Biochemistry Renal Function Flashcards Preview

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Flashcards in Biochemistry Renal Function Deck (31)
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1
Q

• Glomerular function tests

A

o Urea
o Creatinine
o eGFR

2
Q

Functions of the kidney

A

Excretion of metabolic waste products
Water and solute homeostasis
Synthetic activity

3
Q

Synthetic activity of the kidney

A
  • Renin
  • 1,25 (OH)2 vit D
  • Erythropoietin
4
Q

Inulin

A

gold standard renal function test

5
Q

Glomerular filtration Rate (GFR) Definition

A

The quantity of glomerular filtrate formed each minute in all nephrons of both kidneys

6
Q

GFR depends

A
  • Number of functioning nephrons
  • Glomerular function (acute)
  • Intra-capillary pressure (shock)
  • Tubular luminal pressure (BPH – outflow block)
7
Q

Proximal Tubule:

A

• Bulk reclamation of solutes
o 70% Na, K, Ca, Cl
o 100% HCO3-, Glucose, Urate, Amino Acids
• Isosmotic reabsorption of water (70%)

8
Q

High glycosuria: 2 causes

A
  1. Renal glomerular disease - High glucose blood levels

2. Renal tubular disease - Defect in renal

9
Q

Counter-current multiplication →

A
  • Active
  • Loop of Henle
  • Dilutes urine
  • Generates hypertonic medulla
10
Q

Counter-current exchange →

A
  • Passive

* Distal tubule and collecting duct

11
Q

Distal Tubule

A

• Homeostatic solute adjustment
→ Sodium – hydrogen exchange
→ Sodium – potassium exchange
• Isosmotic water reabsorption

12
Q

Renin-aldosterone system: Triggers

A

Low arterial pressure (via carotid sinus detection)
Low sodium intake
Low renal blood flow
High potassium –promotes sodium potassium exchange (potassium excretion)

13
Q

Renin-aldosterone system: Detection of stimuli at

A

Kidney – juxtaglomerular apparatus

14
Q

Renin-aldosterone system: Triggers release of

A

Renin

15
Q

Renin-aldosterone system: Renin pathway

A

Renin substrate stimulates Angiotensin I (inactive)

Angiotensin I stimulates Angiotensin II release

16
Q

Renin-aldosterone system: Angiotensin II action

A

Stimulates thirst
Causes Vasoconstriction
Aldosterone secretion

17
Q

Renin-aldosterone system: Vaso-constriction causes

A

Increased perfusion pressures

18
Q

Renin-aldosterone system:Aldosterone action

A

Renal sodium and water retention

19
Q

Renin-aldosterone system: Aldosterone secretion

A

High potassium

Angiotensin I

20
Q

Renin-aldosterone system: Inhibition of R-A-A

A

Increased perfusion pressure

21
Q

Antidiuretic Hormone: Stimulants

A
  • Drugs e.g. opiates, chlorpropamide
  • Stress e.g. pain and nausea
  • Decreased blood volume (stretch receptors and baroreceptors)
  • Increased plasma osmolality
22
Q

Antidiuretic Hormone: Stimulants act on the

A

• Hypothalamus – Supra-optic and Para-ventricular nuclei

23
Q

Antidiuretic Hormone: Stimulant of hypothalamus

A

ADH release

24
Q

Antidiuretic Hormone: ADH action on the kidney

A

Increased water permeability

Causing increased water reabsorption and decreased plasma osmolality (negative feedback)

25
Q

Antidiuretic Hormone: Relying on ADH solely?

A

Reabsorb water and cause hyponatraemia – decreases osmolaity

26
Q

Urea – breakdown of proteins increases

A

o Poor nutrition = urea is low (conserve proteins)

o Gastrointestinal bleed – urea increases as globulin presence and so urea increases

27
Q

Glomerular Function Tests →

A

Serum creatinine concentration proportional to 1/GFR

28
Q

Direct estimates of GFR:

A

Measured Creatinine Clearance

CCL = Urine [creatinine] x (Urine volume/collection time)
Serum [creatinine]

29
Q

Indirect estimates of GFR:

A

eGFR

30
Q

eGFR

A

Creatinine production rate is related to muscle mass, which can be estimated from age and sex

31
Q

eGFR

A

1.86 x (serum [creatinine] x 0.0113) -1.154 x age (age) -0.203

  • x 0.742 if female
  • x 1.21 if African

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