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Urinary System Chapter 17
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Functions Filtration of blood Body fluid regulation Waste removal
Water/salt balance pH balance Waste removal
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Key Structures Kidneys Renal Veins Renal Arteries Ureters
Urinary Bladder Urethra
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Path of Urine Blood to kidney Urine Out Ureter Bladder Urethra Out
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Kidneys Red/Brown color, bean shaped 12 cm long Enclosed by a capsule
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Functions of Kidneys Filter blood
Keep what is needed; excrete what is not Maintain content, volume, pH of body fluid Other functions Maintain RBC production Regulate blood volume and pressure
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Kidney Structures Renal Medulla Renal Cortex Major Calyx Minor Calyx
Nephrons Major Calyx Minor Calyx
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Blood Flow to Kidneys Blood from abdominal aorta to renal arteries
Blood filtered 1st Gas exchange 2nd Renal veins take deoxygenated blood from kidneys Veins lead to inferior vena cava
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Nephrons A kidney has 1 million of these Smallest unit of filtration
Blood supply to nephron Blood taken to nephron by afferent arteriole Efferent arteriole takes filtered (but not deoxygenated blood) to peritubular capillaries (surround tubes of nephron)
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Fig17.02 Renal capsule Renal cortex Renal corpuscle Nephrons
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Renal capsule Renal cortex Renal corpuscle Nephrons Renal cortex Renal medulla Minor calyx Major calyx Renal sinus Renal medulla Renal column Renal tubule Collecting duct Fat in renal sinus Papilla Renal pelvis Minor calyx Renal papilla (b) (c) Renal pyramid Ureter (a)
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Fig17.03 Cortical radiate artery and vein Proximal convoluted tubule
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cortical radiate artery and vein Proximal convoluted tubule Cortical radiate artery and vein Cortex Afferent arteriole Arcuate vein and artery Medulla Efferent arteriole Distal convoluted tubule Interlobar vein and artery Peritubular capillary Renal artery Renal vein Renal pelvis Ureter
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Blood Supply cont. Glomerulus: cluster of blood capillaries
Bowman’s capsule: cup like structure that surrounds blood capillaries
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Parts of Nephron Bowman’s Capsule Proximal (Convoluted) Tubule
Loop of Henle (Desecending/Ascending) Distal (Convoluted) Tubule Collecting Duct
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Fig17.03 Cortical radiate artery and vein Proximal convoluted tubule
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cortical radiate artery and vein Proximal convoluted tubule Cortical radiate artery and vein Cortex Afferent arteriole Arcuate vein and artery Medulla Efferent arteriole Distal convoluted tubule Interlobar vein and artery Peritubular capillary Renal artery Renal vein Renal pelvis Ureter
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Fig17.06 Glomerular capsule Cortical radiate artery Proximal
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glomerular capsule Cortical radiate artery Proximal convoluted tubule Cortical radiate vein Glomerulus Afferent arteriole Efferent arteriole Renal cortex Distal convoluted tubule From renal artery Peritubular capillary To renal vein Renal medulla Descending limb Nephron loop Ascending limb Collecting duct
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Fig17.07 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glomerular capsule Afferent arteriole Glomerulus Juxtaglomerular apparatus Distal convoluted tubule Efferent arteriole Proximal convoluted tubule Glomerulus Podocyte Afferent arteriole Nephron loop (a) Juxtaglomerular cells Juxtaglomerular apparatus Macula densa Ascending limb of nephron loop Glomerular capsule Efferent arteriole (b)
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Urine Formation Three Stages 2 & 3 happen in rest of the nephron
1. Filtration Glomerulus/Bowman’s Capsule 2. Secretion 3. Reabsorption 2 & 3 happen in rest of the nephron
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Filtration Glomerulus is leaky; so portion of the blood is filtered out of it and into the Bowman’s capsule Filtration depends on pressure
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Pressure High Pressure
Forces small things from glomerulus to Bowman’s capsule Anything that leaves blood and enters capsule is called filtrate
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Pressures to Know Hydrostatic pressure: pressure due to presence of water Osmotic pressure: pressure due to high concentration of dissolved solutes “Pulling pressure” Water is pulled toward solutes
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Outward force, glomerular hydrostatic pressure = +60 mm
Fig17.10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood flow Blood flow Plasma colloid osmotic pressure Glomerular hydrostatic pressure Net filtration pressure Capsular hydrostatic pressure Net Outward Pressure Outward force, glomerular hydrostatic pressure = +60 mm Inward force of plasma colloid osmotic pressure = –32 mm Inward force of capsular hydrostatic pressure = –18 mm Net filtration pressure = +10 mm
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Overall Net filtration pressure forces substances out of glomerulus and into capsule
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Factors Affecting Filtration
Change in diameter of arterioles Smaller afferent arteriole = less filtration Smaller efferent arteriole = more filtration Less proteins in blood = less glomerular osmotic pressure = more filtration More pressure in capsule = less filtration
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Reabsorption Mostly in proximal tubule
Microvilli Glucose, amino acids, water, protein There is a limit to reabsorption, so these are still excreted in urine as well
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Fig17.06 Glomerular capsule Cortical radiate artery Proximal
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glomerular capsule Cortical radiate artery Proximal convoluted tubule Cortical radiate vein Glomerulus Afferent arteriole Efferent arteriole Renal cortex Distal convoluted tubule From renal artery Peritubular capillary To renal vein Renal medulla Descending limb Nephron loop Ascending limb Collecting duct
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Secretion Opposite of reabsorption Excess H ions and organic compounds
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Urine Composition Varies from time to time; reflects the amounts of water/solutes that the kidneys eliminate to maintain homeostasis 95% water, and also contains urea, uric acid, a trace of amino acids, and electrolytes
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Urine Elimination Pathway of urine after forming in nephron:
Collecting Duct Minor calyces Major calyces Renal Pelvis Ureter Bladder Urethra OUT!
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Fig17.03 Cortical radiate artery and vein Proximal convoluted tubule
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cortical radiate artery and vein Proximal convoluted tubule Cortical radiate artery and vein Cortex Afferent arteriole Arcuate vein and artery Medulla Efferent arteriole Distal convoluted tubule Interlobar vein and artery Peritubular capillary Renal artery Renal vein Renal pelvis Ureter
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Ureters 1 per kidney Peristalsis forces urine down
Valve at end allows urine into bladder
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Bladder Muscular, hollow, sphere, highly folded
Stores urine, forces it into urethra
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Micturition Reflex Process by which urine leaves bladder
Stretching of bladder detected by micturition reflex center of spinal cord Causes: Bladder muscle contraction Urge to urinate Internal urethral sphincter relaxes External urethral sphincter relaxes (voluntary control)
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Urethra Opening from bladder to external environment
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Diuretics
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Kidney Stones
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