to-pathophysiology","status":"web-only","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/chapter\/introduction-to-pathophysiology\/","title":{"raw":"Introduction to Pathophysiology","rendered":"Introduction to Pathophysiology"},"content":{"raw":"

Vocabulary<\/h1>\r\nIn this section, we will outline<\/span> several\u00a0<\/span>vocabulary terms<\/strong> that are used in<\/span>\u00a0pathophysiology,<\/span>\u00a0as well as <\/span>cellular responses<\/span><\/strong> to <\/span>stress, <\/span><\/strong>injury, and aging<\/strong>.<\/span>\r\n
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P is for Pathology, Pathophysiology, Pathogen, and Pathogenesis - What is the difference between these terms?<\/h1>\r\nFirst of all, what is this term pathology<\/strong>?<\/span> \u00a0If we break that word pathology down, <\/span>you probably know that<\/span>\u00a0'-ology'<\/strong> means 'the study of',<\/span>\u00a0and pathos<\/strong> is Greek in origin, and refers to disease or pain.<\/span> \u00a0So it might make sense that<\/span>\u00a0pathology is the study of<\/span><\/span>\u00a0<\/span>cell or tissue changes due to disease<\/span>.<\/span>\r\n\r\nThe next term, pathophysiology,<\/strong><\/span> if we were to look at the components of that word - you may already know the term physiology,<\/strong><\/span>\u00a0having likely studied anatomy<\/strong> and<\/span>\u00a0physiology<\/strong> previously.<\/span>\r\n\r\nAnatomy<\/strong> is the study of a particular structure<\/span> within the human body and remember, physiology<\/strong> is defined<\/span>\u00a0as the study of the function<\/span><\/span>\u00a0of a particular structure within<\/span>\u00a0the human body. <\/span>\r\n\r\nSo therefore you might guess that<\/span>\u00a0<\/span>pathophysiology<\/strong> refers to the study of<\/span>\u00a0abnormalities in physiology as<\/span>\u00a0a result of disease, or study of abnormalities in the function of a particular structure of the human body as a result of disease<\/span>.<\/span>\u00a0\u00a0<\/span>\r\n\r\nThe next term is <\/span>pathogen,<\/span><\/strong> refers to <\/span>any microorganism that<\/span>\u00a0causes disease; it might be a bacterium,<\/span> a virus, a fungi\/yeast,<\/span> a helminth, or protozoa.<\/span>\r\n\r\nLet's go through some more terms,<\/span> the next is\u00a0pathogenesis.<\/strong><\/span>\u00a0So you know that the Greek word, pathos-<\/strong> is referring to 'suffering<\/em>' and<\/span>\u00a0genesis<\/strong> means the 'creation of<\/em>' (Latin and Greek). Ok,<\/span>\u00a0So we're basically when we<\/span>\u00a0talking about the pathogenesis of something,<\/span>\u00a0we're talking about the creation or<\/span>\u00a0the mechanism of that disease, in particular we are referring to all of the steps that occur at the cellular and molecular level, as well as at the organ and organ system level.\u00a0 Therefore, pathogenesis refers to the mechanism of the disease, and all of the steps that unfold as the disease progresses in the body.\u00a0 \u00a0<\/span>\r\n

<\/h2>\r\nThe term lesion<\/strong> is defined<\/span>\u00a0as the anatomic abnormality of that disease.<\/span>\u00a0It might be an open wound,<\/span>\u00a0tissue damaged or destroyed by a pathogen, a broken bone, or<\/span>\u00a0a cancerous growth.<\/span>\r\n\r\n[caption id=\"attachment_159\" align=\"alignnone\" width=\"200\"]\"\"<\/a> Ancient Romans often dedicated objects of devotion to specific gods associated with healing in the hopes of recovery. These objects were in the form or representation of the affected body part and would be left at the temple of a god.
This torso was created in the image of a man's torso, dissected so that the internal organs could be seen, and was probably dedicated to heal someone suffering from internal disease or injury. Made c. 200 BCE - 200 CE, most likely in Isola Farnese, Italy. The piece is now part of the collection of the Science Museum in London, UK<\/em>.[\/caption]\r\n\r\n
<\/div>\r\n\r\n[caption id=\"attachment_160\" align=\"alignnone\" width=\"260\"]\"\"<\/a> A fresco depicting the Greco-Roman mythology of Iapyx (the healer) removing an arrowhead from the Trojan hero Aeneas' thigh. Venus stands over while beside Aeneas stands his young son Ascanius. 1st century CE (between 45 and 79 CE), from Pompeii. (Naples National Archaeological Museum)<\/em>.[\/caption]\r\n

What is disease?\u00a0 What is considered healthy?<\/h1>\r\n

It is important to be able to determine what<\/span>\u00a0is considered healthy<\/strong> and what is considered disease<\/strong>.\u00a0 \u00a0Disease most often is accompanied by indicators that signal that something is negatively affecting the normal physiology, either in a temporary or permanent manner.\u00a0 To determine what signs, symptoms, and measurements may indicate disease, it is important to think about the range of physiological measurements that are considered normal,<\/strong> and fall inside the normal and expected functioning range of the human body.\u00a0 This normal range is most conducive to organ and tissue homeostasis<\/strong> and the physical well being of the human body.\u00a0<\/span><\/p>\r\n

As each human is slightly<\/span>\u00a0different, i<\/span>t is to be expected that there is a range<\/strong> of physiological measurements that can indicate optimal health.\u00a0 For example, there is a normal range of<\/span> healthy blood pressure readings, of <\/span>heart rate measurements, and of body temperatures.<\/span>\u00a0 It is also true that with these measurements,<\/span> for example, your own blood pressure, heart rate, and body temperature - they will<\/span> all change depending on if you are at rest<\/strong> or exercising.<\/strong><\/span>\u00a0 \u00a0In this case, elevations in heart rate, blood pressure and body temperature, if within the expected range for exercise, is considered normal and doesn't mean that you're<\/span>\u00a0sick.\u00a0 I<\/span>t might just mean that you're<\/span> taking a break from sitting and studying and have gone for a run or a bike ride<\/span>.<\/span><\/p>\r\n

So of course it's very important<\/span>\u00a0for health care professionals to know<\/span>\u00a0what the normal range<\/strong> of<\/span> blood pressure and heart rate is, including<\/span> knowledge that in some cases, these normal ranges are<\/span>\u00a0going to be different depending on<\/span>\u00a0how old a person is, and at times what<\/span> biological sex a person is as well as other lifestyle factors.\u00a0 For example, most often, individuals that are biologically female (XX) have higher heart rates during rest and during exercise, in comparison with age-matched, biological males (XY)<\/span>.<\/span>\u00a0 Additionally, it is known that trained athletes typically have lower resting heart rates than age-matched individuals that are sedentary.\u00a0 Heart rate is age-dependent as well, with infants have higher heart rates than children, and children having higher heart rates than adults.\u00a0 Smokers also typically have higher heart rates than non-smokers.\u00a0 Therefore heart rate typically depends on several factors including: body size, biological sex, age, fitness level, exertion level (during rest or exercise) and lifestyle.\u00a0 Certainly some diseases can affect heart rate, and<\/p>\r\n

This range of normal, healthy functioning of the human body, may bring to mind the word homeostasis.<\/strong>\u00a0 \u00a0Homeostasis (from two Greek words homoiosis<\/em> meaning the 'same' and stasis<\/em> meaning 'standing' or 'state') refers to the relatively stable internal environment that allows for optimal functioning of all of the tissues, organs, and organ systems of your body.\u00a0 You may recall more examples, besides, blood pressure, body temperature, and heart rate which are internally regulated to maintain conditions that are ideal for survival.\u00a0 Try to list as many as you can:\u00a0 water and electrolyte levels, oxygen, carbon dioxide and pH levels. Appropriate levels of nutritional compounds, waste compounds, hormones, growth and other regulatory factors, and the list goes on.<\/p>\r\n

[h5p id=\"12\"]<\/p>\r\n\r\n

How does Disease affect Homeostasis?<\/h1>\r\n

When we think about disease,<\/strong> we know that it may be negatively affecting the functioning of cells, tissues, organs, and possibly even whole organ systems, depending on how widespread its level of impact is.\u00a0 If cells, tissues, and\/or organs are not able to maintain homeostasis<\/strong> over time, then more and more cells throughout the body will be affected and start slowing in function, and possibly even begin to die. <\/span><\/p>\r\n

Now, as humans, we don't<\/span>\u00a0all have the same abilities.<\/span>\u00a0Some of us, for example,<\/span>\u00a0might be born blind or<\/span>\u00a0perhaps were born hard of hearing.<\/span>\u00a0 If that's the case, you don't have hearing or<\/span>\u00a0sight within what is considered the normal range.<\/span> Does that mean that <\/span>you were born with a disease?<\/span> \u00a0No, we wouldn't consider<\/span>\u00a0blindness or hearing in<\/span>\u00a0these particular cases to<\/span>\u00a0be considered a disease.\u00a0 It is not negatively impacting the function or health of organs and homeostasis is being maintained in all body systems.\u00a0 <\/span>So when we speak of disease<\/strong> or disorder<\/strong> or pathophysiology,<\/strong> we're thinking of things that again,<\/span>\u00a0are going to affect cellular homeostasis<\/span>\u00a0in a negative way.<\/span><\/p>\r\n

So this brings us to back to the question. <\/span>\u00a0What is normal<\/strong>?<\/span> \u00a0Again, this is really important<\/span>\u00a0to understand about yourself,<\/span>\u00a0but also your patients\/clients if you enter a Health Care Profession.<\/span>\u00a0\u00a0What are these measurements<\/span>\u00a0supposed to be in terms<\/span>\u00a0of the body's expected normal range, and ensuring homeostasis of the body?\u00a0 Can we think of measurements that may fluctuate with your circadian rhythm (your wake\/sleep cycle?<\/span><\/p>\r\n \r\n

Diagnostic Test Results Need to Accommodate for Circadian Rhythm and Expected Fluctuations in Body Temperature and Hormone Levels<\/h1>\r\n \r\n\r\n[caption id=\"attachment_181\" align=\"alignnone\" width=\"300\"]\"\"<\/a> The normal synchronous relationships between sleep and daytime-activity and cortisol.
Hickie, I, Naismith, S., Robillard, R, Scott, E, Hermens, D. (2013). BMC medicine. 11. 79. 10.1186\/1741-7015-11-79<\/em>.[\/caption]\r\n

This graph<\/span> <\/span>is awesome in<\/span>\u00a0that there are normal expected daily fluctuations<\/strong> in physiological measurements such as body temperature and hormone levels.\u00a0 <\/span>When you go to sleep, your body temperature<\/strong> drops by approximately 1\u03bf<\/sup>C.<\/span>\u00a0 This graph also depicts the circadian rhythm of the production and release of two hormones.\u00a0 Cortisol,<\/strong> produced by the adrenal cortex plays many important roles in the body as does melatonin<\/strong> which is secreted by the pineal gland and also induces sleepiness.\u00a0 Both hormones are responsible for the maintenance of the daily circadian rhythm.\u00a0 The graph documents the concentrations levels of both of these hormones as they circulate the blood stream.\u00a0 The plasma cortisol levels rise in the morning which is thought to induce wakefulness and alertness.\u00a0 Whereas, the plasma melatonin levels rise in the evening in response to darkness and are partly responsible for inducing sleep and maintenance of the daily circadian rhythm.<\/span><\/strong><\/p>\r\n \r\n\r\n[h5p id=\"16\"]\r\n

D is for Disease or Disorder - what is the difference? And what is a Syndrome?<\/h1>\r\nAt times the following words are used somewhat interchangeably: disease, disorder, syndrome.\u00a0 What's the difference?<\/span>\r\n\r\nDisease<\/strong> is typically defined as a physiological or biological ailment that has an underlying cause.\u00a0 It may result in anatomical changes that are temporary or become permanent.\u00a0<\/span>\r\n\r\nA disorder<\/strong> as defined by the National Institutes of Health (NIH), as a \"disturbance of normal functioning of the mind or body. Disorders may be caused by genetic factors, disease, or trauma.\"\r\n\r\nA syndrome<\/strong> refers to a cluster of various signs and symptoms that can vary over time.\u00a0 The NIH defines syndrome as \"a set of symptoms or conditions that occur together and suggest the presence of a certain disease or an increased chance of developing the disease\".\r\n\r\n \r\n\r\n[caption id=\"attachment_188\" align=\"alignnone\" width=\"291\"]\"\"<\/a> Woodcutting of a plague-stricken man lying in bed, attended by three physicians. From the Pestbuch, a 16th Century CE medical treatise by Hieronymous Brunschwig (c. 1450-1512 CE). (Courtesy of the Historical Medical Library of The College of Physicians of Philadelphia)[\/caption]\r\n

What are some Terms to Describe the Duration, Severity, and Stages of Disease?<\/h1>\r\nThere are several terms to convey the severity and speed of disease progression.<\/span>\r\n

The phrase acute onset,<\/strong><\/span> indicates the onset was sudden and the symptoms were severe.\u00a0 C<\/span>onversely, the phrase<\/span>\u00a0insidious onset.<\/strong><\/span>\u00a0is used when signs and symptoms developed more gradually, being mild at first and then becoming more pronounced. The phrase<\/span>\u00a0acute illness,<\/strong><\/span> most often refers to a sudden and severe illness that is short-term.\u00a0 With illnesses that have either acute or insidious onsets, the person afflicted may either recover fully, or be left with long-term physical damage, or perhaps even succumb from the illness.\u00a0 The outcomes typically depending on many factors including, the availability of effective treatments as well as the individual's overall health and ability to overcome the underlying cause.\u00a0\u00a0<\/span><\/p>\r\n

A chronic illness,<\/strong> is an illness that lasts longer than 3 months, most often starts with<\/span> milder symptoms in comparison with <\/span>an acute form of illness.<\/span>\u00a0 With chronic illnesses, there can be\u00a0remissions<\/strong> where<\/span>\u00a0that person recovers somewhat and feels a<\/span>\u00a0little bit better, and then there can be<\/span>\u00a0exacerbations<\/strong> or relapses,<\/strong> in which the disease has progressed and<\/span>\u00a0that person feels worse for a time.<\/span><\/p>\r\n

Current literature suggests that pain, especially chronic pain<\/strong> is not necessarily always indicative of damage.\u00a0 At times, there are cases where a disease or injury has caused damage, yet there has been no pain<\/strong>.\u00a0 Conversely, at times there is chronic pain, when there is no longer any indication of damage.\u00a0 Pain has been found to not always be proportional to the biological or physiological state.\u00a0 The literature suggests that many factors (internal as well as external) can contribute to chronic pain.\u00a0 Therefore treatment of chronic pain can take on many forms that are individual in nature, at times involving physical rehabilitation and exercise strategies, various lifestyle strategies, and therapeutic counselling.<\/p>\r\n

The next term is subacute,<\/strong><\/span> and if we were to break that word down,<\/span>\u00a0sub- means below, and acute,<\/span>\u00a0we know means sudden and severe, right?<\/span> \u00a0So we would say a subacute illness<\/strong> i<\/span>s not as severe as in an acute illness<\/strong><\/span>\u00a0and is shorter than a chronic illness.<\/span>\u00a0I<\/span><\/p>\r\n

The next word subclinical<\/strong> has the prefix,<\/span>\u00a0sub- which means below or lower down.<\/span> \u00a0So if someone is subclinical, that means<\/span>\u00a0that they are not experiencing any symptoms.<\/span>\u00a0That means it's<\/span> a very early stage in the disease a<\/span>nd the person themselves is not<\/span>\u00a0even aware that they<\/span>\u00a0have any disease.<\/span>\u00a0 So likely this person would not be seeking medical attention, and even if they did it would be unlikely that a a physician<\/span>\u00a0or nurse would be able to notice any disease present.\u00a0 All routine<\/span> clinical exams<\/span>\u00a0would would come up negative,<\/span> and there would be no signs or symptoms of something wrong.<\/span>\u00a0 The only way we could to determine that this person has<\/span>\u00a0a disease is if some very sensitive,<\/span>\u00a0very specific tests (e.g. imaging or lab tests) were done.\u00a0 <\/span><\/p>\r\n\r\n

[h5p id=\"13\"]<\/h2>\r\n

Can You Think of Any <\/span>Good Examples of When<\/span>\u00a0a Disease or Disorder is Subclinical? Latent?\u00a0<\/span><\/strong><\/h1>\r\n

You might well think of cancer.<\/span>\u00a0Cancerous cells, of course,<\/span>\u00a0when they first started growing,<\/span>\u00a0are largely undetectable by<\/span>\u00a0the patient or a nurse or<\/span>\u00a0doctor and by routine clinical exam.<\/span>\u00a0So you'd have to do very specific,<\/span>\u00a0very sensitive tests to actually know that,<\/span>\u00a0that cancer is there.<\/span> \u00a0Hence, cancer can present the problem of remaining undetectable in the early, more treatable stages, only causing signs and symptoms in late stages when it becomes more challenging to treat.\u00a0 <\/span>So of course scientists are always trying to design earlier and more sensitive tests, in order to detect cancer (and other diseases) at earlier and more treatable stages, therefore increasing success and survival rates.\u00a0<\/span><\/p>\r\n

The next phrase is latent<\/strong> stage<\/strong>.<\/span>\u00a0 There are\u00a0two different scenarios in which the term latent stage stage is used.<\/span>\u00a0There could be<\/span>\u00a0an infectious<\/strong> scenario or there could be<\/span>\u00a0a non-infectious<\/strong> scenario in which<\/span>\u00a0the term latent stage is used.<\/span>\u00a0 The latent stage in an infection<\/strong> begins<\/span> when<\/span>\u00a0the infection first has taken place, when the pathogen has entered the body.\u00a0 The<\/span> pathogen, that microbe (e.g. <\/span>virus, bacteria, protozoa, helminth, prion, or fungi\/yeast)<\/span>\u00a0will eventually begin to replicate (or amplify) inside the body.<\/span>\u00a0 At the beginning of an infection prior to any significant pathogen replication, a person is<\/span>\u00a0usually not<\/span><\/span>\u00a0experiencing any signs or symptoms.<\/span> For example, if it is a cold or flu, they're not sneezing or coughing yet,<\/span>\u00a0and therefore usually they're not spreading<\/span>\u00a0the virus or that bacteria (which in that case is usually through respiratory droplets).<\/span>\u00a0 We would say in this scenario, the latent stage ends<\/span><\/span>\u00a0when that person does become infectious (or contagious).<\/strong><\/span> \u00a0Now as mentioned most often, a person becomes<\/span>\u00a0infectious once that bacteria or virus (such as a cold or flu virus)<\/span>\u00a0has replicated and that person<\/span>\u00a0starts having signs and symptoms, perhaps a runny nose<\/span>\u00a0and sneezing and coughing.<\/span>\u00a0 And of course, <\/span>we know that that microbe is<\/span> infectious when it is carried in respiratory droplets through<\/span>\u00a0the air and on hands<\/span>\u00a0and on surfaces of things and is thus transmitted to someone else.\u00a0 However, studies of the COVID19 pathogen, SARS-CoV2 virus, have found that in this case, the infectious stage can occur before<\/span> signs and symptoms develop, and even in the absence<\/span> of signs of symptoms this virus can be transmitted to someone else, as in the case of 'silent spreaders'.\u00a0 So in this case, the latent stage still ends with the beginning of the infectious stage, however, with SARS-CoV2, the infectious stage does not coincide with the onset of signs and symptoms.\u00a0 For non-infectious conditions (e.g., cancer), the latent period ends when the cancer is detectable either by the onset of signs and symptoms or through the results of diagnostic testing.\u00a0<\/span><\/p>\r\n

Now in the absence of signs and symptoms, it can be hard to determine exactly when the infectious stage begins unless perhaps that person is being frequently tested to determine viral load numbers and estimating the probability of that person being now in the infectious stage, rather than the latent stage.<\/span><\/p>\r\n

Moving on to the second scenario in which you will <\/span>hear the phrase latent<\/strong><\/span>\u00a0stage<\/strong>, it is when a non-infectious disease<\/strong><\/span>, such as a cancer<\/strong><\/span> has\u00a0begun,<\/span>\u00a0but there are no signs or symptoms <\/strong>yet.\u00a0 In this case we would say the latent stage<\/strong> begins<\/span> with the start of the disease (e.g. the first cancerous cell) and ends<\/span> when it becomes detectable by testing<\/strong>, perhaps in either routine testing before signs or symptoms are present, or testing that is being done as a result of the emergence of signs and symptoms.<\/span>.<\/span><\/p>\r\n

Now, the next terms\u00a0incubation<\/strong> and incubation stage<\/strong> only occur during<\/span>\u00a0infectious diseases<\/strong>.<\/span>\u00a0Incubation never refers to a growing cancer.<\/span> \u00a0It's always during infection, a<\/span>nd specifically, the incubation stage begins<\/span> when<\/span>\u00a0the infection<\/strong> has taken place (the pathogen has entered the body).\u00a0 The incubation stage ends<\/span> when signs and symptoms develop.<\/span>\u00a0 Typically, at the beginning of the incubation stage, a person has\u00a0been infected with that virus<\/span>\u00a0or that bacteria or that fungus,<\/span>\u00a0but is not exhibiting any signs or symptoms.<\/span>\u00a0Most often, the signs and<\/span>\u00a0symptoms are start to occur<\/span>\u00a0once that microbe has replicated<\/span>\u00a0and signs or symptoms have developed, which marks the end of the incubation stage.<\/span>\u00a0 Looking back at the definition of latent stage, you will notice that\u00a0with many infections (e.g. cold, flu) you usually see<\/span>\u00a0a pretty big overlap between<\/span>\u00a0the latency stage<\/strong> and<\/span>\u00a0the incubation stage<\/strong> of<\/span>\u00a0of an infection.<\/span><\/p>\r\n

So students always find these terms quite similar.<\/span>\u00a0You may have to read through them a few<\/span>\u00a0times before you get<\/span>\u00a0the differences subclinical,<\/strong><\/span>\u00a0latent<\/strong> and incubation,<\/strong> ok.<\/span><\/p>\r\n

The next vocabulary word is prodromal.<\/strong><\/span>\u00a0The prodromal period is defined as the first time<\/span>\u00a0you become aware that you have<\/span>\u00a0signs or symptoms that indicate an illness is present.<\/span> It might be the first time you feel the scratchiness of the throat when you have been infected with a cold or flu virus.<\/p>\r\n \r\n\r\n[caption id=\"attachment_5727\" align=\"alignnone\" width=\"300\"]\"Graph<\/a> Four Stages of Infection: All infections (localize and systemic) go through four stages. The first stage known as the Incubation Period begins when a pathogen enters the body and ends when a person begins to show signs and symptoms. The incubation period typically lasts 1-3 days and is characterized by pathogen amplification (by multiplying) and spread to affect many cells. The incubation period often overlaps with the Latent Period, which also begins once the pathogen has successfully adhered to host cells. Latency is said to end when the person becomes infectious and is capable of spreading the pathogen to other hosts. The next stage is the Prodromal Stage which is characterized by the initial appearance of mild or vague symptoms. The third stage is termed Illness and is when a person experiences signs and symptoms related to the damage being caused by the pathogen along with the effects of the immune system's response. The period of Convalescence is characterized by healing and recovery and coincide with the diminishment of pathogen particle numbers in the body as well as the fading out of signs and symptoms.[\/caption]\r\n

Where does it hurt? - Is this ailment Local or Systemic?<\/h1>\r\n

The next important terms are<\/span>\u00a0local<\/strong> and systemic.<\/strong><\/span>\u00a0 When we start investigating<\/span> diseases and disorders,<\/span>\u00a0we need to examine<\/span>\u00a0the location of the body that's been affected<\/span>.<\/span>\u00a0 If the area is discrete, meaning that only a specific section of the body is affected, we<\/span>\u00a0would say that that the injury or infection is localized.\u00a0 <\/span>If the illness is affecting<\/span>\u00a0your whole body,<\/span>\u00a0for example, you've got<\/span>\u00a0a fever and your whole body is hot, we would call that a systemic symptom.\u00a0 Another example would be hypertension (high blood pressure) affects the whole body, so we would consider hypertension to be affect the body systemically.\u00a0<\/span><\/p>\r\n\r\n

Complication, Sequelae, or Convalescence?<\/h1>\r\nLet's go to some more terms, complication<\/strong><\/span>, which refers to the <\/span>development of further negative conditions.<\/span>\u00a0 Complications are variable and can take many forms depending on the underlying situation.\u00a0 For example, if a person has had a heart attack, there's a chance that they will recover without any subsequent complications.\u00a0 However, it may be that a blood clot is produced which lodges in a blood vessel downstream of the heart, causing complications to occur as now there is an organ that is being deprived of adequate blood flow.\u00a0 Other complications of a heart attack may include tears in a weakened or damaged ventricular wall, or the filling of the pericardial sac with too much fluid resulting in the inability of the heart to expand and fill, a condition called cardiac tamponade.\r\n\r\nWith both the initial illness and with any subsequent complications, there is a chance that permanent damage may be prevented through the body's own ability to recover and heal, or perhaps the required medical interventions and treatments are 100% successful.\u00a0 \u00a0If there is a complication,<\/span> However, if tissues are damaged beyond repair that result in a permanent or long-term impairment, the term sequelae<\/strong> is used.\u00a0 For example, spinal cord damage can lead to quadriplegia.\u00a0 This would be considered and example of a sequelae.<\/strong>\r\n\r\nCertainly sequelae may result from either acute or chronic conditions.\u00a0 <\/span>So let's see if I can give<\/span>\u00a0you some more examples of sequelae.<\/span>\r\n\r\nThe first example is diabetes.<\/span>\u00a0Diabetes is a chronic<\/strong> condition<\/span>\u00a0and if someone is<\/span>\u00a0perhaps not taking their medications<\/span>\u00a0properly,<\/span>\u00a0they may start accumulating biological damage that becomes permanent. <\/span>\u00a0Some common complications of long-term diabetes include<\/span> chronic kidney disease, which can lead to the<\/span> kidneys deteriorating and eventually failing<\/span>.<\/span> \u00a0So in this case, we would see diabetes<\/span>\u00a0developing complications that lead to the sequelae of kidney failure and the requirement of dialysis and\u00a0 placement on the wait list for kidney organ donation and transplantation<\/span>. <\/span>\r\n\r\nLet's think of<\/span>\u00a0an acute<\/strong> condition that can lead to sequelae.<\/span>\u00a0 In this example, someone has had a stroke (CVA, cerebrovascular accident).<\/span> Unfortunately as a result of this particular stroke which has occurred on the left cerebral hemisphere in the frontal lobe,<\/span>\u00a0that person now has paralysis<\/span>\u00a0on the right side of their body.<\/span> \u00a0That paralysis on one side of<\/span>\u00a0their body may recover somewhat depending on the extent of the stroke and available treatment.\u00a0 However, some paralysis incurred is usually permanent,<\/span>\u00a0and we would call that a sequelae <\/strong>(from the the Latin word sequi<\/em>, meaning 'follow').<\/span>\r\n\r\nA final example of sequelae, that you might not think<\/span>\u00a0of, is something that's<\/span>\u00a0that's not really a deterioration<\/span>\u00a0of an organ per se,<\/span>\u00a0but is a deterioration<\/span>\u00a0of mental health.\u00a0 In this example we will consider how <\/span>Post-Traumatic Stress Disorder,<\/span>\u00a0PTSD is considered<\/span> a sequelae.\u00a0 \u00a0Perhaps you can picture the cause of PTSD, which is that this individual<\/span>\u00a0has suffered<\/span>\u00a0some trauma in their lives.\u00a0 Certainly<\/span>\u00a0soldiers coming back from war,<\/span>\u00a0or at any individual who's witnessed or experienced trauma can be at risk for developing <\/span>\u00a0PTSD.\u00a0 PTSD<\/span>\u00a0can become a long term,<\/span>\u00a0maybe even a permanent<\/span>\u00a0mental health impairment.<\/span>\u00a0 Thankfully a variety of new and individualized treatments for PTSD are emerging all of the time and as with some other mental health problems, there can be recovery.\r\n\r\nMoving on to the term convalescence,<\/strong><\/span>\u00a0that's an easier one.<\/span>\u00a0Convalescence refers to the period of recovery.<\/span> \u00a0Potentially this recovery is<\/span>\u00a0facilitated by rehabilitation exercises.\u00a0 In some cases,<\/span> convalescence involves speech therapy or improved mobility through using a cane, or<\/span> walker or participation in a stretching or<\/span>\u00a0exercise program,<\/span>\u00a0et cetera<\/span>.<\/span> \u00a0There are many treatment strategies and lifestyle changes<\/span> that can improve recovery.<\/span>\r\n\r\n[caption id=\"attachment_2389\" align=\"alignnone\" width=\"263\"]\"Convalescence<\/a> Convalescence is the period following illness, injury, or surgery during which the body recovers and may require changes in lifestyle. During convalescence following a total knee replacement, patients are encouraged to walk to aid in the healing process.[\/caption]\r\n

Can you Define: Diagnosis, Prognosis, Morbidity and Mortality?<\/h1>\r\nDiagnosis<\/strong> is defined as the identification of the disease, disorder, and syndrome.\u00a0 An accurate diagnosis is essential in ensuring appropriate means of treatment are provided and also helps in making a prognosis.\u00a0 \u00a0<\/span>\r\n\r\nOften an up-to-date patient medical history<\/strong> can be helpful in revealing an accurate diagnosis.\u00a0 Can you think of what might be listed in a patient's medical history that would be informative for making a diagnosis?\r\n\r\n[h5p id=\"21\"]\r\n\r\n \r\n\r\nThe term prognosis<\/strong> refers to\u00a0the predicted\u00a0outcome of the illness or injury.\u00a0 <\/span>\r\n\r\nMorbidity,<\/strong><\/span>\u00a0you probably know, <\/span>refers to the rate<\/span>\u00a0of a particular disease within a population. <\/span>\u00a0Mortality<\/strong> refers to the typical death rate<\/span>\u00a0associated with a disease or disorder.<\/span>\r\n\r\nThese terms, brings us to the word etiology,<\/strong><\/span>\u00a0which refers to study of the cause,<\/span> for example, what is the cause of the disease or disorder or syndrome?<\/span>\r\n

Etiology - Causes of Concern?<\/h1>\r\nEtiology<\/strong>, as we<\/span>\u00a0just mentioned is<\/span>\u00a0the study of causes of an illness.<\/span>\u00a0 Let's see if we can\u00a0list<\/span>\u00a0some categories of causes of diseases, disorders, and syndromes?\u00a0 You can probably think of some already.\u00a0<\/span>\r\n\r\nWe've already talked about infectious diseases<\/strong> caused by viruses,<\/span> bacteria,<\/span>\u00a0fungi, and parasites (e.g. protozoan-caused malaria)<\/span>.<\/span>\u00a0There's immune dysfunction.<\/strong><\/span>\u00a0which refers to an illness that arises when <\/span>your immune system is either deficient or when the immune system is <\/span>over-active as in the case of allergies and autoimmune diseases. <\/span>\u00a0We'll dive more into the details of immune dysfunction diseases in Lesson Five.<\/span>\r\n\r\nOther causes include: trauma<\/strong> (e.g. bone fractures, wounds, injuries)<\/span>, nutritional deficiencies,<\/strong><\/span> cancer, lifestyle, toxins, genetics, congenital defects.<\/strong>\r\n\r\nAlso, we should take the time to investigate the terms: c<\/strong><\/span>ongenital defects<\/strong> and genetic disorders<\/strong><\/span>\u00a0and hereditary diseases.\u00a0 What is the difference?<\/span>\r\n\r\nNow, genetic disorders,<\/strong><\/span> refers to an ailment caused by a DNA mutation.\u00a0 Unfortunately, you can be born with these DNA mutations having inherited them, or DNA mutations can occur later in life.\u00a0 DNA mutations most often occur spontaneously as DNA polymerase makes occasional errors while duplicating DNA each time a cell divides.\u00a0 Most often these errors are repaired by special DNA repair enzymes, although at times, the mistake goes unnoticed, and if it happens to be in a coding section of a gene, it can result in that protein either not being produced, or being produced in a manner that changes its function.\u00a0 In both cases, all the cells that express and require that protein can be negatively affected.\u00a0 Cancer<\/strong> is a result of DNA mutations in genes that are responsible for controlling the rate of cell division or cell cycling (mitosis and apoptosis).\u00a0 This leads cancerous cells to become non-functional and divide uncontrollably.\u00a0 We can therefore say that cancer is a genetic disorder.\u00a0 There are other genetic disorders, which you have likely heard of, that most often a person is born with.\u00a0 C<\/strong><\/span>ystic fibrosis<\/strong> for example is a recessive genetic disease caused by<\/span>\u00a0a mutation in a gene on chromosome 7.\u00a0 Sickle Cell Anemia<\/strong> is a recessive genetic disease caused by a mutation in the hemoglobin beta chain gene on chromosome 11.\u00a0 Marfan syndrome<\/strong> is an autosomal dominant disorder with a mutation found on chromosome 15.\u00a0 Huntington's disease<\/strong> is also autosomal dominant, caused by a mutation on chromosome 4.\u00a0\u00a0<\/span>\r\n\r\nA hereditary disease<\/strong> is defined as a genetic disease which you have inherited.\u00a0 Hemophilia<\/strong> resulting from a mutation in one of the clotting factor proteins is most often inherited.\u00a0<\/span>\r\n\r\nIf we were to analyze the word congenital,<\/strong><\/span>\u00a0the prefix, con-<\/strong>, in Latin, means<\/span> 'with', and genesis<\/strong> refers to 'the creation of'.<\/span> \u00a0The phrase congenital defects therefore is used to categorize<\/span> anatomical or function defects that occur during embryonic or fetal development, resulting in defects that a person is born with.\u00a0 Examples of the most common congenital defects are:\u00a0 congenital heart defects<\/strong>, hypospadias<\/strong> (slight misplacement of urethra within penis), clubfoot<\/strong> (inward turn of foot), Down syndrome<\/strong>, cleft lip<\/strong> and cleft palate<\/strong> (incomplete fusion of right and left palatine and\/or maxillae bones in the roof of the mouth), limb defects<\/strong>, and mental dysfunction<\/strong>.\u00a0 Nowadays, many of these defects can be corrected through surgery, or physical therapy (clubfoot).\u00a0 There are many causes of congenital (birth) defects, and most are thought to be multifactorial,<\/strong> meaning that likely many factors were responsible.\u00a0 \u00a0Some congenital defects are caused by genetics.\u00a0 For example Down syndrome is referred to as Trisomy 21, as it results from inheriting three copies of chromosome 21 instead of two.\u00a0 \u00a0Each case of Down Syndrome<\/strong> is unique with differing degrees of physical and cognitive impairments.\u00a0 At times some of the anatomical defect that may be present (e.g. congenital heart defects) can be repaired. Cleft palate, cleft lip, and limb defects have been linked to many potential factors: genetic susceptibilities, fetal exposure to toxins (mercury, lead)<\/strong>, radiation<\/strong>, alcohol<\/strong>, drugs<\/strong>, and\/or malnourishment<\/strong>.\u00a0 \u00a0 \u00a0\u00a0<\/span>\r\n\r\nAt times, fetal exposure to alcohol and drugs can occur when a person doesn't know that they are pregnant, leading to sequelae such as Fetal Alcohol Syndrome.<\/strong>\u00a0 <\/span>\r\n\r\nSo drugs, alcohol and<\/span>\u00a0even infections (e.g. rubella virus, measles virus, mumps virus<\/strong>)\u00a0including<\/span>\u00a0some of the sexually transmitted infectious diseases,<\/span>\u00a0such as chlamydia,<\/strong><\/span> and syphilis,<\/strong> can all cause congenital defects,<\/span> which in those cases can include blindness, deafness,<\/strong> and cognitive delay<\/strong> and\/or impairment<\/strong><\/span>.<\/strong> <\/span>\r\n\r\nA growing embryo<\/strong> and the later stage of fetus<\/strong> are especially susceptible to<\/span> all of these factors as they are going through very critical stages of development<\/strong> including organogenesis<\/strong> (formation of new organs), which is when these toxins can have the most negative effect.<\/span> \u00a0\u00a0Of course, there are other risk factors that are at play, in the development of congenital defects, including overall maternal health, maternal age, and exposure to cigarette smoke.<\/span>\u00a0 As an example that has been in the news in recent years, you've likely heard of the Zika virus<\/strong> which is spread by mosquitos that tend to exist in countries in tropical climates (e.g. Uganda, Central America).\u00a0 Zika virus infections during pregnancy put babies at risk for being born with c<\/span>ongenital defects, which can be fatal<\/strong> and include microcephaly,<\/strong> reduced brain development, and subsequent cognitive impediments. All of these agents<\/strong> (microbes, alcohol, drugs, toxins, radiation, x-rays, nutritional deficiencies) that can cause congenital defects (and miscarriages or stillbirths) are frequently grouped together and are called teratogens.<\/strong>\u00a0 <\/span>\r\n\r\nThe severity of the congenital defects typically depend<\/span>\u00a0<\/span>on the timing of the exposure to the teratogens, the duration of exposure, the amount and concentration of teratogen, as well as the fetus's genetic composition.<\/span>\u00a0<\/span>Some people are more genetically<\/span>\u00a0<\/span>susceptible to different toxins than others.<\/span>\u00a0<\/span><\/span>\r\n\r\nCauses of diseases are sometimes arranged in the following categories.\u00a0 Can you think of examples of each one?\r\n\r\n[h5p id=\"51\"]\r\n

Clinical Manifestations - Signs or Symptoms?<\/h1>\r\nClinical Manifestations<\/strong> is really just a fancy way of saying<\/span>\u00a0signs or symptoms.<\/span>\r\n\r\nSigns <\/span><\/strong>are defined as observable indicators of illness.\u00a0 Signs include:\u00a0 fever, rash, lab test results, imaging results.\u00a0<\/span>\r\n\r\nSymptoms<\/span><\/strong> are defined as indicators of illness that are not observable by another person (e.g. a health care practitioner)\u00a0 \u00a0Symptoms can include: pain, weakness, fatigue, nausea, headache, cramps, and sleeplessness.\r\n\r\n \r\n\r\n[h5p id=\"14\"]\r\n\r\n \r\n\r\nOne lab test that you may have heard of involves taking a biopsy.<\/strong><\/span> The word biopsy means excision, for the purposes of<\/span>\u00a0cutting out and then<\/span>\u00a0examining tissue samples,<\/span>\u00a0usually under a microscope<\/span>\u00a0for signs of disease.<\/span>\u00a0At times a biopsy may involve scraping rather than cutting<\/span>\u00a0out.\u00a0 For example if you'<\/span>ve gone for a Pap smear you may know<\/span>\u00a0that cervical cells are scrapped and sent to the lab to be examined as means by which to detect early signs of cervical cancer.\u00a0 A Pap smear is a routine test typically performed every 2-3 years (as per personal physician's recommendations) after an individual has become sexually active.\u00a0 The\u00a0cervical cells<\/span>\u00a0are examined under<\/span>\u00a0a microscope to see if there's been any morphological changes indicative of cancer.<\/span>\u00a0 \u00a0Early detection of cervical cancer ensures early treatment and an increased chance of survival.\r\n\r\nLet's go to the next term, idiopathic disease.<\/strong><\/span>\u00a0That's a term used when<\/span>\u00a0the cause of the disease is unknown. The prefix idios<\/em> is Greek for \"one's own\".\u00a0 At times, the term essential<\/strong> is used as a synonym for idiopathic, for example essential hypertension<\/strong>, which is high blood pressure that is not<\/span> a result of a medical condition (most often essential hypertension is linked to obesity, unhealthy diet, sedentary behaviour, and family history).<\/span>\r\n\r\nHere's another one that sounds<\/span>\u00a0similar, iatrogenic disease<\/strong><\/span>\u00a0though is used to refer to a disease that is caused by the health care practitioner, or the treatment.\u00a0 The prefix iatro<\/em> is Greek for \"doctor\".\r\n\r\n \r\n\r\n[h5p id=\"15\"]\r\n\r\n \r\n\r\nThe next term, predisposing factor,<\/strong><\/span>\u00a0is used as another word for risk factor.<\/span>\u00a0 Let's see if we can think of risk factors for different diseases and disorders.\r\n\r\nAge<\/strong> is a risk factor.<\/span>\u00a0Usually the older you are,<\/span>\u00a0the more at risk you<\/span>\u00a0are for cancer and other diseases as a lifetime of exposure to different damaging agents has occurred, plus the cells in your body are gradually slowing down are less able to battle infections and heal tissue. <\/span>\r\n\r\nBiological sex<\/strong>, for example being XX or XY can be a risk factors for different illnesses.<\/span>\u00a0 To name a few, it has been found that biological females (XX) are more at<\/span>\u00a0risk for autoimmune diseases as well as have a greater susceptibility to lung cancer.\u00a0 Biological males (XY) are more at risk for cardiovascular disease and X-linked colour blindness and Duchenne muscular dystrophy.<\/span>\r\n\r\nGenetics,<\/strong> as we have mentioned, can make you<\/span>\u00a0more<\/span>\u00a0susceptible to a disease, for example,<\/span> sickle cell anemia and cystic fibrosis<\/span>.<\/span>\r\n\r\nCongenital defects<\/strong>, as you can imagine can sometimes (e.g. congenital heart defects) make the affected organs less robust and more susceptible to the normal wear and tear of aging, injury, and at times disease.\r\n\r\nDiet<\/strong> can be a risk factor.\u00a0 There can be two categories of problems, the first affecting the greatest number of people in the world, is<\/span> malnutrition, which is not<\/span>\u00a0very<\/span>\u00a0beneficial for your growth as a child, your cognitive function and for your organ function and survival rates in general.<\/span>\u00a0 Conversely, many Western countries are facing an obesity crisis, in which diets that are high in fat, sugar and\/or salt<\/span>\u00a0put individuals at risk for heart disease,<\/span> diabetes, and may even be linked to Alzheimer's disease.\r\n\r\nOccupation<\/strong> can be a risk factor.<\/span>\u00a0If you're exposed to a lot of radiation,<\/span> asbestos, coal dust, and\/or other pollutants,<\/span>\u00a0for example, these are <\/span>risk factors for many different diseases including cancer and lung disease.<\/span>\u00a0 \u00a0There is research that is linking pesticide use to the onset of Parkinson's Disease.\r\n\r\nAnother predisposing factor<\/strong> or<\/span>\u00a0risk factor<\/strong> is where you live - location.<\/strong><\/span> \u00a0So this, of course is not avoidable for most people - you live most often where you are born and are supported unless you have the means to travel.<\/span>\u00a0 \u00a0Every part of the world, hosts its own ecology and spectrum of infectious microbes, sociodemographic and cultural factors.\u00a0 For example,\u00a0 Malaria, which affects millions of people each year, <\/span>is caused by<\/span>\u00a0a single-celled microorganism (a protozoan) that<\/span>\u00a0is transmitted from person to person by a mosquito bite.<\/span> The mosquitoes that carry<\/span>\u00a0this particular Plasmodium parasite<\/span>\u00a0live in certain regions of the world, requiring a tropical climate.<\/span> \u00a0So if you live in one of<\/span>\u00a0these regions,<\/span>\u00a0you're more at risk for developing malaria.\u00a0 Another example is within Canada, where asbestos was mined until 2011.\u00a0 We know that exposure to asbestos puts you at risk for developing mesothelioma cancer. Cardiovascular disease is the number one killer in the world and again, certain parts of the globe experience higher rates of this disease, most often due to societal lifestyle choices.\u00a0 Take a look through these maps to get a sense as the world's burden of different disease.<\/span>\r\n\r\n[h5p id=\"17\"]\r\n

Neglected Tropical Diseases<\/h1>\r\nNow while we are looking at these maps,\u00a0 you will notice that<\/span>\u00a0there are different regions of<\/span>\u00a0the world that are highlighted as<\/span>\u00a0hotspots illustrating:<\/span>\r\n\r\na) Number of people requiring interventions against neglected tropical diseases<\/span>\r\n\r\nb) The global distribution of the disease burden<\/span>\r\n\r\nc) The disease burden from non-communicable diseases<\/span>\r\n\r\nd) The burden from communicable, neonatal, maternal and nutritional diseases<\/span>\r\n\r\ne)\u00a0 The burden of injury, violence, self-harm and accidents\u00a0<\/span>\r\n\r\nNow what are<\/span>\u00a0Neglected Tropical Diseases<\/strong><\/span>?\u00a0 As the name suggests, this is a group of diseases that are most prevalent in the tropics and despite affecting millions of people each year, there just isn't enough of an effective prevention or treatment plan in place yet. In this category, Malaria and Tuberculosis alone<\/span>\u00a0kill 2 million people a year.<\/span>\u00a0It's staggering.<\/span> So of course, the World Health Organization as well as other government agencies (including universities), and private donors are<\/span> funding research to<\/span>\u00a0try and alleviate or eliminate some of<\/span>\u00a0these neglected tropical diseases<\/span>\u00a0that affect millions and millions of people, causing suffering, disability, and even death.\u00a0 Though more work needs to be done.<\/span>\r\n\r\nThese diseases are called neglected<\/strong> because pharmaceutical companies and largely neglect putting research money into the development of preventions (e.g. vaccines) and treatments for those diseases.\u00a0 \u00a0Part of the problem is that the Western nations are largely unscathed by<\/span>\u00a0these diseases, (e.g. malaria,<\/span>\u00a0tuberculosis) and therefore companies anticipate that treatments addressing these tropical<\/span>\u00a0diseases would be less profitable and instead focus on developing drugs to combat cardiovascular disease and other diseases more prevalent in Western nations. Another p<\/span>art of the problem is that some of these neglected diseases require large amounts of money to be spent on improving local infrastructure (e.g. sanitized water, access to clean and healthy food and food preparation and health care, mosquito netting, public safety measures for workplace etc.) and at times health education.\u00a0 <\/span>\r\n\r\n \r\n
<\/div>\r\n\r\n[caption id=\"attachment_227\" align=\"alignnone\" width=\"1024\"]\"\"<\/a> The World Health Organization (WHO) prioritizes 18 neglected tropical diseases (NTDs) that affect over a billion of the world\u2019s poorest people and pose a significant economic burden to developing economies.\u00a0 NTDs don\u2019t just affect low- and middle-income countries, although their victims are often socioeconomically disadvantaged. Cysticercosis, echinococcus, toxocariasis, Dengue virus, West Nile virus, and Chagas disease all have appeared in the United States, disproportionately afflicting the poor. Peter Hotez of the Sabin Vaccine Institute and Baylor College of Medicine has estimated that half of the 20 million people living in poverty in the US are infected with at least one NTD. ~Rachel Cotton, Harvard Immunology Program[\/caption]\r\n\r\nLet's briefly describe a few more of these Neglected Tropical Diseases (NTDs), just to give you an idea as to what is on the list:\r\n\r\nChagas<\/strong><\/span>\u00a0<\/strong>disease<\/strong> , like Malaria is caused by a <\/span>protozoa carried by an insect vector.\u00a0 <\/span>Rabies<\/strong> and Dengue fever<\/strong>, both are caused by viruses and Leprosy<\/strong> is caused by a bacteria. <\/span>\u00a0There are many diseases caused by different helminths,<\/strong><\/span>\u00a0which are tiny little parasitic worms (e.g. Guinea-worms).\u00a0 They generally enter the body through contaminated water that is consumed or even waded in.\u00a0 Some helminths can penetrate the skin of ankles and feet and rest of the body while standing or swimming in water and some types of helminths enter the body through contaminated food or water.\u00a0 <\/span>\r\n\r\nThe case numbers of NTDs are staggering. with<\/span>\u00a01.4 billion people currently affected.<\/span>\u00a0 \u00a0And just to give you some numbers,<\/span>\u00a0there was a study found that<\/span>\u00a0more than 1500 drugs came to market between<\/span>\u00a01975 and 2004 and only 10 were<\/span>\u00a0targeted at<\/span>\u00a0these neglected tropical<\/span>\u00a0diseases out of 1500.<\/span>\u00a0Now, a large number of those drugs,<\/span>\u00a01500 were targeted against diseases and<\/span>\u00a0disorders that the<\/span>\u00a0Western nations experience.<\/span>\u00a0So things that are involved<\/span>\u00a0with heart disease, high cholesterol,<\/span>\u00a0and a lot of those diseases that can<\/span>\u00a0be offset by healthy lifestyle<\/span>.<\/span>\r\n\r\n \r\n

What is Epidemiology?<\/h2>\r\nSo this brings us to the word epidemiology<\/strong><\/span>\u00a0- what is epidemiology?<\/span> \u00a0Epidemiology is the science of<\/span>\u00a0tracking the pattern and<\/span>\u00a0the occurrence of disease.<\/span> This is very important, because we want to be prepared each year and be able to ensure that we are developing and putting in place\u00a0effective prevention strategies<\/span>\u00a0and treatment strategies.<\/span> \u00a0We want to be really<\/span>\u00a0efficient with tax-payers' money in health care money.\u00a0 As well as be proactive with training and hiring health care professionals.\u00a0 We want to have<\/span>\u00a0a very targeted approach.<\/span>\u00a0So typically these prevention strategies<\/span>\u00a0involve ensuring education,<\/span> healthy food security, travel advisories, vaccinations, equipping health facilities with medical equipment, staff, testing labs, and medicines.\u00a0 Education can involve teaching the public about healthy food, exercise, safe driving and hygiene strategies to minimize risk of exposure to contagious diseases, such as during COVID19 with the hygiene strategies of masking and gloving being put in place.<\/span>\u00a0 Most often\u00a0<\/span>education strategies<\/span>\u00a0involve providing public information on how to avoid preventable diseases.\u00a0 For example, the prevention of sexually transmitted diseases through the use of barrier protection.<\/span>\u00a0 So, if you are an epidemiologist in Canada, y<\/span>ou're going to be involved in tracking the diseases<\/span>\u00a0that affect Canadians each year and then<\/span>\u00a0ensure that money<\/span> is spent on the most effective prevention and treatment strategies for those particular diseases.<\/span>\r\n\r\nThat brings us to our next term. What is a communicable<\/strong> disease?<\/span> \u00a0Communicable is used interchangeably with infectious.<\/span>\r\n\r\nThe next term is notifiable disease<\/strong>.\u00a0 Now you might expect that epidemiologists are tracking\u00a0notifiable diseases<\/strong> - what is a notifiable disease in Canada?\u00a0 <\/span>Notifiable diseases,<\/span>\u00a0typically are defined as diseases that are tracked in number as they are\u00a0 regular, frequent,<\/span>\u00a0and timely information<\/span> is<\/span> necessary in planning the prevention<\/span>\u00a0and control of the disease in order to maintain public safety.<\/span>\u00a0 Enough medications and resources need to be purchased and made available.\u00a0 Appropriate and timely public education needs to be delivered.\u00a0 So if I were to ask you to list some diseases that you think are notifiable in Canada which diseases would you list?\u00a0 \u00a0<\/span>\r\n\r\nYou may start thinking of serious ones, such as AIDS, which is definitely a notifiable disease.<\/span> Take a look through this list and point out the diseases you recognize.\u00a0 How many of these diseases are infectious?\u00a0 More than half or less than half?\r\n\r\nNotifiable Diseases in Canada and the Years Notifiable:<\/strong>\r\n\r\n[h5p id=\"19\"]\r\n\r\n \r\n\r\nOver the next year or so if you continue your studies in this field you will begin to notice that most of these diseases are microbial and they are infectious.\r\n\r\nDo you think this may explain why epidemiology, health care planning and public announcements are important?\r\n

What is the difference between prevalence and incidence?<\/h2>\r\nIncidence is defined as the number of<\/span>\u00a0<\/span>new cases, while prevalence is defined as the number of new cases plus the number of older but current cases.\u00a0 <\/span>So you can tell by the math, that prevalence<\/span>\u00a0<\/span>is always going to be higher than<\/span>\u00a0<\/span>incidence because it's new plus old cases.<\/span>\u00a0<\/span>So this is the type of thing that<\/span>\u00a0<\/span>epidemiologists track.\u00a0 Let's take a look at this graph:<\/span>\r\n\r\n[h5p id=\"18\"]\r\n\r\n \r\n

Endemic, Epidemic or Pandemic - which is which?<\/h2>\r\nAs we have done previously, looking at the etymology<\/strong> (study of word origins<\/em>) of each of these terms can be helpful in remembering the difference between them.\r\n\r\nEndemic<\/strong><\/span> is made up of two Greek words: \u00a0'demos' translating to people, and 'e<\/span>ndo-' referring to within.<\/span>\u00a0So if a disease or disorder is endemic,<\/span>\u00a0we would say that disease is maintained<\/span>\u00a0in a population at expected levels, and occurs without an outside source.<\/span> \u00a0For example, we know that<\/span>\u00a0there's going to be a certain number of<\/span>\u00a0cold virus infections in Canada every winter, which is most often caused by rhinoviruses or adenoviruses<\/span>.<\/span> \u00a0These infections do not need to be brought into<\/span>\u00a0Canada from another country.<\/span>\u00a0 Although these cold viruses have a seasonal peak of infections, these viruses are maintained at a low level year round, evolving, and then causing yearly increase in infections typically rising in the fall and peaking over the winter.\u00a0 A certain approximate number of infections is expected in Canada each year, and we would say the the cold viruses are endemic to Canada.\r\n\r\nThe next term, <\/span>epidemic.<\/span><\/strong> again consists of two Greek words:\u00a0 'demos' (people) and 'epi-',<\/span>\u00a0meaning above. <\/span>\u00a0So epidemic is used to refer to an outbreak of a<\/span> specific disease that is occurring<\/span>\u00a0at a higher rate, affecting more people than expected within a set population.<\/span>\u00a0So if we think of the flu virus,<\/span> again, similarly to the cold viruses,<\/span>\u00a0we expect a certain number of<\/span>\u00a0flu cases to occur in Canada every year.<\/span>\u00a0So we would say that the flu virus is endemic to Canada.<\/span>\u00a0 Occasionally there are years, when\u00a0all of a sudden there's<\/span>\u00a0a higher flu rate than expected.<\/span>\u00a0 During that time, we would say there's, there's<\/span>\u00a0a flu epidemic in Canada.<\/span>\r\n\r\nIf we examine the word pandemic,<\/strong><\/span> with 'demos' meaning people and 'pan-' meaning all or global, you may guess as to this term's usage.<\/span> \u00a0A pandemic is used at a time when an<\/span>\u00a0infectious disease,<\/span>\u00a0such as the flu or<\/span>\u00a0the coronavirus (e.g. SARS-CoV2 also known as COVID19) has spread across borders.<\/span> \u00a0During a pandemic a pathogen has spread <\/span>across regions, and may even spread worldwide.<\/span>\u00a0 You may know of the more recent examples of pandemics which have included: the Spanish flu of 1918, the H1N1 flu<\/span>\u00a0in the early 2000s,<\/span>\u00a0and then <\/span>SARS (CoV1) in 2003 and<\/span>\u00a0the novel corona virus (SAR-CoV2)<\/span>\u00a0COVID-19 in 2019.<\/span>\r\n\r\n \r\n

How hard is to cure cancer (or find cures for other diseases<\/em>)?<\/h1>\r\nLet's take a brief pause and consider how new medications<\/strong> and treatments<\/strong> (e.g. new surgeries and other procedures<\/em>) are developed and then tested before being approved for use.<\/span>\r\n\r\nI think if we quickly go through the steps, we'll have a new appreciation for how much money,<\/strong> work labour,<\/strong> and time<\/strong> it requires, not to mention innovative ideas as well as et<\/strong>hical safety measures<\/strong>.<\/span>\r\n\r\nDue to the expense, pharmaceutical companies fund approximately 80% of health research, with the rest funded by philanthropists (e.g. Bill and Melinda Gates), governments (which include universities).\r\n\r\nWhy is it so expensive and why does it take so long?<\/strong>\r\n\r\nLet's look at the 4 big stages of drug development:\r\n\r\nStage Zero:<\/strong>\u00a0 At this stage either,\r\n\r\na) Combinatorial chemistry<\/strong> is used to create and purify a synthetic compound.\u00a0 Often these compounds are developed using previously-researched data that projects what type of chemical properties (size, shape, charge, enzymatic qualities, etc.) are desired in combating this disease.\u00a0 Frequently the process of synthetic compound design is informed by detailed knowledge of disease-specific cellular targets that this new medical compound is being designed to interact with, and what type of interaction would be beneficial.\r\n\r\nAlso at Stage Zero, instead of synthetic approaches it may be that,\r\n\r\nb) a natural compound<\/strong> is purified.\u00a0 For example if a plant is suspected to have medicinal properties, it would be important to purify the exact compound(s) which is thought to be helpful and prepare it for testing.\u00a0 \u00a0We have to keep in mind that all plants consist of thousands of different compounds, some of which may be inadvertently harmful.\u00a0 So it is important to isolate and identify compounds that are of value and that any negative side-effects or interferences of other components are avoided.\r\n\r\nStage One<\/strong>, most often involves testing these purified (synthetic or natural) compounds in Petri plates full of human cells.\u00a0 There are many human cell lineages that can be used to test the safety and effectiveness of these new compounds.\u00a0 Some cell lineages are epithelial cells, others are muscle cells, some are neural cells.\u00a0 There are even cell lineages that have been designed to mimic certain disease conditions.\u00a0 \u00a0At this stage you can perform dose-dependent studies, in which different plates of cells are exposed to increasing amounts of the new compound.\u00a0 \u00a0Each of these plates can be investigated to determine whether the cells were harmed in any way, as well as whether the new compound was effective in off-setting any of the disease qualities of the cells that are mimicking the disease.\u00a0 \u00a0At the end of this stage, decisions are made as to whether this new compound should go forward to Stage Two.\u00a0 If the compound has been found to be harmful, the study will end, and the researchers will go back to Stage Zero to find another chemical that might be a good candidate.\r\n\r\nStage Two<\/strong>, is most often conducted in an animal model, typically in mice or rats that has been bred in a lab specifically for this purpose.\u00a0 At this point, it has been determined that the compound is safe and may be effective in alleviating the disease.\u00a0 The mice or rats are used as they are mammals and genetically and physiologically quite similar to humans.\u00a0 The benefit of this type of lab animal model, is that the genome sequence of mice is known.\u00a0 Mice and rats produce large litter sizes frequently (every 21 days), meaning that there can be sufficient numbers of test subjects that can be used, meaning that the statistical analysis that is required to properly verify the results of the study can be done.\u00a0 At this point, the compound is still too experimental to be ethically tested in humans.\u00a0 Further testing is required, to make sure that the compound is indeed safe.\u00a0 It is important to determine whether exposure to this compound is safe for all organ systems and that no negative side-effects are present.\u00a0 It is equally importantly to determine if the compound is indeed effective in diminishing the negative effects of the disease.\u00a0 Again, dose-dependent studies are performed and often mice that are bred to exhibit disease-like qualities are used in the study.\u00a0 In this way, it can be determined whether the new compound is helpful in curing or lessening the effects of the disease.\u00a0 At the end of Stage Two, if the compound has been deemed to be effective with zero to minimal side effects, it will move on to Stage Three.\r\n\r\nStage Three<\/strong> involves performing a double-blind study <\/strong>in a small group of humans<\/strong> that are effected by the disease and have signed up for this experimental drug trial.\u00a0 Frequently this group is not responding well to current therapies and are interested in trying out a drug which may work better.\u00a0 Should studies find this experimental drug to be successful, it will be ramped up to include larger groups of humans<\/strong> and the study will be repeated.\u00a0 At this time it is important to document any differences in how different age groups respond, as well as groups of humans that differ in biological sex or other key factors that may be of impact.\u00a0 It may be that different dosages or modes of administration (oral, injection) are examined at this time.\r\n\r\n \r\n\r\nWhat is a double-blind study?<\/strong>\r\n\r\nA double-blind study is a study in which there are two conditions:\r\n\r\na) The person receiving the drug or treatment is not<\/span> told whether this is the new drug (or treatment) or whether it is a placebo or sham treatment.\r\n\r\nb) Additionally the health practitioner giving out the new drug\/treatment is also not<\/span> aware of whether they are giving out the experimental drug\/treatment or a placebo\/sham treatment.\r\n\r\nThe reason this is done, is because there is what is called the placebo effect<\/strong>.\u00a0 The placebo effect typically means that ~30% of people that have received the placebo\/sham treatment will feel better.\u00a0 It is believed that a positive mindset and anticipating improvement, actually can make a person feel better.\r\n\r\nIn a study in which the goal is determining whether the new drug\/treatment is effective, it is deemed only effective if it's improvements in alleviating signs and symptoms is better<\/span> than what is observed in those that have received a placebo\/sham treatment.\r\n\r\nStudies have shown that even being in the presence of a health care practitioner can stimulate a placebo effect.\u00a0 Possible explanations include the comfort of being cared for.\r\n\r\n[h5p id=\"22\"]\r\n\r\nWhat is a placebo drug?<\/strong>\r\n\r\nNow for a placebo drug, sometimes a sugar pill is used, but most often, the drug that is currently on the market is used, as the idea is that researchers would like to prove whether the experimental drug is indeed better than what is currently available.\u00a0 Additionally, it is more ethical to have patients continue the best treatment possible during the study.\u00a0 The current drug is of course better for the patient than a sugar pill.\r\n\r\nWhat is a sham treatment?<\/strong>\r\n\r\nA sham or mock treatment mimics the actual treatment in a way that the patient is not aware that the treatment didn't occur.\u00a0 There are examples of sham acupuncture, in which needles that look and feel like acupuncture needles are used, however the sham needles do not actually enter the skin.\r\n\r\nIf a placebo drug makes 30% of people feel better why is it unethical to just use sugar pills to treat diseases?<\/strong>\r\n\r\nYou probably know the answer to this one: the reason is because the positive effects of placebo drugs (or sham treatments) do not last.\u00a0 Typically after a certain amount time (weeks to months) the patient again begins to feel the effects of the disease.\u00a0 This is not surprising as the disease has not been cured, but is continuing to cause negative effects within the body.\r\n\r\nMovie Time:\u00a0<\/strong> Click here to watch the 4 minute TEDEx animation: The Power of the Placebo Effect<\/a> <\/strong>and then answer the following question:\r\n\r\n[h5p id=\"48\"]\r\n\r\nUnfortunately most new drugs, get thrown out after Stage One or Stage Two for one of 3 reasons:<\/span><\/strong>\r\n\r\na) They don't work<\/span>\r\n\r\nb) They cause harm<\/span>\r\n\r\nc) They aren't better than drugs that are currently on the market and are more expensive to make.<\/span>\r\n\r\nHowever, very rarely, there is a success story, and a new drug skips the large-scale human study and is immediately approved for use.\u00a0 When does this occur?<\/strong>\r\n\r\na) When the drug works so well, it is deemed most ethical to make it available to the public at once.\u00a0 This did occur with the drug AZT, azidothymidine, which is an anti-viral drug used in cases of HIV.\u00a0\u00a0<\/span>\r\n\r\nWhat is an Off-Label Drug?<\/strong>\r\n\r\nAnother term you may hear is off-label drug.\u00a0 An off-label drug has been through all of the stages of testing and has been found to effective at alleviating a different condition than what it was initially designed for.\r\n\r\nI can give you two examples of off-label drug use.\r\n
    \r\n \t
  1. Thalidomide<\/strong> was made in the 1950s in Germany. It was initially thought to be really helpful for alleviating morning sickness in pregnant women.\u00a0 Unfortunately, even though it did help with morning sickness, they found that it actually caused a lot of congenital defects in addition to miscarriages.\u00a0 In terms of congenital defects, there were a lot of babies born that were blind or deaf or had a cleft palate, or who had missing or disfigured limbs. It took them about six years to figure this out and get the drug off the market. In the meantime, thousands of babies were affected across Canada, Germany, the United Kingdom, the US, throughout Europe.\u00a0 \u00a0Since this time, thalidomide, although not safe to use during pregnancy, has been found to be good for some cancer treatments.<\/li>\r\n \t
  2. Another example is Viagra<\/strong> which is a vasodilator that was developed for use in heart disease in which it would be beneficial to dilate the coronary (heart) arteries.\u00a0 However, the researchers found the vasodilation of penile arteries occurred resulting in enhanced male erections.\u00a0 So of course, it had gone through all of these tests and was found to be safe and effective.\u00a0 As Viagra, is used for purposed other than heart disease, use for erectile dysfunction would be considered an off-label use.<\/li>\r\n<\/ol>\r\n \r\n\r\nWhat is an example of a natural compound that is medicinal?<\/strong>\r\n\r\na) Antibiotics are antibacterial agents that are most often produced by other micro-organisms (including yeast\/fungi).\u00a0 Humans have found it to be useful to mass-produce some of these antibiotics (e.g. penicillin) to combat bacterial infections, which can be fatal.\r\n\r\n \r\n

    What can a biopsy tell you?<\/strong><\/h3>\r\nMicroscopic analysis of cells and tissues is used to detect signs of disease and can be helpful in determining the cause and extent of disease progression.\u00a0 The study of the appearance of tissues, specifically the structure, shape, and arrangement of cells, is termed cell morphology.\u00a0 Now, it is important to know that diseases as well as just normal adaptations to the environment can cause changes in cell morphology, though usually in different ways.\r\n\r\nIn this section let's take a look at the terms that are used to describe changes in cellular shape and growth patterns.\r\n\r\n\"\"\r\n\r\n \r\n\r\nIn the figure, the artist has illustrated some of the non-cancerous (non-neoplastic) cell morphology and growth pattern changes that can occur.\u00a0 So let's go through them one at a time.\r\n\r\nFirst of all, you will notice that the normal cells<\/strong> have been drawn to resemble stratified<\/strong> (many layer) cuboidal epithelial cells.<\/strong>\u00a0 Each of these cells contains one purple nucleus. Okay, notice this is our starting point. Each human cell type has a typical diameter, shape, and set of organelles which would be considered to fall in the normal, healthy range.\r\n\r\nIf a biopsy was taken and the cells examined were much smaller than expected, we would conclude that these cells had shrunk, and would say that there has been some atrophy.<\/strong>\r\n\r\nNow, if I asked you, what do you think causes atrophy?<\/strong>\r\n\r\nYou may be able to think of many examples.\u00a0 One might be the skeletal muscle atrophy that occurs, while a person is not able to use those muscles, either due to bedrest,<\/strong> or due to the restraint of wearing a cast<\/strong> when a bone is broken.\u00a0 Even astronauts that have been in space experience muscle atrophy as their muscles are not required to generate as much force in a low-gravity<\/strong> environment have\u00a0 \u00a0The body is quite efficient and it is often a use-it-or-lose-it natural phenomenon that takes place, as the body remodels itself.\u00a0 Cells will reduce the expense of making muscle proteins (e.g. myosin, actin, troponin, tropomyosin) if they are not required, and skeletal muscle cells will shrink or atrophy as a result.\u00a0 At times it is quite visible. For instance when a cast is removed from an arm, comparisons to the non-casted arm, can show a noticeable difference in diameter.\u00a0 The recently casted arm may be smaller in diameter than that of the non-casted arm.\u00a0\u00a0Luckily in these 3 scenarios, skeletal muscle cells can build up their proteins and strength when the person begins to use that muscle again.\r\n\r\nThere's actually at least 7 causes of skeletal muscle atrophy.\u00a0 \u00a0In addition to the first 3 examples (bed rest, low gravity, casted), the 4th example would be caused by reduced neural input<\/strong> to your muscle.\u00a0 This occurs when there's been neural damage, perhaps even as much as a spinal cord injury.\u00a0 If someone's been in a car accident and they've had a spinal cord injury, perhaps it has resulted in becoming paraplegic or quadriplegic.\u00a0 In both of these instances, the nerves in their spine were severed and there is no longer neural input to their leg muscles.\u00a0 Without neural input, they can't move their legs.\u00a0 As a result, their leg muscle cells start atrophying (again the body remodels to be efficient, and it is a use-it-or-lose-it phenomenon involved in maintaining skeletal muscle size).\u00a0 The net effect of this might become visible over time, and a person's legs may become thinner in diameter.\r\n\r\nThe 5th example, which is unfortunately common in the world, is starvation or poor nutrition<\/strong>. In this instance, if a person is not getting enough dietary amino acids and other nutrients, the skeletal muscle cells (and in fact all of the cells of the body) will not have the building blocks needed for growth and maintenance and they might start atrophying.\u00a0 iskhein \u2018keep back\u2019 + haima \u2018blood\u2019\r\n\r\nA 6th example would be: ischemia<\/strong>, a term that refers to poor blood flow.\u00a0 Ischemia originates from the Greek words ischein<\/em> 'hold back' and haima<\/em> 'blood'.\u00a0 So let's examine the instance when there's not much blood flow to this muscle.\u00a0 It may be\u00a0 that the blood vessels are damaged or partially blocked with atherosclerotic plaque resulting in less blood flow.\u00a0 Reduced blood flow, means there is reduced nutrient and oxygen delivery, which means this cell can't produce proteins and it can't maintain itself at its proper size.\r\n\r\nThe 7th cause of atrophy, just a reduction in hormones.<\/strong>\u00a0 For example when people get older, their bodies produce less estrogen, less testosterone, less growth hormone, amongst other growth factors and hormones. As a result there is less cellular stimulation to produce and maintain proteins leading to noticeable atrophy of muscle, bone, and other tissues.\r\n\r\nNow the reverse of atrophy, of course, is hypertrophy.<\/strong> I should point out that in biology the prefix, a-<\/strong> means 'without', and trophy<\/strong> means 'growth'.\u00a0 The prefix hyper-<\/strong> means 'more', so hypertrophy refers to more growth, or bigger.\u00a0 In the above illustration, you can see that these 4 cells have grown in size.\r\n\r\nLet's now define the difference between physiologic hypertrophy<\/strong> and pathologic hypertrophy.<\/strong>\r\n\r\nAn example of physiologic hypertrophy<\/strong> occurs when a person starts an exercise program, perhaps going for a run every day, resulting in their leg muscles getting bigger and bigger. In this case, the skeletal muscles that are being used more frequently produce more muscle proteins (e.g. myosin and actin), and as a result the skeletal muscle cells' diameters increase in diameter. Additionally these cells become stronger due to the increased number of myosin and actin cross-bridges that can form and build tension to lift load (or generate force).\u00a0 You may be aware there can be two very distinct types of exercise training:\u00a0 resistance and cardiovascular.\r\n\r\n \r\n\r\n \r\n\r\n[caption id=\"attachment_358\" align=\"alignnone\" width=\"293\"]\"\" Figure: Skeletal muscle physiologic hypertrophy[\/caption]\r\n\r\nSome athletes that perform a lot of resistance training (e.g. weight lifting) at the gym and other athletes predominantly perform cardiovascular training (e.g. long distance running), and of course there are other individuals that do a mix of both types of activities (resistance and cardiovascular).\u00a0 In all instances, athletes that train frequently, will experience remodeling in their body that contribute to improved performance (e.g. faster times, greater weight lifts) over time.\u00a0 As mentioned, skeletal muscular hypertrophy of the specific muscles being used in these activities will occur.\u00a0 Additionally the heart muscle may also hypertrophy, with the walls of both left and right ventricles increasing in width and even increasing the diameter of the ventricular cavities.\u00a0 This heart remodeling is beneficial in athletes in that it helps to deliver more blood to the working tissues of the body per minute during exercise.\u00a0 Therefore these muscles will receive sufficient oxygen to support ATP production which is required for muscle activity.\r\n\r\n \r\n\r\n[caption id=\"attachment_327\" align=\"alignnone\" width=\"800\"]\"\" Figure: Exercise-induced cardiac growth. Aerobic and resistance exercise elicit different forms of physiological cardiac remodeling. Hypertrophic responses are primarily eccentric in nature for aerobic exercise and concentric in nature for resistance exercise. LA, left atrium; LV, left ventricle; LVWT, left ventricular wall thickness; RA, right atrium; RV, right ventricle.[\/caption]\r\n\r\nIn the above figure, if you look carefully the remodeling that occurs during resistance training<\/strong> is different than with cardiovascular (aerobic) training<\/strong>.\u00a0 With resistance training the ventricles don't increase in their fill volume, but do increase ventricular wall thickness.\u00a0 The rationale is that the myocardium will be able to generate more pressure which will help send blood through that bodybuilder's blood vessels.\u00a0 You can imagine that a body builder has bigger skeletal muscles that have increased in vasculature as well - to support the activity of these larger skeletal muscles.\u00a0 So the heart will have remodeled at the same time in order to push blood into a lot of blood vessels that are potentially compressed while lifting weights. So we would say, this is a nice, healthy heart for a bodybuilder.\u00a0 With the endurance runner, their myocardium thicken this, and the fill volume also increases.\u00a0 The rationale is that if the heart can send a larger volume through your blood vessels, it doesn't have to beat quite as quickly which helps with reducing fatigue, which of course is important during 3 hour marathons.\u00a0 Notice in both hearts, that progenitor cells are activated, which means hyperplasia (increased cell number due to mitosis or cell division) is occurring and is contributing to the increased thickness of the ventricular walls.\u00a0 You'll also notice that both conditions are reversible, meaning that if a person stops training and becomes sedentary, the cellular changes will reverse.\r\n\r\n[caption id=\"attachment_362\" align=\"alignleft\" width=\"225\"]\"\" Figure: Pathologic hypertrophy of the heart due to cardiomyopathy (a disease that affects the myocardium).[\/caption]\r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\nNow with pathologic hypertrophy<\/strong>, you might guess correctly that hypertrophy has occurred as a result of a disease.\u00a0 In this instance, the underlying disease is causing an organ to become larger.\u00a0 There could be several reasons for this phenomenon.\u00a0 There may be infiltration by a large number of immune system cells, or there may be inflammation (swelling or edema), or perhaps abnormal accumulations of inclusion bodies or vacuoles within the organ's cells.\u00a0 In the case of heart disease and hypertension (high blood pressure), the heart's ventricular muscles need to work harder, and to generate the increased force required to deliver blood flow.\u00a0 Perhaps there's a lot of blood vessel damage through out the body and the heart has to push blood through these damaged vessels, which is much harder.\u00a0 Thus, the workload (for the heart) has gone up and the heart has hypertrophied in response.\u00a0 So it can be a sign of damaged blood vessels, or blood vessels full of atherosclerotic plaque, or even abnormally narrowed vessels, that can no longer dilate.\u00a0 In these instances, hypertrophy is not a sign of a healthy heart. In fact, the heart shape is no longer that beautiful cylinder shape that you would see with an athlete or normal, healthy person.\u00a0 The cylinder shape is very effective at pushing blood out of it.\u00a0 When a heart hypertrophies during heart disease, instead of a beautiful cylinder, it becomes more of a sphere. So even though the wall is thicker, the muscle itself becomes less effective and less efficient.\u00a0 It is not pushing blood nearly as effectively.\u00a0 It is a sign of deterioration and it's a sign that the heart is not working as well and is under duress.\u00a0 In these instances, we would use the term pathologic hypertrophy, and instead of making a person more athletic (with larger cardiac output as in the case of physiologic hypertrophy), it is often a sign that this organ is starting to deteriorate.\r\n\r\n \r\n\r\n\"\"\r\n\r\nLet's go to the next term, hyperplasia.<\/strong>\u00a0 Can you tell what's happened in the illustration?\u00a0 The cells are the same size as the cells depicted as normal, but there's more cells, instead of four cells, now there's eight.\u00a0 You can see that's growth in cell number, there has been mitosis (or cell division).\u00a0 The suffix -plasis<\/strong>, comes from the Greek word meaning 'formation'.\u00a0 As with hypertrophy, there can be both physiologic and pathologic hypertrophy.\r\n\r\nSo when would you see physiologic hyperplasia?<\/strong>\r\n\r\nOne example of physiologic hyperplasia<\/strong>, is in the growing that occurs during childhood (starting prenatally from fetus to embryo to baby to child to teenager to adult).\u00a0 The second example of physiologic hyperplasia occurs during pregnancy (in the growing of the uterus, abdomen, breasts, and other tissues which are designed to support the pregnancy and newborn).\r\n\r\nWhen would you see pathologic hyperplasia?<\/strong>\r\n\r\nMost example of pathologic hyperplasia<\/strong>, occur due to a disease that is causing an imbalance of growth hormones (which may be temporary).\u00a0 This can be rectified by treating the underlying disease or through use of medication that re-establishes hormones at normal levels.\u00a0 At times, pathologic hyperplasia occurs for other reasons.\u00a0 Sometimes pathologic hyperplasia results in the formation of a benign tumour.\u00a0 If this tumour is pressing on tissues and causing negative clinical manifestations, it may be surgically removed.\r\n\r\n \r\n\r\nLet's go to the next term, metaplasia<\/strong>, originating from the Greek words for 'change form'.\u00a0 In the above figure, the cells have become more round, to illustrate a type of change in structure\/form.\u00a0 Within the human body, we see metaplasia occur in the trachea (windpipe) of smokers.\u00a0 Prior to metaplasia, the trachea consists of a healthy single layer of tall ciliated cells.\u00a0 This tissue is therefore composed of simple, pseudostratified, columnar ciliated epithelial cells<\/strong>.\u00a0 \u00a0This tissue contains Goblet cells that secretes mucus in order to trap pathogens and debris, to prevent that material from entering (and potentially damaging) the lungs.\u00a0 The cilia are going to sweep the mucus containing any debris upwards to eventually be swallowed sending that material to the stomach for destruction and removal.\u00a0 Now if you're a smoker and these cells in the trachea are being perpetually damaged, the tissue remodels itself to become more robust and resilient.\u00a0 The simple columnar ciliated cells replace themselves with multiple layers of squamous cells now, in a tissue we would call stratified squamous epithelium with no cilia and fewer Goblet cells<\/strong>.\u00a0 As a result the tracheal wall becomes more resilient to smoke, but is also less functional.\u00a0 This tissue is less functional because the cells are not producing the mucus as they should and they don't have the cilia. So if you've got a long-term smoker, you might find they get a smoker's cough because you now need to use coughing to try and clear the debris and mucus out of the trachea.\u00a0 Metaplasia is thought to be reversible if the source of irritant is removed.<\/span>\r\n\r\nThe next term, dysplasia, <\/strong>with the prefix dys<\/strong>- in Greek meaning bad, so altogether the word dysplasia referring to 'bad growth'.\u00a0 In the above figure, you can see these cell shapes are changing are the cells themselves are becoming less functional, becoming de-differentiated (more immature).\u00a0 This type of change potentially makes a cell pre-cancerous.\u00a0 As a cell becomes less and less differentiated (mature), it becomes more and more likely to resume cell cycling (mitosis).\u00a0 Cells that continually go through mitosis are not mature, and not functional, and of course, continue to produce more and more cells.\u00a0\u00a0<\/span>\r\n\r\n[caption id=\"attachment_341\" align=\"alignnone\" width=\"1024\"]\"\" Figure: Cell morphology changes during the development of a tumor, which may be benign (noncancerous and non-spreading) or malignant (cancerous).[\/caption]\r\n\r\nIf dysplastic cells do enter this stage of continually cycling, we would refer to them as anaplastic,<\/strong> and the growth and accumulation of a mass of new cells would be called a neoplasm<\/strong> 'new growth\" or tumour, which may be benign<\/strong> (non-cancerous) or may be malignant, cancerous<\/strong> (metastatic, capable of spreading and infiltrating other tissues and organs).\u00a0 \u00a0Anaplastic cells are often immortal, and have entered a state of uncontrollable cell division.\u00a0 Malignant cells are capable of breaking through basement membranes (shown in blue in the figure below) and spreading to neighbouring tissues.\u00a0<\/span>\r\n\r\n[caption id=\"attachment_306\" align=\"alignnone\" width=\"1024\"]\"\" Figure: Benign Tumour consists of dysplastic cells contained within a capsule, with cells not breaching through the basement membrane. Malignant Tumour consists of anaplastic cells that have breached the basement membrane and are spreading into neighbouring tissues.[\/caption]\r\n\r\nTumour Types:\u00a0<\/strong> Benign (non-cancerous) and Malignant (cancerous)Cells typically become dysplastic<\/strong> due to a particular type of irritant (e.g. cigarette smoke, pollutants, some viruses, UV and radiation exposure) that has led to either DNA mutations, or changes in gene expression.\u00a0 If the irritant is removed, and normal gene expression resumes, the cells may revert from dysplastic back to normal.<\/strong>\u00a0 However, if further more permanent changes in gene expression occur due to more irritation causing further DNA mutations which can no longer be compensated for, the dysplastic cells may become anaplastic<\/strong> (completely de-differentiated, non-functional, and continually cell cycling).\u00a0 As mentioned earlier, these anaplastic cells may give rise to either a benign neoplasm or a metastatic (or malignant) neoplasm.\u00a0 The progression of morphological changes that occur as a cell cancer is illustrated below.\u00a0 Carcinoma in situ<\/em><\/strong> is depicted as pre-malignant as the basement membrane is still intact.\u00a0 Most carcinomas in situ<\/em> <\/strong>eventually progress to become malignant carcinomas.<\/span>\r\n\r\n[caption id=\"attachment_297\" align=\"alignnone\" width=\"423\"]\"\" Figure: Cell morphology and cell number changes during the development of cancer.[\/caption]\r\n\r\n \r\n\r\nOnce malignant cancerous cells have broken through the basement membrane they can enter the blood or lymph vessels and spread to distant sites in the body infiltrating tissues and developing into secondary cancers.\u00a0 If untreated this can lead to the failure of multiple organs.\r\n\r\n \r\n\r\n[caption id=\"attachment_318\" align=\"alignnone\" width=\"685\"]\"\" Figure: Cancer invasion is the first step of the metastatic cascade. Tumour cells penetrate the basement membrane and invade the surrounding tissues using two modes of movement\u2014individual and collective invasion. Invading tumour cells reach the blood vessel, enter the blood flow and disseminate, eventually giving rise to secondary tumours.[\/caption]\r\n\r\n \r\n

    Let's look at three examples using these terms (hyperplasia, metaplasia, dysplasia):<\/span>\u00a0\u00a0<\/span><\/strong><\/h3>\r\n1.\u00a0 It is known that smoking<\/strong> causes irritation to cells within the respiratory tract and that it is the leading cause of lung cancer<\/strong>, in addition to being a risk factor for other cancers.<\/span>\r\n\r\n[caption id=\"attachment_296\" align=\"alignnone\" width=\"1024\"]\"\" Figure: Stages of morphological cellular adaptations and molecular changes leading to lung cancer. Representative illustration highlighting morphological alterations of the epithelial cells during the gradual transition towards lung cancer and key molecular alterations contributing to this process.[\/caption]\r\n\r\n \r\n\r\n2.\u00a0 It is known that Ultraviolet light (UV)<\/strong> causes DNA mutations within skin cells, and is the leading risk factor for the most common forms of skin cancers<\/strong> (e.g. basal cell carcinoma, squamous cell carcinoma, and melanoma<\/em>).<\/span>\r\n\r\n[caption id=\"attachment_313\" align=\"alignnone\" width=\"765\"]\"\" Figure: The skin is comprised of 3 main layers: the epidermis, dermis and subcutaneous fat. UV light from the sun can penetrate the skin and damage DNA in the nucleus of skin cells. If the cells are not able to repair this damage, or repair it improperly, it can lead to uncontrolled cell growth and formation of a tumor. A tumor is considered cancerous when it is able to metastasize, or grow outside of its normal tissue. Developing skin cancer is more likely to happen with more or more frequent sun exposure, sunburns, or with age, as the cells lose their ability to repair DNA because there is too much or too repeated damage. Wearing sunscreen can help shield your skin cells from UV light and can help prevent skin cancer[\/caption]\r\n\r\n \r\n\r\n3.\u00a0 There are many strains of Human Papilloma Virus, HPV<\/strong>, some of which are known to be risk factors for the development of cervical cancer, some of which cause warts on the skin (including genital warts).\u00a0 Some strains (types) of HPV are therefore termed oncoviruses<\/strong> (a virus that can cause cancer).\u00a0 As a preventative measure for cervical cancer<\/strong>, in Canada, the HPV vaccine is available for youth.\u00a0 HPV is transmitted by skin-to-skin contact as well as sexually, ideally the vaccine is given to all youth prior to sexual activity, which increases risk of viral exposure.\u00a0 HPV is also linked to penile cancers and cancers of the mouth, throat, anus and vagina.\u00a0 With all cancers, we know that early detection makes for a better prognosis and better chance of recovery.\u00a0 To ensure early detection, in Canada, it is recommended that abnormalities in the mouth, throat, anus, vagina and penis are reported to the physician early.\u00a0 The cervix (entrance to the uterus) is more difficult to self examine.\u00a0 In this case, it is recommended that once individuals become sexually active that they have regular Pap smears (tests)<\/strong> done in which cervical cells are swabbed or scraped, sent to a lab to be looked at under the microscope.\u00a0 The lab technicians that perform this test are looking at the cellular morphology of the these cervical epithelial cells to see if any dysplasia or anaplasia has occurred. A physician's recommendations on the frequency of Pap smear tests, should be followed, which is usually every 2-3 yrs.\u00a0 The Pap test is named after the physician that discovered this test in 1923, Georgios Papanikolaou.\u00a0 Pap tests may be full automated in the future and\/or replaced with HPV testing as tests evolve and improve.<\/span><\/span>\r\n\r\n[caption id=\"attachment_304\" align=\"alignnone\" width=\"1024\"]\"\" Figure 1. Classification of normal squamous epithelial cells and human papillomavirus (HPV) infections in normal precancerous lesions (cervical intraepithelial neoplasia grades 1, 2, and 3 \u201cCIN 1, CIN 2, and CIN 3\u201d) and cervical cancer.[\/caption]\r\n\r\n \r\n\r\n \r\n\r\nLet's take a look at cervical cells from various Pap tests to illustrate the change in morphology that occur.\u00a0 <\/span>\r\n\r\n\"\"<\/span>\r\n\r\n[caption id=\"attachment_338\" align=\"alignleft\" width=\"300\"]\"\" Pap Test: The Bethesda system classifies cells into multiple diagnostic categories, including (but not limited to) Negative for Intraepithelial Malignancy (NILM, normal, no abnormal cells), Low Grade Squamous Intraepithelial Lesion (LSIL, mild dysplasia), High Grade Squamous Intraepithelial Lesion (HSIL, moderate or severe dysplasia, doesn't necessarily progress to cancer), and Squamous Cell Carcinoma (SCC, cancer).[\/caption]\r\n\r\n\u00a0<\/span>\r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\n \r\n\r\nTEDEx\u00a0 How to Hack HeadLines - Fake medical news or real?<\/a>\r\n\r\nWhat is healthium?\u00a0 Does it reduce cholesterol?\r\n\r\nDoes chocolate reduce stress?\r\n\r\nHow do you make sure news about medical research is believable?\u00a0 Ask yourselves these questions:\r\n\r\nHas the research been submitted for peer-evaluation?\u00a0 \u00a0Has the research been found to be reproducible?\u00a0 Was a large enough sample size (# of people) used to ensure robust statistical analysis is possible?\r\n\r\nWhat is that actual difference?\u00a0 Is the difference\/cure\/alleviation of symptoms statistically significant?\u00a0 Were there negative side effects?\r\n\r\nHas this been proven to be a short-term effect or long-term effect?\u00a0 How long?\r\n\r\nWas the study double blind?\u00a0 Has it been reproduced by another research team?\u00a0 Was this study done in humans or mice or fish etc.?","rendered":"

    Vocabulary<\/h1>\n

    In this section, we will outline<\/span> several\u00a0<\/span>vocabulary terms<\/strong> that are used in<\/span>\u00a0pathophysiology,<\/span>\u00a0as well as <\/span>cellular responses<\/span><\/strong> to <\/span>stress, <\/span><\/strong>injury, and aging<\/strong>.<\/span><\/p>\n

    <\/div>\n

    P is for Pathology, Pathophysiology, Pathogen, and Pathogenesis – What is the difference between these terms?<\/h1>\n

    First of all, what is this term pathology<\/strong>?<\/span> \u00a0If we break that word pathology down, <\/span>you probably know that<\/span>\u00a0‘-ology’<\/strong> means ‘the study of’,<\/span>\u00a0and pathos<\/strong> is Greek in origin, and refers to disease or pain.<\/span> \u00a0So it might make sense that<\/span>\u00a0pathology is the study of<\/span><\/span>\u00a0<\/span>cell or tissue changes due to disease<\/span>.<\/span><\/p>\n

    The next term, pathophysiology,<\/strong><\/span> if we were to look at the components of that word – you may already know the term physiology,<\/strong><\/span>\u00a0having likely studied anatomy<\/strong> and<\/span>\u00a0physiology<\/strong> previously.<\/span><\/p>\n

    Anatomy<\/strong> is the study of a particular structure<\/span> within the human body and remember, physiology<\/strong> is defined<\/span>\u00a0as the study of the function<\/span><\/span>\u00a0of a particular structure within<\/span>\u00a0the human body. <\/span><\/p>\n

    So therefore you might guess that<\/span>\u00a0<\/span>pathophysiology<\/strong> refers to the study of<\/span>\u00a0abnormalities in physiology as<\/span>\u00a0a result of disease, or study of abnormalities in the function of a particular structure of the human body as a result of disease<\/span>.<\/span>\u00a0\u00a0<\/span><\/p>\n

    The next term is <\/span>pathogen,<\/span><\/strong> refers to <\/span>any microorganism that<\/span>\u00a0causes disease; it might be a bacterium,<\/span> a virus, a fungi\/yeast,<\/span> a helminth, or protozoa.<\/span><\/p>\n

    Let’s go through some more terms,<\/span> the next is\u00a0pathogenesis.<\/strong><\/span>\u00a0So you know that the Greek word, pathos-<\/strong> is referring to ‘suffering<\/em>‘ and<\/span>\u00a0genesis<\/strong> means the ‘creation of<\/em>‘ (Latin and Greek). Ok,<\/span>\u00a0So we’re basically when we<\/span>\u00a0talking about the pathogenesis of something,<\/span>\u00a0we’re talking about the creation or<\/span>\u00a0the mechanism of that disease, in particular we are referring to all of the steps that occur at the cellular and molecular level, as well as at the organ and organ system level.\u00a0 Therefore, pathogenesis refers to the mechanism of the disease, and all of the steps that unfold as the disease progresses in the body.\u00a0 \u00a0<\/span><\/p>\n

    <\/h2>\n

    The term lesion<\/strong> is defined<\/span>\u00a0as the anatomic abnormality of that disease.<\/span>\u00a0It might be an open wound,<\/span>\u00a0tissue damaged or destroyed by a pathogen, a broken bone, or<\/span>\u00a0a cancerous growth.<\/span><\/p>\n

    \"\"<\/a>
    Ancient Romans often dedicated objects of devotion to specific gods associated with healing in the hopes of recovery. These objects were in the form or representation of the affected body part and would be left at the temple of a god.
    This torso was created in the image of a man’s torso, dissected so that the internal organs could be seen, and was probably dedicated to heal someone suffering from internal disease or injury. Made c. 200 BCE – 200 CE, most likely in Isola Farnese, Italy. The piece is now part of the collection of the Science Museum in London, UK<\/em>.<\/figcaption><\/figure>\n
    <\/div>\n
    \"\"<\/a>
    A fresco depicting the Greco-Roman mythology of Iapyx (the healer) removing an arrowhead from the Trojan hero Aeneas’ thigh. Venus stands over while beside Aeneas stands his young son Ascanius. 1st century CE (between 45 and 79 CE), from Pompeii. (Naples National Archaeological Museum)<\/em>.<\/figcaption><\/figure>\n

    What is disease?\u00a0 What is considered healthy?<\/h1>\n

    It is important to be able to determine what<\/span>\u00a0is considered healthy<\/strong> and what is considered disease<\/strong>.\u00a0 \u00a0Disease most often is accompanied by indicators that signal that something is negatively affecting the normal physiology, either in a temporary or permanent manner.\u00a0 To determine what signs, symptoms, and measurements may indicate disease, it is important to think about the range of physiological measurements that are considered normal,<\/strong> and fall inside the normal and expected functioning range of the human body.\u00a0 This normal range is most conducive to organ and tissue homeostasis<\/strong> and the physical well being of the human body.\u00a0<\/span><\/p>\n

    As each human is slightly<\/span>\u00a0different, i<\/span>t is to be expected that there is a range<\/strong> of physiological measurements that can indicate optimal health.\u00a0 For example, there is a normal range of<\/span> healthy blood pressure readings, of <\/span>heart rate measurements, and of body temperatures.<\/span>\u00a0 It is also true that with these measurements,<\/span> for example, your own blood pressure, heart rate, and body temperature – they will<\/span> all change depending on if you are at rest<\/strong> or exercising.<\/strong><\/span>\u00a0 \u00a0In this case, elevations in heart rate, blood pressure and body temperature, if within the expected range for exercise, is considered normal and doesn’t mean that you’re<\/span>\u00a0sick.\u00a0 I<\/span>t might just mean that you’re<\/span> taking a break from sitting and studying and have gone for a run or a bike ride<\/span>.<\/span><\/p>\n

    So of course it’s very important<\/span>\u00a0for health care professionals to know<\/span>\u00a0what the normal range<\/strong> of<\/span> blood pressure and heart rate is, including<\/span> knowledge that in some cases, these normal ranges are<\/span>\u00a0going to be different depending on<\/span>\u00a0how old a person is, and at times what<\/span> biological sex a person is as well as other lifestyle factors.\u00a0 For example, most often, individuals that are biologically female (XX) have higher heart rates during rest and during exercise, in comparison with age-matched, biological males (XY)<\/span>.<\/span>\u00a0 Additionally, it is known that trained athletes typically have lower resting heart rates than age-matched individuals that are sedentary.\u00a0 Heart rate is age-dependent as well, with infants have higher heart rates than children, and children having higher heart rates than adults.\u00a0 Smokers also typically have higher heart rates than non-smokers.\u00a0 Therefore heart rate typically depends on several factors including: body size, biological sex, age, fitness level, exertion level (during rest or exercise) and lifestyle.\u00a0 Certainly some diseases can affect heart rate, and<\/p>\n

    This range of normal, healthy functioning of the human body, may bring to mind the word homeostasis.<\/strong>\u00a0 \u00a0Homeostasis (from two Greek words homoiosis<\/em> meaning the ‘same’ and stasis<\/em> meaning ‘standing’ or ‘state’) refers to the relatively stable internal environment that allows for optimal functioning of all of the tissues, organs, and organ systems of your body.\u00a0 You may recall more examples, besides, blood pressure, body temperature, and heart rate which are internally regulated to maintain conditions that are ideal for survival.\u00a0 Try to list as many as you can:\u00a0 water and electrolyte levels, oxygen, carbon dioxide and pH levels. Appropriate levels of nutritional compounds, waste compounds, hormones, growth and other regulatory factors, and the list goes on.<\/p>\n

    \n

    \n