Week 6: Kidney Histo Flashcards
What are the largest collecting ducts in the kidney called?
Papillary ducts
Minor calyx epithelium type
Transitional
Where is transitional epithelium found?
Unique to urinary system. Found in minor and major calyx, ureter, bladder, (+prostatic urethra in males)
What are the “basketball-like) structures in the lobules?
Renal corpuscles
Where in the kidney are arcuate vessels found?
Between the cortex and medulla
What are the components of a nephron?
Renal corpuscle/glomerulus + proximal convoluted tubule + Loop of Henle + distal convoluted tubule
What structures make up medullary rays?
Ascending and descending Loops of Henle + collecting tubule
What is the vasa recta?
A loop of capillaries that lies parallel to the Loop of Henle
What makes up the glomerulus?
Entirely arterial vascular apparatus with afferent and efferent arterioles
What are podocytes?
Cells that make up the visceral layer of Bowman’s capsule. They have primary and secondary processes that interdigitate to form slit pores.
What composes the glomerular basement membrane?
Fusion of secondary processes of podocyte with endothelial cells.
How can the macula densa be recognized?
Closely packed cells in distal tubule with Golgi apparatuses are on the opposite side of the cell, away from the lumen.
What does the macula densa do?
Senses NaCl concentration. When low -> release of renin by juxtaglomerular cells + vasodilation of afferent glomerular arterioles which increases GFR
What regulates the flow of particles across the GBM?
Size of capillary pore + heparan sulfate’s highly negative charge.
Which collagen type makes up the lamina densa of the GBM?
4
Mesangial cell function
GBM constantly getting plugged up. Mesangial cells clean out and turn over the GBM (and support it)
What makes up the bulk of the cortex?
Proximal tubules
How can proximal tubules be identified histologically?
Fuzzy/brush luminal border. Most eosinophilic tubule type, interdigitation via lateral membrane folding, mitochondria in cytoplasmic folds -> striated appearance
What is the role of apical canaliculi? Where are they?
Proximal tubules. Resorption of proteins from the initial filtrate.
Proximal convoluted tubule and thick segment of descending limb epithelium type
Cuboidal
Thin segment (distal portion of desc LoH) epithelium type
Simple squamous
Vasa recta descending and ascending component names
Arterioli recti and veni recti respectively
Distal straight tubule epithelium type
Simple cuboidal
How are distal straight tubules recognizable histologically?
Less eosinophilic and larger lumen than prox tub. Cleaner apical and lateral borders. More nuclei around circ of tubules. Basal memb folds & mitochondria.
Which component of the kidney is sensitive to ADH?
Distal convoluted tubules
Collecting tubule epithelium type
Cuboidal to low columnar
What are the two cell types for collecting tubules, and what do they do?
Light (CD): respond to ADH. Dark (IC/intercalated): adjust pH (alpha -> H+ prod and release to urine, beta -> bicarbonate)
Where are juxtaglomerular cells found?
Wall of afferent (and occasionally efferent) arterioles at vascular pole
Juxtaglomerular cell function
Release renin, maintenance of normal blood pressure
Angiotensin II activity
Constriction of arterioles and stimulates release of aldosterone from adrenal cortex
What does aldosterone do? Where is its site of action?
Acts on distal tubules to increase Na and water reabsorption -> inc BP
Inferior capillary network via vasa recta - what do the midcortical and supra regions have?
Much shorter loops that for the peritubular network
Nerve supply of kidney
Sympathetic -> contraction of vasc smooth muscle.
Result of sympathetic activity in kidney
Contraction. In afferent arteriole -> dec filtration rate. Opposite in efferent.
Effect of loss of kidney nerve supply
Increased urinary output. Innervation is not functionally necessary.
What layers make up the ureter?
Mucosa (submucosa indistinguishable) - muscular coat - adventitia.
Ureter epithelium
transitional
Stellate cross-section suggestive of…
Ureter cross section
Smooth muscular pattern in ureter
inner longitudinal, outer circular
Layers of urinary bladder and how they compare to the ureter
Same layers but has 3 muscular layers that go spiral - longitudinal - circular.
