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Physiology > Renal- GFR and Clearance > Flashcards

Renal- GFR and Clearance Flashcards

1
Q

main functions of the kidney

A
  1. Regulation of fluid and electrolyte balance
  2. Regulation of plasma osm
  3. Elimination of waste products
  4. production and conversion of hormones
  5. Metabolism (prod of ammonia and gluconeogenesis
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2
Q

Erythropoietin

A

produced in kidney, stimulates RBC production in bone marrow

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3
Q

Role of Vitamin D

A

Converted in renal tubules into active form which has kidney, intestine and bone regulate Ca balance

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4
Q

What are the two types of nephrons?

A
  1. Cortical (superficial)
    1. make up 80%
    2. short loops of Henle
  2. Juxtamedullary (deep)
    1. make up 20%
    2. Long Loops of Henle
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5
Q

How much blood flows to the Kidneys?

A

approx 1 L/min

or 20% of CO

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6
Q

What is the Glomerulus?

A
  • capillary system that filters blood to form the UF of plasma that flows into Bowman’s space
  • Fenestrated endothelium and basement membrane
    • allows filtration but keeps blood cells, proteins and macromolecules out of UF
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7
Q

Podocytes

A
  • the single layer of epithelial cells which surround the glomerulus
  • part of filtration barrier; has a negative charge
    • ​prevents negatively charged proteins from getting through the epithelial barrier and into the UF
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8
Q

Juxtaglomerular apparatus

A
  • located where the distal convoluted tubule returns to its “parent” glomerulus
  • special macula densa cells in the distal convoluted tubule are in contact with the juxtaglomerular cells of the afferent arteriole
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9
Q

Macula densa

A
  • sense tubular fluid flow and Na delivery to the distal nephron.
  • because of their proximity to the afferent arteriole, macula densa cells can regulate renal plasma flow and GFR
  • also participate in release of Renin
  • receive input from SNS through B1 receptors
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10
Q

What are the pressures that determine glomerular filtration?

A
  1. Glomerular capillary hydrostatic pressure
  2. glomerular capillary oncotic pressure
  3. Bowman’s space hydrostatic pressure
  4. Bowman’s space oncotic pressure (typically insignificant because there is little to no protein in bowman’s space)
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11
Q

Net filtration equation

A

Net filtration pressure = (HPGC-HPBS)-πGC

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12
Q

What things can control the afferent and efferent arteriolar resistance?

A
  1. sympathetic nerves
  2. circulating horomones (Ang II)
  3. myogenic regulation
  4. tubuloglomerular feedback signals
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13
Q

What is GFR?

A
  • The benchmark of renal function
  • the volume of plasma (w/o protein and cells) that is filtered across all of the glomeruli in the kidneys, per unit time
  • normal = 100-125 ml/min
    • men have higher GFR than women
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14
Q

GRF equation

calculated using forces

A

GFR = Kf[(HPGC-HPBS) - πGC

Kf = filtration coefficient

HPGC = Glomerular capillary hydrostatic pressure

HPBS = Bowman’s space hydrostatic pressure

πGC = Glomerular capillary oncotic pressure

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15
Q

GFR equation

using Inulin

A

GFR = (Uin x V)/Pin

Uin = urine inulin concentration

V = urine volume/minute

Pin = plasma inulin concentration

*must be 24 hr urine collection

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16
Q

For freely filtered substances:

A
  • the filtered load (amt of substance filtered per unit time) of a substance is equal to the plasma concentration of that substance
    • All of it gets filtered.
  • the urinary excretion of a substance is the urine concentration times the volume of urine produced per unit of time
  • most things are reabsorbed to an extent
    • reabsorption = filtered load - urinary excretion
  • Some things are excreted
    • secretion rate = urinary excretion - filtered load
17
Q

tubuloglomerular feedback (TGF)

A
  • there are arterioles on both ends of the capillary network within the kidneys, allowing for very rapid changes to HPGC
  • The amt of tubular flow through the distal convoluted tubule and macula densa will trigger the afferent arteriole to dilate or constrict, thereby increasing or decreasing blood flow and GFR
18
Q

If the GFR is decreased to 25% of normal, what will happen to the plasma creatinine?

GFR decreased by 50%?

A

normal plasma level x4

normal plasma level x2

19
Q

What causes the release of Renin?

A
  • Baroreceptor
    • increased pressure in afferent arteriole inhibits renin release from JG cells, decreased pressure promotes renin release
  • Sympathetic nerve mechanism
    • B1 nerves stimulate renin release
  • Macula densa mechanism
    • increased NaCl concentration in the distal tubule inhibits renin release; decreased NaCl promotes renin release

Physiology (31 decks)

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