26 The Urinary System PowerPoint® Lecture Presentations prepared by Steven Bassett Southeast Community College Lincoln, Nebraska © 2012 Pearson Education, Inc. Introduction • The urinary system does more than just get rid of liquid waste. It also: • Regulates plasma ion concentrations • Regulates blood volume and blood pressure • Stabilizes blood pH • Prevents the loss of valuable nutrients • Eliminates organic matter • Synthesizes calcitriol (active form of vitamin D) • Prevents dehydration • Aids the liver with some of its functions © 2012 Pearson Education, Inc. Introduction • The urinary system consists of: • Kidneys • And the associated nephrons • Ureters • Urinary bladder • Urethra © 2012 Pearson Education, Inc. Figure 26.1a An Introduction to the Urinary System Kidney Produces urine Suprarenal gland Ureter Renal artery Transports urine and vein toward the urinary bladder Inferior vena cava Urinary bladder Aorta Temporarily stores urine prior to elimination Urethra Conducts urine to exterior; in males, transports semen as well Anterior view showing the components of the urinary system © 2012 Pearson Education, Inc. The Kidneys • The right kidney • Covered by the liver, hepatic flexure, and duodenum • The left kidney • Covered by the spleen, stomach, pancreas, splenic flexure, and jejunum • The left kidney is positioned higher than the right kidney • Both kidneys are capped with the suprarenal glands © 2012 Pearson Education, Inc. The Kidneys • There are three layers of connective tissue that serve to protect the kidneys • Fibrous capsule • Perinephric fat • Renal fascia © 2012 Pearson Education, Inc. Figure 26.1c An Introduction to the Urinary System External Renal vein oblique Stomach Renal artery Inferior Parietal Pancreas vena cava peritoneum Ureter Aorta Adipose Spleen tissue Vertebra Anterior renal fascia Left kidney Fibrous capsule Posterior Perinephric Quadratus Pararenal Psoas Spinal renal fascia fat lumborum fat major cord Diagrammatic cross section, as viewed from above, at the level indicated in part (b) © 2012 Pearson Education, Inc. The Kidneys • Superficial Anatomy of the Kidney • The medial indentation is the hilum • Renal arteries enter at the hilum • Renal veins and ureters exit at the hilum © 2012 Pearson Education, Inc. Figure 26.2a The Urinary System in Gross Dissection Esophagus (cut) Diaphragm Left suprarenal gland Inferior vena cava Celiac trunk Right suprarenal Left kidney gland Left renal artery Right kidney Left renal vein Hilum Superior mesenteric artery Quadratus Left ureter lumborum Abdominal muscle aorta Iliacus muscle Left common Psoas major iliac artery muscle Gonadal artery Peritoneum and vein (cut) Rectum (cut) Urinary bladder Diagrammatic anterior view of the abdominopelvic cavity showing the kidneys, suprarenal glands, ureters, urinary bladder, and blood supply to the kidneys © 2012 Pearson Education, Inc. The Kidneys • Sectional Anatomy of the Kidney • Consists of: • Renal cortex • Renal medulla, which consists of: • Renal pyramids • Renal papillae • Renal columns • Renal lobe, which consists of: • Minor calyx • Major calyx • Renal pelvis © 2012 Pearson Education, Inc. Figure 26.3a Structure of the Kidney Outer layer of Cortex fibrous capsule Medulla Medulla Renal Inner layer of pyramids fibrous capsule Renal pyramid Renal sinus Renal sinus Connection to Inner layer of Adipose tissue minor calyx fibrous capsule in renal sinus Minor Renal pelvis Renal pelvis Hilum calyx Major calyx Hilum Renal lobe Ureter Minor calyx Renal papilla Renal columns Renal papilla Ureter Outer layer of Renal lobe fibrous capsule Fibrous capsule Major calyx Frontal section through the left kidney showing major structures. The outlines of a renal lobe and a renal pyramid are indicated by dotted lines. © 2012 Pearson Education, Inc. The Kidneys • The Blood Supply to the Kidneys • Beginning with blood in the renal arteries • Segmental arteries • Interlobar arteries • Arcuate arteries • Cortical radiate arteries • Afferent arterioles • Glomerular capillaries • Waste is dropped in the nephrons © 2012 Pearson Education, Inc. The Kidneys • The Blood Supply to the Kidneys (continued) • After waste is dropped off at the nephrons, blood leaves the kidneys via the following vessels: • Glomerular capillaries • Efferent arteriole • Peritubular capillaries or vasa recta capillaries • Interlobular veins • Arcuate veins • Interlobar veins • Renal vein • Inferior vena cava © 2012 Pearson Education, Inc. Figure 26.4a Blood Supply to the Kidneys Interlobular veins Cortical radiate arteries Interlobar arteries Segmental artery Suprarenal artery Renal artery Renal vein Interlobar Arcuate veins veins Arcuate arteries Sectional view showing major arteries and veins. Compare with Figures 26.3 and 26.8. © 2012 Pearson Education, Inc. The Kidneys • Structure and Function of the Nephron • Waste (glomerular filtrate) material leaves the glomerular capillaries and enters: • Glomerular capsule • Proximal convoluted tubule (PCT) • Nephron loop • Distal convoluted tubule (DCT) © 2012 Pearson Education, Inc. The Kidneys • Structure and Function of the Nephron • Filtrate enters the DCT of several nephrons and empties into a common tube called the collecting duct • Filtrate enters the papillary duct • Minor calyx • Major calyx • Ureter • Urinary bladder • Urethra © 2012 Pearson Education, Inc. Figure 26.7a Histology of the Nephron Proximal convoluted tubule Cortical nephron Renal corpuscle Juxtamedullary Distal convoluted nephron Cortex tubule Connecting tubules Thin descending limb Nephron Medulla loop Thick ascending limb Collecting duct Papillary duct Renal papilla Minor calyx Orientation of cortical and juxtamedullary nephrons © 2012 Pearson Education, Inc. Figure 26.7ac Histology of the Nephron Proximal convoluted tubule Cortical nephron Renal corpuscle Juxtamedullary Distal convoluted nephron Cortex tubule Connecting tubules Visceral epithelium Parietal epithelium Glomerulus Thin descending Capsular space limb Distal convoluted Nephron Medulla tubule loop Thick ascending limb Proximal convoluted tubule Renal corpuscle LM 140 Collecting duct The renal corpuscle Papillary duct Renal papilla Minor calyx Orientation of cortical and juxtamedullary nephrons © 2012 Pearson Education, Inc. The Kidneys • Functions of the PCT • Absorbs organic nutrients, ions, and plasma protein from the filtrate • Water is absorbed from the PCT to the bloodstream • The capillaries in the PCT region are called the peritubular capillaries © 2012 Pearson Education, Inc. The Kidneys • Functions of the Nephron Loop • Descending portion • Water leaves this portion and enters the bloodstream (thereby preventing dehydration) • The capillaries surrounding the nephron loop are called the vasa recta • Ascending portion • Pumps ions (sodium ions and chloride ions) out of the ascending loop thereby preventing the loss of these ions © 2012 Pearson Education, Inc. The Kidneys • Functions of the DCT • Active secretion of ions and acids • Selective reabsorption of sodium and calcium ions • Very little reabsorption of water © 2012 Pearson Education, Inc. The Kidneys • Functions of the Collecting Duct • The DCTs of several nephrons drain into the collecting duct • The cells of the collecting ducts make final adjustments to the concentration of the urine that is about to exit the kidneys © 2012 Pearson Education, Inc. Figure 26.6 A Typical Nephron NEPHRON COLLECTING SYSTEM DISTAL CONVOLUTED TUBULE PROXIMAL CONVOLUTED TUBULE Secretion of ions, acids, drugs, toxins Nucleus Microvilli Variable reabsorption of water, sodium ions, and calcium ions (under hormonal control) Mitochondria Connecting tubules Reabsorption of water, ions, and Renal tubule all organic nutrients Collecting duct CONNECTING TUBULES Efferent arteriole AND COLLECTING DUCT Afferent arteriole Variable reabsorption of water and RENAL CORPUSCLE Descending Ascending reabsorption or limb of limb of secretion of Parietal (capsular) loop ends loop ends sodium, potassium, epithelium hydrogen, and Capsular space Ascending bicarbonate ions limb Descending Visceral limb (glomerular) epithelium Capillaries of glomerulus PAPILLARY DUCT Production of filtrate Delivery of NEPHRON LOOP urine to Thin Thick Minor minor calyx descending ascending calyx limb limb Further reabsorption of water (descending limb) and both sodium and chloride ions (ascending limb) © 2012 Pearson Education, Inc. The Kidneys • Functions of the Juxtaglomerular Complex • Located in the region of the vascular pole • Consists of: • Macula densa cells • Juxtaglomerular cells • Mesangial cells • This is an endocrine structure • Produces renin and erythropoietin • Renin: involved in regulating blood pressure • Erythropoietin: involved in erythrocyte production © 2012 Pearson Education, Inc. Figure 26.8c The Renal Corpuscle Glomerular capsule Parietal Visceral Vascular pole epithelium epithelium (podocyte) Efferent arteriole Tubular pole Distal convoluted tubule Macula densa Juxtaglomerular Juxtaglomerular cells Proximal complex Extraglomerular convoluted mesangial cells tubule Capsular space Glomerular Afferent capillary arteriole The renal corpuscle. Arrows show the pathway of blood flow. © 2012 Pearson Education, Inc. Structures for Urine Transport, Storage, and Elimination • The Ureters • Exit the kidney at the hilum area • Extend to the urinary bladder • Enter the urinary bladder on the posterior/inferior side • The entrance to the urinary bladder is the ureteral openings in the trigone area © 2012 Pearson Education, Inc. Figure 26.10c Organs Responsible