The document provides an overview of the urinary system, including the anatomy and functions of the kidneys and other components. The kidneys filter blood to remove waste and regulate fluid balance. The nephron is the functional unit of the kidney that filters blood and reabsorbs water and nutrients while secreting wastes. Urine is stored in the bladder and eliminated through the urethra under voluntary control.

1. The Urinary System

2. TABLE OF CONTENT 1) General Introduction 2) Anatomy of Urinary System 3) Urine Formation 4) Urine Storage and Elimination

3. Composition of the Urinary System

4. Functions of the Kidneys 1) filter blood plasma, separate wastes, return useful materials to the blood, and eliminate the wastes. Toxic nitrogenous wastes - ammonia, urea, uric acid, creatine, and creatinine - cause diarrhea, vomiting, and cardiac arrhythmia, convulsions, coma, and death.

5. Functions of the Kidneys 1) filter blood plasma, separate wastes, return useful materials to the blood, and eliminate the wastes. 2) regulate blood volume and osmolarity.

7. ANATOMY OF THE KIDNEYS

8. - The kidneys lie along the posterior abdominal wall

10. Extensions of the cortex ( renal columns ) project toward the sinus, dividing the medulla into 6-10 renal pyramids . Each pyramid is conical with a blunt point called the papilla facing the sinus.

11. The papilla is nestled into a cup called a minor calyx , which collects its urine. Two or three minor calyces merge to form a major calyx . The major calyces merge to form the renal pelvis .

12. - The kidney contains 1.2 million nephrons , which are the functional units of the kidney. - A nephron consists of : i. blood vessels afferent arteriole glomerulus efferent arteriole ii. renal tubules proximal convoluted tubule loop of Henle distal convoluted tubule The Nephron

13. afferent arteriole glomerulus efferent arteriole proximal convoluted tubule distal convoluted tubule Loop of Henle blood blood The Nephron

14. - Most components of the nephron are within the cortex. The Nephron

15. Nephrons are connected to renal artery/vein and ureter.

16. The glomerulus is enclosed in a two-layered glomerular (Bowman's) capsule. Proximal tubule

17. URINE FORMATION

18. The kidney produces urine through 4 steps.

19. Glomerular Filtrate Tubular fluid Urine

20. 1) Glomerular Filtration

21. The Filtration Membrane From the plasma to the capsular space, fluid passes through three barriers. fenestrated epithelium basement membrane foot processes

22. The Filtration Membrane Almost any molecule smaller than 3 nm can pass freely through the filtration membrane into the capsular space. These include: Water, electrolytes, glucose, amino acids, lipids, vitamins, and nitrogenous wastes Kidney infections and trauma commonly damage the filtration membrane and allow plasma proteins or blood cells to pass through.

23. Blood cells in urine Plasma proteins

24. Filtration Pressure Glomerular filtration follows the same principles that govern filtration in other capillaries.

28. The nephron has two ways to prevent drastic changes in GFR when blood pressure rises: 1) Constriction of the afferent arteriole to reduce blood flow into the glomerulus 2) Dilation of the efferent arteriole to allow the blood to flow out more easily. Change in an opposite direction if blood pressure falls

32. 1) Glomerular Filtration 2) Tubular Reabsorption 3) Tubular Secretion 4) Concentrating Urine by Collecting Duct

33. About 99% of Water and other useful small molecules in the filtrate are normally reabsorbed back into plasma by renal tubules.

34. Reabsorption in Proximal Convoluted Tubules

35. - The proximal convoluted tubule (PCT) is formed by one layer of epithelial cells with long apical microvilli. - PCT reabsorbs about 65% of the glomerular filtrate and return it to the blood.

36. 1) transcellular route 2) paracellular route Routes of Proximal Tubular Reabsorption PCT peritubular capillary

37. Mechanisms of Proximal Tubular Reabsorption 1) Solvent drag 2) Active transport of sodium. 3) Secondary active transport of glucose, amino acids, and other nutrients. 4) Secondary water reabsorption via osmosis 5) Secondary ion reabsorption via electrostatic attraction 6) Endocytosis of large solutes

38. Osmosis Water moves from a compartment of low osmolarity to the compartment of high osmolarity. low osmolarity ( high H 2 O conc.) high osmolarity ( low H 2 O conc.) H 2 O

40. 2) Active transport of sodium Sodium pumps ( Na-K ATPase ) in basolateral membranes transport sodium out of the cells against its concentration gradient using ATP. capillary PCT cell Tubular lumen Na + Na + K +

41. There are also pumps for other ions capillary PCT cell Tubular lumen Ca ++ Ca ++

42. - Various cotransporters can carry both Na+ and other solutes. For example, the sodium-dependent glucose transporter (SDGT) can carry both Na+ and glucose. 3) Secondary active transport of glucose, amino acids, and other nutrients Na + Glucose capillary PCT cell Na + K +

43. Amino acids and many other nutrients are reabsorbed by their specific cotransporters with sodium. Na + capillary PCT cell amino acids 3) Secondary active transport of glucose, amino acids, and other nutrients Na + K +

44. Sodium reabsorption makes both intracellular and extracellular fluid hypertonic to the tubular fluid. Water follows sodium into the peritubular capillaries. 4) Secondary water reabsorption via osmosis H2O Na + Na + capillary PCT cell Tubular lumen

45. Negative ions tend to follow the positive sodium ions by electrostatic attraction. 5) Secondary ion reabsorption via electrostatic attraction Na Na + Cl - capillary PCT cell Tubular lumen

46. The glomerulus filters a small amount of protein from the blood. The PCT reclaims it by endocytosis , hydrolzes it to amino acids, and releases these to the ECF by facilitated diffusion. 6) Endocytosis of large solutes protein capillary PCT cell Tubular lumen amino acids

48. Glucose in urine high glucose in blood high glucose in filtrate Exceeds Tm for glucose

49. Reabsorption in the Nephron Loop

50. - The primary purpose is to establish a high extracellular osmotic concentration. - The thick ascending limb reabsorbs solutes but is impermeable to water. Thus, the tubular fluid becomes very diluted while extracellular fluid becomes very concentrated with solutes. mOsm/L

51. The high osmolarity enables the collecting duct to concentrate the urine later.

52. Reabsorption in Distal Convoluted Tubules

56. 1) Glomerular Filtration 2) Tubular Reabsorption 3) Tubular Secretion 4) Concentrating Urine by Collecting Duct

58. 1) Glomerular Filtration 2) Tubular Reabsorption 3) Tubular Secretion 4) Concentrating Urine by Collecting Duct

60. 1. Driving force The high osmolarity of extracellular fluid generated by NaCl and urea , provides the driving force for water reabsorption. 2. Regulation The medullary portion of the CD is not permeable to NaCl but permeable to water , depending on ADH. Cortex mOsm/L medulla urine

61. a. In a state of full hydration , antidiuretic hormone (ADH) is not secreted and the CD permeability to water is low, leaving the water to be excreted. Cortex mOsm/L medulla Control of Urine Concentration depends on the body's state of hydration. urine b. In a state of dehydration , ADH is secreted; the CD permeability to water increases. With the increased reabsorption of water by osmosis, the urine becomes more concentrated.

62. Cortex medulla urine No more reabsorption after tubular fluid leaving CD urine

64. Substance Blood Plasma (total amount) Urine (amount per day) Urea 4.8 g 25 g Uric acid 0.15 g 0.8 g Creatinine 0.03 g 1.6 g Potassium 0.5 g 2.0 g Chloride 10.7 g 6.3 g Sodium 9.7 g 4.6 g Protein 200 g 0.1 g HCO 3 - 4.6 g 0 g Glucose 3 g 0 g

69. Diabetes insipidus - is caused by inadequeate ADH secretion. - Due to the shortage of ADH, water reabsorption in CD is compromised, leading to polyuria.  urine

70. Diuresis refers to excretion of large amount of urine. Natriuresis refers to enhanced urinary excretion of sodium

71. Diuretics - are chemicals that increase urine volume. They are used for treating hypertension and congestive heart failure because they reduce overall fluid volume. - work by either increasing glomerular filtration or reducing tubular reabsorption. Caffeine falls into the former category; alcohol into the latter (alcohol suppresses the release of ADH).

72. Many diuretics produce osmotic diuresis by inhibiting sodium reabsorption

73. Renal Function Tests

76. Hemodialysis artificially clearing wastes from the blood

77. 1) Dialysis machine - efficient - inconvenient

78. 2) Continuous ambulatory peritoneal dialysis (CAPD) Dialysis fluid - The peritoneal membrane is a natural dialysis membrane - convenient - less efficient

79. Urine Storage and Elimination

80. The Ureters The ureters are muscular tubes leading from the renal pelvis to the lower bladder.

81. The Urinary Bladder - is a muscular sac on the floor of the pelvic cavity. - is highly distensible and expands superiorly.

82. The openings of the two ureters and the urethra mark a triangular area called the trigone on the bladder floor.

83. The Urethra - conveys urine from the urinary bladder to the outside of the body. Females male 3-4 cm ~18 cm greater risk of urinary tract infections

85. In both sexes: - internal urethral sphincter- under involuntary control. - external urethral sphincter - under voluntary control internal urethral sphincter external urethral sphincter

86. Voiding Urine in infants micturition reflex When the bladder contains about 200 ml of urine, stretch receptors in the wall send impulses to the spinal cord. Parasympathetic signals return to stimulate contraction of the bladder and relaxation of the internal urethral sphincter. Spinal cord

87. 2. Once voluntary control has developed, emptying of the bladder is controlled predominantly by a micturition center in the pons. This center receives signals from stretch receptors and integrates this information with cortical input concerning the appropriateness of urinating at the moment. It sends back impulses to stimulate relaxation of the external sphincter. Once voluntary control has developed, emptying of the bladder is controlled predominantly by a micturition center in the pons. This center receives signals from stretch receptors and integrates this information with cortical input concerning the appropriateness of urinating at the moment. It sends back impulses to stimulate relaxation of the external sphincter. Voiding Urine in adults Voluntary control

88. SUMMARY 1) General Introduction 2) Anatomy of Urinary System 3) Urine Formation 4) Urine Storage and Elimination