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4/22/2016 Waste Urinary System Anatomy Urinary Section pages 5-8 • Metabolism produces waste products • What is the primary waste product of cellular respiration? How does the body dispose of it? Urinary System • • • • Disposes of water soluble wastes Maintains fluid balance Regulates electrolytes Regulates acid-base balance Urinary System • Other functions – Kidneys • Renin stored and secreted – Enzyme involved in angiotensin II activation • Erythropoietin – Hormone that stimulates RBC production • Vitamin D activation – Enzymes convert dietary and manufactured vitamin D to calcitrol Nitrogenous Wastes Nitrogenous Wastes TOXIC! • Urine is about 95% water • Second largest component is urea – Urea derived from breakdown of amino acids 1. Dietary amino acids → NH2 removed → NH2 + H+ → NH3 – 500 ml of urine removes only 1 gram of nitrogen as ammonia 2. Ammonia can be converted to urea – Requires energy – 50 ml of urine removes 1 gram of nitrogen as urea 3. Ammonia can be converted to uric acid – Requires lots of energy – 10 ml of urine removes 1 gram of nitrogen as uric acid 1 4/22/2016 Fill in the blanks… Urinary System • Organs Ammonia Toxicity Urea • Major excretory organs Energy Costs – Urinary bladder High = 3 ATP Water Required 50 ml/g Nitrogen Solubility Examples – Kidneys Uric acid Very toxic • Temporary storage reservoir for urine Low – Ureters Fish & aquatic invertebrates • Transport urine from the kidneys to the bladder – Urethra • Transports urine out of the body Hepatic veins (cut) Esophagus (cut) Inferior vena cava Renal artery Adrenal gland Anterior Renal hilum Inferior vena cava Renal vein Aorta Kidney Iliac crest Peritoneum Ureter Rectum (cut) Uterus (part of female reproductive system) Peritoneal cavity (organs removed) Renal vein Renal artery Body wall (a) Urethra Posterior Figure 25.1 Figure 25.2a Kidneys • External anatomy – Retroperitoneal position – Embedded in pararenal fat Supportive tissue layers • Renal fascia anterior posterior • Perirenal fat capsule • Fibrous capsule Body of vertebra L2 Urinary bladder Aorta Kidneys • External anatomy – Hilus (or hilum) • Where blood vessels, nerves, and ureter pass 2 4/22/2016 Kidneys • External anatomy – 3 tissue layers surround & support • Fibrous capsule • Perirenal fat capsule • Renal fascia Hydronephrosis • Backup of urine causes excess fluid in the kidney • Common causes – Kidney stones – Infection – Enlarged prostate – Blood clot – Tumor Kidneys Kidneys – Renal medulla • Internal Anatomy – Renal cortex • Superficial region • Renal columns extend into medulla • Where urine is produced • Cone-shaped medullary (renal) pyramids • Separated by the renal columns • Consist of tubules that transport urine to the calyces Kidneys Kidneys – Renal pelvis – Renal medulla • The papilla (point) of each pyramid drains into a minor calyx • Several minor calyces drain into one major calyx • Major calyces drain into renal pelvis • Funnel-shaped tube that collects urine from calyces • Continuous with ureter 3 4/22/2016 Kidneys Renal hilum Renal cortex • Blood Supply Renal medulla – Renal arteries deliver ~ 22 % of cardiac output (1.2 L/min) Major calyx Papilla of pyramid Renal pelvis • 90% directed to cortex • Urine formation Minor calyx Ureter Renal pyramid in renal medulla Renal column Fibrous capsule (a) Photograph of right kidney, frontal section (b) Diagrammatic view Figure 25.3 Aorta Cortical radiate vein Cortical radiate artery Arcuate vein Arcuate artery Interlobar vein Interlobar artery Segmental arteries Renal vein Renal artery Segmental artery Interlobar vein Arcuate vein Arcuate artery Cortical radiate vein Cortical radiate artery Peritubular capillaries and vasa recta Renal pelvis Afferent arteriole Renal medulla Renal vein Interlobar artery Renal artery Ureter Inferior vena cava Efferent arteriole Glomerulus (capillaries) Nephron-associated blood vessels (see Figure 25.8) (b) Path of blood flow through renal blood vessels Renal cortex (a) Frontal section illustrating major blood vessels Figure 25.4a Figure 25.4b Nephrons • • • Structural and functional units that form urine ~1 million per kidney Two main parts 1. Blood capillaries (glomeruli) 2. Renal tubule: begins as cup-shaped glomerular (Bowman’s) capsule surrounding the glomerulus Figure 25.5 4 4/22/2016 Nephrons Nephrons • Renal corpuscle • Glomerular endothelium – Glomerulus + Bowman’s capsule Efferent arteriole – Fenestrated capillary endothelium – Layer of highly branched and interlaced podocytes – Allows filtrate to pass from plasma into the glomerular capsule Glomerular capsule Glomerulus Afferent arteriole Parietal layer of glomerular capsule Capsular space Foot processes of podocytes Podocyte cell body (visceral layer) Red blood cell Proximal tubule cell Efferent arteriole Cortical nephron • Has short loop of Henle and glomerulus further from the corticomedullary junction • Efferent arteriole supplies peritubular capillaries Efferent arteriole Glomerular capillaries Renal corpuscle (glomerulus) Glomerular (Bowman’s) capsule Proximal convoluted tubule Peritubular capillaries Juxtaglomerular apparatus Cortex Medulla Renal pelvis Ureter • Macula densa cells Lumens of glomerular capillaries Endothelial cell of glomerular capillary Mesangial cells between capillaries • Extraglomerular mesangial cells • Granular cells Afferent arteriole Juxtaglomerular apparatus Renal corpuscle Loop of Henle Juxtamedullary nephron • Has long loop of Henle and glomerulus closer to the corticomedullary junction • Efferent arteriole supplies vasa recta Afferent arteriole Collecting duct Distal convoluted tubule Afferent arteriole Efferent arteriole Corticomedullary junction Vasa recta loop of Henle Kidney (a) Figure 25.8 Figure 25.7a Nephrons • Renal tubules – Proximal convoluted tubule (PCT) • So-called because it is proximal to renal corpuscle • Functions – Major site of reabsorption (amino acids, glucose, water, Na+) – Secretion (medications, nitrogenous wastes) – Exchange of ions important for pH (H+, HCO3-) Nephrons • Renal tubules – Loop of Henle • Descends from the cortex to the medulla, turns, and comes back to the cortex • More later… • Confined to the cortex 5 4/22/2016 Nephrons Nephrons • Renal tubules • Renal tubules – Distal convoluted tubule (DCT) – Collecting tubules (CT) • Important site for secretion, aldosterone & ADH activity • Exchange of ions important for pH (H+, HCO3-) • Reabsorption of some electrolytes such as Na+ • Confined to the cortex • Receive filtrate from many nephrons • Fuse together to deliver urine through papillae into minor calyces • Functions – Important site for secretion, aldosterone & ADH activity – Site of reabsorption of water and electrolytes – Exchange of ions important for pH (H+, HCO3-) Nephrons Glomerular capsule: parietal layer Renal cortex Basement membrane Renal medulla Renal corpuscle • Glomerular capsule • Glomerulus Renal pelvis Podocyte Distal convoluted tubule Ureter Kidney Fenestrated endothelium of the glomerulus Glomerular capsule: visceral layer Microvilli Mitochondria Proximal convoluted tubule Highly infolded plasma membrane Proximal convoluted tubule cells Cortex – Distal convoluted tubule and afferent arteriole contact one another – modified at the point of contact • One per nephron – Function Medulla Thick segment Thin segment Loop of Henle • Descending limb • Ascending limb • Juxtaglomerular Apparatus (JGA) Distal convoluted tubule cells Collecting duct • Regulation of filtrate formation and blood pressure Loop of Henle (thin-segment) cells Principal cell Intercalated cell Collecting duct cells Figure 25.5 Nephrons • Juxtaglomerular Apparatus (JGA) – 3 components 1) Macula densa • Group of columnar cells on DCT • Chemoreceptors that monitor NaCl content of filtrate entering DCT • Sense DCT flow and release chemicals that alter diameter of afferent arteriole Nephrons • Juxtaglomerular Apparatus (JGA) – 3 components 2) Granular cells • AKA juxtaglomerular cells • In wall of afferent arteriole • Enlarged smooth muscle cells • Mechanoreceptors that sense blood pressure in afferent arteriole • Store and secrete renin in response 6 4/22/2016 Nephrons Efferent arteriole Glomerular capsule Glomerulus Afferent arteriole Parietal layer of glomerular capsule Capsular space • Juxtaglomerular Apparatus (JGA) – 3 components 3) Extraglomerular mesangial cells • Lie between arteriole and DCT • Connected by gap junctions • Pass regulatory signals between macula densa and granular cells Foot processes of podocytes Podocyte cell body (visceral layer) Red blood cell Proximal tubule cell Efferent arteriole Juxtaglomerular apparatus • Macula densa cells Lumens of glomerular capillaries Endothelial cell of glomerular capillary Mesangial cells between capillaries • Extraglomerular mesangial cells • Granular cells Afferent arteriole Juxtaglomerular apparatus Renal corpuscle Figure 25.8 Nephron Capillary Beds 1. Glomerulus – Afferent arteriole → glomerulus → efferent arteriole – Specialized for filtration Nephron Capillary Beds 2. Peritubular capillaries – Low-pressure, porous capillaries adapted for absorption – Arise from efferent arterioles – Cling to adjacent renal tubules in cortex – Empty into venules Nephrons • Cortical nephrons – 85% of nephrons; almost entirely in the cortex • Short loops of Henle extend barely into medulla • Juxtamedullary nephrons – Long loops of Henle deeply invade the medulla – Extensive thin segments – Important in the production of concentrated urine • Much more on this later… 7 4/22/2016 Ureters Urinary Bladder • Muscular sac for temporary storage of urine • On pelvic floor posterior to pubic symphysis • Convey urine from kidneys to bladder • Retroperitoneal location • Enter base of bladder through posterior wall – Males—prostate gland surrounds the neck inferiorly – Females—anterior to the vagina and uterus – ↑ bladder pressure = distal ends of the ureters close • Prevents backflow of urine – Mucus is protective Urinary Bladder Urinary Bladder – Stretch receptors in bladder create desire to void – Epithelium is specialized to accommodate stretching and recoil as bladder fills and empties • Micturition • Urge to void usually occurs with about 300ml urine • Can hold up to about 500ml Urethra Hepatic veins (cut) Esophagus (cut) Inferior vena cava Adrenal gland Renal artery Renal hilum Aorta Renal vein Rectum (cut) Uterus (part of female reproductive system) • Internal – ANS control • External Kidney Iliac crest – Sphincters – Voluntary control Ureter Urinary bladder Urethra Figure 25.1 8 4/22/2016 Peritoneum Ureter Rugae Detrusor muscle Adventitia Ureteric orifices Trigone of bladder Bladder neck Internal urethral sphincter Prostate Prostatic urethra Urogenital diaphragm External urethral sphincter Membranous urethra Peritoneum Ureter Rugae Detrusor muscle Ureteric orifices Bladder neck Internal urethral sphincter External urethral sphincter Urogenital diaphragm Trigone Urethra External urethral orifice (b) Female. Spongy urethra Erectile tissue of penis External urethral orifice (a) Male. The long male urethra has three regions: prostatic, membranous and spongy. Figure 25.21b Incontinence Brain Higher brain centers Urinary bladder filling stretches bladder wall Allow or inhibit micturition as appropriate Pontine micturition center Afferent impulses from stretch receptors • Damage to spinal cord • Frequent micturition in infants Pontine storage center Promotes micturition by acting on all three spinal efferents Simple spinal reflex Inhibits micturition by acting on all three spinal efferents Spinal cord Spinal cord Parasympathetic activity Figure 25.21a Sympathetic activity Detrusor muscle contracts; internal urethral sphincter opens Somatic motor nerve activity – Incontinence is normal: control of the voluntary urethral sphincter develops with the nervous system Parasympathetic activity Sympathetic activity Somatic motor nerve activity External urethral sphincter opens Inhibits Micturition Figure 25.22 Pathway of Urine Flow Urine formed in nephrons Calyces Renal pelvis Ureters Bladder Urethra 9