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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 and vein Transports urine 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 oblique Renal vein Stomach Renal artery Inferior vena cava Pancreas Parietal peritoneum Ureter Aorta Spleen Adipose tissue Vertebra Anterior renal fascia Left kidney Fibrous capsule Posterior Perinephric renal fascia fat Quadratus lumborum Pararenal fat Psoas major Spinal 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 Diaphragm Esophagus (cut) Left suprarenal gland Inferior vena cava Celiac trunk Right suprarenal gland Right kidney Left kidney Left renal artery Left renal vein Hilum Superior mesenteric artery Quadratus lumborum muscle Left ureter Iliacus muscle Psoas major muscle Peritoneum (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. Abdominal aorta Left common iliac artery Gonadal artery and vein 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 fibrous capsule Cortex Medulla Inner layer of fibrous capsule Medulla Renal pyramid Renal sinus Adipose tissue in renal sinus Renal pelvis Hilum Renal sinus Connection to minor calyx Inner layer of fibrous capsule Minor calyx Renal pelvis Renal lobe Renal papilla Hilum Major calyx Ureter Renal columns Ureter Outer layer of fibrous capsule Major calyx © 2012 Pearson Education, Inc. Renal pyramids Frontal section through the left kidney showing major structures. The outlines of a renal lobe and a renal pyramid are indicated by dotted lines. Minor calyx Renal papilla Renal lobe Fibrous capsule 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 veins Arcuate veins Arcuate arteries © 2012 Pearson Education, Inc. Sectional view showing major arteries and veins. Compare with Figures 26.3 and 26.8. 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 nephron Distal convoluted tubule Cortex Connecting tubules Thin descending limb Nephron loop Thick ascending limb Collecting duct Papillary duct Renal papilla Minor calyx Orientation of cortical and juxtamedullary nephrons © 2012 Pearson Education, Inc. Medulla Figure 26.7ac Histology of the Nephron Proximal convoluted tubule Cortical nephron Renal corpuscle Juxtamedullary nephron Distal convoluted tubule Cortex Connecting tubules Visceral epithelium Parietal epithelium Glomerulus Capsular space Thin descending limb Nephron loop Thick ascending limb Medulla Distal convoluted tubule Proximal convoluted tubule Renal corpuscle Collecting duct The renal corpuscle Papillary duct Renal papilla Minor calyx Orientation of cortical and juxtamedullary nephrons © 2012 Pearson Education, Inc. LM 140 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 Mitochondria Variable reabsorption of water, sodium ions, and calcium ions (under hormonal control) Connecting tubules Reabsorption of water, ions, and all organic nutrients Renal tubule Collecting duct CONNECTING TUBULES AND COLLECTING DUCT Efferent arteriole Afferent arteriole RENAL CORPUSCLE Descending limb of loop ends Parietal (capsular) epithelium Capsular space Descending limb Visceral (glomerular) epithelium Variable reabsorption of water and reabsorption or secretion of sodium, potassium, hydrogen, and bicarbonate ions Ascending limb of loop ends Ascending limb Capillaries of glomerulus PAPILLARY DUCT Production of filtrate NEPHRON LOOP Thin descending limb Thick ascending limb Further reabsorption of water (descending limb) and both sodium and chloride ions (ascending limb) © 2012 Pearson Education, Inc. Minor calyx Delivery of urine to minor calyx 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 Vascular pole Parietal epithelium Efferent arteriole Visceral epithelium (podocyte) Tubular pole Distal convoluted tubule Macula densa Juxtaglomerular complex Juxtaglomerular cells Proximal convoluted tubule Extraglomerular mesangial cells Capsular space Glomerular capillary Afferent 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 for the Conduction and Storage of Urine Median umbilical ligament (urachus) Ureter Lateral umbilical ligament Detrusor muscle Rugae Trigone Ureteral openings Center of trigone Neck of urinary bladder Internal urethral sphincter Prostate gland External urethral sphincter (in urogenital diaphragm) © 2012 Pearson Education, Inc. Prostatic urethra Membranous urethra Anatomy of the urinary bladder in a male Structures for Urine Transport, Storage, and Elimination • Histology of the Ureters • Each ureter consists of three layers • Inner mucosa • Middle muscular layer (consisting of longitudinal and circular muscles) • Adventitia (this is continuous with the fibrous capsule) © 2012 Pearson Education, Inc. Structures for Urine Transport, Storage, and Elimination • The Urinary Bladder • Males • The base of the urinary bladder is between the rectum and the symphysis pubis • Females • The base of the urinary bladder is inferior to the uterus and anterior to the vagina © 2012 Pearson Education, Inc. Figure 26.10a Organs Responsible for the Conduction and Storage of Urine Left ureter Peritoneum Rectum Urinary bladder Pubic symphysis Prostate gland External urethral sphincter Spongy urethra External urethral orifice Urethra [see part c] Urogenital diaphragm Position of the ureter, urinary bladder, and urethra in the male © 2012 Pearson Education, Inc. Figure 26.10b Organs Responsible for the Conduction and Storage of Urine Rectum Right ureter Uterus Peritoneum Urinary bladder Pubic symphysis Internal urethral sphincter Urethra External urethral sphincter (in urogenital diaphragm) Vagina Vestibule © 2012 Pearson Education, Inc. Position of the ureter, urinary bladder, and urethra in the female Structures for Urine Transport, Storage, and Elimination • The Urinary Bladder • There are peritoneal folds that assist in maintaining the position of the urinary bladder • Median umbilical ligament: extends from the anterior/superior border to the umbilical region • Lateral umbilical ligament: extends from the lateral edges to the umbilical region © 2012 Pearson Education, Inc. Figure 26.10c Organs Responsible for the Conduction and Storage of Urine Median umbilical ligament (urachus) Ureter Lateral umbilical ligament Detrusor muscle Rugae Trigone Ureteral openings Center of trigone Neck of urinary bladder Internal urethral sphincter Prostate gland External urethral sphincter (in urogenital diaphragm) © 2012 Pearson Education, Inc. Prostatic urethra Membranous urethra Anatomy of the urinary bladder in a male Structures for Urine Transport, Storage, and Elimination • Histology of the Urinary Bladder • The muscular layer of the urinary bladder is called the detrusor muscle • At the exit of the urinary bladder and entrance to the urethra is a smooth muscle that makes up the internal urethral sphincter • This is under involuntary control © 2012 Pearson Education, Inc. Structures for Urine Transport, Storage, and Elimination • Histology of the Urinary Bladder (continued) • As the urethra passes through the urogenital diaphragm there is a skeletal muscle that makes up the external urethral sphincter • This is under voluntary control – this is the sphincter we learned to control as an infant • We lose control as we age • We lose control due to some spinal cord injuries © 2012 Pearson Education, Inc. Figure 26.10c Organs Responsible for the Conduction and Storage of Urine Median umbilical ligament (urachus) Ureter Lateral umbilical ligament Detrusor muscle Rugae Trigone Ureteral openings Center of trigone Neck of urinary bladder Internal urethral sphincter Prostate gland External urethral sphincter (in urogenital diaphragm) © 2012 Pearson Education, Inc. Prostatic urethra Membranous urethra Anatomy of the urinary bladder in a male Structures for Urine Transport, Storage, and Elimination • The Urethra • Female • 3 to 5 cm in length • The external urethral orifice is near the anterior wall of the vagina • Male • 18 to 20 cm in length • Subdivided to form the prostatic urethra, membranous urethra, and spongy urethra © 2012 Pearson Education, Inc. Structures for Urine Transport, Storage, and Elimination • The Urethra • Male (continued) • Prostatic urethra passes through the prostate gland • Membranous urethra is a short segment that goes through the urogenital diaphragm • Spongy urethra (penile urethra) extends through the penis to the external urethral orifice © 2012 Pearson Education, Inc. Figure 26.10 Organs Responsible for the Conduction and Storage of Urine Left ureter Peritoneum Rectum Rectum Right ureter Uterus Urinary bladder Peritoneum Pubic symphysis Urinary bladder Prostate gland Pubic symphysis External urethral sphincter Internal urethral sphincter Spongy urethra Urethra External urethral orifice External urethral sphincter (in urogenital diaphragm) Urethra [see part c] Vagina Urogenital diaphragm Vestibule Position of the ureter, urinary bladder, and urethra in the male Position of the ureter, urinary bladder, and urethra in the female Median umbilical ligament (urachus) Peritoneum Ureter Lateral umbilical ligament Right ureter Detrusor muscle Base of urinary bladder Rugae Trigone Ureteral openings Center of trigone Ductus deferens Seminal gland Neck of urinary bladder Internal urethral sphincter Prostate gland Prostatic urethra Membranous urethra External urethral sphincter (in urogenital diaphragm) © 2012 Pearson Education, Inc. Anatomy of the urinary bladder in a male Posterior surface of prostate gland Prostatic urethra The male urinary bladder and accessory reproductive structures as seen in posterior view Structures for Urine Transport, Storage, and Elimination • The micturition reflex and urination • The first urge to urinate is when the urinary bladder fills to about 200 ml • Greater than 200 ml will cause the internal urethral sphincter to open • The external urethral sphincter will open (voluntarily) to expel the stored urine • Between 500 ml and 800 ml, even the external urethral sphincter will open © 2012 Pearson Education, Inc. Aging and the Urinary System • Age related problems include: • Nephrons decrease in number • Glomerular filtration rate declines • Reduced sensitivity to hormones such as antidiuretic hormone (ADH) resulting in frequent urination • Micturition problems • Urethral sphincters lose muscle tone leading to incontinence • Urinary retention may lead to infections © 2012 Pearson Education, Inc.
