1. 1 Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Chapter 17 Lecture Outline See separate PowerPoint slides for all figures and tables pre- inserted into PowerPoint without notes.

2. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Chapter 17 Urinary System 2

3. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 17.1 Introduction 3

4. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. A.The urinary system consists of two kidneys that filter the blood, two ureters, a urinary bladder, and a urethra to convey nitrogenous waste substances to the outside. 1.Helps maintain normal concentration of electrolytes and water. 2.Regulates pH and fluid volume. 3.Helps control red blood cell production and blood pressure. 4

5. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.1 5

6. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 17.2 Kidneys 6

7. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. A.The kidney is a reddish brown, bean-shaped organ 12 centimeters long; it is enclosed in a tough, fibrous capsule. B.Location of the Kidneys 1.The kidneys are positioned retroperitoneally on either side of the vertebral column between the twelfth thoracic and third lumbar vertebrae, with the left kidney slightly higher than the right. 2.Connective tissue and adipose tissue hold the kidneys in place. 7

8. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.1 8

9. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. C.Kidney Structure 1.A medial depression in the kidney (hilum) leads to a hollow renal sinus into which blood vessels, nerves, lymphatic vessels, and the ureter enter. 2.Inside the renal sinus lies a renal pelvis that is subdivided into major and minor calyces; small renal papillae project into each minor calyx. 9

10. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Kidney structure, cont. 3.Two distinct regions are found within the kidney: a renal medulla and a renal cortex. a.The renal medulla houses renal pyramids leading to the papillae. b.The renal cortex surrounds the medulla and dips down in-between the renal pyramids (renal columns). c.The functional unit of the kidney is the nephron. 10

11. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.2 11

12. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. D.Kidney Functions 1.The kidneys function to regulate the volume, composition, and pH of body fluids and remove metabolic wastes from the blood in the process. 2.The kidneys also help control the rate of red blood cell formation by secreting erythropoietin, and regulate blood pressure and volume by secreting renin. 3.Plays a role in activation of vitamin D. 12

13. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. E.Renal Blood Vessels 1.The abdominal aorta gives rise to renal arteries that enter the kidneys. 2.As renal arteries pass into the kidneys, they branch into successively smaller arteries: interlobar arteries, arcuate arteries, cortical radiate arteries (interlobular arteries), and afferent arterioles leading to the nephrons. 3.Venous blood is returned through a series of vessels that generally correspond to the arterial pathways. The renal vein then joins the inferior vena cava in the abdominal cavity. 13

14. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.3 14

15. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. F.Nephrons 1.Nephron Structure a.A kidney contains one million nephrons, each of which consists of a renal corpuscle and a renal tubule. b.The renal corpuscle is the filtering portion of the nephron; it is made up of a ball of capillaries called the glomerulus and a glomerular capsule that receives the filtrate. 15

16. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Nephron Structure, cont. c.The renal tubule leads away from the glomerular capsule and first becomes a highly coiled proximal convoluted tubule, then leads to the nephron loop (ascending and descending limbs), and finally to the distal convoluted tubule. d.Several distal convoluted tubules join to become a collecting duct which passes into the medulla, emptying into a minor calyx at the papilla. 16

17. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.6a 17

18. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.7 18

19. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 2.Blood Supply of a Nephron a.The glomerulus receives blood from a fairly large afferent arteriole and passes it to a smaller efferent arteriole. b.The efferent arteriole gives rise to the peritubular capillary system, which surrounds the renal tubule. c.The blood then enters the venous system of the kidney. 19

20. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.6b 20

21. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 3.Juxtaglomerular Apparatus a.At the point of contact between the afferent and efferent arterioles and the distal convoluted tubule, the epithelial cells of the distal tubule form the macula densa. b.Near the macula densa on the afferent arteriole are smooth muscle cells called juxtaglomerular cells. c.The macula densa together with the juxtaglomerular cells make up the juxtaglomerular apparatus. 21

22. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.8 22

23. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 17.3 Urine Formation 23

24. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. A.Urine formation involves glomerular filtration, tubular reabsorption, and tubular secretion. 1.Glomerular Filtration - urine formation begins when the fluid portion of the blood is filtered by the glomerulus and enters the glomerular capsule as glomerular filtrate. 2.Produces about 180 liters of fluid per day, most of which must be returned to the blood during the process of tubular reabsorption. 3.The last step, tubular secretion, moves additional substances from the blood into the tubule to rid the body of those things. 24

25. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. B.Glomerular filtration 1.Water and certain dissolved substances are filtered out of the glomerular capillaries and captured in the glomerular capsule. 2.Glomerular capillaries have many fenestrations that allow more filtration than other capillaries. 3.Cells called podocytes help prevent plasma proteins from being filtered out of the blood. 4.Glomerular filtrate is mostly water, electrolytes, glucose, urea, and uric acid. 25

26. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.9 26

27. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.10 27

28. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Table 17.1 28

29. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. C.Filtration Pressure 1.The main force responsible for moving substances by filtration through the glomerular capillary wall is the hydrostatic pressure of the blood inside. The net pressure forcing substances out of the glomerulus is the net filtration pressure which is always positive. 2.The smaller diameter of the efferent arteriole compared to the afferent arteriole, raises the blood pressure in the glomerulus and favors filtration. 3.Due to plasma proteins, osmotic pressure of the blood resists filtration, as does hydrostatic pressure inside the glomerular capsule. 29

30. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.11 30

31. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. D.Filtration Rate 1.The factors that affect the glomerular filtration rate (GFR) are filtration pressure, glomerular plasma osmotic pressure, and hydrostatic pressure in the glomerular capsule. 2.When the afferent arteriole constricts filtration pressure, and thus filtration rate, declines. 3.When the efferent arteriole constricts, filtration pressure increases, increasing the rate of filtration. 4.When osmotic pressure of the glomerular plasma is high, filtration rate decreases. 31

32. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Filtration Rate, cont. 5.When hydrostatic pressure inside the glomerular capsule is high, filtration rate declines. 6.On the average, filtration rate is 125 milliliters per minute or 180 liters in 24 hours, most of which is reabsorbed further down the nephron. 32

33. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. E.Regulation of Filtration Rate 1.Glomerular filtration rate is relatively constant, although sympathetic impulses may decrease the rate of filtration. a.Constriction and dilation of the afferent and efferent arterioles will help maintain peripheral resistance, systemic blood pressure, GFR, and blood volume. 33

34. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Regulation of Filtration Rate, cont. 2.Another control over filtration rate is the renin- angiotensin system, which regulates sodium excretion. a.Juxtaglomerular cells will secrete renin in response to three stimuli: 1)Afferent arteriole cells sense a drop in blood pressure. 2)Sympathetic stimulation 3)Macula densa cells sense decreased Cl -, K +, or Na + ions at the end of the ascending limb of the nephron loop. 34

35. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Regulation of Filtration Rate, cont. b. Secretion of renin triggers a series of reactions leading to the production of angiotensin II, which acts as a vasoconstrictor of the efferent arteriole; this may, in turn, increase the filtration pressure and the GFR. c. Presence of angiotensin II also increases the secretion of aldosterone, which stimulates reabsorption of sodium. d. The heart can also increase filtration rate when blood volume is high by secreting atrial natriuretic peptide (ANP). 35

36. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.12 36

37. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. F.Tubular Reabsorption 1.Changes in the fluid composition from the time glomerular filtrate is formed when urine arrives at the collecting duct are largely the result of tubular reabsorption of selected substances. 2.Most of the reabsorption occurs in the proximal convoluted tubule, where cells possess microvilli with carrier proteins. 3.Carrier proteins have a limited transport capacity, so excessive amounts of a substance will be excreted into the urine (renal plasma threshold). 37

38. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Tubular Reabsorption, cont. 4.Glucose and amino acids are reabsorbed by active transport, water by osmosis, and proteins by pinocytosis. 5.Other substances reabsorbed by active transport with limited transport capacities include: creatine, lactic acid, citric acid, uric acid, ascorbic acid, phosphate, sulfate, calcium, potassium, and sodium. 38

39. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. G.Sodium and Water Reabsorption 1.Sodium ions are reabsorbed by active transport, and negatively charged ions (Cl - and HCO 3 - ) follow passively (passive transport). 2.As sodium is reabsorbed, water follows by osmosis. 39

40. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.14 40

41. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. H.Tubular Secretion 1.Tubular secretion transports certain substances from the plasma into the renal tubule. 2.Active transport mechanisms move excess hydrogen and potassium ions into the renal tubule along with various organic compounds. 41

42. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.13 42

43. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.15 43

44. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. I.Regulation of Urine Concentration and Volume 1.Aldosterone from the adrenal glands, stimulates the distal convoluted tubule to reabsorb sodium ions (water follows by osmosis) and secrete potassium ions. 2.Normally the distal convoluted tubule and collecting duct are impermeable to water unless the hormone ADH is present. 3.Antidiuretic hormone increases the tube’s permeability to water and water is reabsorbed. 44

45. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Table 17.2 45

46. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. J.Urea and Uric Acid Excretion 1.Urea is a by-product of amino acid metabolism; uric acid is a by-product of nucleic acid metabolism. 2.Urea is passively reabsorbed by diffusion but about 20% of urea is excreted in the urine. 3.Most uric acid is reabsorbed by active transport and a small amount is secreted into the renal tubule. 46

47. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Table 17.3 47

48. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. K.Urine Composition 1.Urine composition varies from time to time and reflects the amounts of water and solutes that the kidneys eliminate to maintain homeostasis. 2.Urine is 95% water, and also contains urea, uric acid, a trace of amino acids, and electrolytes. 3.Volume produced is 0.6 – 2.5 liters/day. 4.Glucose, proteins, ketones, and blood cells are normally not found in urine, so their presence may indicate disease. 48

49. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 17.4 Urine Elimination 49

50. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. A.After forming in the nephrons, urine passes from the collecting ducts to the renal papillae, then to the minor and major calyces, and out the renal pelvis to the ureters, urinary bladder, and finally to the urethra, which conveys urine to the outside. 50

51. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. B.Ureters 1.The ureters are muscular tubes extending from the kidneys to the base of the urinary bladder. 2.The wall of the ureter is composed of three layers: mucous coat, muscular coat, and outer fibrous coat. 3.Muscular peristaltic waves convey urine to the urinary bladder where it passes through a flaplike valve in the mucous membrane of the urinary bladder. 51

52. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. C.Urinary Bladder 1.The urinary bladder is a hollow, distensible, muscular organ lying in the pelvic cavity. 2.The internal floor of the bladder includes the trigone, which is composed of the openings of the two ureters and the urethra. 3.The wall of the urinary bladder is made up of four coats: inner mucous coat of transitional epithelium, submucosa coat, muscular coat made up of detrusor muscle, and outer serous coat. a.The portion of the detrusor muscle that surrounds the neck of the bladder forms an internal urethral sphincter muscle. 52

53. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Fig 17.17 53

54. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. D.Micturition 1.Urine leaves the bladder by the micturition reflex. 2.The detrusor muscle contracts and the external urethral sphincter (in the urogenital diaphragm) must also relax. 3.Stretching of the urinary bladder triggers the micturition reflex center located in the sacral portion of the spinal cord. 54

55. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Micturition, cont. 4.Return parasympathetic impulses cause the detrusor muscle to contract in waves, and an urge to urinate is sensed. 5.When these contractions become strong enough, the internal urethral sphincter is forced open. 6.The external urethral sphincter is composed of skeletal muscle and is under conscious control. 55

56. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. E.Urethra 1.The urethra is a tube that conveys urine from the urinary bladder to the outside via the external urethral orifice. 2.It is a muscular tube with urethral glands that secrete mucus into the urethral canal. 3.In females, it is 4cm long with its opening between the vaginal opening and the clitoris. 4.In males, the urethra serves both the urinary and reproductive systems and runs through the prostate gland and penis. 56

57. Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. The End 57