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  1. Each human kidney has about 1-1.3 million nephrons.
  2. The human PCT is about 15 mm long, DCT is about 5 mm long and collecting ducts are 20 mm long.
  3. Glomerulus- tuft of capillaries where filtration occurs. Formed from Afferent & efferent arteriole
  4. Bowman's capsule- surrounds glomerulus, collects filtrate
  5. Proximal convoluted tubule: brush border, leaky tight junction, rich in mitochondria & carbonic anhydrase. Reabsorbs 70-85% Na+,Cl-,HCO3- & Water.100% of glucose, K+ & amino acids.
  6. Loop of Henle : Ascending & descending limbs.
  7. Distal convoluted tubule : no brush border, forms macula densa
  8. Collecting duct- P & I cells(acid secretion), adjusts volume & concentration of urine
  9. Glomerulus has large pores(4-8 nm)also has sialoproteins in basement membrane –vely charged repel protein & prevent their filtration, allowing filtration of large volumes of fluid
  10. Number of nephrons declines with age, to about 50% at age 60; this causes the GFR to drop to 50% of value in a young person
  11. Kidney receives 1.2-1.3 L/min blood (25% of cardiac output) at rest.
  12. Normal GFR is 125ml/min or 180L/day.
  13. Net filtration pressure (PUF) is 10 mmHg.
  14. Renal plasma flow is measured by p-amino hippuric acid(PAH).
  15. Mesangial cells do not form filtration barrier.
  16. Electrolytes such as sodium (Na+), and small organic compounds such as glucose, inulin are freely filterd (filterability =- 1)
  17. Myoglobin and albumin are not filtered
  18. Negatively charged large molecules are filtered less easily than positively charged molecules of equal molecular size.
  19. Inulin is the standard substance and extensively used to measure GFR.
  20. Juxtaglomerular Apparatus: 1)Juxtaglomerular cells – modified smooth muscle cells in tunica media of the afferent arteriole. Contain renin. Act as volume receptors 2) Macula Densa cells : formed by DCT. Act as Na+ sensor 3) Lacis or mesengial cells : contractile, secrete chemicals.
  21. Renin : Decreased by increase afferent arteriolar pressure, ADH, increased Naat Macula Densa Increased by inc sympathetic activity, shock, catecholamines, PGs, low sodium
  22. Renal vasodilation : Dopamine, PGs, Ach, High protein diet
  23. Renal vasoconstriction: angiotensin II (efferent more than afferent arteriole), NE (opposite)
  24. Renal clearance: it is a measurement of the renal excretion ability, it is given by UV/P
  25. U = urinary conc. of a substance   V= urine flow rate in ml/min                              P= plasma conc. of a substance
  26. If renal clearance is more than GFR- tubular secretion, If renal clearance is less than GFR -tubular reabsorption., If no sec and no reabsorption then Clearance = GFR (inulin)
  27. Transport maximum TmG for glucose in normal adult is 375 mg/min., Renal threshold is 180-200 mg%
  28. Water reabsorption in DCT- early part of distal tubular is impermaeable to water. Late part of DCT becomes permeable under the influence of ADH.
  29. The segments of nephron that are impermeable to water: thin ascending limb, thick ascending limb, 1st part of distal tubule (DCT)
  30. Hyperosmolarity is due to high Na+ , K+, Cl- & Urea in renal medulla.
  31. Acidification of tubular fluid starts in distal nephron, maximum the collecting duct (CD), but maximum secretion of acid in PCT (pH remain unchanged due to buffers in PCT , like bicarbonate, phosphate and ammonia (from glutamine)
  32. Concentration of urine depends on the action of ADH and Counter current system.
  33. The minimum volume of urine necessary to remove all products is 500 ml/day and is called obligatory volume.
  34. The amount of protein in urine is normally less than 100 mg/day.
  35. First urge to void is felt at a bladder volume of 150 ml and a marked sense of fullness at about 400mL in adult the volume of urine that normally initiates a reflex contraction is about 300­-400mL
  36. Concentration and dilution of urine i.e free water and osmotic clearances is regulated by anti diuretic hormone (ADH).
  37. The only physiological stimulus for erythropoietin secretion is hypoxia or decreased partial pressure of oxygen.
  38. Erythropoietin is a plasma protein that act as a hormone. It's a major regulator of human erythropoiesis.
  39. Vasopressin acts by increasing permeability of collecting ducts to water. itopens aquaporin-2 via V2 receptors increasing cAMP.
  40. Anion Gap- Represents unmeasured anions in plasma
  41. High anion gap - lactic acidosis, diabetic ketoacidosis, alcoholic ketoacidosis, starvation, renal failure.
  42. Non- anion gap- Diarrhoea, uretero sigmoidostomy. Normal level of creatinine in serum is 0.6 to 1.2 mg%

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