1 PowerPoint Lecture Outlines to accompany Hole’s Human Anatomy and Physiology Eleventh Edition Shier  Butler  Lewis Chapter 20 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 Chapter 20 Urinary System consists of the kidneys, ureters, urinary bladder and urethra

3 Location of Kidneys The kidneys which are positioned retroperitoneally lie on either side of the vertebral column, high on the posterior wall of the abdominal cavity

4 Kidney Structure

5 Overview of Kidney Functions Regulation of blood ionic composition –Na+, K+, Ca+2, Cl- and phosphate ions Regulation of blood pH, osmolarity & glucose Regulation of blood volume –conserving or eliminating water Regulation of blood pressure –secreting the enzyme renin –adjusting renal resistance Release of erythropoietin & calcitriol Excretion of wastes & foreign substances

6 OSMOLARITY The osmolarity of a solution is a measure of the total number of dissolved particles per liter of solution. The particles may be molecules, ions, or a mixture of both.

7 Renal Blood Vessels

8 Blood Supply of Nephron The glomerular capillary receives blood from the afferent arteriole and passes it to the efferent arteriole The efferent arteriole gives rise to the peritubular system, which surrounds the tubule Capillary loops called vasa recta dip down into the medulla

9 Pathway of Blood Flow Through Kidney and Nephron

10 Structure of a Nephron Renal corpuscle –Glomerulus –Bowman’s capsule

11 Glomerular Capsule

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14 Juxtaglomerular Apparatus

15 –provides feedback control of extracellular fluid volume and glomerular filtration rate by activating the renin-angiotensin system. Juxtaglomerular Apparatus

16 Cortical and Juxtamedullary Nephrons cortical nephrons 80% of nephrons located close to the surface of the kidney juxtamedullary nephrons regulate water balance located near the renal medulla

17 Urine Formation nephrons remove wastes from the blood and regulate water and electrolyte concentrations urine is the final product of the processes of: glomerular filtration tubular reabsorption tubular secretion

18 Urine Formation Glomerular Filtration substances move from blood to glomerular capsule Tubular Reabsorption substances move from renal tubules into blood of peritubular capillaries glucose, water, urea, proteins, creatine amino, lactic, citric, and uric acids phosphate, sulfate, calcium, potassium, and sodium ions Tubular Secretion substances move from blood of peritubular capillaries into renal tubules drugs and ions

19 Glomerular Filtration The first step in urine formation is filtration of substances out of the glomerular capillaries into the glomerular capsule Glomerular filtrate passes through the fenestrae of the capillary endothelium

20 Glomerular Filtrate and Urine Composition

21 Filtration Pressure and Rate Net Filtration Pressure = force favoring filtration – forces opposing filtration (glomerular capillary ( capsular hydrostatic pressure hydrostatic pressure) and glomerular capillary osmotic pressure ) Glomerular Filtration Rate directly proportional to the net filtration pressure

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23 Filtration Pressure and Rate normally the glomerular net filtration pressure is positive causing filtration the forces responsible include hydrostatic pressure and osmotic pressure of plasma and the hydrostatic pressure of the fluid in the glomerular capsule

24 Amounts of Glomerular Filtrate and Urine Average/24 hours –180 L filtered –1.5 L urine

25 Control of Filtration Rate Primarily three mechanisms are responsible for keeping the GFR constant Increased sympathetic impulses decrease GFR by causing afferent arterioles to constrict Renin-angiotensin system Autoregulation Renin-Angiotensin system

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28 Two processes of urine formation Slide number: 8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood flow Glomerular capsule Glomerulus Glomerular filtrate Tubular reabsorption Renal tubule Blood flow Peritubular capillary Afferent arteriole Efferent arteriole A

29 Tubular Reabsorption transports substances from the glomerular filtrate into the blood within the peritubular capillary

30 Osmosis in proximal portion of renal tubule Slide number: 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood flow Blood flow Glomerulus Glomerular capsule Glomerular filtrate Proximal convoluted tube Blood flow Peritubular capillary

31 Osmosis in proximal portion of renal tubule Slide number: 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood flow Blood flow Glomerulus Glomerular capsule Glomerular filtrate Proximal convoluted tube Blood flow Peritubular capillary Sodium ions are reabsorbed by active transport Na +

32 Osmosis in proximal portion of renal tubule Slide number: 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood flow Blood flow Glomerulus Glomerular capsule Glomerular filtrate Proximal convoluted tube Blood flow Peritubular capillary Sodium ions are reabsorbed by active transport 1 Negatively charged ions are attracted to positively charged ions Na + – – – – Cl – PO 4 –3 HCO 3 –

33 Osmosis in proximal portion of renal tubule Slide number: 5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood flow Blood flow Glomerulus Glomerular capsule Glomerular filtrate Proximal convoluted tube Blood flow Peritubular capillary Sodium ions are reabsorbed by active transport 1 Negatively charged ions are attracted to positively charged ions 2 As concentration of ions (solute) increases in plasma, osmotic pressure increases Na + + – + – + + – – + Cl – Na + – – – – Cl – PO 4 –3 HCO 3 –

34 Osmosis in proximal portion of renal tubule Slide number: 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood flow Blood flow Glomerulus Glomerular capsule Glomerular filtrate Proximal convoluted tube Blood flow Peritubular capillary Sodium ions are reabsorbed by active transport 1 Negatively charged ions are attracted to positively charged ions 2 As concentration of ions (solute) increases in plasma, osmotic pressure increases 3 Water moves from proximal tubule to capillary by osmosis Na + + – + – + + – – + Cl – Na + – + – + ++ – + + – –– ++ –– H2OH2O H2OH2O H2OH2O – – – – Cl – PO 4 –3 HCO 3 –

35 Osmosis in proximal portion of renal tubule Slide number: 7 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood flow Blood flow Glomerulus Glomerular capsule Glomerular filtrate Proximal convoluted tube Isotonic tubular fluid Blood flow Peritubular capillary Sodium ions are reabsorbed by active transport 1 Negatively charged ions are attracted to positively charged ions 2 As concentration of ions (solute) increases in plasma, osmotic pressure increases 3 Water moves from proximal tubule to capillary by osmosis Na + + – + – + + – – + Cl – Na + – + – + ++ – + + – –– ++ –– H2OH2O H2OH2O H2OH2O – – – – Cl – PO 4 –3 HCO 3 –

36 Sodium and Water Reabsorption osmosis reabsorbs water in response to active transport reabsorbing sodium and other solutes in the proximal portion of the renal tubule

37 Sodium and Water Filtration, Reabsorption, and Excretion

38 Tubular Secretion transports substances from the blood within the peritubular capillary into the renal tubule

39 Tubular Secretion In distal convoluted tubules, potassium ions or hydrogen ions may be passively secreted in response to active reabsorption of sodium ions

40 Regulation of Urine Concentration and Volume the distal convoluted tubule and collecting duct are impermeable to water, so water may be excreted as dilute urine if ADH is present, these segments become permeable, and water is reabsorbed by osmosis into the hypertonic medullary interstitial fluid

41 The Countercurrent Multiplier helps maintain the NaCl concentration gradient in the medullary interstitial fluid

42 Countercurrent Mechanism of Vasa Recta fluid in ascending limb becomes hypotonic as solute is reabsorbed fluid in descending limb becomes hypertonic as it loses water by osmosis

43 Countercurrent Mechanism Descending limb is very permeable to water –higher osmolarity of interstitial fluid outside the descending limb causes water to move out of the tubule by osmosis at hairpin turn, osmolarity can reach 1200 mOsm/liter Ascending limb is impermeable to water, but active transport removes Na+ and Cl- so osmolarity drops to 100 mOsm/liter, but less urine is left Vasa recta blood flowing in opposite directions than the loop of Henle -- provides nutrients & O2 without affecting osmolarity of interstitial fluid

44 Formation of Dilute Urine Dilute = having fewer solutes than plasma (300 mOsm/liter). –diabetes insipidus Filtrate and blood have equal osmolarity in PCT Water reabsorbed in thin limb, but ions reabsorbed in thick limb of loop of Henle create a filtrate more dilute than plasma –can be 4x as dilute as plasma –as low as 65 mOsm/liter Cells do not reabsorb water if ADH is low

45 Role of ADH in Regulating Urine Concentration and Volume

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47 Functions of Nephron Components

48 Urea and Uric Acid Excretion Urea by-product of amino acid / protein catabolism plasma concentration reflects the amount or protein in diet enters renal tubules through glomerular filtration contributes to the reabsorption of water from the collecting duct Uric Acid product of nucleic acid metabolism enters renal tubules through glomerular filtration most reabsorption occurs by active transport ~10% secreted and excreted

49 Urine Composition about 95% water usually contains urea, uric acid, and creatinine may contain trace amounts of amino acids and varying amounts of electrolytes volume varies with fluid intake and environmental factors

50 Renal Clearance the rate at which a chemical is removed from the plasma tests of renal clearance inulin clearance test (best for GFR, neither secreted or reabsorbed creatinine clearance test (most commonly used because cheapest and easiest) para-aminohippuric acid (PAH) test tests of renal clearance used to calculate glomerular filtration rate

51 Elimination of Urine nephrons collecting ducts renal papillae minor and major calyces renal pelvis ureters urinary bladder urethra outside

52 Micturition