{"id":921,"date":"2017-09-05T21:20:08","date_gmt":"2017-09-06T01:20:08","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/?post_type=chapter&#038;p=921"},"modified":"2018-07-20T19:02:05","modified_gmt":"2018-07-20T23:02:05","slug":"25-3-gross-anatomy-of-the-kidney-1203","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/chapter\/25-3-gross-anatomy-of-the-kidney-1203\/","title":{"raw":"25.3 Gross Anatomy of the Kidney","rendered":"25.3 Gross Anatomy of the Kidney"},"content":{"raw":"<div class=\"bcc-box bcc-highlight\">\r\n<h3>Learning Objectives<\/h3>\r\nBy the end of this section, you will be able to:\r\n<ul>\r\n \t<li>Describe the size, shape, and gross anatomy of the kidney<\/li>\r\n \t<li>Describe the location of the renal cortex, renal medulla, and renal pelvis<\/li>\r\n \t<li>Describe the blood supply of the kidney<\/li>\r\n \t<li>Describe the blood supply of a nephron<\/li>\r\n \t<li>Describe the structure of a nephron<\/li>\r\n \t<li>Explain how the nephrons are arranged in the kidney<\/li>\r\n \t<li>Define and idenfity the pathological conditions causing:\r\n<ul>\r\n \t<li>Nephritis<\/li>\r\n \t<li>Pyelonephritis<\/li>\r\n \t<li>Glomerulonephritis<\/li>\r\n \t<li>Nephrosis<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/div>\r\nThe kidneys lie on either side of the spine in the retroperitoneal space between the parietal peritoneum and the posterior abdominal wall, well protected by muscle, fat, and ribs. They are roughly the size of your fist, and the male kidney is typically a bit larger than the female kidney. The kidneys are well vascularized, receiving about 25 percent of the cardiac output at rest.<strong>\r\n<\/strong>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"120\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-content\/uploads\/sites\/150\/2017\/08\/TED-1.png\" alt=\"QR Code representing a URL\" width=\"120\" height=\"1225\" \/> Watch this <a href=\"http:\/\/openstaxcollege.org\/l\/TED\">video<\/a> to learn about the TED (Technology, Entertainment, Design) Conference held in March 2011.[\/caption]\r\n\r\n<section id=\"fs-id2434228\">\r\n<h1>External Anatomy<\/h1>\r\n<p id=\"fs-id1592078\">The left kidney is located at about the T12 to L3 vertebrae, whereas the right is lower due to slight displacement by the liver. Upper portions of the kidneys are somewhat protected by the eleventh and twelfth ribs (<a class=\"autogenerated-content\" href=\"#fig-ch26_03_01\">Figure 1<\/a>). Each kidney weighs about 125\u2013175 g in males and 115\u2013155 g in females. They are about 11\u201314 cm in length, 6 cm wide, and 4 cm thick, and are directly covered by a fibrous capsule composed of dense, irregular connective tissue that helps to hold their shape and protect them. This capsule is covered by a shock-absorbing layer of adipose tissue called the <strong>renal fat pad<\/strong>, which in turn is encompassed by a tough renal fascia. The fascia and, to a lesser extent, the overlying peritoneum serve to firmly anchor the kidneys to the posterior abdominal wall in a retroperitoneal position.<\/p>\r\n\r\n<figure id=\"fig-ch26_03_01\"><figcaption>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"425\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-content\/uploads\/sites\/150\/2017\/08\/2608_Kidney_Position_in_Abdomen-1.jpg\" alt=\"This image shows a human torso and shows the location of the kidneys within the torso.\" width=\"425\" height=\"1204\" \/> Figure 1. Kidneys. The kidneys are slightly protected by the ribs and are surrounded by fat for protection (not shown).[\/caption]\r\n\r\n<\/figcaption><\/figure>\r\n<p id=\"fs-id2488605\">On the superior aspect of each kidney is the adrenal gland. The adrenal cortex directly influences renal function through the production of the hormone aldosterone to stimulate sodium reabsorption.<\/p>\r\n\r\n<\/section><section id=\"fs-id2519880\">\r\n<h1>Internal Anatomy<\/h1>\r\n<p id=\"fs-id2303293\">A frontal section through the kidney reveals an outer region called the <strong>renal cortex<\/strong> and an inner region called the <strong>medulla<\/strong> (<a class=\"autogenerated-content\" href=\"#fig-ch26_03_02\">Figure 2<\/a>). The <strong>renal columns<\/strong> are connective tissue extensions that radiate downward from the cortex through the medulla to separate the most characteristic features of the medulla, the <strong>renal pyramids<\/strong> and <strong>renal papillae<\/strong>. The papillae are bundles of collecting ducts that transport urine made by nephrons to the <strong>calyces<\/strong> of the kidney for excretion. The renal columns also serve to divide the kidney into 6\u20138 lobes and provide a supportive framework for vessels that enter and exit the cortex. The pyramids and renal columns taken together constitute the kidney lobes.<\/p>\r\n\r\n<figure id=\"fig-ch26_03_02\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"475\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-content\/uploads\/sites\/150\/2017\/08\/2610_The_Kidney-1.jpg\" alt=\"The left panel of this figure shows the location of the kidneys in the abdomen. The right panel shows the cross section of the kidney.\" width=\"475\" height=\"1129\" \/> Figure 2. Left Kidney.[\/caption]<\/figure>\r\n<\/section><section>\r\n<h1>Renal Hilum<\/h1>\r\n<p id=\"fs-id1764618\">The <strong>renal hilum<\/strong> is the entry and exit site for structures servicing the kidneys: vessels, nerves, lymphatics, and ureters. The medial-facing hila are tucked into the sweeping convex outline of the cortex. Emerging from the hilum is the renal pelvis, which is formed from the major and minor calyxes in the kidney. The smooth muscle in the renal pelvis funnels urine via peristalsis into the ureter. The renal arteries form directly from the descending aorta, whereas the renal veins return cleansed blood directly to the inferior vena cava. The artery, vein, and renal pelvis are arranged in an anterior-to-posterior order.<\/p>\r\n\r\n<section>\r\n<h2>Nephrons and Vessels<\/h2>\r\n<p id=\"fs-id2718604\">The renal artery first divides into segmental arteries, followed by further branching to form interlobar arteries that pass through the renal columns to reach the cortex (<a class=\"autogenerated-content\" href=\"#fig-ch26_03_03\">Figure 3<\/a>). The interlobar arteries, in turn, branch into arcuate arteries, cortical radiate arteries, and then into afferent arterioles. The afferent arterioles service about 1.3 million nephrons in each kidney.<\/p>\r\n\r\n<figure id=\"fig-ch26_03_03\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"475\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-content\/uploads\/sites\/150\/2017\/08\/2612_Blood_Flow_in_the_Kidneys-1.jpg\" alt=\"This figure shows the network of blood vessels and the blood flow in the kidneys.\" width=\"475\" height=\"1565\" \/> Figure 3. Blood Flow in the Kidney.[\/caption]<\/figure>\r\n<p id=\"fs-id2532837\"><strong>Nephrons<\/strong> are the \u201cfunctional units\u201d of the kidney; they cleanse the blood and balance the constituents of the circulation. The afferent arterioles form a tuft of high-pressure capillaries about 200 \u00b5m in diameter, the <strong>glomerulus<\/strong>. The rest of the nephron consists of a continuous sophisticated tubule whose proximal end surrounds the glomerulus in an intimate embrace\u2014this is <strong>Bowman\u2019s capsule<\/strong>. The glomerulus and Bowman\u2019s capsule together form the <strong>renal corpuscle<\/strong>. As mentioned earlier, these glomerular capillaries filter the blood based on particle size. After passing through the renal corpuscle, the capillaries form a second arteriole, the <strong>efferent arteriole<\/strong> (<a class=\"autogenerated-content\" href=\"#fig-ch26_03_04\">Figure 4<\/a>). These will next form a capillary network around the more distal portions of the nephron tubule, the <strong>peritubular capillaries<\/strong> and <strong>vasa recta<\/strong>, before returning to the venous system. As the glomerular filtrate progresses through the nephron, these capillary networks recover most of the solutes and water, and return them to the circulation. Since a capillary bed (the glomerulus) drains into a vessel that in turn forms a second capillary bed, the definition of a portal system is met. This is the only portal system in which an arteriole is found between the first and second capillary beds. (Portal systems also link the hypothalamus to the anterior pituitary, and the blood vessels of the digestive viscera to the liver.)<\/p>\r\n\r\n<figure id=\"fig-ch26_03_04\"><figcaption>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"380\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-content\/uploads\/sites\/150\/2017\/08\/2611_Blood_Flow_in_the_Nephron-1.jpg\" alt=\"This image shows the blood vessels and the direction of blood flow in the nephron.\" width=\"380\" height=\"1946\" \/> Figure 4. Blood Flow in the Nephron. The two capillary beds are clearly shown in this figure. The efferent arteriole is the connecting vessel between the glomerulus and the peritubular capillaries and vasa recta.[\/caption]\r\n\r\n<\/figcaption><\/figure>\r\n<div id=\"fs-id2128542\" class=\"note anatomy interactive\"><\/div>\r\n<\/section><section id=\"fs-id2753827\">\r\n<h2>Cortex<\/h2>\r\n<p id=\"fs-id2506359\">In a dissected kidney, it is easy to identify the cortex; it appears lighter in color compared to the rest of the kidney. All of the renal corpuscles as well as both the <strong>proximal convoluted tubules (PCTs)<\/strong> and <strong>distal convoluted tubules<\/strong> are found here. Some nephrons have a short <strong>loop of Henle<\/strong> that does not dip beyond the cortex. These nephrons are called <strong>cortical nephrons<\/strong>. About 15 percent of nephrons have long loops of Henle that extend deep into the medulla and are called <strong>juxtamedullary nephrons<\/strong>.<\/p>\r\n\r\n<\/section><\/section>","rendered":"<div class=\"bcc-box bcc-highlight\">\n<h3>Learning Objectives<\/h3>\n<p>By the end of this section, you will be able to:<\/p>\n<ul>\n<li>Describe the size, shape, and gross anatomy of the kidney<\/li>\n<li>Describe the location of the renal cortex, renal medulla, and renal pelvis<\/li>\n<li>Describe the blood supply of the kidney<\/li>\n<li>Describe the blood supply of a nephron<\/li>\n<li>Describe the structure of a nephron<\/li>\n<li>Explain how the nephrons are arranged in the kidney<\/li>\n<li>Define and idenfity the pathological conditions causing:\n<ul>\n<li>Nephritis<\/li>\n<li>Pyelonephritis<\/li>\n<li>Glomerulonephritis<\/li>\n<li>Nephrosis<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/div>\n<p>The kidneys lie on either side of the spine in the retroperitoneal space between the parietal peritoneum and the posterior abdominal wall, well protected by muscle, fat, and ribs. They are roughly the size of your fist, and the male kidney is typically a bit larger than the female kidney. The kidneys are well vascularized, receiving about 25 percent of the cardiac output at rest.<strong><br \/>\n<\/strong><\/p>\n<figure style=\"width: 120px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-content\/uploads\/sites\/150\/2017\/08\/TED-1.png\" alt=\"QR Code representing a URL\" width=\"120\" height=\"1225\" \/><figcaption class=\"wp-caption-text\">Watch this <a href=\"http:\/\/openstaxcollege.org\/l\/TED\">video<\/a> to learn about the TED (Technology, Entertainment, Design) Conference held in March 2011.<\/figcaption><\/figure>\n<section id=\"fs-id2434228\">\n<h1>External Anatomy<\/h1>\n<p id=\"fs-id1592078\">The left kidney is located at about the T12 to L3 vertebrae, whereas the right is lower due to slight displacement by the liver. Upper portions of the kidneys are somewhat protected by the eleventh and twelfth ribs (<a class=\"autogenerated-content\" href=\"#fig-ch26_03_01\">Figure 1<\/a>). Each kidney weighs about 125\u2013175 g in males and 115\u2013155 g in females. They are about 11\u201314 cm in length, 6 cm wide, and 4 cm thick, and are directly covered by a fibrous capsule composed of dense, irregular connective tissue that helps to hold their shape and protect them. This capsule is covered by a shock-absorbing layer of adipose tissue called the <strong>renal fat pad<\/strong>, which in turn is encompassed by a tough renal fascia. The fascia and, to a lesser extent, the overlying peritoneum serve to firmly anchor the kidneys to the posterior abdominal wall in a retroperitoneal position.<\/p>\n<figure id=\"fig-ch26_03_01\"><figcaption>\n<figure style=\"width: 425px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-content\/uploads\/sites\/150\/2017\/08\/2608_Kidney_Position_in_Abdomen-1.jpg\" alt=\"This image shows a human torso and shows the location of the kidneys within the torso.\" width=\"425\" height=\"1204\" \/><figcaption class=\"wp-caption-text\">Figure 1. Kidneys. The kidneys are slightly protected by the ribs and are surrounded by fat for protection (not shown).<\/figcaption><\/figure>\n<\/figcaption><\/figure>\n<p id=\"fs-id2488605\">On the superior aspect of each kidney is the adrenal gland. The adrenal cortex directly influences renal function through the production of the hormone aldosterone to stimulate sodium reabsorption.<\/p>\n<\/section>\n<section id=\"fs-id2519880\">\n<h1>Internal Anatomy<\/h1>\n<p id=\"fs-id2303293\">A frontal section through the kidney reveals an outer region called the <strong>renal cortex<\/strong> and an inner region called the <strong>medulla<\/strong> (<a class=\"autogenerated-content\" href=\"#fig-ch26_03_02\">Figure 2<\/a>). The <strong>renal columns<\/strong> are connective tissue extensions that radiate downward from the cortex through the medulla to separate the most characteristic features of the medulla, the <strong>renal pyramids<\/strong> and <strong>renal papillae<\/strong>. The papillae are bundles of collecting ducts that transport urine made by nephrons to the <strong>calyces<\/strong> of the kidney for excretion. The renal columns also serve to divide the kidney into 6\u20138 lobes and provide a supportive framework for vessels that enter and exit the cortex. The pyramids and renal columns taken together constitute the kidney lobes.<\/p>\n<figure id=\"fig-ch26_03_02\">\n<figure style=\"width: 475px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-content\/uploads\/sites\/150\/2017\/08\/2610_The_Kidney-1.jpg\" alt=\"The left panel of this figure shows the location of the kidneys in the abdomen. The right panel shows the cross section of the kidney.\" width=\"475\" height=\"1129\" \/><figcaption class=\"wp-caption-text\">Figure 2. Left Kidney.<\/figcaption><\/figure>\n<\/figure>\n<\/section>\n<section>\n<h1>Renal Hilum<\/h1>\n<p id=\"fs-id1764618\">The <strong>renal hilum<\/strong> is the entry and exit site for structures servicing the kidneys: vessels, nerves, lymphatics, and ureters. The medial-facing hila are tucked into the sweeping convex outline of the cortex. Emerging from the hilum is the renal pelvis, which is formed from the major and minor calyxes in the kidney. The smooth muscle in the renal pelvis funnels urine via peristalsis into the ureter. The renal arteries form directly from the descending aorta, whereas the renal veins return cleansed blood directly to the inferior vena cava. The artery, vein, and renal pelvis are arranged in an anterior-to-posterior order.<\/p>\n<section>\n<h2>Nephrons and Vessels<\/h2>\n<p id=\"fs-id2718604\">The renal artery first divides into segmental arteries, followed by further branching to form interlobar arteries that pass through the renal columns to reach the cortex (<a class=\"autogenerated-content\" href=\"#fig-ch26_03_03\">Figure 3<\/a>). The interlobar arteries, in turn, branch into arcuate arteries, cortical radiate arteries, and then into afferent arterioles. The afferent arterioles service about 1.3 million nephrons in each kidney.<\/p>\n<figure id=\"fig-ch26_03_03\">\n<figure style=\"width: 475px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-content\/uploads\/sites\/150\/2017\/08\/2612_Blood_Flow_in_the_Kidneys-1.jpg\" alt=\"This figure shows the network of blood vessels and the blood flow in the kidneys.\" width=\"475\" height=\"1565\" \/><figcaption class=\"wp-caption-text\">Figure 3. Blood Flow in the Kidney.<\/figcaption><\/figure>\n<\/figure>\n<p id=\"fs-id2532837\"><strong>Nephrons<\/strong> are the \u201cfunctional units\u201d of the kidney; they cleanse the blood and balance the constituents of the circulation. The afferent arterioles form a tuft of high-pressure capillaries about 200 \u00b5m in diameter, the <strong>glomerulus<\/strong>. The rest of the nephron consists of a continuous sophisticated tubule whose proximal end surrounds the glomerulus in an intimate embrace\u2014this is <strong>Bowman\u2019s capsule<\/strong>. The glomerulus and Bowman\u2019s capsule together form the <strong>renal corpuscle<\/strong>. As mentioned earlier, these glomerular capillaries filter the blood based on particle size. After passing through the renal corpuscle, the capillaries form a second arteriole, the <strong>efferent arteriole<\/strong> (<a class=\"autogenerated-content\" href=\"#fig-ch26_03_04\">Figure 4<\/a>). These will next form a capillary network around the more distal portions of the nephron tubule, the <strong>peritubular capillaries<\/strong> and <strong>vasa recta<\/strong>, before returning to the venous system. As the glomerular filtrate progresses through the nephron, these capillary networks recover most of the solutes and water, and return them to the circulation. Since a capillary bed (the glomerulus) drains into a vessel that in turn forms a second capillary bed, the definition of a portal system is met. This is the only portal system in which an arteriole is found between the first and second capillary beds. (Portal systems also link the hypothalamus to the anterior pituitary, and the blood vessels of the digestive viscera to the liver.)<\/p>\n<figure id=\"fig-ch26_03_04\"><figcaption>\n<figure style=\"width: 380px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-content\/uploads\/sites\/150\/2017\/08\/2611_Blood_Flow_in_the_Nephron-1.jpg\" alt=\"This image shows the blood vessels and the direction of blood flow in the nephron.\" width=\"380\" height=\"1946\" \/><figcaption class=\"wp-caption-text\">Figure 4. Blood Flow in the Nephron. The two capillary beds are clearly shown in this figure. The efferent arteriole is the connecting vessel between the glomerulus and the peritubular capillaries and vasa recta.<\/figcaption><\/figure>\n<\/figcaption><\/figure>\n<div id=\"fs-id2128542\" class=\"note anatomy interactive\"><\/div>\n<\/section>\n<section id=\"fs-id2753827\">\n<h2>Cortex<\/h2>\n<p id=\"fs-id2506359\">In a dissected kidney, it is easy to identify the cortex; it appears lighter in color compared to the rest of the kidney. All of the renal corpuscles as well as both the <strong>proximal convoluted tubules (PCTs)<\/strong> and <strong>distal convoluted tubules<\/strong> are found here. Some nephrons have a short <strong>loop of Henle<\/strong> that does not dip beyond the cortex. These nephrons are called <strong>cortical nephrons<\/strong>. About 15 percent of nephrons have long loops of Henle that extend deep into the medulla and are called <strong>juxtamedullary nephrons<\/strong>.<\/p>\n<\/section>\n<\/section>\n","protected":false},"author":10,"menu_order":3,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-921","chapter","type-chapter","status-publish","hentry"],"part":907,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/pressbooks\/v2\/chapters\/921","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/wp\/v2\/users\/10"}],"version-history":[{"count":6,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/pressbooks\/v2\/chapters\/921\/revisions"}],"predecessor-version":[{"id":1347,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/pressbooks\/v2\/chapters\/921\/revisions\/1347"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/pressbooks\/v2\/parts\/907"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/pressbooks\/v2\/chapters\/921\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/wp\/v2\/media?parent=921"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/pressbooks\/v2\/chapter-type?post=921"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/wp\/v2\/contributor?post=921"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol12031209\/wp-json\/wp\/v2\/license?post=921"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}