Structural Basis of Kidney Function Flashcards

1
Q

State some endocrine functions of the kidneys.

A

Production of erythropoietin
Hydroxylation of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol by 1 alpha hydroxylase (in other words: production of calcitriol)
Activation of the renin-angiotension system by secreting renin

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2
Q

What is the renal corpuscle?

A

The glomerulus and bowman’s capsule

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3
Q

Describe some features of the glomerulus.

A

The capillaries are fenestrated. There is a specialised basal lamina that filters the blood.

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4
Q

State the five stages of urine production.

A
Ultrafiltration 
Selective Reabsorption
Creation of hyper-osmotic ECF
Adjustment of ion concentration in urine 
Final adjustments of urine concentration
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5
Q

Where does most reabsorption take place?

A

Proximal convoluted tubule (70% reabsorbed)

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6
Q

State some features of the proximal convoluted tubule.

A

Larger diameter than the distal convoluted tubule
Brush border
Abundant mitochondria
CUBOIDAL epithelium sealed with tight junctions
Aquaporins
Basolateral interdigitations

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7
Q

What mechanism creates the hyperosmotic extracellular fluid?

A

Countercurrent mechanism

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8
Q

Describe features of the descending and ascending limbs of the loop of Henle.

A
Descending
Thin, squamous epithelium 
Permeable to water 
Ascending
Thick, cuboidal epithelium
Few microvilli
Prominent mitochondria (for active transport of ions) 
Na+ and Cl- are pumped out into the ECF
Water impermeable
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9
Q

State some features of the distal convoluted tubule. Which features are different from the proximal convoluted tubule?

A

Smaller diameter than the proximal convoluted tubule
Few microvilli
Numerous mitochondria
Complex lateral membrane interdigitations
Adjusts Na+, K+, H+ and NH4+ under the influence of aldosterone
Macula densa cells

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10
Q

What is the role of the collecting duct?

A

Final adjustment of urine concentration

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11
Q

Which transporters are involved in the movement of water into the cell via the apical membrane and out of the cell via the basolateral membrane?

A

Aquaporin 2 - apical membrane

Aquaporin 3 - basolateral membrane (not affected by vasopressin)

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12
Q

What type of epithelium do the calyces and the renal pelvis have and what are its properties?

A

Urothelium - resistant to urine, ability to stretch, low permeability

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13
Q

What does the juxtaglomerular apparatus respond to? What does it do?

A

Macula Densa - detects NaCl concentration
Juxtaglomerular Cells - detect stretch in afferent arterioles (renal perfusion pressure)
Leads to secretion of renin resulting in angiotensin II production

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