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Medical Science - Physiology > Kidney Function > Flashcards

Kidney Function Flashcards

1
Q

How many nephrons in the kidneys?

A

2.5 million

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2
Q

What are the three stages of urine formation and where do they occur?

A

Filtration (renal corpuscle)
Reabsorption (convoluted tubule)
Secretion (distal convoluted tubule)

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3
Q

What happens in filtration?

A

Blood pressure forces water and solutes across walls of glomerular capillaries

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4
Q

What happens in reabsorption?

A

Water and solutes removed from filtrate across tubular epithelium into peritubular fluid (fluid surrounding tubule), via diffusion or carrier proteins
Reabsorbed substances eventually reenter blood

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5
Q

What happens in secretion?

A

Solutes transported from peritubular fluid across tubular epithelium into tubular fluid

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6
Q

What is the net filtration rate?

A

Net filtration pressure acting across glomerular membrane, depends on:

  • Glomerular hydrostatic pressure
  • Capsular hydrostatic pressure (acts against)
  • Colloid osmotic pressure (acts against)
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7
Q

What effects the glomerular filtration rate?

A

Renal blood flow

Arteriolar constriction

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8
Q

What is the glomerular filtration rate (GFR)?

A

Amount of filtrate produced by kidneys each minute

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9
Q

What is the structure of the glomerular membrane?

A
  • Endothelial layer of capillary
  • Basement membrane
  • Layer of epithelial cells lining capsule
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10
Q

What is clearance?

A

The volume of plasma passing through the kidneys per unit time to produce the amount of a solute in urine

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11
Q

When does clearance equal the GFR?

A

When a substance is not reabsorbed from urine or secreted into the tubules

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12
Q

How can GFR be accurately measured?

A

Inulin

- An inert polysaccharide not metabolised in the body and neither reabsorbed or secreted by tubules

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13
Q

What is the creatinine clearance test?

A

Compares creatinine level in blood and urine
A value of 100 means kidneys working 100%
(Creatinine elimination per hour/plasma creatinine conc.)

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14
Q

What is countercurrent multiplication?

A

Exchange of substances between descending (thin) and ascending (thick) segments of a nephron

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15
Q

What is the purpose of the countercurrent?

A
  • Effectively reabsorbs water and solutes

- Establishes concentration gradient in peritubular fluid that passively reabsorbs water from collecting ducts

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16
Q

How does the countercurrent work?

A
  • Na and Cl ions actively pumped out from ascending loop
  • Interstitial fluid ion concentration increases
  • Osmotic movement of water out of thin loop
17
Q

How is concentrated urine produced following dehydration?

A
  • Increase in osmotic pressure detected by osmoreceptors in hypothalamus, so ADH produced by pos. pituitary gland
  • ADH increases reabsorption of water in collecting tubules
  • Blood is diluted, osmotic pressure decreases, ADH release decreases
18
Q

What is it called when the body produces a large volume of urine?

A

Diuresis

19
Q

What does ADH do?

A

Increases the permeability of the collecting ducts to water

20
Q

What controls osmolarity?

A

Concentration of sodium, which is controlled by ADH, thirst centre and aldosterone

21
Q

Where is aldosterone produced?

A

Adrenal glands

22
Q

What does aldosterone do?

A

Increases K+ secretion into distal and collecting tubules

23
Q

What is Addison’s disease?

A

Destruction of adrenal gland - Hyperkalaemia

- Cardiac arrhythmias

24
Q

What is the effect of an adrenal gland tumour?

A

Very low blood potassium

  • Failure of nerve transmission due to hyperpolarisation of membranes
  • Hypokalaemia
25
Q

What regulates aldosterone release?

A
  • Extracellular K+ concentration
  • Renin-angiotensin system
  • Body sodium ion concentrations
  • ACTH
26
Q

What is ACTH?

A

Hormone released by ant. pituitary which controls release of aldosterone

27
Q

From where is renin released?

A

Juxtaglomerular apparatus (distal tubule)

28
Q

What does renin do?

A

Converts angiotensinogen (plasma protein from liver) to angiotensin I

29
Q

How is angiotensin I converted to angiotensin II?

A

By convertase enzyme in the lung

30
Q

What does angiotensin II do?

A
  • Stimulates release of aldosterone
  • Vasoconstrictor
  • Stimulates thirst

Medical Science - Physiology (11 decks)

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