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 Urinary System Disposes of water soluble wastes Maintains fluid balance Regulates electrolytes Regulates acid-base balance Other functions 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 Urine is about 95% water Second largest component is urea Urea derived from breakdown of amino acids Nitrogenous Wastes TOXIC! 1. Dietary amino acids NH 2 removed NH 2 + H + NH 3 500 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
Toxicity Energy Costs Water Required Solubility Examples Fill in the blanks Ammonia Urea Uricacid Very toxic Fish & aquatic invertebrates 50 ml/g Nitrogen High = 3 ATP Low Urinary System Organs Major excretory organs Urinary bladder Temporary storage reservoir for urine s Transport urine from the kidneys to the bladder Transports urine out of the body Hepatic veins (cut) Esophagus (cut) Inferior vena cava Adrenal gland Aorta Iliac crest Rectum (cut) Uterus (part of female reproductive system) Renal artery Renal hilum Renal vein Kidney Urinary bladder Peritoneum Renal vein Renal artery Body of vertebra L 2 Body wall (a) Anterior Peritoneal cavity (organs removed) Posterior Inferior vena cava Aorta Supportive tissue layers Renal fascia anterior posterior Perirenal fat capsule Fibrous capsule Figure 25.1 Figure 25.2a External anatomy Retroperitoneal position Embedded in pararenal fat External anatomy Hilus(or hilum) Where blood vessels, nerves, and ureter pass 2
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 Internal Anatomy Renal cortex Superficial region Renal columns extend into medulla Where urine is produced Renal medulla Cone-shaped medullary(renal) pyramids Separated by the renal columns Consist of tubules that transport urine to the calyces 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
Renal hilum Renal cortex Renal medulla Major calyx Papilla of pyramid Minor calyx Blood Supply Renal arteries deliver ~ 22 % of cardiac output (1.2 L/min) 90% directed to cortex Urine formation Renal pyramid in renal medulla Renal column Fibrous capsule (a) Photograph of right kidney, frontal section (b) Diagrammatic view Figure 25.3 Cortical radiate vein Cortical radiate artery Arcuate vein Arcuate artery Interlobar vein Interlobarartery Segmental arteries Renal vein Renal artery Renal medulla Renal cortex (a) Frontal section illustrating major blood vessels Aorta Renal artery Segmental artery Interlobar artery Arcuate artery Cortical radiate artery Afferent Inferior vena cava Renal vein Interlobar vein Arcuate vein Cortical radiate vein Peritubular capillaries and vasa recta Efferent Glomerulus (capillaries) Nephron-associated blood vessels (see Figure 25.8) (b) Path of blood flow through renal blood vessels Figure 25.4a Figure 25.4b 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
Renal corpuscle Glomerulus + Bowman s capsule Glomerular endothelium Fenestrated capillary endothelium Layer of highly branched and interlaced podocytes Allows filtrate to pass from plasma into the glomerular capsule Efferent Afferent Glomerular capsule Glomerulus Efferent Parietal layer of glomerular capsule Capsular space Foot processes of podocytes Podocyte cell body (visceral layer) Red blood cell Proximal tubule cell Cortical nephron Has short loop of Henle and glomerulus further from the corticomedullary junction Efferent supplies peritubular capillaries Efferent Renal Glomerular capillaries corpuscle (glomerulus) Glomerular (Bowman s) capsule Proximal convoluted tubule Peritubular capillaries Juxtamedullary nephron Has long loop of Henle and glomerulus closer to the corticomedullary junction Efferent supplies vasarecta Afferent Collecting duct Distal convoluted tubule Afferent Efferent Juxtaglomerular apparatus Macula densa cells Extraglomerular mesangial cells Granular cells Afferent Lumens of glomerular capillaries Endothelial cell of glomerular capillary Mesangial cells between capillaries Kidney Cortex Medulla Loop of Henle loop of Henle Corticomedullary junction Vasa recta Juxtaglomerular apparatus Renal corpuscle (a) Figure 25.8 Figure 25.7a 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 +, HCO 3- ) Confined to the cortex Renal tubules Loop of Henle Descends from the cortex to the medulla, turns, and comes back to the cortex More later 5
Renal tubules Distal convoluted tubule (DCT) Important site for secretion, aldosterone & ADH activity Exchange of ions important for ph (H +, HCO 3- ) Reabsorption of some electrolytes such as Na + Confined to the cortex Renal tubules Collecting tubules (CT) 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 +, HCO 3- ) Renal cortex Glomerular capsule: parietal layer Renal medulla Kidney Renal corpuscle Glomerular capsule Glomerulus Proximal convoluted tubule Cortex Medulla Thick segment Thin segment Loop of Henle Descending limb Ascending limb Distal convoluted tubule Collecting duct Basement membrane Podocyte Fenestrated endothelium of the glomerulus Glomerular capsule: visceral layer Microvilli Mitochondria Highly infolded plasma membrane Proximal convoluted tubule cells Distal convoluted tubule cells Loop of Henle (thin-segment) cells Principal cell Intercalated cell Juxtaglomerular Apparatus (JGA) Distal convoluted tubule and afferent contact one another modified at the point of contact One per nephron Function Regulation of filtrate formation and blood pressure Collecting duct cells Figure 25.5 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 Juxtaglomerular Apparatus (JGA) 3 components 2) Granular cells AKA juxtaglomerular cells In wall of afferent Enlarged smooth muscle cells Mechanoreceptors that sense blood pressure in afferent Store and secrete renin in response 6
Juxtaglomerular Apparatus (JGA) 3 components 3) Extraglomerular mesangial cells Lie between and DCT Connected by gap junctions Pass regulatory signals between macula densa and granular cells Efferent Afferent Juxtaglomerular apparatus Glomerular capsule Glomerulus Efferent Macula densa cells Extraglomerular mesangial cells Granular cells Afferent Parietal layer of glomerular capsule Capsular space Juxtaglomerular apparatus Foot processes of podocytes Renal corpuscle Podocyte cell body (visceral layer) Red blood cell Proximal tubule cell Lumens of glomerular capillaries Endothelial cell of glomerular capillary Mesangial cells between capillaries Figure 25.8 1. Glomerulus Nephron Capillary Beds Afferent glomerulus efferent Specialized for filtration Nephron Capillary Beds 2. Peritubular capillaries Low-pressure, porous capillaries adapted for absorption Arise from efferent s Cling to adjacent renal tubules in cortex Empty into venules Cortical nephrons 85% of nephrons; almost entirely in the cortex Short loops of Henle extend barely into medulla Juxtamedullary nephrons Long loops of Henledeeply invade the medulla Extensive thin segments Important in the production of concentrated urine Much more on this later 7
s Convey urine from kidneys to bladder Retroperitoneal location Enter base of bladder through posterior wall bladder pressure = distal ends of the ureters close Prevents backflow of urine Mucus is protective Urinary Bladder Muscular sac for temporary storage of urine On pelvic floor posterior to pubic symphysis Males prostate gland surrounds the neck inferiorly Females anterior to the vagina and uterus Urinary Bladder Stretch receptors in bladder create desire to void Micturition Urge to void usually occurs with about 300ml urine Can hold up to about 500ml Urinary Bladder Epithelium is specialized to accommodate stretching and recoil as bladder fills and empties Hepatic veins (cut) Esophagus (cut) Inferior vena cava Adrenal gland Aorta Iliac crest Renal artery Renal hilum Renal vein Kidney Sphincters Internal ANS control External Voluntary control Rectum (cut) Uterus (part of female reproductive system) Urinary bladder Figure 25.1 8
Peritoneum Rugae Detrusor muscle ic orifices Bladder neck Internal urethral sphincter External urethral sphincter Urogenital diaphragm (b) Female. Trigone External urethral orifice Figure 25.21b Peritoneum Rugae Detrusor muscle Adventitia ic orifices Trigone of bladder Bladder neck Internal urethral sphincter Prostate Prostatic urethra Urogenital diaphragm External urethral sphincter Membranous urethra Spongy urethra Erectile tissue of penis External urethral orifice (a) Male.The long male urethra has three regions: prostatic, membranous and spongy. Figure 25.21a Urinary bladder filling stretches bladder wall Afferent impulses from stretch receptors Simple spinal reflex Spinal cord Parasympathetic activity Brain Higher brain centers Allow or inhibit micturition as appropriate Pontine micturition Pontine storage center center Promotes micturition Inhibits micturition by acting on all three by acting on all three spinal efferents spinal efferents Spinal cord Sympathetic Somatic motor Parasympathetic activity activity nerve activity Sympathetic activity Somatic motor nerve activity Incontinence Damage to spinal cord Frequent micturition in infants Incontinence is normal: control of the voluntary urethral sphincter develops with the nervous system Detrusor muscle contracts; internal urethral sphincter opens External urethral sphincter opens Micturition Inhibits Figure 25.22 Pathway of Urine Flow Urine formed in nephrons Calyces s Bladder 9