1. ** Digestive System (cont’d) ** Lecture Notes Pages 110-111 Urinary System I Lecture Notes Pages 122-140

2. 2 Lecture Overview CHO, protein, lipid metabolism Urinary System –Overview –Gross anatomy/blood supply of kidney –The nephron, its blood supply; fluid flow –Urinary elimination system –Urine formation Filtration Reabsorption/Secretion Countercurrent multiplier and water conservation –Renin-angiotensin pathway

3. 3 Pyruvate is a Key Junction in Metabolism Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Pyruvate is used to synthesize amino acids and Acetyl CoA Pyruvate can also be used to synthesize glucose via gluconeogenesis. * Lipolysis   Lipo- genesis  Glycogenesis Glycogenolysis 

4. Carbohydrate Metabolism 4

5. Protein Metabolism 5 Very toxic even in small quantities Ketone bodies - acetoacetic acid - betahydroxybutyric acid - Acetone

6. Lipid Metabolism 6 (lipogenesis) (Ketone body)

7. The Urinary System Lecture Notes Pages 122-140

8. 8 Functions of the Urinary System Make urine Regulate blood volume and blood pressure Regulate plasma concentrations of Na +, K +, Cl -, HCO 3 -, and other ions Help to stabilize blood pH Conserve valuable nutrients Assist the liver in detoxification and deamination

9. 9 Urinary System Kidneys receive about 1.2 L of blood per minute and filter nearly 180 L of fluid from the bloodstream every day! Figure from: Hole’s Human A&P, 12 th edition, 2010

10. 10 Location of Kidneys Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Located retroperitoneally from T12 to L3 Left kidney is slightly higher than right kidney Adrenal glands sit on the medial and superior part of kidneys Nephro(s) = kidney

11. 11 Location of Kidneys Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Helps maintain position of kidney

12. 12 Gross Anatomy of the Kidneys Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Renal capsule is tough, fibrous capsule (tunica fibrosa) Hilus is entry point for renal artery, vein, and nerve (mostly sympathetic fibers) Bases of renal pyramids face the cortex, apices face the renal pelvis and end at renal papillae [Pyel(o)-] ( 2-3 per kidney) ( 8-14 per kidney) [p. 123-124]

13. 13 Overview of the Nephron Nephrons are the structural and functional units of the kidney About 1 million nephrons/kidney (80%) (20%) Figure from: Hole’s Human A&P, 12 th edition, 2010 [p. 124;128] tubule (CT)

14. 14 The Nephron 1. PCT – simple cuboidal with a brush border 2. Thin segment of the descending nephron loop - simple squamous epithelium 3. Thick ascending nephron loop - cuboidal/low columnar 4. DCT/CT - simple cuboidal with no microvilli (PCT) (DCT) Figure from: Hole’s Human A&P, 12 th edition, 2010 [p. 125-127] (JGA) (Bowmans’s capsule - BC) (EA) (AA) (Loop of Henle - LoH) (CT; in renal pyramids) To papillae of renal pyramid, then minor calyx (NOW IT’S URINE!) Note: CT is not part of nephron

15. 15 Renal Blood Vessels Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Nerves, mainly sympathetic postganglionic fibers of the ANS, follow arteries to nephrons [p. 129]

16. 16 Blood Vessels of the Nephron The capillary loop of the vasa recta is a type of capillary that is closely associated with the nephron loop of juxtamedullary nephrons Medulla Figure from: Hole’s Human A&P, 12 th edition, 2010 [p. 125-127] tubule

17. 17 Blood Flow Through Kidney and Nephron Figure from: Hole’s Human A&P, 12 th edition, 2010 [p. 129]

18. 18 Elimination of Urine nephrons collecting ducts renal papillae minor and major calyces renal pelvis ureters urinary bladder urethra outside world Flow of Urine Know this…

19. 19 Ureters 25 cm long extend downward posterior to the parietal peritoneum parallel to vertebral column in pelvic cavity, joins urinary bladder peristaltic contractions Mucous coat – transitional epithelium continuous with linings of the renal tubules and urinary bladder Muscular coat – smooth muscle in longitudinal and circular bundles; carries out peristalsis to move urine toward bladder Fibrous coat (adventitia)– CT layer continuous with the renal capsule and peritoneum Walls of the ureters: Figure from: Hole’s Human A&P, 12 th edition, 2010 [p. 130]

20. 20 Urinary Bladder [Cyst(o)] Four layers: 1.Mucous layer; (transitional epi., with rugae) 2.Muscular coat (detrusor; 3 layers) 3.Serous layer (adventitia) Temporary reservoir for storage of urine Note the internal sphincter at neck of bladder Frontal section, anteriorposterior Figure from: Hole’s Human A&P, 12 th edition, 2010 [p. 130]

21. 21 Micturition (Urination) Reflex trigger = bladder distention & stimulation of stretch receptors micturition center activated in sacral portion of spinal cord parasympathetic nerve impulses cause detrusor muscle to contract (short reflex) and internal urethral sphincter to open need to urinate is sensed (spinal cord -> thalamus - > cortex) - urge to urinate at about 150-200 ml of urine - discomfort at about 300 ml of urine - maximum capacity of bladder is about 600-1000 ml voluntary (tonal) contraction of external urethral sphincter prevents urination and also closes the internal sphincter when decision is made to urinate, external and internal urethral sphincters relax, detrusor muscle contracts, and urine is expelled [p. 131]

22. 22 Urinary Bladder and Urethra - Male Base of the urinary bladder lies between the rectum and pubis symphysis. Pelvic region, midsagittal section Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 [p. 131]

23. 23 Urinary Bladder and Urethra - Male Note the long urethra (about 18-20 cm). There are three sections to the male urethra: - Prostatic urethra - Membranous urethra - Penile (cavernous) urethra Urethra in males serves 2 functions: 1)urination 2)passage of semen (ejaculation) Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007 [p. 131]

24. 24 Urinary Bladder and Urethra - Female Urinary bladder is inferior to the uterus and is separated from the rectum by the vagina. Note the short urethra (about 4 cm) Proximity of urethra to anus, and short length of the urethra in females may make it easier for women to get UTIs. Pelvic region, midsagittal section Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 [p. 132]

25. 25 Simplified Overview of Urine Formation Renal corpuscle – provides the raw materials to the nephron for processing PCT – reclaims those substances the body can use; gets rid of some things DCT – gets rid of those substances the body doesn’t want or need; reabsorbs some more Na +, Ca 2+ Collecting tubule (duct) – provides the OPTION of reclaiming H 2 O or letting it pass out of the body Characteristics of urine Volume – about 1,500 ml/day (95% H2O) Color – clear (dilute) to amber (conc.) Specific gravity – 1.0002 – 1.04 pH – 4.8 – 7.5 (avg ~ 6.0) Smell – nearly odorless to characteristic; ammonia smell if standing [p. 132-133]

26. 26 Urine Formation Glomerular Filtration (GF) *Adds to volume of urine produced substances move from blood to glomerular capsule Tubular Reabsorption (TR) *Subtracts from volume of urine produced reabsorbs 168,500 ml of filtrate and returns to IVF (plasma)! 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 (TS) *Adds to volume of urine produced substances move from blood of peritubular capillaries into renal tubules drugs and ions, urea, uric acid, H +  Urine formation = GF + TS - TR About ~120-125 ml/minute (170,000-180,000 ml/day) of the total 1200 ml/min of blood that passes through the glomerulus becomes filtrate [p. 133]

27. 27 Overview of Reabsorption and Secretion Figure from: Hole’s Human A&P, 12 th edition, 2010

28. 28 Renal Corpuscle (Glomerulus + Capsule) Notice that the efferent arteriole is smaller than the afferent arteriole This creates a high hydrostatic pressure (~55-60 mm Hg) in the glomerular capillary bed Filtrate in capsular space Figure from: Hole’s Human A&P, 12 th edition, 2010 Tubular fluid in PCT up to minor calyx [p. 133-134] (Bowman’s)

29. 29 Visceral Glomerular Epithelium Material passing out of the blood must be small enough to fit through the filtration slits (slit pores) Figure from: Hole’s Human A&P, 12 th edition, 2010 [p. 133-134]

30. 30 Glomerular Filtrate and Urine Composition Glomerular filtrate is about the same composition as plasma: H 2 O, glucose, amino acids, urea, uric acid, creatine, creatinine, Na, Cl, K, HCO 3 -, PO 4 3-, SO 4 2-. But notice how different the composition of urine is. Additionally, note that protein is not normally present in urine. (1.69 L/day) [p. 134]

31. 31 Sodium and Water Filtration, Reabsorption, and Excretion Because of the large volumes involved, small changes in tubular reabsorption amount to LARGE changes in excretion of Na + and H 2 O (since “water follows salt (solute)”) Figure from: Hole’s Human A&P, 12 th edition, 2010 [p. 134]

32. 32 Glomerular Filtration Glomerular filtrate is plasma that passes through 1) the fenestrae of the capillary endothelium, 2) the basement membrane around the endothelium, and 3) the filtration slits (slit pores) of the pedicels This is called the ‘filtration membrane’ Glomerular filtration is a mechanical process based primarily on molecule size Figure from: Hole’s Human A&P, 12 th edition, 2010

33. 33 Glomerular Filtration Rate (GFR) Net filtration pressure is normally positive, i.e., favors the movement of fluid out of the glomerular capillaries GFR = amount of filtrate produced each minute (~120-125 ml/min) Net Filtration Pressure = force favoring filtration – forces opposing filtration (*glomerular capillary ( capsular hydrostatic pressure hydrostatic pressure) + glomerular capillary osmotic pressure ) NFP = HP g – (HP c + OP g ) Figure from: Hole’s Human A&P, 12 th edition, 2010 [p. 134]

34. 34 Afferent/Efferent Arterioles – Effect on GFR Afferent arteriole (AA) –Δ radius  GFR –  radius  GFR;  radius  GFR Efferent arteriole (EA) –Δ radius  1/GFR –  radius  GFR;  radius  GFR AA and EA Innervated by sympathetic nerves

35. 35 Amounts of Glomerular Filtrate and Urine average amounts over a 24 hour period Glomerular Filtration Rate (GFR) is directly proportional to the net filtration pressure GFR  120-125 ml/min (168,500 ml/day) This means that all of the plasma is filtered ~ 60x every day (How did we get this number?) Notice that urine output is only 600 – 2,500 ml per day (an average of about 1,500 ml, or about 1% of glomerular filtrate); 99% of filtrate is reabsorbed!! Figure from: Hole’s Human A&P, 12 th edition, 2010 [p. 134]

36. 36 Glomerular Filtration Rate (GFR) Net filtration pressure, although normally positive, is relatively low (  10 mm Hg) Glomerular hydrostatic pressure is the blood pressure in the glomerular capillaries, and is usually higher than other capillary pressures Capsular hydrostatic pressure tends to push water and filtrate BACK into the capillaries Anything that alters the filtration pressures will alter GFR * Blood pressure is the most important factor altering the glomerular hydrostatic pressure (and NFP). A MAP fall of 10% will severely impair glomerular filtration; a fall of 15-20% will stop it. [p. 134]

37. 37 Summary of Factors Affecting GFR FactorEffect Vasoconstriction (↑ Sympathetic stimulation) Afferent arteriole  GFR Efferent arteriole ↑ GFR Vasodilation (  Sympathetic stimulation) Afferent arteriole↑ GFR Efferent arteriole  GFR Increased capillary hydrostatic pressure↑ GFR Increased colloid osmotic pressure  GFR Increased capsular hydrostatic pressure  GFR [p. 134]