Histology of Renal System

sinus of the kidney

concave region - w/ fat and the hilum (ureter, renal a + v, lymph)

capsule layers

• outer layer of fibroblasts and collagen

• fibers, inner layer of cells and myofibroblasts

parenchyma consists of

cortex + medulla

cortex

reddish brown from vascularization, granular from renal corpuscles, also contains convoluted proximal and distal tubules

medulla

pale and striated from tubules, containing straight proximal and distal tubules, Henle loops and collecting tubules and ducts of Bellini

renal cortex is made of

cortex corticis, cortical columns of Bertini (separate pyramids), cortical labrynth (bw medullary rays)

renal medulla contains

6-12 renal pyramids of Malpighi, medullary rays of Ferrein

borders of renal pyramids of Malpighi

base has corticomedullary border, apex has renal papilla

apex/renal papilla is perforated by _________, called __________

ducts of Bellini, area cribrosa

what represents a lobe?

renal pyramid with its cortical substance

what represents a kidney lobule?

medullary ray w/ part of cortical labyrinth around it

nephron is composed of

renal corpuscles Malphigi, renal tube

renal corpuscle poles

vascular pole (enters arterioles) and urinary pole (→ proximal convoluted renal tube)

renal corpuscle contains

bowman’s capsule, glomerulus and mesangium

___________ is made of a tuft of fenestrated capillaries (a cap bed)

glomerulus

renal artery → _______ → arcuate arteries → _______ + _________

interlobar a, vasa recta vera + interlobular arteries

blood supply from the cortical glomeruli

peritubular capillary network around cortical tubes

blood supply from juxtamedullary glomeruli

descend into medulla along loops of Henle → descending vessels → ascending vessels → vasa recta spuriae

peritubular cortical capillaries drain into ________ → arcuate veins → interlobar veins → __________ → IVC

interlobular veins, renal vein

peritubular capillaries near kidney surface + capsule capillaries drain into

stellate veins

2 layers epithelium of bowman’s capsule

parietal layer of SS epithelium + BM, inner layer w/ podocytes

podocytes processes

primary processes parallel to BM, secondary processes called pedicels

filtration slits

openings bw pedicles of podocytes, covered by diaphragm w/ a protein structure

subpodocyte space

bw foot processes + body of podocyte, fxn in regulating glomerular fluid

nephrin + actin

main fxnal components of slit diaphragm

layers of glomerular BM

outer lamina rara externa, middle lamina densa, inner lamina rara internal

lamina densa of glomerular BM

type 4 collagen, proteoglycans, glycoproteins

lamina rara ext of glomerular bm is rich in

heparan sulfates (passage - charged molecules)

endothelial surface layer of glomerular capillaries are covered by

glycocalyx, proteoglycans, glycosaminoglycans, membrane + plasma proteins

glomerular filtration barrier structure contains

fenestrated endothelium, glomerular bm, podocytes

mesangium

inside renal corpuscle

mesangium consists of

ECM and intraglomerular mesangial cells (contractile m)

functions mesangial cells

support cap network, contract glomerulus (by ATII), phagocytosis, secretion immune + inflamation cells

proximal tubule epithelium

simple cuboidal, granular, brush border + enzymes, tight jxns, folds on lat surface, interdigitations in basal processes

2 major proteins involved in reabsorption within proximal tubule

na/k-atpase pumps, AQP-1

reabsorption water and electrolytes in proximal tubule

active transport na+, passive of water + cl

reabsorption aas, sugar and polypeptides in proximal tubule

thru microvilli glycocalyx

reabsorption proteins s in proximal tubule

endocytosis

diff bw descending and ascending thin limb of loop of henle

descending permeable to water (hyperosmotic), ascending impermeable to water (hypoosmotic)

lining cells of loop of henle secretion

uromodulin (protein)

epithelium of loop of henle

SS

distal tubule epithelium

cuboidal, extensive basolat foldings

apical cell membrane has _______ in distal straight tubule

synporters (Na actively, Cl + K diffuse)

__________ exchange Na for K under ALD regulation

distal convoluted tubule

juxtaglomerular apparatus has 3 components

macula densa of distal tubule, juxtaglomerular cells of arterioles, extraglomerular mesangial cells

macula densa

of distal tubule, has ion-carrying molecules acting on Na+ levels and in a paracrine manner on juxtaglomerular cells to secrete renin

juxtaglomerular cells

modified smooth m cells in tunica media of afferent arterioles, w/ granules of renin

extraglomerular mesangial cells fxn

transmit signals of macula densa cells to juxtaglomerular cells

role juxtaglomerular apparatus

secretes renin, sense blood v + fluid composition

if sodium concentration is below a specific threshold, macula densa cells do two things:

1. dilate afferent a

2. instruct juxtaglomerular cells to release renin

epithelium of collecting tubules

simple cuboidal

cells of collecting tubules

principal cells (pale, controls Na), intercalated cells (dark, secrete H and HCO3)

end part of collecting tubules contain

ducts of bellini

interstitial tissue of kidney/stroma contains

ground substance and interstitial cells (ressemble fibroblasts)

what is part of the countercurrent multiplier system

loop henle, vasa recta and collecting duct

urothelium

stratified epithelium, impermeable and can distend

3 layers ureter

mucosa (urothelium and lamina propria), muscular coat (long + circ), fibrous CT

renal corpuscle of malphigi consists of

bowman’s capsule + glomerulus

ducts of Bellini have the same histo structure as

collecting tubule

urothelium of bladder is a stratified epithlium made of which layers of cells

basal (cuboidal), intermediary (pear-shaped), superficial (umbrella)

intraglomerular mesangial cells derive from

smooth muscle cell precursor

mesangial cells are involved in phagocytosis of _______ from glomerular bm

protein aggregates

where are EPO secreting endothelial cells?

cortex

___________ arteriole travels down from cortex to medulla → vasa recta

efferent

___________ secrete interleukins and cytokines

mesangial cells

_________ has a complex zipper-like sheet configuration

filtration slit diaphragm

65% of ultrafiltrate reabsorbed in

proximal convoluted tubule

______ are tall, narrow pale cells

macula densa cells