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Digestive and Urinary System Lecture Notes with Metabolism Overview

This lecture provides an overview of the digestive and urinary systems, with a focus on metabolism and the functions of the urinary system. Topics covered include carbohydrate, protein, and lipid metabolism, as well as the formation of urine and the gross anatomy of the kidneys.

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Digestive and Urinary System Lecture Notes with Metabolism Overview

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

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

  4. Carbohydrate Metabolism

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

  6. Lipid Metabolism (lipogenesis) (Ketone body)

  7. The Urinary System Lecture Notes Pages 122-140

  8. Functions of the Urinary System • Make urine • Regulate blood volume and blood pressure • Regulate plasma concentrations of Na+, K+, Cl-, HCO3-, and other ions • Help to stabilize blood pH • Conserve valuable nutrients • Assist the liver in detoxification and deamination

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

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

  12. Gross Anatomy of the Kidneys 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 ( 8-14 per kidney) ( 2-3 per kidney) [Pyel(o)-] [p. 123-124] Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

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

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

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

  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 tubule [p. 125-127] Figure from: Hole’s Human A&P, 12th edition, 2010

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

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

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

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

  21. Micturition (Urination) Reflex [p. 131] • 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

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

  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 [p. 131] Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007 • Urethra in males serves 2 functions: • urination • passage of semen (ejaculation)

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

  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+, Ca2+ Collecting tubule (duct) – provides the OPTION of reclaiming H2O 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. Urine Formation [p. 133] 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 • 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

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

  28. Renal Corpuscle (Glomerulus + Capsule) [p. 133-134] Figure from: Hole’s Human A&P, 12th edition, 2010 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 (Bowman’s) Filtrate in capsular space Tubular fluid in PCT up to minor calyx

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

  30. Glomerular Filtrate and Urine Composition (1.69 L/day) Glomerular filtrate is about the same composition as plasma: H2O, glucose, amino acids, urea, uric acid, creatine, creatinine, Na, Cl, K, HCO3-, PO43-, SO42-. But notice how different the composition of urine is. Additionally, note that protein is not normally present in urine. [p. 134]

  31. Sodium and Water Filtration, Reabsorption, and Excretion [p. 134] Figure from: Hole’s Human A&P, 12th edition, 2010 Because of the large volumes involved, small changes in tubular reabsorption amount to LARGE changes in excretion of Na+ and H2O (since “water follows salt (solute)”)

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

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

  34. Amounts of Glomerular Filtrate and Urine Figure from: Hole’s Human A&P, 12th edition, 2010 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!! [p. 134] average amounts over a 24 hour period

  35. 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]

  36. Summary of Factors Affecting GFR [p. 134]

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