URINARY SYSTEMS ,.......... ..........

URINARY SYSTEMS

1. URINARY SYSTEM

2. Learning objectives To outline the renal system; To describe the function of the Urinary System To describe the structure of the Urinary System To describe briefly the processes of urine formation; To describe the renin-angiotensin system; To describe the regulation of potassium , calcium and pH.

3. Introduction The urinary system produces, stores, and excretes urine via a filtration mechanism in which potentially harmful molecules are removed from the body. The Urinary System plays a vital role in maintenance of human wellbeing. Dysregulation of the system can bring about a lot of problem for the patient.

4. Organs of the Urinary system Kidneys Ureters Urinary bladder Urethra Figure 15.1a

5. Functions of the Urinary System Filter . Every day, the kidneys filter gallons of fluid from the bloodstream . Filter blood and remove waste products, toxins, extra water and salt, in the form of urine. 2. Waste processing : The kidneys then process this filtrate, allowing wastes and excess ions to leave the body in urine while returning needed substances to the blood in just the right proportions.

6. 3. Elimination : Although the lungs and the skin also play roles in excretion, the kidneys bear the major responsibility for eliminating nitrogenous wastes, toxins, and drugs from the body.

7. 4. Regulation : The kidneys also regulate the blood’s volume and chemical makeup so that the proper balance between water and salts and between acids and bases is maintained

8. 5. Other regulatory functions : By producing the enzyme renin, they help regulate blood pressure, and their hormone erythropoietin stimulates red blood cell production in the bone marrow . 6.Conversion . Kidney cells also convert vitamin D to its active form. 7. Store and transport urine out of the body through the ureters, bladder and urethra .

9. Location of the Kidneys Against the dorsal body wall At the level of T 12 to L 3 The right kidney is slightly lower than the left Attached to ureters, renal blood vessels, and nerves at renal hilus top of each kidney is an adrenal gland

10. KIDNEY Paired organs in abdominal cavity Held firmly by peritoneum Embedded in fat Solid, dark red & bean shape Below stomach

11. Coverings of the Kidneys Renal capsule Surrounds each kidney Adipose capsule Surrounds the kidney Provides protection to the kidney Helps keep the kidney in its correct location

12. The Internal Anatomy of the Kidneys (cont’d.) Medulla: inner area Renal pyramids: tips point inward Cortex: outer area Cortical material between pyramids Cortex and renal pyramids contain nephrons

13. The Internal Anatomy of the Kidneys

14. The Internal Anatomy of the Kidneys (cont’d.) Nephrons: functional units of the kidney Minor calyx Funnel shaped, collects urine from pyramid ducts Major calyces: formed from minor calyces Join to form renal pelvis Renal pelvis narrows to form ureter

15. Blood and Nerve Supply to the Nephrons (cont’d.)

16. Blood and Nerve Supply to the Nephrons (cont’d.) Renal arteries: transport 1200 mL of blood per minute Interlobar arteries Arcuate arteries Interlobular arteries Afferent arterioles divide into glomerular capillaries

17. Blood Flow in the Kidneys Figure 15.2c

18. Nephrons The structural & functional units of the kidneys Responsible for forming urine Main structures of the nephrons Glomerulus Renal tubule

19. Nephron anatomy

20. Glomerulus A specialized capillary bed Attached to arterioles on both sides (maintains high pressure) Large afferent arteriole Narrow efferent arteriole Figure 15.3c

21. Glomerulus Capillaries are covered with podocytes from the renal tubule The glomerulus sits within a glomerular capsule (the first part of the renal tubule) Figure 15.3c

22. Glomerular (Bowman’s) capsule Proximal convoluted tubule Loop of Henle Distal convoluted tubule Renal Tubule

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

24. Urine Formation Processes Filtration Reabsorption Secretion Figure 15.4

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

26. Reabsorption The peritubular capillaries reabsorb several materials Some water Glucose Amino acids Ions Some reabsorption is passive, most is active Most reabsorption occurs in the proximal convoluted tubule

27. Materials Not Reabsorbed Nitrogenous waste products Urea Uric acid Creatinine Excess water

28. Secretion – Reabsorption in Reverse Some materials move from the peritubular capillaries into the renal tubules Hydrogen and potassium ions Creatinine Materials left in the renal tubule move toward the ureter

29. Formation of Urine Figure 15.5

30. Characteristics of Urine Used for Medical Diagnosis Colored somewhat yellow due to the pigment urochrome (from the destruction of hemoglobin) and solutes Sterile Slightly aromatic Normal pH of around 6 Specific gravity of 1.001 to 1.035

31. Ureters Slender tubes attaching the kidney to the bladder Continuous with the renal pelvis Enter the posterior aspect of the bladder Runs behind the peritoneum Peristalsis aids gravity in urine transport

32. Urinary Bladder Smooth, collapsible, muscular sac Temporarily stores urine Figure 15.6

33. Urinary Bladder Trigone – three openings Two from the ureters One to the urethrea Figure 15.6

34. Urinary Bladder Wall Three layers of smooth muscle (detrusor muscle) Mucosa made of transitional epithelium Walls are thick and folded in an empty bladder Bladder can expand significantly without increasing internal pressure

35. Urethra Thin-walled tube that carries urine from the bladder to the outside of the body by peristalsis Release of urine is controlled by two sphincters Internal urethral sphincter (involuntary) External urethral sphincter (voluntary)

36. Urethra Gender Differences Length Females – 3–4 cm (1 inch) Males – 20 cm (8 inches) Location Females – along wall of the vagina Males – through the prostate and penis

37. Urethra Gender Differences Function Females – only carries urine Males – carries urine and is a passageway for sperm cells

38. The Urinary Bladder and the Micturition Reflex (cont’d.) Micturition: expulsion of urine from bladder External urinary sphincter: voluntary control Bladder capacity 700-800 mL 200-400 mL: conscious of need to urinate Stretch receptors initiate micturition reflex

39. The Urinary Bladder and the Micturition Reflex (cont’d.) During urination Detrusor muscle contracts Muscles of pelvic floor and abdominal wall contract External urinary sphincter relaxes and urine moves from bladder to the outside

40. The Link Between Water and Salt Changes in electrolyte balance causes water to move from one compartment to another Alters blood volume and blood pressure Can impair the activity of cells

41. Maintaining Water Balance Dilute urine is produced if water intake is excessive Less urine (concentrated) is produced if large amounts of water are lost Proper concentrations of various electrolytes must be present

42. Regulation of Water and Electrolyte Reabsorption Regulation is primarily by hormones Antidiuretic hormone (ADH) prevents excessive water loss in urine Aldosterone regulates sodium ion content of extracellular fluid Triggered by the rennin-angiotensin mechanism Cells in the kidneys and hypothalamus are active monitors

43. Developmental Aspects of the Urinary System Functional kidneys are developed by the third month Urinary system of a newborn Bladder is small; urine cannot be concentrated Control of the voluntary urethral sphincter starts until age 18 months Urinary infections are the only common problems before old age

44. Aging and the Urinary System There is a progressive decline in urinary function The bladder shrinks with aging Urinary retention is common in males