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