Excretory System (sometimes called Urinary System)

1. Excretory System(sometimes called Urinary System) Function and Parts http://www.youtube.com/watch?v=chhNaLi9P3E

2. Body Water Balance • Drinking & eating provides water • Kidney conserves water so output = intake

3. Why is excretion necessary? • In order for cells to stay alive, they must continually intake water and other molecules. • The cells would continue to get bigger and bigger if they only took in molecules • They must also export molecules • These molecules may be important signaling molecules such as hormones, or they may be molecules of glucose on their way to other cells, or they may be waste products of cellular metabolism that cells need to dispose.

4. Waste Products • Carbon dioxide – a waste product of cellular respiration is dumped into the blood stream and eventually removed by the lungs • Ammonia (NH3) is removed by dissolving in water • This waste comes from the cell’s breakdown of old proteins • In these high physiological concentrations, it is poisonous to the cells and must be removed

5. Removal of Ammonia • Once excreted into the blood stream by cells, it is carried to the liver where it is converted from ammonia into urea which is much less toxic • It is then carried from the liver to the kidneys where it is removed

6. The Job of the Kidneys • They are responsible for cleaning the blood by removing metabolic wastes, excess solutes, and excess water and excreting them as urine • Besides removing urea, it also removes excess salts or glucose, the remnants of drugs (rationale for urine tests), and excess water.

7. Regulation of Water Levels • If the blood becomes too dilute or too concentrated with solutes, then it can interfere with normal cellular activity. • The kidneys are able to regulate water concentration in the blood by removing excess water if the blood is too dilute, or conserving water in the blood if it is not dilute enough

8. Kidney Functions • Filter 200 liters of blood daily, allowing toxins, metabolic wastes, and excess ions to leave the body in urine • Regulate volume and chemical makeup of the blood • Maintain the proper balance between water, electrolyte salts, and acids and bases

9. Other kidney functions • Gluconeogenesis during prolonged fasting • Production of rennin to help regulate blood pressure and erythropoietin to stimulate RBC production • Activation of vitamin D

10. The Hard-working Kidneys • The two kidneys in the body receive between 180 – 220 liters of blood per day – about the volume of a car! • Because the body has only about 5.0 - 5.6 liters of blood, your blood runs through the kidneys to be cleaned about once every four minutes.

13. Kidney Location and External Anatomy

14. The Kidney http://youtube.com/watch?v=glu0dzK4dbU&feature=related

15. The Kidney

16. The Kidney http://www.youtube.com/watch?v=vEXx5YLcGmQ&feature=related

17. The nephron The nephron is the functional unit of the kidney Each region is composed of cells suited to perform specific transport functions Distal convoluted tubule Proximal convoluted tubule Collecting duct Ascending thin limb of loop of Henlé Ascending thick limb of loop of Henlé

18. The Kidney

19. Structure of the Bowman’s (glomerular) capsule Parietal layer of glomerular capsule Afferent arteriole Juxtaglomerular cell Capsule space Efferent arteriole Proximal convoluted tubule Endothelium of glomerulus Podocyte Pedicel http://www.youtube.com/watch?v=_XL_uxFseYQ&feature=related

20. Formation of Urine • The kidneys filter the body’s entire plasma volume 60 times each day • The filtrate: • Contains all plasma components except protein • Loses water, nutrients, and essential ions to become urine • The urine contains metabolic wastes and unneeded substances

21. Formation of Urine • If there is too much water in the blood, then it is removed and put in urine. • If there is not enough water in the blood, the kidneys will not remove any. • If there is too much urea or other solutes in the blood, the kidneys will remove these excess solutes. • By regulating solute numbers and water volume, the kidneys normally maintain homeostasis in blood solute concentration.

22. Mechanisms of Urine Formation • Urine formation and adjustment of blood composition involves three major processes • Glomerular filtration • Tubular reabsorption • Secretion

23. Nephron Recycling: Overview

24. Water Reabsorption in Descending Loop of Henle • Countercurrent multiplier exchange • Medullary osmotic gradient • H2OECFvasa recta vessels

25. Factors that affect kidney function • Antidiuretic hormone (ADH) – prevents excess water loss from kidneys • Alcohol – inhibits secretion of ADH = more urine volume, leading to dehydration • Aldosterone – prevents excess loss of sodium and water from kidneys • Caffeine – increases rate of salt and water loss from kidneys • Increased blood pressure – increase rate of water loss from kidneys.

26. Chronic kidney disease Normal kidneys Kidneys beyond help! End-stage kidneys

27. 25 The Urinary System Part B

28. Tubular Reabsorption • All organic nutrients are reabsorbed • Water and ion reabsorption is hormonally controlled • Reabsorption may be an active (requiring ATP) or passive process

29. Sodium Reabsorption: Primary Active Transport • Sodium reabsorption is almost always by active transport • Na+ enters the tubule cells at the luminal membrane • Is actively transported out of the tubules by a Na+-K+ ATPase pump

30. Sodium Reabsorption: Primary Active Transport • From there it moves to peritubular capillaries due to: • Low hydrostatic pressure • High osmotic pressure of the blood • Na+ reabsorption provides the energy and the means for reabsorbing most other solutes

31. Osmotic Gradient in the Renal Medulla

32. Loop of Henle: Countercurrent Multiplier • The descending loop of Henle: • Is relatively impermeable to solutes • Is permeable to water • The ascending loop of Henle: • Is permeable to solutes • Is impermeable to water • Collecting ducts in the deep medullary regions are permeable to urea

33. Loop of Henle: Countercurrent Exchanger • The vasa recta is a countercurrent capillary exchanger that: • Maintains the osmotic gradient • Delivers blood to the cells in the area

34. Loop of Henle: Countercurrent Mechanism Figure 25.14

35. Formation of Dilute and Concentrated Urine Figure 25.15a, b

36. Diuretics • Chemicals that enhance the urinary output include: • Any substance not reabsorbed • Substances that exceed the ability of the renal tubules to reabsorb it • Substances that inhibit Na+ reabsorption

37. Diuretics • Osmotic diuretics include: • High glucose levels – carries water out with the glucose • Alcohol – inhibits the release of ADH • Caffeine and most diuretic drugs – inhibit sodium ion reabsorption • Lasix and Diuril – inhibit Na+-associated symporters

38. Renal Clearance • The volume of plasma that is cleared of a particular substance in a given time • Renal clearance tests are used to: • Determine the GFR • Detect glomerular damage • Follow the progress of diagnosed renal disease

39. Renal Clearance Calculations RC = UV/P RC = renal clearance rate U = concentration (mg/ml) of the substance in urine V = flow rate of urine formation (ml/min) P = concentration of the same substance in plasma

40. Chemical Composition of Urine • Urine is 95% water and 5% solutes • Nitrogenous wastes include urea, uric acid, and creatinine • Other normal solutes include: • Sodium, potassium, phosphate, and sulfate ions • Calcium, magnesium, and bicarbonate ions • Abnormally high concentrations of any urinary constituents may indicate pathology

41. Micturition (Voiding or Urination) • The act of emptying the bladder • Distension of bladder walls initiates spinal reflexes that: • Stimulate contraction of the external urethral sphincter • Inhibit the detrusor muscle and internal sphincter (temporarily) • Voiding reflexes: • Stimulate the detrusor muscle to contract • Inhibit the internal and external sphincters

42. Kidney dissection • http://www.youtube.com/watch?v=JBsUUYZKAlU&feature=related • http://www.youtube.com/watch?v=YnU6REgJU74&feature=related • http://www.youtube.com/watch?v=AU-CGGzcSRg&feature=related