Overview of Renal Physiology Flashcards Preview

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Flashcards in Overview of Renal Physiology Deck (10)
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1

Main physiologic fxn of the kidneys

  • maintenance of composition and volume of extracellular fluid

2

Size of (standard=70kg) bodily fluid compartments

  • Intracellular fluid = contained w/in body cells
    • non-circulating = 24L
    • blood cells = 3L
    • total = 27L
  • extracellular fluid = remaining fluid outside of cells
    • interstitial fluid = 12L
    • plasma = 3L
    • total = 15L

3

Daily water balance volumes (inputs & outputs for 70kg persn)

  • Inputs:
    • ingestion in fluid/food = 2L
    • metabolic processes = 0.5L
    • total = 2.5L
  • Output
    • sweat and feces = 0.1L
    • Respiration, skin "leaks" = 0.9L
    • urine = 1.5L
    • total = 2.5L

4

Main mechanism for regulation of composition of ECF

  • for any given substance, ingestion is generally in excess of incidental loss
  • ECF constancy is acheved b regulating urinary output

5

Nephron characteristics

  • =basic structural unit of the kidney
  • =blood supply + epithelial tube (aka "tubule")
    • blood supply = 2 capillary beds in serious ==> glomerular & peritubular capillaries

6

Major fxnl processes of nephron

  1. glomerular filtration = filter plasma into initial part of tubule ("filtration) ==> allows water, solutes to pass but retains larger mlx
  2. tubular reabsorption = recapture filtered components via membrane transporters ==> just enough ECF components returned to plasma
  3. excretion = regulated substances in excess pass through tubule and are excreted
    1. secretion = blood ==> tubule to achieve balance

7

Renal blood flow (RBF) = 

Renal plasma flow (RPF) =

  • RBF = ~1.3L (25% of CO)
  • RPF (hematocrit=50%) = .65L

8

Filtration fraction = 

Glomerular filtration rate (GFR) =

  • FF = 20% = .2
  • GFR = .2 x 650 ml/min = 130 ml/min
    • =50 gallons/day

9

Renin-angiotensis axis characteristics

  • angiotensin = potent vasopressor hormone
  • decrease in BP ==> increase renal secretion of renin ==> converts agiotensinogen into angiotensin I (AgI) ==> angiotensin converting enzyme converts AgI ==> Angiontensin II (AgII)
  • AgII ==> constriction of arteriolar smooth muscle ==> peripheral resistance ==> increased blood pressure
  • **Renin = rate-limiting for the production of AgII = determines axis activity

10

Approximations of normal values for plasma constituents 

  • Bicarb = 22
  • Cl- = 100
  • Creatinine = 1
  • Osmolality = 290
  • K+ = 4
  • Protein = 7
  • Na+ = 140
  • BUN = 12