55-140 Lecture Notes - Microvillus, Brush Border, Mesothelium
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Published on 1 Feb 2013
School
Department
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Professor
Renal Histology--Dintzis
GROSS ANATOMY
- Kidney cortex: contains distinctive glomeruli, convoluted tubules, parts of
collecting ducts
- Kidney medulla: below the cortex, contains limbs of Henle & collecting ducts
- Medullary ray: groups of collecting ducts that extend from cortex to medulla
- Calyx: terminal expansions of ureter in the kidney, minor calyces meet up with
papilla (papilla → minor calyx → major calyx → pelvis → ureter)
- Papilla: termination of collecting duct into a minor calyx
- Lobe: a medullary pyramid and the overlying cortex
- Lobule: lateral borders marked by medullary rays
- Arteries in order: abdominal aorta, renal artery, interlobar, arcuate, interlobular,
intralobular, afferent arteriole, glomerulus, efferent arteriole, vasa recta
RENAL CORPUSCLE
-Renal corpuscle: glomerulus + Bowman’s capsule
-Glomerulus: tufts of capillaries with fenestrated (“holey”) endothelium
-Parietal Epithelium: squamous pariental epithelium of Bowman’s capsule
that’s continuous w/ epithelium of proximal tubule
-Visceral Epithelium: composed of podocytes
-Podocytes: easily seen at border of glomerulus, obvious under EM, have
filtration slits that act as filtration barrier; Fxn: manufacture basement
membrane, provide filtration support
-Mesangial cells: produce & breakdown basement membrane; uptake
macromolecules; can respond to local injury; embedded in mesangial
substance (stains bright purple/blue—PAS-positive)
-Basement membrane: very thick (3500A), PAS-positive, trilaminar (lamina
rara interna, lamina densa, lamina rara externa), primary glomerular filtration
barrier
oContains type IV collagen, glycoproteins, & proteoglycans
* Blood must pass through 1) endothelium, 2) basement membrane, 3) podocyte
feet, before entering bowman’s space
TUBULES
Cortical nephrons—shorter loops, common
Corticomedullary nephrons—less numerous, long loops, key in establishing gradient
-Proximal convoluted tubule: longest thickest tubule, reabsorbs ~80% H2O
& salts as well as all Glu, aa, & proteins; secretes organic cations/anions
oProminent brush border of microvilli for reabsorption (PAS+)
oTall columnar cells w/ interdigitation of cell surfaces
omany mitochondria arranged perpendicular to basement membrane
-Descending Thick Limb of Henle: sim. to proximal convoluted tubule
-Thin limb of Henle: may be hard to distinguish from vasa recta (thin limb has
thicker basement membrane than vasa recta), ascending (ATL) and
descending (DTL) limbs cannot be distinguished
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