renal 2
nuclei of endothelial cells sit close to
mesangium at base of capillary tuft where mesangial cells also reside
brush border is absent in distal tubule but cells may bear
microvilli
proximal tubules have shaggy apical membrane because apical cell margins bear
microvilli that make up prominent brush border
proximal tubules have many ___ in cytoplasm
mitochondria
basal striations are due. to
mitochondria in channels created by infolding of basal PM
podocytes resemble
octopus perched outside of capillary with pedicels interdigitating with adjacent podocytes
podocytes can divide into smaller branches or end directly as
pedicels that attach to outer wall of glomerular capillaries
each podocyte has several
primary processes (trabecular) which give rise to many secondary processes that end as pedicels
longest segment of nephron
proximal tubules
slit membrane
sieve-like diaphragm with unique filamentous mesh substructure
walls of proximal tubules
simple cuboidal to low columnar surrounding irregular shaped lumen
glomerular capillary endothelium fenestra
- 70nm - lack diaphragms - highly permeable - larger and irregular shaped than fenestrated capillaries elsewhere
renal podocytes
- highly modified epithelial cell with remarkable ultrastructure appearance - cell bodies have nucleus and cytoplasmic organelles - 3-6 primary process to smaller processes
podocytes
- highly specialized ells that form the visceral layer of bowman's capsule - ultimately embrace the outer endothelium
pedicels of adjacent podocytes
- interdigitate and form a series of filtration slits ~20-25nm wide. - a thin, non-membranous diaphragm (slit membrane) spans each filtration slit
glomerular basement membrane in 320nm thick and consists of
- laminin, fibroxnectin, collagen - proteoglycans, heparin sulfate anionic sites in lattice network
distal tubules are
- shorter - less complex - small cuboidal cells - less eosinophilic - smaller dm - no brush border - basal striations
extraglomerular mesangial cells
- sit bw capillary loops - provide support, phagocytosis - do NOT form glomerular filtration barrier
proximal tubules resorb >60% of glomerular filtrate including
- water, glucose, AA - bicarb, ascorbic acid, & ALL PROTEIN
3 distinct posed parts of renal corpuscles
1. glomerular capillary fenestrated endothelium 2. intervening basement membrane 3. visceral layer of bowman capsule
_____ dominate podocyte cytoplasm and contract to widen slits
actin microfilaments
tubular invaginations of proximal tubules are consistent with epithelial cells engaged in
active transport
basement membrane between endothelium and podocytes is made of
central e- dense layer (lamina densa) and 2 external layers (lamina rare)
renal corpuscles
complex filter through which fluid passes from blood in glomerular capillaries to bowman's space
proximal tubules are convoluted in ___; straight in ____
cortex; medulla
_____ cells can contract and regulate blood flow in glomerular capillaries
mesangial
lateral cell borders of proximal tubules are indistinct by light microscopy due to
extensive interdigitations
fluid then passes through glomerular basement membrane aka
filter that prevents passage of only large molecules
fluid then passes through
filtration slits between pedicels of podocytes where slit membrane prevents passage of smaller molecules
_____ is filtered into bowman's space by first passing through fenestra of capillary endothelium
fluid from glomerular capillary
organization of renal corpuscles correlates with role in
glomerular filtration, transport, permeability
tripartite renal filtration barrier allows
water and ions to pass from capillary lumen to bowman's space but retains large molecules and cells
