BSC2086 A P II Final Exam Study Guide Lesson 19 Lesson 19 The Urinary System Part I Urinary System Functions Three 3 Functions of the Urinary System o Excretion Removal of organic wastes from body fluids o Elimination Discharge of waste products o Homeostatic regulation of blood plasma volume solute concentration Urination Micturition Process of eliminating urine o Contraction of muscular urinary bladder forces urine through urethra out Kidneys Organs that produce urine Urinary Tract Organs that eliminate urine o Ureters paired tubes o Urinary Bladder muscular sac o Urethra exit tube of body Homeostatic Functions of the Urinary System o Regulates blood volume blood pressure By adjusting volume of water lost in urine Releasing erythropoietin rennin o Regulates plasma ion concentrations Sodium potassium chloride ions Controls quantities of these ions lost in urine Calcium ion levels Through synthesis of calcitriol o Parathyroid hormone PTH stimulates calcitriol release from kidneys Increases Ca2 absorption By controlling loss of hydrogen ions bicarbonate ions in urine o Helps stabilize blood pH o Conserves valuable nutrients 1 BSC2086 A P II Final Exam Study Guide Lesson 19 By preventing their excretion while excreting organic waste products o Assists liver in Detoxifying poisons During starvation Deaminates amino acids so other tissues can metabolize them for energy The Kidneys Kidneys located on either side of vertebral column o Left kidney superior to right kidney o Superior surface capped by adrenal gland o Position is maintained by Overlying peritoneum Contact with adjacent visceral organs Supporting connective tissues Floating Kidney Suspensory fibers damaged kidney displaced o Can cause pain distortion of ureter blood vessels during movement Kidneys protected stabilized by three 3 concentric layers of connective tissue o Fibrous Capsule innermost layer Layer of collagen fibers Covers outer surface of entire organ o Perinephric Fat Capsule middle layer Thick layer of adipose tissue Surrounds renal capsule o Renal Fascia outermost layer Dense fibrous outer layer Anchors kidney to surrounding structures Typical adult kidney o 10 cm 4 in long o 5 5 cm 2 2 in wide o 3 cm 1 2 in thick o Weighs 150 g 5 25 oz Hilum o Point of entry for renal artery renal nerves o Point of exit for renal vein ureter Renal Cortex Superficial portion of kidney in contact with renal capsule o Reddish brown granular Renal Pyramids 6 18 conical or triangular structures in renal medulla o Base adjacent to cortex o Renal papilla tip projects into renal sinus Renal Columns Bands of cortical tissue separate adjacent renal pyramids o Have distinct granular texture o Extend into medulla Renal Lobe o Consists of Renal pyramid 2 BSC2086 A P II Final Exam Study Guide Lesson 19 o Ducts discharge urine into minor calyx cup shaped drain Overlying area of renal cortex Adjacent tissues of renal columns o Produces urine Renal Papilla Major Calyx Formed by 4 5 minor calyces Renal Pelvis Large funnel shaped chamber o Consists of 2 3 major calyces o Fills most of renal sinus o Connected to ureter which drains kidney Blood Supply to the Kidneys Kidneys receive 20 25 of total cardiac output 1 200 mL blood flows through kidneys each minute Kidney receives blood through renal artery Blood Flow o Renal artery o Segmental arteries Interlobar arteries o o Arcuate arteries o Cortical radiate interlobular arteries o Afferent arterioles o Glomerulus efferent arteriole o Peritubular capillaries o Venules o Cortical radiate interlobular veins o Arcuate veins o o Renal vein Interlobar veins 3 BSC2086 A P II Final Exam Study Guide Lesson 19 Renal Nerves Innervate kidneys ureters o Enter each kidney at hilum o Follow tributaries of renal arteries to individual nephrons o Sympathetic Innervation Adjusts rate of urine formation by changing blood flow blood pressure at nephrons Stimulates release of renin Restricts losses of water and salt in urine by stimulating reabsorption at nephron Renin angiotensin system stimulates aldosterone release from adrenal cortex Nephron functional unit of the kidney o Microscopic tubular structures in cortex of each renal lobe Each kidney has 1 25 million nephrons o Where urine production begins o Consists of renal tubule renal corpuscle Renal Corpuscle Spherical structure consisting of 4 BSC2086 A P II Final Exam Study Guide Lesson 19 Glomerular Capsule Bowman s Capsule Cup shaped chamber Capillary network glomerulus o Glomerulus Consists of 50 intertwining capillaries Blood delivered via afferent arteriole Blood leaves in efferent arteriole Flows into peritubular capillaries Drain into small venules Return blood to venous system Blood leaves the capillary network through the efferent arteriole and NOT through a venule Filtration occurs in renal corpuscle o Blood pressure forces water dissolved solutes out of glomerular capillaries into capsular space o Produces filtrate protein free solution Similar to blood plasma but lacks proteins Renal Tubule Long tubular passageway that begins at the renal corpuscle Three 3 Functions of the Renal Tubule o Reabsorb useful organic nutrients that enter filtrate o Reabsorb more than 90 of water in filtrate o Secrete waste products that failed to enter renal corpuscle through filtration at glomerulus Segments of Renal Tubule o Located in cortex Proximal Convoluted Tubule PCT Nephron Loop Loop of Henle U shaped tube Extends partially into medulla In juxtamedullary nephrons nephron loop extends deeper into medulla Important to their function o Distal Convoluted Tubule DCT 5 BSC2086 A P II Final Exam Study Guide Lesson 19 o Organization of the Nephron Filtrate tubular fluid gradually changes composition as it travels along the tubule Due to reabsorption secretion of substances Changes vary with activities in each segment of nephron o Each nephron Empties into the collecting system series of tubes that carries filtrate away from nephron Collecting Ducts Receive fluid from many nephrons Each collecting duct o Begins in cortex o Descends into medulla o Carries fluid to papillary duct that drains into a minor calyx 6 BSC2086 A P II Final Exam Study Guide Lesson 19 o Cortical Nephrons 85 of all nephrons Located mostly within superficial cortex of kidney Nephron loop Loop of Henle relatively short Efferent arteriole delivers blood to a network of peritubular capillaries o Juxtamedullary Nephrons 15 of nephrons Nephron loops extend deep into medulla Peritubular capillaries connect
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