Renal Histology Flashcards
What is the blood supply to the kidney?
- arcuate vessels from the renal artery and vein
- lie at boundary of cortex and medulla
- form interlobar vessels between pyramids
- form interlobular vessels that supply the cortex
Cortical nephrons
- 85%
- higher in cortex
- tubule loops halfway into medulla
Juxta-medullary nephrons
- 15%
- base of cortex near medulla
- tubule loops deep into medulla
- produce more hyper-osmotic urine than cortical nephrons
Mesangial cells
- type of pericyte
- surround glomerular capillaries
- support capillaries, filtration and phagocytosis
- hard to see on histo sections
What is unusual about glomerular capillary structure?
fenestrated endothelium - allows more things through capillary walls
Podocytes
- form the inner layer of Bowman’s capsule
- part on basal lamina of the glomerular capillaries
- cover them with interdigitating foot processes
- gaps in between are where filtration occurs into Bowman’s space
What is the function of slit membranes?
- pores between podocyte foot processes (pedicles)
- where filtration occurs
What comprises the filtration barrier?
thick basal lamina + slit membranes between pedicles of podocytes
What are the histological features of the proximal tubule?
- thick wall
- simple cuboidal epithelium with brush border of many very tall microvilli
- very folded basolateral membrane
- both increase surface area for secretion and reabsorption
- large concentration of pumps and mitochondria
What are the histological features of the loop of Henle?
- ascending has very very thin cuboidal epithelial cells that look almost squamous
- thick ascending limb has relatively thicker cells, thin relative to PCT and DCT
- thicker portions of PCT and DCT at start and end of LOH
What are the histological features of the distal tubule?
- simple cuboidal epithelium
- no microvilli
- more mitochondria than PCT for ion reabsorptopn processes
- larger lumen than PCT
- many ion pumps
What are the histological features of the macula densa?
- nuclei are very condensed
- lined up in a row
- in PCT they are much further apart and less regular
What are the histological features of the collecting duct?
- simple cuboidal epithelium
- becomes more columnar along duct
- taller than tubule epithelium
- large lumen
- larger on histo bc less torturous path than tubules
What are the histological features of the ureter?
- smooth muscle outside
- lined by transitional epithelium (goes down to bladder and first part of urethra)
- peristalsis occurs by autonomic nervous innervation, few cell bodies
What are the histological features of the bladder?
- lined with mucosa of transitional epithelium
- on lamina propria
- surrounded by multi-layered smooth muscle that contracts during voiding
- controlled by ANS, but somatic control of sphincter on outside
What are the features of the transitional epithelium of the bladder?
- multi-layered non-permeable epithelium
- umbrella cells that change form as bladder distends - flatten out
- very tight junctions between cells
- plaques can be inserted into the outer membrane as the bladder fills to enlarge it
- can signal to nearby nerves in response to stretch
What are the histological features of the urethra?
- lined first with transitional epithelium
- then stratified squamous epithelium
- distal urethra surrounded by striated muscle sphincter (external urethral, somatic NS control)
- rest is fibromuscular tube innervated by ANS nerves
- male urethra penetrates prostate gland
- has more glands, ejaculatory ducts etc. empyting into it
