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GU1 - Nephrology > Phys 2 > Flashcards

Phys 2 Flashcards

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

A
  • normal: filtrate

- abnormal: urine

17
Q

Active transport carriers

A
  • specific for their solute

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

18
Q

Tm

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

A

Glucose Tm is 375 mg/min

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

Glucose transport

- transporter

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

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

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?

A

osmotic pressure of medullary gradient

- moves water into peritubular capillaries

24
Q

Location of water absorption

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
Q

What are three things that are not reabsorbed

A
  1. Urea
  2. Uric acid
  3. Creatinine

*mostly nitrogenous waste products from aa and nucleotide metabolism

26
Q

Urea

A

In liver:

  • deamination of aa releases NH4+ (toxic)
  • urea cycle detoxifies ammonia to produce urea
  • non-toxic, neutral, soluble in water
27
Q

Uric Acid

A
  • breakdown product of purine nucleotide metabolism

- urate is uric acid salt

28
Q

Creatinine

A

breakdown product of phosphocreatine

GU1 - Nephrology (16 decks)

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