The Urinary System Ch 15 Part A

1. The Urinary SystemCh 15 Part A

2. Functions of the Urinary System • Elimination of waste products • Nitrogenous wastes • Toxins • Drugs • Lungs, skin and digestive system also eliminate wastes

3. Functions of the Urinary System • Regulate aspects of homeostasis • Water balance • Electrolytes • Acid-base balance in the blood • Blood pressure – by enzyme renin • Red blood cell production – by hormone erythropoietin • Activation of vitamin D • Blood volume

4. Organs of the Urinary System • Kidneys - 2 • Ureters -2 • Urinary bladder • Urethra • Video Clip: Urinary System Overview Figure 15.1a

5. Organs of the Urinary System Figure 15.1a

6. Organs of the Urinary System Figure 15.1b

7. Location of the Kidneys • Against the dorsal body wall • Retroperitoneal; superior lumbar; • At the level of the T12 to L3 vertebrae • 5” x 2½” x 1” • The right kidney is slightly lower than the left; (due to the position of the liver) • Renal Hilum: • A medial indentation where several structures enter or exit the kidney (ureters, renal blood vessels, and nerves) • An adrenal gland sits atop each kidney

8. Coverings of the Kidneys • Fibrous capsule • Surrounds each kidney • Perirenal fat capsule • Surrounds the kidney • Provides protection to the kidney • Renal fascia • Outermost capsule that helps hold the kidney in place against the muscles of the trunk wall

9. Regions of the Kidney • Renal cortex – outer region • Renal medulla – inside the cortex • Renal pelvis – inner collecting tube Figure 15.2b

10. Regions of the Kidney Figure 15.2b

11. Kidney Structures • Renal or Medullary pyramids – triangular regions of tissue in the medulla • Apex toward inner region • Renal columns – extensions of cortex-like material inward • Separates pyramids • Calyx (pl = calyces)– cup-shaped structures that funnel urine towards the renal pelvis from the pyramids

12. Regions of the Kidney Figure 15.2a

13. Blood Supply • One-quarter of the total blood supply of the body passes through the kidneys each minute • Renal artery provides each kidney with arterial blood supply • Renal artery divides into segmental arteries  interlobar arteries  arcuate arteries  cortical radiate arteries • Venous blood flow • Cortical radiate veins  arcuate veins  interlobar veins  renal vein • There are no segmental veins

14. Blood Flow in the Kidneys Figure 15.2c

15. Nephron Anatomy and Physiology • The structural and functional units of the kidneys • >1 million/kidney • Responsible for forming urine • Main structures of the nephrons • Glomerulus – knot of capillaries • Renal tubule – cup-shaped end is bowman’s capsule

16. Nephrons Figure 15.3a

17. Nephron Anatomy: Glomerulus • A specialized knot of capillaries • Capillaries are covered with podocytes from the renal tubule • Have filtration slits for filtrate to enter • Glomerulus sits within a glomerular (Bowman’s) capsule (the first part of the renal tubule) • For filtration • Attached to arterioles on both sides (maintains high pressure) • Large afferent arteriole • Narrow efferent arteriole Figure 15.3c

18. Nephron Anatomy Figure 15.3c

19. Nephron Anatomy Figure 15.3d

20. Nephron Anatomy • Renal tubule extends from glomerular capsule and ends at the collecting duct • Glomerular(Bowman’s) capsule • Proximal convoluted tubule (PCT) • Loop of Henle • Distal convoluted tubule (DCT)

21. Nephron Anatomy Figure 15.3b

22. Types of Nephrons • Cortical nephrons • Located entirely in the cortex • Includes most nephrons • Juxtamedullarynephrons • Found at the boundary of the cortex and medulla Figure 15.3a

23. Types of Nephrons Figure 15.3a

24. Collecting Duct • Receives urine from many nephrons • Run through the medullary pyramids • Deliver urine into the calyces and renal pelvis

25. Nephron Anatomy • Nephrons are associated with two capillary beds • Glomerulus • Peritubular capillary bed

26. Glomerulus • Fed and drained by arterioles • Afferent arteriole—arises from a cortical radiate artery and feeds the glomerulus • Efferent arteriole—receives blood that has passed through the glomerulus • Specialized for filtration • High pressure forces fluid and solutes out of blood and into the glomerular capsule

27. Nephron Anatomy Figure 15.3c

28. Nephron Anatomy Figure 15.4

29. Peritubular Capillaries • Speicalized for absorption • Arise from efferent arteriole of the glomerulus • Normal, low pressure capillaries • Attached to a venule • Adapted for absorption instead of filtration • Cling close to the renal tubule so they can reabsorb some substances from collecting tubes • Drain into interlobular veins

30. Nephron Anatomy Figure 15.3b

31. Urine Formation Processes • Glomerular Filtration • Tubular Reabsorption • Tubular Secretion • Video Clip: Urine Formation Figure 15.4

32. Urine Formation Figure 15.4

33. Filtration • Nonselective passive process • Water and solutes smaller than proteins are forced through capillary walls because of pressure in afferent arterioles • Blood cells cannot pass out to the capillaries • Filtrate is collected in the glomerular capsule and leaves via the renal tubule

34. Tubular Reabsorption • The peritubular capillaries reabsorb several materials • Some water • Glucose • Amino acids • Ions • Some reabsorption is passive (H2O), most is active (amino acids, glucose) • Most reabsorption occurs in the proximal convoluted tubule

35. Sites of Filtration, Reabsorption, and Secretion in a Kidney Figure 15.5

36. Materials Not Reabsorbed • Nitrogenous waste products • Urea – protein breakdown for energy from liver • Uric acid – nucleic acid breakdown • Creatinine – creatine metabolism of muscle • Excess water

37. Tubular Secretion – Reabsorption in Reverse • Some materials move from the peritubular capillaries into the renal tubules • Hydrogen and potassium ions • Creatinine • Process is important for getting rid of substances not already in the filtrate • Materials left in the renal tubule move toward the ureter

38. Formation of Urine Figure 15.5

39. Characteristics of Urine Used for Medical Diagnosis • Per 24 hours: 150-180L of plasma filtered; 1-1.8L urine formed • Urine and filtrate are different • Filtrate contains everything that blood plasma does (except proteins) • Urine is what remains after the filtrate has lost most of its water, nutrients, and necessary ions • Urine contains nitrogenous wastes and substances that are not needed by the body

40. Characteristics of Urine • Yellow color due to the pigment urochrome (from the destruction of hemoglobin) and solutes • Sterile • Slightly aromatic • Normal pH of around 6 • Alkaline pH – bacteria can form • Ammonia smell due to bacteria in old urine • Specific gravity of 1.001 to 1.035 • Specific gravity of H2O – 1.000 • Shows dissolved solutes

41. Characteristics of Urine • Solutes normally found in urine: • Sodium and potassium ions • Urea, uric acid, creatinine • Ammonia • Bicarbonate ions

42. Characteristics of Urine • Solutes NOT normally found in urine • Glucose • Blood proteins • Red blood cells • Hemoglobin • White blood cells (pus) • Bile

43. Abnormal Urine Constituents Table 15.1