GU1 - Nephrology > Phys 2 > Flashcards

Phys 2 Flashcards

(28 cards)

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1
Q

GFR

  • definition
  • how to measure
A
  • Glomerular filtration rate
  • amount of plasma filtrate formed per minute
  • can be measured by known plasma level of a freely filtered substance and the amt secreted in urine
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2
Q

GFR equation

A

(urine concentration)(urine flow) / (plasma concentration)

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3
Q

What is normal GFR

A

125 mL/min

  • women 10% less than men
  • 7.5 L/h
  • 180 L/d
  • normal urine volume 1 L/d
  • 99% filtrate normally reabsorbed
  • indicator of kidney function
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4
Q

Chronic Kidney Disease Stages

A

1: kidney damage, normal GFR (>90)
2: kidney damage, mild decrease GFR (60-89)
3: moderate decrease GFR (30-59)
4: severe decrease GFR (15-29)
5: kidney failure (<15) or dialysis

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5
Q

Creatinine Clearance

- definition

A
  • volume of plasma that is cleared of creatinine per unit of time
  • creatinine is a metabolic byproduct eliminated by the kidney
  • even though small amount of creatinine is lost through tubular secretion, CrCl is used as a measurement of GFR
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6
Q

What is normal CrCl

A

85-135

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7
Q

where is creatine produced? How is it related to creatinine

A
  • produced by the liver
  • phosphorylated by ATP to form phosphocreatine
  • stored in brain & muscle
  • serves as anaerobic phosphorylation source to create ATP (when ADP is plentiful and need ATP)
  • creatinine is a breakdown product of phosphocreatine
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8
Q

Filtration membrane

  • permeability
  • layers
A
  • highly permeable to water and solutes in kidney
  • function of membrane’s anatomy
  • 3 layers:
    1. Fenestrated capillary endothelium
  1. Visceral membrane of glomerular capsule composed of podocytes
  2. basement membrane fused between 1 & 2
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9
Q

Filtration Membrane

  • capillary pores
  • basement membrane
A
  • pore: prevent passage of RBCs

- BM: restricts proteins > 4nm

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10
Q

Filtration Membrane

- what easily passes through

A 
water
glucose
amino acids
electrolytes
nitrogenous wastes
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11
Q

What are the three pressures that affect glomerular filtration

A
  1. Glomerular hydrostatic pressure (BP): chief force pushing water across filtration membrane (55 mmHg)
  2. glomerular osmotic pressure: pressure of protein in blood (30 mmHg)
  3. capsular hydrostatic pressure (15 mmHg)
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12
Q

What is the net filtration pressure through the glomerular capsule

A

glom. hydrostatic pressure - glom. osmotic pressure + cap. hydrostatic pressure

55 - (30 + 15) = 10 mmHg

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13
Q

How similar are plasma and filtrate?

A

very similar except for protein content in plasma

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14
Q

how similar are urine and filtrate

A

very different

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15
Q

Reabsorption and secretion

A

Reabsorption
- reclaim needed nutrients (glucose, amino acids, etc.)

Secretion
- elimination and pH regulation

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16
Q

where is glucose normal, where is it abnormal

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A
  • normal: filtrate

- abnormal: urine

17
Q

Active transport carriers

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A
  • specific for their solute

- most ATP dependent carriers utilize a co-transporter (often Na+)

18
Q

Tm

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A
  • transport maximum
  • most quantity of a substance that can be absorbed
  • once saturated, no more solutes can be resorbed
  • excess substance is eliminated in urine
19
Q

Tm example

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A

Glucose Tm is 375 mg/min

  • hyperglycemia levels >400 mg/ 100 mL
  • glucose spills into urine (glucosuria)
20
Q

Glucose transport

- transporter

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A
  • SGLT-2: sodium dependent glucose transporter
  • apical membrane of PCT cells
  • Na+ and glucose bind to carrier
  • Na+ moves down concentration gradient along with glucose into cell
  • both solutes are pumped from peritubular lumen to peritubular capillaries (reabsorbed)
21
Q

Sodium reabsorption

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A
  • Na+ single most abundant cation in filtrate
  • 80% of active transport energy moves Na+
  • cotransport usually sodium-potassium pump
22
Q

Location of sodium absorption

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A
  • 65% in PCT
  • 25% in thick ascending limb of Henle
  • 5% in DCT
  • 4-5% in CD
    approx 1% lost in urine
23
Q

What is the primary force that moves water out of the tubules?

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A

osmotic pressure of medullary gradient

- moves water into peritubular capillaries

24
Q

Location of water absorption

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A
  • 65% in PCT
  • 15% in descending loop of Henle
  • 19% DCT and CD (more volume as drop down CD)

** can’t have water follow Na+ because it is being reabsorbed, instead, use concentration of medulla to pull the water out instead

25
What are three things that are not reabsorbed
1. Urea 2. Uric acid 3. Creatinine *mostly nitrogenous waste products from aa and nucleotide metabolism
26
Urea
In liver: - deamination of aa releases NH4+ (toxic) - urea cycle detoxifies ammonia to produce urea - non-toxic, neutral, soluble in water
27
Uric Acid
- breakdown product of purine nucleotide metabolism | - urate is uric acid salt
28
Creatinine
breakdown product of phosphocreatine
GU1 - Nephrology
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