urinary Flashcards
(46 cards)
functions of urinary system
- produce and secrete urine
- regulate plasma volume and BP
- regulate water + electrolyte balance
- excrete toxic by-products (urea)
Nephron
blood -> renal corpuscle (cortex) -> proximal tubule (cortex) -> loops of henle (medulla) -> distal tubule (cortex) -> collecting duct (medulla)
renal corpuscle
produces glomerular filtrate from blood -> released into bowman’s space -> flows to proximal tubule (blood leaves via efferent arteriole)
bowman’s capsule, bowman’s space inside, glomerulus (network of capillaries)
bowman’s capsule
parietal layer on outside, visceral layer covering glomeruli (contains podocytes)
podocytes
cells covering glomeruli, allow filtering of blood
- primary processes, secondary processes (pedicels) wrap around capillaries
- filtration slits between pedicels
- slit membrane composed of nephrin protein
filtration barrier
filtrate passes through:
capillary
1. fenestrated glomerular capillary endothelium
2. basement membrane (prevent passage of large proteins)
3. podocyte processes w pedicels
(precent passage of some small molec)
bowman space
renal corpuscle filtrate composition
water, glucose. AAs, ions, urea, small amount of proteins
Large molec and cells stay in blood
vasa recta
Efferent arteriole from renal corpuscle forms vasa recta, surrounding all parts of the nephron
- secretes and reabsorbs solutes
diabetes mellitus
loss of functional glomeruli, resulting in kidney failure
- histology: sclerosed glomeruli (amorphous, pink hyaline material)
hyperglycemia -> down-reg of nephrin -> flattening of pedicels + thickening of basement membrane (more porous to large proteins) -> proteinuria
proximal tubule
in nephron, cortex, b/w corpuscle and loops of henle
- simple cuboidal
- tall microvilli increase surface area -> reabsorption
- Capillaries reabsorb 65% of ions, water, glucose, AAs from filtrate
loops of henle
in nephron, medulla, b/w proximal tubule and distal tubule
1. thin descending loop
2. thin ascending loop
3. thick ascending loop
thin descending loop
first loop of henle
- simple squamous
- aquaporin channels -> water permeable
- water resorption to vasa recta
thin ascending loop
second loop of henle
- simple squamous
- no aquaporins -> water impermeable
thick ascending loop
final loop of henle
- simple cuboidal
- reabsorption of electrolytes to vasa recta
distal tubule
in nephron, cortex, b/w loops of henle and collecting duct
- simple cuboidal
- water impermeable
- Fine-tuning reabsorption of Na+ to capillaries
- macula dense pumps Na out of filtrate
- short microvilli
histology - proximal vs distal tubule
Proximal: tall microvilli
distal: short microvilli, more basophilic
juxtaglomerular complex
where afferent arteriole and distal tubule are in close proximity
- regulating blood pressure and salt levels
juxtaglomerular cells
In tunica media of afferent arteriole
- modified smooth muscle cell
- secretes renin into blood
macula densa
part of epithelium of distal tubule
- simple columnar
- detects low Na+ levels
extraglomerular mesangial cells
thought to help signalling between macula densa and juxtaglomerular cells
renin-angiotensin-aldosterone system
Liver prod angiotensinogen -> kidney’s renin converts it to angiotensin I -> ACE converts it to angiotensin II -> many effects
If BP and BV decr, filtrate flow slows and sodium loss occurs. Low Na is detected by macula densa, signals to JG cells to release renin
aldosterone
stimulates Na+ reabsorption in thick ascending loop
anti-diuretic hormone
incr water permeability of collecting ducts -> less urine -> incr BV + BP
angiotensin II
increases Na+:
- incr aldosterone
- constricts efferent arteriole -> incr pressure and glomerular filtration rate -> incr Na+ in distal tubule
incr BV and BP:
- incr ADH
- vasoconstrictor
