Renal

Question 1

functions of the kidney

Answer 1

• regulation of water & electrolyte volume & osmolarity
• excretion of metabolic waste and foreign chemicals
• secretion of hormones
• regulation of acid-base balance

Question 2

structure of the kidney

Answer 2

• bowmans capsule
• proximal convoluted tubule
• loop of henle (descending & ascending limbs)
• distal tubule
• collecting duct

Question 3

excretion equation

Answer 3

excretion = filtration - reabsorption + secretion

Question 4

glomerular filtration barriers

Answer 4

Endothelial fenestrations
- capillary wall
basement membrane
- negative charge
podocytes and slit diaphragm
- lining bowmens capsule

Question 5

filterability of solutes through glomerulus

Answer 5

passive, no selective process

glomerular capillaries are efficient filters
- due to large fenestrations and high hydrostatic pressure driving filtration

small molecules filtered freely
- glucose, Na, amino acids
large molecules get trapped
- proteins, RBC (if in urine = injury)

Question 6

forces acting on glomerular filtration

Answer 6

increase glomerular filtration blood pressure
= increased filtration
increased bowmens capsule pressure (interstitial fluid)
= decrease filtration
increased osmotic pressure (plasma protein)
= decreased filtration

Question 7

control of glomerular capillary pressure

Answer 7

arterial pressure
- increased AP = increased GFR
afferent arterial resistance (diameter)
- increased resistance = decreased GFR
- decreased resistance = increased GFR
efferent arteriole resistance (diameter)
- increased resistance = more blood in glomerulus = increased GFR

Question 8

Transport Maximum

Answer 8

• limit to amount of substance that can be reabsorbed (mg/min)
• due to full saturation of carrier proteins
• eg: diabetes mellitis & glucose transport
• normal filtered load - no glucose in urine
• diabetes - too much filtered so not all glucose can be reabsorbed - glucose in urine

Question 9

The countercurrent multiplier system

Answer 9

Proximal tubule
- always reabsorbs Na and H2O in same proportion
ascending tubule
- NaCl actively transported out
- H2O impermeable
- causes medullary interstitial fluid to be hypertonic
descending tubule
- H2O diffuses out into the hypertonic solution created by the active transport of NaCl
- NaCl impermeable
- keeps occurring until the osmolarity is equal (1400mM)
Collecting ducts
- fluid entering collecting ducts is hypotonic (interstitial fluid is 1400mM)
- allows for fine control of H2O resorption by ADH

Question 10

ADH when hydrated

Answer 10

1) drink lots of water
2) decrease ECF osmolarity
3) osmorecpetors detect
4) decrease aquaporins in collecting duct
5) decrease H2O reabsorption
6) increase H2O excretion

Question 11

ADH when dehydrated

Answer 11

1) dehydrated
2) osmoreceptors
3) increase ADH (& THIRST)
4) increase aquaporins in collecting duct
5) increase H2O reabsorption

Question 12

4 ECF volume and composition receptors

Answer 12

Composition changes

• osmoreceptors - in hypothalamus - trigger release of ADH
• adrenal cortex - zona glomerulosa cells - release aldosterone

Volume changes

• peripheral chemoreceptors
• – baroreceptors - detect pressure change (aortic arch, carotid artery)
• – stretch receptors (atrium, ventricles, pulmonary vessels)
• renal baroreceptors
• – cells of afferent arteriole in JGA region

Question 13

3 factors that control renin release

Answer 13

1) renal baroreceptor
- detects pressure changes
- decrease P = increased renin release from JGA = Na retention
2) sympathetic nerves
- increase SNS activity = increased renin from JGA = Na retention
3) Macula Densa Cells
-