Lecture 35: Renal System Microanatomy Flashcards
what anatomical structures make up the renal system
- 2 kidneys
- 2 ureters
- bladder
- urethra
what is the function of the kidneys
filter the blood to form filtrate
how many lobes does a kidney have
10-18 lobes (multilobar)
what is each lobe of the kidney divided into
- outer cortex
- inner medulla w/ renal papilla (apex)
describe how urine passes from papillae to medulla
papillae –> minor calyces –> major calyces –> renal pelvis –> ureter
how can you distinguish between cortex and medulla histologically
- cortex appears more granulated
- medulla appears more striated
why does the cortex appear more granulated histologically
rounded shape of renal corpuscles
what is the renal corpuscle comprised of
- Bowman’s capsule
- glomerulus
what structures make up the nephron
- renal corpuscle
- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule
what is the role of the nephron
functional unit of the kidney responsible for filtration, reabsorption, and excretion
why is it important that each kidney has so many nephrons (1.5million)
loss or dysfunction of a nephron is irreversible
name the two epitheliums of the Bowman’s capsule
- parietal (outer)
- visceral (inner, in contact with glomerulus)
what specialised cell type makes up the visceral epi of Bowman’s capsule
podocytes
through which vessel does blood enter glomerulus
afferent arteriole
through which vessel does blood exit glomerulus
efferent arteriole
describe the significance of the efferent arteriole lumen being narrower than the afferent arteriole
- blood can’t leave glomerulus as fast as it enters
- causes blood to back up in the glomerulus
- increases the pressure of blood entering the glomerulus
- increased filtration
what cells make up the juxtaglomerular complex/apparatus
- macula densa
- juxtaglomerular cells
- lacis cells
what is the role of the macula densa in the juxtaglomerular apparatus
- chemoreceptor cells of DCT
- sensitive to Na+ conc.
describe the role of the juxtaglomerular cells in juxtaglomerular apparatus
- specialised smooth muscle in tunica media of AA
- secrete renin that induces release of ang2
- causes constriction of EA which adjusts GFR
describe the blood supply to the nephron
renal artery
- -> interlobar a.
- -> arcuate a.
- -> cortical radial/ interlobular a.
- -> afferent arterioles
- -> glomeruli
- -> efferent arterioles
- -> peritubular/intertubular caps
- -> venous return (parallels arterial flow)
what does the blood-filtration barrier consist of
- fenestrated endothelium of glomerular caps
- fused basal laminae
- pedicles of podocytes
describe the structure of a podocyte
- nucleus
- primary processes
- secondary processes
- filtration slits
describe the lining of the PCT
- simple cuboidal epi
- numerous microvilli
- basal invaginations w/ sodium complexes
function of the PCT
- reabsorb water, K+, ions, glucose, a.a. etc
at what part of the nephron does most glomerular filtrate get reabsorbed
PCT - 70%
describe the lining of the loop of Henle
- thin portion lined by simple squamous epi
- thick portion lined by simple cuboidal epi
what is the function of the loop of Henle
special permeability properties for concentrating urine by counter current multiplier
what vessels are parallel to loop of Henle
vasa recta branches of efferent arteriole
describe the lining of the DCT
cuboidal cells w/ few/no microvilli
which is more convoluted; PCT or DCT
PCT
what vessels wrap around the DCT
peritubular/intertubular caps from efferent arteriole
describe the lining of the collecting ducts
simple cuboidal/columnar epi
outline the flow of filtrate through the CD
collecting tubules
- -> collecting ducts
- -> ducts of Bellini
- -> deliver urine to papillae
describe the lining of the renal calyces and renal pelvis
lined by transitional epi (2-3 cells thick)
do the renal calyces and renal pelvis contain muscle, why
yes
peristaltic contractions (smooth muscle) promote emptying of tubules into the calyces
what is the function of the ureters
transport urine to the bladder by peristalsis
describe the lining of the ureters
transitional epi (4-5 cells thick) w/ underlying lamina propria containing elastic fibres
describe the lumen of the ureter
stellate
describe the smooth muscle in the ureter vs renal pelvis
Renal Pelvis:
- well developed
- ill defined layers
Ureters:
- well developed
- ill defined layers EXCEPT
- better defined in distal end where there is an extra layer of longitudinal fibres
what is the function of the bladder
reservoir for both storage and expulsion of urine into the urethra
describe the lining of the bladder
- transitional epi (6-8 cells thick when contracted)
- can be called urothelium
- specialised cells called umbrella cells
other than lining, describe the wall of the bladder histologically
- underlying lamina propria w/ bv and fibroelastic CT
- smooth muscle –> 3 large distinct layers
