The Urinary System

1. The Urinary System Prepared by Assoc. Prof Dr Mohammad Iqbal Omar MBBS, DRM, M Med Program KejuruteraanBioperubatanElektronik PPK Mekatronik, UniMAP iqbalomar@unimap.edu.my

2. Introduction to the Urinary System • Three Functions of the Urinary System • Excretion: • Removal of organic wastes from body fluids • Elimination: • Discharge of waste products • Homeostatic regulation: • Of blood plasma volume and solute concentration

3. Functions of the Urinary System • Nitrogenous wastes (The liver converts harmful ammonia to urea which are eliminated in urine) • Toxins • Drugs

4. Functions of the Urinary System • Regulate aspects of homeostasis • Water balance • Electrolytes • Acid-base balance in the blood • Blood pressure • Red blood cell production • Activation of vitamin D(synthesize calcitrol, one of the vitamin D’s that increases calcium absorption in the intestines)

5. Introduction to the Urinary System • Homeostatic Functions of Urinary System • Regulates blood volume and blood pressure: • By adjusting volume of water lost in urine • Releasing erythropoietin and renin • Regulates plasma ion concentrations: • Sodium, potassium, and chloride ions (by controlling quantities lost in urine) • Calcium ion levels (through synthesis of calcitriol)

6. Introduction to the Urinary System • Homeostatic Functions of Urinary System 3. Helps stabilize blood pH: • By controlling loss of hydrogen ions and bicarbonate ions in urine 4. Conserves valuable nutrients: • By preventing excretion while excreting organic waste products 5. Assists liver in detoxifying poisons

7. Organs of the Urinary System • Kidneys • Ureters • Urinary bladder • Urethra

8. Location of the Kidneys • Against the dorsal body wall • At the level of the T12 to L3 vertebrae • The right kidney is slightly lower than the left (due to position of the liver)

9. The Kidneys • Typical Adult Kidney • Is about 10 cm long, 5.5 cm wide, and 3 cm thick (4 in. x 2.2 in. x 1.2 in.) • Weighs about 150 g (5.25 oz)

10. The Kidneys The Structure of the Kidney.

11. Kidney Features • 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

12. Organs of the Urinary System Figure 15.1a

14. Coverings of the Kidneys • Fibrous capsule • Surrounds each kidney • Perirenal fat capsule • Surrounds the kidney and cushions against blows • Renal fascia • Outermost capsule that helps hold the kidney in place against the muscles of the trunk wall

15. Regions of the Kidney • Renal cortex—outer region • Renal medulla—inside the cortex • Renal pelvis—inner collecting tube

17. Regions of the Kidney

18. Kidney Structures • Renal or medullary pyramids • triangular regions of tissue in the medulla • Renal columns • extensions of cortex-like material inward that separate the pyramids

19. Kidney Structures • Calyces Cup-shaped structures that funnel urine towards the renal pelvis

20. Regions of the Kidney

21. 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

22. Blood Supply • Venous blood flow • Cortical radiate veins  arcuate veins  interlobar veins  renal vein • There are no segmental veins

23. The Kidneys The Blood Supply to the Kidneys: A Sectional View.

24. The Kidneys The Blood Supply to the Kidneys: Flowchart of Renal Circulation.

25. Nephron Anatomy and Physiology • Nephrons are the structural and functional units of the kidneys • > a million nephron in each kidney • Responsible for forming urine • Main structures of the nephrons • Glomerulus • Renal tubule

26. Structures and functions of a nephron Renal tubule and collecting duct Renal tubule and collecting duct Renal tubule and collecting duct Renal corpuscle Renal corpuscle Renal corpuscle Afferent arteriole Afferent arteriole Afferent arteriole Glomerular capsule Glomerular capsule Glomerular capsule Urine (contains excreted substances) Urine (contains excreted substances) Urine (contains excreted substances) Fluid in renal tubule Fluid in renal tubule Fluid in renal tubule 1 1 1 Filtration from blood plasma into nephron Filtration from blood plasma into nephron Filtration from blood plasma into nephron 2 2 3 Tubular reabsorption from fluid into blood Tubular reabsorption from fluid into blood Tubular secretion from blood into fluid Efferent arteriole Efferent arteriole Efferent arteriole Blood (contains reabsorbed substances) Blood (contains reabsorbed substances) Blood (contains reabsorbed substances) Peritubular capillaries Peritubular capillaries Peritubular capillaries

27. Nephrons

29. Nephron Anatomy • Glomerulus • Knot of capillaries-consists of 50 intertwining capillaries • Capillaries are covered with podocytes from the renal tubule • Glomerulus sits within a glomerular (Bowman’s) capsule (the first part of the renal tubule)

30. Nephron Anatomy • Glomerulus • Blood delivered via afferent arteriole • Blood leaves in efferent arteriole • Flows into peritubular capillaries • Which drain into small venules • And return blood to venous system

31. Nephron Anatomy

32. Nephron Anatomy

33. 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)

34. Nephron Anatomy

36. Types of Nephrons • Cortical nephrons • Located entirely in the cortex • 85% of all nephrons • Juxtamedullary nephrons • Found at the boundary of the cortex and medulla • 15% of nephrons

37. Types of Nephrons

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

39. Nephron Anatomy

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

41. 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 • Diameter of Afferent arteriole > Efferent arteriole

42. Nephron Anatomy

43. Nephron Anatomy

44. Peritubular Capillary Beds • Arise from efferent arteriole of the glomerulus • Normal, low pressure capillaries • Adapted for absorption instead of filtration • Cling close to the renal tubule to reabsorb (reclaim) some substances from collecting tubes

46. Nephron Anatomy

47. Urinary System Review PLAY Kidney Function: Urinary System Structure

48. Urine Formation

49. Glomerular Filtration • Nonselective passive process • Water and solutes smaller than proteins are forced through capillary walls • Proteins and blood cells are normally too large to pass through the filtration membrane • Filtrate is collected in the glomerular capsule and leaves via the renal tubule

50. Renal Physiology • The goal of urine production • Is to maintain homeostasis • By regulating volume and composition of blood • Including excretion of metabolic waste products