Structural Basis of Kidney Function Flashcards
State some endocrine functions of the kidneys.
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
What is the renal corpuscle?
The glomerulus and bowman’s capsule
Describe some features of the glomerulus.
The capillaries are fenestrated. There is a specialised basal lamina that filters the blood.
State the five stages of urine production.
Ultrafiltration Selective Reabsorption Creation of hyper-osmotic ECF Adjustment of ion concentration in urine Final adjustments of urine concentration
Where does most reabsorption take place?
Proximal convoluted tubule (70% reabsorbed)
State some features of the proximal convoluted tubule.
Larger diameter than the distal convoluted tubule
Brush border
Abundant mitochondria
CUBOIDAL epithelium sealed with tight junctions
Aquaporins
Basolateral interdigitations
What mechanism creates the hyperosmotic extracellular fluid?
Countercurrent mechanism
Describe features of the descending and ascending limbs of the loop of Henle.
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
State some features of the distal convoluted tubule. Which features are different from the proximal convoluted tubule?
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
What is the role of the collecting duct?
Final adjustment of urine concentration
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?
Aquaporin 2 - apical membrane
Aquaporin 3 - basolateral membrane (not affected by vasopressin)
What type of epithelium do the calyces and the renal pelvis have and what are its properties?
Urothelium - resistant to urine, ability to stretch, low permeability
What does the juxtaglomerular apparatus respond to? What does it do?
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
