{"id":28,"date":"2023-05-23T17:41:59","date_gmt":"2023-05-23T21:41:59","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/?post_type=chapter&#038;p=28"},"modified":"2026-06-10T15:27:05","modified_gmt":"2026-06-10T19:27:05","slug":"host-resistance-and-innate-defenses","status":"web-only","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/chapter\/host-resistance-and-innate-defenses\/","title":{"raw":"Section 1:  Host Resistance and Innate (Non-specific) Defenses","rendered":"Section 1:  Host Resistance and Innate (Non-specific) Defenses"},"content":{"raw":"<h3><span style=\"color: #1f5c99\"><strong>Section 1: Host Resistance and Innate Defenses<\/strong><\/span><\/h3>\r\n<p style=\"text-align: justify\"><span class=\"transcription-time-part\" data-time-start=\"252.739\" data-time-end=\"256.415\">The human body must constantly protect itself against microorganisms capable of harming our cells.\u00a0 The capacity to prevent microorganisms from causing diseases is termed <strong>host resistance<\/strong>, categorized as either <strong>non-specific<\/strong> (protecting against many different foreign agents) or <strong>specific<\/strong> (targeting only particular antigens).\u00a0 This chapter focuses on non-specific innate defense, the inflammatory response, fever, and the cellular processes underlying healing.<\/span><\/p>\r\n\r\n<h3><span style=\"color: #1f5c99\"><strong>Pathogenic Microorganisms<\/strong><\/span><\/h3>\r\n<p style=\"text-align: justify\"><span class=\"transcription-time-part\" data-time-start=\"252.739\" data-time-end=\"256.415\">Most<\/span> microorganisms are beneficial - <strong>decomposing<\/strong> organic material, forming <strong>food-web<\/strong> foundations, and <strong>fixing atmospheric gases<\/strong> (e.g., nitrogen N<sub>2<\/sub> and carbon dioxide CO<sub>2<\/sub>) into usable forms for plants and other organisms.\u00a0 Microorganisms also synergistically inhabit the intestines of mammals, including humans, producing <strong>vitamins<\/strong> (e.g. Vitamin K and B<sub>12<\/sub>) which are required for enzymatic functions.\u00a0 Humans also benefit from <strong>industrial usage<\/strong> of microorganisms which are utilized in waste and sewage treatment, as well as in the fermentation and preparation of many foods and beverages (e.g. cheese, bread, yogurt, beer, wine, sauerkraut).<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">While most microorganisms are beneficial, certain species of each type of microorganism are pathogenic:<\/p>\r\n\r\n<ul>\r\n \t<li style=\"text-align: justify\"><strong style=\"text-align: initial;font-size: 1em\">Pathogenic bacteria<\/strong><span style=\"text-align: initial;font-size: 1em\">:\u00a0 Unicellular prokaryotes that cause surface infections of eyes or skin, or deeper-tissue infections, often secreting toxins that cause further damage.<\/span><\/li>\r\n \t<li style=\"text-align: justify\"><strong>Pathogenic viruses<\/strong>:\u00a0 Acellular agents that cause damage by entering human cells and replicating inside of them.<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Pathogenic f<\/strong><span style=\"text-align: initial;font-size: 1em\"><strong>ungi<\/strong>:\u00a0 Unicellular (yeast) or multicellular organisms that are capable of damaging skin (e.g. athlete's foot), mucous membranes (e.g. oral thrush, vaginal yeast infections) or lungs (e.g. aspergillosis).\u00a0 Some produce lethal toxins.<\/span><\/li>\r\n \t<li style=\"text-align: justify\"><strong>Helminths<\/strong> (parasitic worms):\u00a0 Multicellular eukaryotes that can be ingested with contaminated food or water - infesting the intestines, disrupting nutrient absorption and causing cellular damage.\u00a0 Can also penetrate the skin when wading in contaminated water.\u00a0 Range in size from microscopic to visible to the naked eye.<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Pathogenic protozoa<\/strong>:\u00a0 Unicellular eukaryotes such as <em>Plasmodium falciparum<\/em>, which is transmitted by mosquito bite and responsible for malaria.<\/li>\r\n<\/ul>\r\n<h3><span style=\"color: #1f5c99\"><strong>Breaking the Chain of Transmission<\/strong><\/span><\/h3>\r\nPreventing infections involves disrupting pathogen transmission at multiple points:\r\n<ul>\r\n \t<li style=\"text-align: justify\"><strong>Destroy disease reservoirs<\/strong>:\u00a0 e.g. eliminate standing water where mosquitos breed (harbouring malarial protozoa or West Nile virus).<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Proper disposal<\/strong> of garbage and sewage, which can harbour pathogens such as hepatitis viruses and cholera-inducing bacteria.<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Physical barriers<\/strong> include gloves, masks, lab coats, safety goggles, isolation rooms, and sterile equipment in health care.<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Condoms:<\/strong>\u00a0 barrier protection against sexually transmitted infections.<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Hand washing and thoroughly cooking food<\/strong> to prevent ingestion of pathogens.<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Wound care:<\/strong>\u00a0 proper cleaning and suturing to prevent infection.<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Vaccination<\/strong>, optimal <strong>nutrition<\/strong>, and adequate <strong>sleep<\/strong> reduce susceptibility to disease.<\/li>\r\n<\/ul>\r\n[caption id=\"attachment_5725\" align=\"alignnone\" width=\"300\"]<a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission.png\" target=\"_blank\" rel=\"noopener\"><img class=\"wp-image-5725 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission-300x108.png\" alt=\"Pathogens are infectious agents that can be transmitted by multiple routes, including direct contact, indirect contact, droplets, the air, water, food, and vectors (e.g., mosquitoes, ticks). Transmission of pathogens can occur through contact with saliva, mucous, blood, feces, or animals or areas that may be contaminated (e.g., locker room floors, linen, door knobs, soil, and waterways).\" width=\"300\" height=\"108\" \/><\/a> Pathogens are infectious agents that can be transmitted by multiple routes, including direct contact, indirect contact, droplets in the air, water, food, and vectors (e.g., mosquitoes, ticks). Transmission of pathogens can occur through contact with bodily secretions (saliva, mucous, blood, feces), or contact with animals or areas that may be contaminated (e.g., locker room floors, linen, door knobs, soil, and waterways).[\/caption]\r\n<h3><span style=\"color: #1f5c99\"><strong>Innate (Non-Specific) Defenses:\u00a0 An Overview<\/strong><\/span><\/h3>\r\n<p style=\"text-align: justify\">The body's first line of defense - called <strong>innate<\/strong> or<strong> non-specific defense<\/strong> - provides immediate, broad protection.\u00a0 <strong>Innate<\/strong> reflects that these defenses are present from birth (Latin <strong>nati<\/strong> for 'birth');\u00a0 <strong>non-specific<\/strong> reflects the wide range of pathogens covered.\u00a0 Categories include:\u00a0 physical and mechanical, biochemical, normal flora, phagocytes, complement proteins, interferons, inflammation, and fever.<\/p>\r\n\r\n<h3><span style=\"color: #1f5c99\"><strong>Physical and Mechanical Innate Defenses<\/strong><\/span><\/h3>\r\n<ul>\r\n \t<li style=\"text-align: justify\"><strong>Skin<\/strong>:\u00a0 Multiple tightly-bound, dehydrated, water-tight, keratin-filled epithelial layers resist microbial penetration.\u00a0 Frequent cell shedding continuously renews this layer.<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Fingernails<\/strong> and <strong>hair<\/strong>:\u00a0 Modified epithelial cells providing physical protection and warmth.<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Cilia:<\/strong>\u00a0 In the respiratory mucosa, cilia sweep mucus containing trapped pathogens toward the glottis for swallowing - a mechanism called the mucociliary escalator.<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Mucus:<\/strong>\u00a0 Produced by goblet cells lining the digestive, respiratory, urinary, and reproductive tracts.\u00a0 Contains sticky mucin proteins that trap debris and microbes.<\/li>\r\n \t<li style=\"text-align: justify\"><strong>Urine flow:<\/strong>\u00a0 Flushing action through the urinary tract provides physical protection.<\/li>\r\n<\/ul>\r\n[caption id=\"attachment_5719\" align=\"alignnone\" width=\"293\"]<a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Innate-Defense-Open-University.png\" target=\"_blank\" rel=\"noopener\"><img class=\"wp-image-5719 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Innate-Defense-Open-University-293x300.png\" alt=\"Non-Specific Defense: Physical and Chemical Barriers Against Infection\" width=\"293\" height=\"300\" \/><\/a> <strong>Physical and Chemical Barriers Against Infection:<\/strong> This is a diagram of the human body annotated with descriptions of the various barriers against infection. These comprise: intact skin and the acid in sweat; coughing and sneezing which expel infectious agents; enzymes in mucus, tears and saliva, in the nose and mouth; the mucus and intact mucous membranes of the respiratory tract; cilia in the respiratory tract, which trap foreign material; acid in the stomach; the mucus and intact mucous membranes of both the gut and the genital tract; competition from commensal bacteria in the gut and genital tract; and, in males, antibacterial proteins in semen.[\/caption]\r\n\r\n[caption id=\"attachment_6771\" align=\"alignnone\" width=\"300\"]<a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2.png\" target=\"_blank\" rel=\"noopener\"><img class=\"wp-image-6771 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2-300x300.png\" alt=\"This scanning electron micrograph shows ciliated and non-ciliated epithelial cells from the human trachea. The mucociliary escalator pushes mucus away from the lungs, along with any debris or microorganisms that may be trapped in the sticky mucus, and the mucus moves up to the esophagus where it can be removed by swallowing.\" width=\"300\" height=\"300\" \/><\/a> This scanning electron micrograph shows ciliated and non-ciliated epithelial cells from the human trachea. The mucociliary escalator pushes mucus away from the lungs, along with any debris or microorganisms that may be trapped in the sticky mucus, and the mucus moves up to the esophagus where it can be removed by swallowing.[\/caption]\r\n\r\n[caption id=\"attachment_6773\" align=\"alignnone\" width=\"300\"]<a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus.png\" target=\"_blank\" rel=\"noopener\"><img class=\"wp-image-6773 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus-300x193.png\" alt=\"Goblet cells produce and secrete mucus. The arrows in this micrograph point to the mucus-secreting goblet cells (magnification 1600\u2a2f) in the intestinal epithelium. Mucus consists of 95% water and 5% mix of proteins sugars, and salts. The mucins are sticky glycoproteins. IgA antibodies and enzymes (lysozyme and lactoferrin) help destroy bacteria and viruses.\" width=\"300\" height=\"193\" \/><\/a> Goblet cells produce and secrete mucus. The arrows in this micrograph point to the mucus-secreting goblet cells (magnification 1600\u2a2f) in the intestinal epithelium. Mucus consists of 95% water and 5% mix of proteins sugars, and salts. The mucins are sticky glycoproteins. IgA antibodies and enzymes (lysozyme and lactoferrin) help destroy bacteria and viruses.[\/caption]\r\n<h3><span style=\"color: #1f5c99\"><strong>Biochemical Innate Defenses<\/strong><\/span><\/h3>\r\nSecretions from glands and organs create a chemically hostile environment for pathogens:\r\n<table class=\"grid landscape\" style=\"border-collapse: collapse;width: 100%;height: 248px\" border=\"0\">\r\n<tbody>\r\n<tr style=\"height: 47px\">\r\n<td class=\"border\" style=\"width: 19.8842%;height: 47px\"><span style=\"color: #032c80\"><strong>Sebum<\/strong><\/span><\/td>\r\n<td style=\"width: 80.1158%;height: 47px\"><strong>Bactericidal<\/strong> oil secrete by sebaceous glands onto the skin.\r\n\r\nContains <strong>lysozymes,<\/strong> <strong>IgA antibodies<\/strong>, and <strong>defensins<\/strong> (antimicrobial peptides that disrupt bacterial or fungal structure or metabolism)<\/td>\r\n<\/tr>\r\n<tr style=\"height: 31px\">\r\n<td class=\"shaded\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Sweat<\/strong><\/span><\/td>\r\n<td class=\"shaded\" style=\"width: 80.1158%;height: 31px\">Contain <strong>water, ions,<\/strong> and <strong>waste products<\/strong> that flush microorganisms from skin surfaces and make the environment less hospitable to pathogens.<\/td>\r\n<\/tr>\r\n<tr style=\"height: 31px\">\r\n<td class=\"border\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Tears &amp; meibum<\/strong><\/span><\/td>\r\n<td style=\"width: 80.1158%;height: 31px\">Tears contain <strong>lysozymes<\/strong> and <strong>IgA antibodies.<\/strong>\u00a0\u00a0Meibum adds <strong>oils<\/strong> and other protective compound.\u00a0 Together they protect the eye surface.<\/td>\r\n<\/tr>\r\n<tr style=\"height: 31px\">\r\n<td class=\"shaded\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Cerumen (ear wax)<\/strong><\/span><\/td>\r\n<td class=\"shaded\" style=\"width: 80.1158%;height: 31px\">Produced by modified sweat glands.\u00a0 Slightly <strong>acidic<\/strong> and dry with <strong>antifungal<\/strong> and <strong>antibacterial<\/strong> properties.\u00a0 Traps pathogens and resists outer ear infection.<\/td>\r\n<\/tr>\r\n<tr style=\"height: 31px\">\r\n<td class=\"border\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Stomach acid<\/strong><\/span><\/td>\r\n<td style=\"width: 80.1158%;height: 31px\">Destroys most ingested microbes; strong biochemical protection within the digestive tract.<\/td>\r\n<\/tr>\r\n<tr style=\"height: 31px\">\r\n<td class=\"shaded\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Bile<\/strong><\/span><\/td>\r\n<td class=\"shaded\" style=\"width: 80.1158%;height: 31px\">Produced by the liver, stored, and secreted by the gallbladder.\u00a0 <strong>Alkaline;<\/strong> contains <strong>bile salts<\/strong> that are potent antimicrobial agents.<\/td>\r\n<\/tr>\r\n<tr style=\"height: 31px\">\r\n<td class=\"border\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Vaginal secretions<\/strong><\/span><\/td>\r\n<td style=\"width: 80.1158%;height: 31px\">Slightly acidic; contain <strong>lactoferrin<\/strong> (sequesters iron, depriving bacteria of a required resource) and <strong>lysozyme<\/strong> (cleaves bacterial cell wall components)<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td class=\"shaded\" style=\"width: 19.8842%;height: 15px\"><span style=\"color: #032c80\"><strong>Seminal fluid<\/strong><\/span><\/td>\r\n<td class=\"shaded\" style=\"width: 80.1158%;height: 15px\">Contains antimicrobial peptides and enzymes including <strong>lactoferrin<\/strong> and <strong>lysozyme.\u00a0 <\/strong>Composed of secretions from <strong>epididymis, seminal vesicles,<\/strong> and <strong>bulbourethral<\/strong> and <strong>prostate<\/strong> glands.<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n[caption id=\"attachment_6787\" align=\"alignnone\" width=\"300\"]<a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/skin.png\" target=\"_blank\" rel=\"noopener\"><img class=\"wp-image-6787 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/skin-300x278.png\" alt=\"Sebum is also a food source for resident microbes that produce oleic acid,\" width=\"300\" height=\"278\" \/><\/a> Human skin has three layers, the epidermis, the dermis, and the hypodermis, which provide a thick barrier between microbes outside the body and deeper tissues. Dead skin cells on the surface of the epidermis are continually shed, taking with them microbes on the skin\u2019s surface. Sebaceous glands secrete sebum, a chemical mediator that lubricates and protect the skin from invading microbes. Sebum is also a food source for resident microbes that produce oleic acid, making the skin mildly acid and inhospitable to many pathogenic microbes. Sweat glands secrete dermcidin, which disrupts the membrane integrity of bacteria and fungi.[\/caption]\r\n\r\n[caption id=\"attachment_6788\" align=\"alignnone\" width=\"300\"]<a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear.png\" target=\"_blank\" rel=\"noopener\"><img class=\"wp-image-6788 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear-300x183.png\" alt=\"In the ears, cerumen (earwax) exhibits antimicrobial properties due to the presence of fatty acids, which lower the pH to between 3 and 5.\" width=\"300\" height=\"183\" \/><\/a> In the ears, cerumen (earwax) exhibits antimicrobial properties and low pH 3-5.[\/caption]\r\n<h3><span style=\"color: #1f5c99\"><strong>Innate Defenses:\u00a0 Normal Microbiota<\/strong><\/span><\/h3>\r\n<p style=\"text-align: justify\">The <strong>human microbiome<\/strong> encompasses all microorganisms on the skin, eyes, hair, nails, nose, mouth, respiratory and digestive tracts, urethra, and vagina.\u00a0 Microbes in these regions that do not cause disease are called <strong>normal flora<\/strong> or <strong>normal microbiota<\/strong>.\u00a0 They vary by individual, body location, climate, and diet.<\/p>\r\n<p style=\"text-align: justify\">Normal microbiota are <strong>commensals<\/strong>\u00a0 - co-existing without causing harm, benefiting from dead skin cells and secretions.\u00a0 The relationship is often <strong>mutualistic<\/strong>:\u00a0 both host and microbe benefit.\u00a0 Normal microbiota protect against pathogens by both occupying surface area and secreting deterrent biochemicals.\u00a0 Intestinal microbes additionally help break down indigestible compounds (dietary fiber) and produce beneficial vitamins.<\/p>\r\n\r\n\r\n[caption id=\"attachment_2318\" align=\"alignnone\" width=\"300\"]<a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3.png\"><img class=\"wp-image-2318 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3-300x300.png\" alt=\"normal flora\" width=\"300\" height=\"300\" \/><\/a> Human microbiome refers to the microorganisms (bacteria, fungi, protozoa, archaea, and viruses) that naturally inhabit the human body. These microorganisms have a range of roles throughout the body. For example, gut microbiota is known to assist with digestion, the production of vitamins essential to human health (e.g., vitamins B and K, and also provide protection from pathogenic microorganisms. The composition of the gut microbiota is reflective of environmental exposure, diet, and health.[\/caption]\r\n\r\n&nbsp;\r\n\r\n[caption id=\"attachment_5723\" align=\"alignnone\" width=\"300\"]<a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-scaled.png\"><img class=\"size-medium wp-image-5723\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-300x239.png\" alt=\"A schematic representation of the human gut microbiota, which contains 100 trillion microorganisms. These microorganisms, such as bacteria, viruses, fungi, and protozoa, are part of the gut microbiota.\" width=\"300\" height=\"239\" \/><\/a> A schematic representation of the human gut microbiota, which contains 100 trillion microorganisms. These microorganisms (bacteria, viruses, fungi, and protozoa) are part of the gut microbiota.[\/caption]\r\n\r\n&nbsp;\r\n\r\n&nbsp;\r\n\r\n<strong>Think About Questions:<\/strong>\r\n\r\n<strong>Why is inflammation considered a non-specific defense?\u00a0 What are other non-specific defenses of the human body?<\/strong>\r\n\r\n<strong>Why does inflammation occur any time that there is an injury or disease?<\/strong>\r\n\r\n<strong>Did you know that biologists sometimes call the digestive system an external tube that penetrates the body?\u00a0 Name one feature of the digestive system that prevents ingested microbes from causing an infection.\u00a0<\/strong>\r\n\r\n<strong>Why does taking an antacid put you more at risk for stomach infections?<\/strong>\r\n\r\n<strong>Imagine you have a papercut - list the innate factors of your body that will help eliminate the bacteria that enter that cut.\u00a0<\/strong>\r\n\r\n<strong>On a neutrophil, define the following: pseudopod, phagosome, lysosome, granule<\/strong>\r\n\r\n<strong>How does a NK cells kill bacteria?<\/strong>\r\n\r\n<strong>What is properdin?<\/strong>\r\n\r\n<strong>What is an interferon?<\/strong>\r\n\r\n<strong>What is a respiratory burst?<\/strong>\r\n\r\nDid you know that some diseases are caused by auto-antibodies?\u00a0 And some are caused by auto-complement proteins?\u00a0 https:\/\/www.thelancet.com\/journals\/lancet\/article\/PIIS0140-6736(23)01524-6\/fulltext\r\n\r\n&nbsp;\r\n\r\n<span class=\"transcription-time-part\" data-time-start=\"2.21\" data-time-end=\"4.949\"><strong>Inspirational Quote:<\/strong> Healing is an art. It takes time, it takes practice. It takes love. ~ <a href=\"https:\/\/livelifehappy.com\/\" target=\"_blank\" rel=\"noopener\">Maza Dohta<\/a>\u00a0<\/span>\r\n\r\n&nbsp;","rendered":"<h3><span style=\"color: #1f5c99\"><strong>Section 1: Host Resistance and Innate Defenses<\/strong><\/span><\/h3>\n<p style=\"text-align: justify\"><span class=\"transcription-time-part\" data-time-start=\"252.739\" data-time-end=\"256.415\">The human body must constantly protect itself against microorganisms capable of harming our cells.\u00a0 The capacity to prevent microorganisms from causing diseases is termed <strong>host resistance<\/strong>, categorized as either <strong>non-specific<\/strong> (protecting against many different foreign agents) or <strong>specific<\/strong> (targeting only particular antigens).\u00a0 This chapter focuses on non-specific innate defense, the inflammatory response, fever, and the cellular processes underlying healing.<\/span><\/p>\n<h3><span style=\"color: #1f5c99\"><strong>Pathogenic Microorganisms<\/strong><\/span><\/h3>\n<p style=\"text-align: justify\"><span class=\"transcription-time-part\" data-time-start=\"252.739\" data-time-end=\"256.415\">Most<\/span> microorganisms are beneficial &#8211; <strong>decomposing<\/strong> organic material, forming <strong>food-web<\/strong> foundations, and <strong>fixing atmospheric gases<\/strong> (e.g., nitrogen N<sub>2<\/sub> and carbon dioxide CO<sub>2<\/sub>) into usable forms for plants and other organisms.\u00a0 Microorganisms also synergistically inhabit the intestines of mammals, including humans, producing <strong>vitamins<\/strong> (e.g. Vitamin K and B<sub>12<\/sub>) which are required for enzymatic functions.\u00a0 Humans also benefit from <strong>industrial usage<\/strong> of microorganisms which are utilized in waste and sewage treatment, as well as in the fermentation and preparation of many foods and beverages (e.g. cheese, bread, yogurt, beer, wine, sauerkraut).<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">While most microorganisms are beneficial, certain species of each type of microorganism are pathogenic:<\/p>\n<ul>\n<li style=\"text-align: justify\"><strong style=\"text-align: initial;font-size: 1em\">Pathogenic bacteria<\/strong><span style=\"text-align: initial;font-size: 1em\">:\u00a0 Unicellular prokaryotes that cause surface infections of eyes or skin, or deeper-tissue infections, often secreting toxins that cause further damage.<\/span><\/li>\n<li style=\"text-align: justify\"><strong>Pathogenic viruses<\/strong>:\u00a0 Acellular agents that cause damage by entering human cells and replicating inside of them.<\/li>\n<li style=\"text-align: justify\"><strong>Pathogenic f<\/strong><span style=\"text-align: initial;font-size: 1em\"><strong>ungi<\/strong>:\u00a0 Unicellular (yeast) or multicellular organisms that are capable of damaging skin (e.g. athlete&#8217;s foot), mucous membranes (e.g. oral thrush, vaginal yeast infections) or lungs (e.g. aspergillosis).\u00a0 Some produce lethal toxins.<\/span><\/li>\n<li style=\"text-align: justify\"><strong>Helminths<\/strong> (parasitic worms):\u00a0 Multicellular eukaryotes that can be ingested with contaminated food or water &#8211; infesting the intestines, disrupting nutrient absorption and causing cellular damage.\u00a0 Can also penetrate the skin when wading in contaminated water.\u00a0 Range in size from microscopic to visible to the naked eye.<\/li>\n<li style=\"text-align: justify\"><strong>Pathogenic protozoa<\/strong>:\u00a0 Unicellular eukaryotes such as <em>Plasmodium falciparum<\/em>, which is transmitted by mosquito bite and responsible for malaria.<\/li>\n<\/ul>\n<h3><span style=\"color: #1f5c99\"><strong>Breaking the Chain of Transmission<\/strong><\/span><\/h3>\n<p>Preventing infections involves disrupting pathogen transmission at multiple points:<\/p>\n<ul>\n<li style=\"text-align: justify\"><strong>Destroy disease reservoirs<\/strong>:\u00a0 e.g. eliminate standing water where mosquitos breed (harbouring malarial protozoa or West Nile virus).<\/li>\n<li style=\"text-align: justify\"><strong>Proper disposal<\/strong> of garbage and sewage, which can harbour pathogens such as hepatitis viruses and cholera-inducing bacteria.<\/li>\n<li style=\"text-align: justify\"><strong>Physical barriers<\/strong> include gloves, masks, lab coats, safety goggles, isolation rooms, and sterile equipment in health care.<\/li>\n<li style=\"text-align: justify\"><strong>Condoms:<\/strong>\u00a0 barrier protection against sexually transmitted infections.<\/li>\n<li style=\"text-align: justify\"><strong>Hand washing and thoroughly cooking food<\/strong> to prevent ingestion of pathogens.<\/li>\n<li style=\"text-align: justify\"><strong>Wound care:<\/strong>\u00a0 proper cleaning and suturing to prevent infection.<\/li>\n<li style=\"text-align: justify\"><strong>Vaccination<\/strong>, optimal <strong>nutrition<\/strong>, and adequate <strong>sleep<\/strong> reduce susceptibility to disease.<\/li>\n<\/ul>\n<figure id=\"attachment_5725\" aria-describedby=\"caption-attachment-5725\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission.png\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5725 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission-300x108.png\" alt=\"Pathogens are infectious agents that can be transmitted by multiple routes, including direct contact, indirect contact, droplets, the air, water, food, and vectors (e.g., mosquitoes, ticks). Transmission of pathogens can occur through contact with saliva, mucous, blood, feces, or animals or areas that may be contaminated (e.g., locker room floors, linen, door knobs, soil, and waterways).\" width=\"300\" height=\"108\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission-300x108.png 300w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission-1024x367.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission-768x276.png 768w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission-1536x551.png 1536w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission-65x23.png 65w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission-225x81.png 225w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission-350x126.png 350w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Pathogen-Transmission.png 1561w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-5725\" class=\"wp-caption-text\">Pathogens are infectious agents that can be transmitted by multiple routes, including direct contact, indirect contact, droplets in the air, water, food, and vectors (e.g., mosquitoes, ticks). Transmission of pathogens can occur through contact with bodily secretions (saliva, mucous, blood, feces), or contact with animals or areas that may be contaminated (e.g., locker room floors, linen, door knobs, soil, and waterways).<\/figcaption><\/figure>\n<h3><span style=\"color: #1f5c99\"><strong>Innate (Non-Specific) Defenses:\u00a0 An Overview<\/strong><\/span><\/h3>\n<p style=\"text-align: justify\">The body&#8217;s first line of defense &#8211; called <strong>innate<\/strong> or<strong> non-specific defense<\/strong> &#8211; provides immediate, broad protection.\u00a0 <strong>Innate<\/strong> reflects that these defenses are present from birth (Latin <strong>nati<\/strong> for &#8216;birth&#8217;);\u00a0 <strong>non-specific<\/strong> reflects the wide range of pathogens covered.\u00a0 Categories include:\u00a0 physical and mechanical, biochemical, normal flora, phagocytes, complement proteins, interferons, inflammation, and fever.<\/p>\n<h3><span style=\"color: #1f5c99\"><strong>Physical and Mechanical Innate Defenses<\/strong><\/span><\/h3>\n<ul>\n<li style=\"text-align: justify\"><strong>Skin<\/strong>:\u00a0 Multiple tightly-bound, dehydrated, water-tight, keratin-filled epithelial layers resist microbial penetration.\u00a0 Frequent cell shedding continuously renews this layer.<\/li>\n<li style=\"text-align: justify\"><strong>Fingernails<\/strong> and <strong>hair<\/strong>:\u00a0 Modified epithelial cells providing physical protection and warmth.<\/li>\n<li style=\"text-align: justify\"><strong>Cilia:<\/strong>\u00a0 In the respiratory mucosa, cilia sweep mucus containing trapped pathogens toward the glottis for swallowing &#8211; a mechanism called the mucociliary escalator.<\/li>\n<li style=\"text-align: justify\"><strong>Mucus:<\/strong>\u00a0 Produced by goblet cells lining the digestive, respiratory, urinary, and reproductive tracts.\u00a0 Contains sticky mucin proteins that trap debris and microbes.<\/li>\n<li style=\"text-align: justify\"><strong>Urine flow:<\/strong>\u00a0 Flushing action through the urinary tract provides physical protection.<\/li>\n<\/ul>\n<figure id=\"attachment_5719\" aria-describedby=\"caption-attachment-5719\" style=\"width: 293px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Innate-Defense-Open-University.png\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5719 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Innate-Defense-Open-University-293x300.png\" alt=\"Non-Specific Defense: Physical and Chemical Barriers Against Infection\" width=\"293\" height=\"300\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Innate-Defense-Open-University-293x300.png 293w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Innate-Defense-Open-University-65x67.png 65w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Innate-Defense-Open-University-225x230.png 225w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Innate-Defense-Open-University-350x358.png 350w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Innate-Defense-Open-University.png 512w\" sizes=\"auto, (max-width: 293px) 100vw, 293px\" \/><\/a><figcaption id=\"caption-attachment-5719\" class=\"wp-caption-text\"><strong>Physical and Chemical Barriers Against Infection:<\/strong> This is a diagram of the human body annotated with descriptions of the various barriers against infection. These comprise: intact skin and the acid in sweat; coughing and sneezing which expel infectious agents; enzymes in mucus, tears and saliva, in the nose and mouth; the mucus and intact mucous membranes of the respiratory tract; cilia in the respiratory tract, which trap foreign material; acid in the stomach; the mucus and intact mucous membranes of both the gut and the genital tract; competition from commensal bacteria in the gut and genital tract; and, in males, antibacterial proteins in semen.<\/figcaption><\/figure>\n<figure id=\"attachment_6771\" aria-describedby=\"caption-attachment-6771\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2.png\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-6771 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2-300x300.png\" alt=\"This scanning electron micrograph shows ciliated and non-ciliated epithelial cells from the human trachea. The mucociliary escalator pushes mucus away from the lungs, along with any debris or microorganisms that may be trapped in the sticky mucus, and the mucus moves up to the esophagus where it can be removed by swallowing.\" width=\"300\" height=\"300\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2-300x300.png 300w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2-1024x1020.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2-150x150.png 150w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2-768x765.png 768w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2-65x65.png 65w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2-225x224.png 225w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2-350x349.png 350w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/cilia2.png 1029w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-6771\" class=\"wp-caption-text\">This scanning electron micrograph shows ciliated and non-ciliated epithelial cells from the human trachea. The mucociliary escalator pushes mucus away from the lungs, along with any debris or microorganisms that may be trapped in the sticky mucus, and the mucus moves up to the esophagus where it can be removed by swallowing.<\/figcaption><\/figure>\n<figure id=\"attachment_6773\" aria-describedby=\"caption-attachment-6773\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus.png\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-6773 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus-300x193.png\" alt=\"Goblet cells produce and secrete mucus. The arrows in this micrograph point to the mucus-secreting goblet cells (magnification 1600\u2a2f) in the intestinal epithelium. Mucus consists of 95% water and 5% mix of proteins sugars, and salts. The mucins are sticky glycoproteins. IgA antibodies and enzymes (lysozyme and lactoferrin) help destroy bacteria and viruses.\" width=\"300\" height=\"193\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus-300x193.png 300w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus-1024x659.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus-768x494.png 768w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus-1536x988.png 1536w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus-65x42.png 65w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus-225x145.png 225w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus-350x225.png 350w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/Goblet-Cell-Producing-Mucus.png 1554w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-6773\" class=\"wp-caption-text\">Goblet cells produce and secrete mucus. The arrows in this micrograph point to the mucus-secreting goblet cells (magnification 1600\u2a2f) in the intestinal epithelium. Mucus consists of 95% water and 5% mix of proteins sugars, and salts. The mucins are sticky glycoproteins. IgA antibodies and enzymes (lysozyme and lactoferrin) help destroy bacteria and viruses.<\/figcaption><\/figure>\n<h3><span style=\"color: #1f5c99\"><strong>Biochemical Innate Defenses<\/strong><\/span><\/h3>\n<p>Secretions from glands and organs create a chemically hostile environment for pathogens:<\/p>\n<table class=\"grid landscape\" style=\"border-collapse: collapse;width: 100%;height: 248px\">\n<tbody>\n<tr style=\"height: 47px\">\n<td class=\"border\" style=\"width: 19.8842%;height: 47px\"><span style=\"color: #032c80\"><strong>Sebum<\/strong><\/span><\/td>\n<td style=\"width: 80.1158%;height: 47px\"><strong>Bactericidal<\/strong> oil secrete by sebaceous glands onto the skin.<\/p>\n<p>Contains <strong>lysozymes,<\/strong> <strong>IgA antibodies<\/strong>, and <strong>defensins<\/strong> (antimicrobial peptides that disrupt bacterial or fungal structure or metabolism)<\/td>\n<\/tr>\n<tr style=\"height: 31px\">\n<td class=\"shaded\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Sweat<\/strong><\/span><\/td>\n<td class=\"shaded\" style=\"width: 80.1158%;height: 31px\">Contain <strong>water, ions,<\/strong> and <strong>waste products<\/strong> that flush microorganisms from skin surfaces and make the environment less hospitable to pathogens.<\/td>\n<\/tr>\n<tr style=\"height: 31px\">\n<td class=\"border\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Tears &amp; meibum<\/strong><\/span><\/td>\n<td style=\"width: 80.1158%;height: 31px\">Tears contain <strong>lysozymes<\/strong> and <strong>IgA antibodies.<\/strong>\u00a0\u00a0Meibum adds <strong>oils<\/strong> and other protective compound.\u00a0 Together they protect the eye surface.<\/td>\n<\/tr>\n<tr style=\"height: 31px\">\n<td class=\"shaded\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Cerumen (ear wax)<\/strong><\/span><\/td>\n<td class=\"shaded\" style=\"width: 80.1158%;height: 31px\">Produced by modified sweat glands.\u00a0 Slightly <strong>acidic<\/strong> and dry with <strong>antifungal<\/strong> and <strong>antibacterial<\/strong> properties.\u00a0 Traps pathogens and resists outer ear infection.<\/td>\n<\/tr>\n<tr style=\"height: 31px\">\n<td class=\"border\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Stomach acid<\/strong><\/span><\/td>\n<td style=\"width: 80.1158%;height: 31px\">Destroys most ingested microbes; strong biochemical protection within the digestive tract.<\/td>\n<\/tr>\n<tr style=\"height: 31px\">\n<td class=\"shaded\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Bile<\/strong><\/span><\/td>\n<td class=\"shaded\" style=\"width: 80.1158%;height: 31px\">Produced by the liver, stored, and secreted by the gallbladder.\u00a0 <strong>Alkaline;<\/strong> contains <strong>bile salts<\/strong> that are potent antimicrobial agents.<\/td>\n<\/tr>\n<tr style=\"height: 31px\">\n<td class=\"border\" style=\"width: 19.8842%;height: 31px\"><span style=\"color: #032c80\"><strong>Vaginal secretions<\/strong><\/span><\/td>\n<td style=\"width: 80.1158%;height: 31px\">Slightly acidic; contain <strong>lactoferrin<\/strong> (sequesters iron, depriving bacteria of a required resource) and <strong>lysozyme<\/strong> (cleaves bacterial cell wall components)<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td class=\"shaded\" style=\"width: 19.8842%;height: 15px\"><span style=\"color: #032c80\"><strong>Seminal fluid<\/strong><\/span><\/td>\n<td class=\"shaded\" style=\"width: 80.1158%;height: 15px\">Contains antimicrobial peptides and enzymes including <strong>lactoferrin<\/strong> and <strong>lysozyme.\u00a0 <\/strong>Composed of secretions from <strong>epididymis, seminal vesicles,<\/strong> and <strong>bulbourethral<\/strong> and <strong>prostate<\/strong> glands.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<figure id=\"attachment_6787\" aria-describedby=\"caption-attachment-6787\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/skin.png\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-6787 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/skin-300x278.png\" alt=\"Sebum is also a food source for resident microbes that produce oleic acid,\" width=\"300\" height=\"278\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/skin-300x278.png 300w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/skin-65x60.png 65w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/skin-225x208.png 225w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/skin-350x324.png 350w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/skin.png 588w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-6787\" class=\"wp-caption-text\">Human skin has three layers, the epidermis, the dermis, and the hypodermis, which provide a thick barrier between microbes outside the body and deeper tissues. Dead skin cells on the surface of the epidermis are continually shed, taking with them microbes on the skin\u2019s surface. Sebaceous glands secrete sebum, a chemical mediator that lubricates and protect the skin from invading microbes. Sebum is also a food source for resident microbes that produce oleic acid, making the skin mildly acid and inhospitable to many pathogenic microbes. Sweat glands secrete dermcidin, which disrupts the membrane integrity of bacteria and fungi.<\/figcaption><\/figure>\n<figure id=\"attachment_6788\" aria-describedby=\"caption-attachment-6788\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear.png\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-6788 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear-300x183.png\" alt=\"In the ears, cerumen (earwax) exhibits antimicrobial properties due to the presence of fatty acids, which lower the pH to between 3 and 5.\" width=\"300\" height=\"183\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear-300x183.png 300w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear-1024x623.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear-768x467.png 768w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear-1536x935.png 1536w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear-65x40.png 65w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear-225x137.png 225w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear-350x213.png 350w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/06\/ear.png 1581w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-6788\" class=\"wp-caption-text\">In the ears, cerumen (earwax) exhibits antimicrobial properties and low pH 3-5.<\/figcaption><\/figure>\n<h3><span style=\"color: #1f5c99\"><strong>Innate Defenses:\u00a0 Normal Microbiota<\/strong><\/span><\/h3>\n<p style=\"text-align: justify\">The <strong>human microbiome<\/strong> encompasses all microorganisms on the skin, eyes, hair, nails, nose, mouth, respiratory and digestive tracts, urethra, and vagina.\u00a0 Microbes in these regions that do not cause disease are called <strong>normal flora<\/strong> or <strong>normal microbiota<\/strong>.\u00a0 They vary by individual, body location, climate, and diet.<\/p>\n<p style=\"text-align: justify\">Normal microbiota are <strong>commensals<\/strong>\u00a0 &#8211; co-existing without causing harm, benefiting from dead skin cells and secretions.\u00a0 The relationship is often <strong>mutualistic<\/strong>:\u00a0 both host and microbe benefit.\u00a0 Normal microbiota protect against pathogens by both occupying surface area and secreting deterrent biochemicals.\u00a0 Intestinal microbes additionally help break down indigestible compounds (dietary fiber) and produce beneficial vitamins.<\/p>\n<figure id=\"attachment_2318\" aria-describedby=\"caption-attachment-2318\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-2318 size-medium\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3-300x300.png\" alt=\"normal flora\" width=\"300\" height=\"300\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3-300x300.png 300w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3-1024x1024.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3-150x150.png 150w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3-768x768.png 768w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3-1536x1536.png 1536w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3-65x65.png 65w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3-225x225.png 225w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3-350x350.png 350w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2024\/09\/Gut_microbiota-3.png 2048w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-2318\" class=\"wp-caption-text\">Human microbiome refers to the microorganisms (bacteria, fungi, protozoa, archaea, and viruses) that naturally inhabit the human body. These microorganisms have a range of roles throughout the body. For example, gut microbiota is known to assist with digestion, the production of vitamins essential to human health (e.g., vitamins B and K, and also provide protection from pathogenic microorganisms. The composition of the gut microbiota is reflective of environmental exposure, diet, and health.<\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<figure id=\"attachment_5723\" aria-describedby=\"caption-attachment-5723\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-scaled.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-5723\" src=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-300x239.png\" alt=\"A schematic representation of the human gut microbiota, which contains 100 trillion microorganisms. These microorganisms, such as bacteria, viruses, fungi, and protozoa, are part of the gut microbiota.\" width=\"300\" height=\"239\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-300x239.png 300w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-1024x816.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-768x612.png 768w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-1536x1225.png 1536w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-2048x1633.png 2048w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-65x52.png 65w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-225x179.png 225w, https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-content\/uploads\/sites\/1961\/2026\/01\/Gut-Microbiota-350x279.png 350w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-5723\" class=\"wp-caption-text\">A schematic representation of the human gut microbiota, which contains 100 trillion microorganisms. These microorganisms (bacteria, viruses, fungi, and protozoa) are part of the gut microbiota.<\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Think About Questions:<\/strong><\/p>\n<p><strong>Why is inflammation considered a non-specific defense?\u00a0 What are other non-specific defenses of the human body?<\/strong><\/p>\n<p><strong>Why does inflammation occur any time that there is an injury or disease?<\/strong><\/p>\n<p><strong>Did you know that biologists sometimes call the digestive system an external tube that penetrates the body?\u00a0 Name one feature of the digestive system that prevents ingested microbes from causing an infection.\u00a0<\/strong><\/p>\n<p><strong>Why does taking an antacid put you more at risk for stomach infections?<\/strong><\/p>\n<p><strong>Imagine you have a papercut &#8211; list the innate factors of your body that will help eliminate the bacteria that enter that cut.\u00a0<\/strong><\/p>\n<p><strong>On a neutrophil, define the following: pseudopod, phagosome, lysosome, granule<\/strong><\/p>\n<p><strong>How does a NK cells kill bacteria?<\/strong><\/p>\n<p><strong>What is properdin?<\/strong><\/p>\n<p><strong>What is an interferon?<\/strong><\/p>\n<p><strong>What is a respiratory burst?<\/strong><\/p>\n<p>Did you know that some diseases are caused by auto-antibodies?\u00a0 And some are caused by auto-complement proteins?\u00a0 https:\/\/www.thelancet.com\/journals\/lancet\/article\/PIIS0140-6736(23)01524-6\/fulltext<\/p>\n<p>&nbsp;<\/p>\n<p><span class=\"transcription-time-part\" data-time-start=\"2.21\" data-time-end=\"4.949\"><strong>Inspirational Quote:<\/strong> Healing is an art. It takes time, it takes practice. It takes love. ~ <a href=\"https:\/\/livelifehappy.com\/\" target=\"_blank\" rel=\"noopener\">Maza Dohta<\/a>\u00a0<\/span><\/p>\n<p>&nbsp;<\/p>\n<div class=\"media-attributions clear\" prefix:cc=\"http:\/\/creativecommons.org\/ns#\" prefix:dc=\"http:\/\/purl.org\/dc\/terms\/\"><h2>Media Attributions<\/h2><ul><li about=\"https:\/\/openstax.org\/books\/fundamentals-nursing\/pages\/10-1-infection-cycle#fig-00002\"><a rel=\"cc:attributionURL\" href=\"https:\/\/openstax.org\/books\/fundamentals-nursing\/pages\/10-1-infection-cycle#fig-00002\" property=\"dc:title\">Pathogen Transmission<\/a>  &copy;  Christy Bowen, Lindsay Draper, Heather Moore  adapted by  <a rel=\"dc:source\" href=\"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/\">Zo\u00eb Soon<\/a>  is licensed under a  <a rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY (Attribution)<\/a> license<\/li><li about=\"https:\/\/www.open.edu\/openlearn\/mod\/oucontent\/view.php?id=28153&printable=1\"><a rel=\"cc:attributionURL\" href=\"https:\/\/www.open.edu\/openlearn\/mod\/oucontent\/view.php?id=28153&printable=1\" property=\"dc:title\">Innate Defense &#8211; Open University<\/a>  &copy;  Basiro Davey, Carol Midgley, Claire Rostron and Daniel Berwick    is licensed under a  <a rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/\">CC BY-SA (Attribution ShareAlike)<\/a> license<\/li><li about=\"https:\/\/openstax.org\/books\/microbiology\/pages\/17-1-physical-defenses\"><a rel=\"cc:attributionURL\" href=\"https:\/\/openstax.org\/books\/microbiology\/pages\/17-1-physical-defenses\" property=\"dc:title\">cilia2<\/a>  &copy;  Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster    is licensed under a  <a rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA (Attribution NonCommercial ShareAlike)<\/a> license<\/li><li about=\"https:\/\/openstax.org\/books\/microbiology\/pages\/17-1-physical-defenses\"><a rel=\"cc:attributionURL\" href=\"https:\/\/openstax.org\/books\/microbiology\/pages\/17-1-physical-defenses\" property=\"dc:title\">Goblet Cell Producing Mucus<\/a>  &copy;  Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster ( Image credit micrograph: Micrograph provided by the Regents of University of Michigan Medical School \u00a9 2012)    is licensed under a  <a rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA (Attribution NonCommercial ShareAlike)<\/a> license<\/li><li about=\"https:\/\/openstax.org\/books\/microbiology\/pages\/17-1-physical-defenses\"><a rel=\"cc:attributionURL\" href=\"https:\/\/openstax.org\/books\/microbiology\/pages\/17-1-physical-defenses\" property=\"dc:title\">skin<\/a>  &copy;  Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (Image credit: modification of work by National Institutes of Health)    is licensed under a  <a rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA (Attribution NonCommercial ShareAlike)<\/a> license<\/li><li about=\"https:\/\/openstax.org\/books\/clinical-nursing-skills\/pages\/22-3-ears\"><a rel=\"cc:attributionURL\" href=\"https:\/\/openstax.org\/books\/clinical-nursing-skills\/pages\/22-3-ears\" property=\"dc:title\">ear<\/a>  &copy;  Christy Bowen    is licensed under a  <a rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA (Attribution NonCommercial ShareAlike)<\/a> license<\/li><li about=\"https:\/\/togotv.dbcls.jp\/en\/togopic.2020.154.html\"><a rel=\"cc:attributionURL\" href=\"https:\/\/togotv.dbcls.jp\/en\/togopic.2020.154.html\" property=\"dc:title\">Private: Gut_microbiota<\/a>  &copy;  Wakana Sasaki    is licensed under a  <a rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY (Attribution)<\/a> license<\/li><li about=\"https:\/\/doi.org\/10.3390\/microorganisms11061556\"><a rel=\"cc:attributionURL\" href=\"https:\/\/doi.org\/10.3390\/microorganisms11061556\" property=\"dc:title\">Gut Microbiota<\/a>  &copy;  Jawhara, Samir    is licensed under a  <a rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY (Attribution)<\/a> license<\/li><\/ul><\/div>","protected":false},"author":1370,"menu_order":2,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"Pictures coming soon!","pb_authors":["zoe-soon"],"pb_section_license":"cc-by-nc-sa"},"chapter-type":[],"contributor":[60],"license":[57],"class_list":["post-28","chapter","type-chapter","status-web-only","hentry","contributor-zoe-soon","license-cc-by-nc-sa"],"part":25,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/28","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/users\/1370"}],"version-history":[{"count":25,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/28\/revisions"}],"predecessor-version":[{"id":6789,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/28\/revisions\/6789"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/parts\/25"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/28\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/media?parent=28"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapter-type?post=28"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/contributor?post=28"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/license?post=28"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}