Renal Histology

Question 1

What is the blood supply to the kidney?

Answer 1

• 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

Question 2

Cortical nephrons

Answer 2

• 85%
• higher in cortex
• tubule loops halfway into medulla

Question 3

Juxta-medullary nephrons

Answer 3

• 15%
• base of cortex near medulla
• tubule loops deep into medulla
• produce more hyper-osmotic urine than cortical nephrons

Question 4

Mesangial cells

Answer 4

• type of pericyte
• surround glomerular capillaries
• support capillaries, filtration and phagocytosis
• hard to see on histo sections

Question 5

What is unusual about glomerular capillary structure?

Answer 5

fenestrated endothelium - allows more things through capillary walls

Question 6

Podocytes

Answer 6

• 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

Question 7

Question 8

What is the function of slit membranes?

Answer 8

• pores between podocyte foot processes (pedicles)
• where filtration occurs

Question 9

What comprises the filtration barrier?

Answer 9

thick basal lamina + slit membranes between pedicles of podocytes

Question 10

Question 11

What are the histological features of the proximal tubule?

Answer 11

• 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

Question 12

What are the histological features of the loop of Henle?

Answer 12

• 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

Question 13

What are the histological features of the distal tubule?

Answer 13

• simple cuboidal epithelium
• no microvilli
• more mitochondria than PCT for ion reabsorptopn processes
• larger lumen than PCT
• many ion pumps

Question 14

What are the histological features of the macula densa?

Answer 14

• nuclei are very condensed
• lined up in a row
  
  • in PCT they are much further apart and less regular

Question 15

What are the histological features of the collecting duct?

Answer 15

• simple cuboidal epithelium
  
  • becomes more columnar along duct
  • taller than tubule epithelium
• large lumen
  
  • larger on histo bc less torturous path than tubules

Question 16

Question 17

What are the histological features of the ureter?

Answer 17

• 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

Question 18

What are the histological features of the bladder?

Answer 18

• 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

Question 19

What are the features of the transitional epithelium of the bladder?

Answer 19

• 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

Question 20

What are the histological features of the urethra?

Answer 20

• 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