renal system Flashcards
functions of kidneys
regulating total water volume and solute conc. in water
regulating ECF ion conc.
acid-base balance
removal of metabolic wastes, toxins, drugs
activation of vit. D
gluconeogenesis
renin and EPO secretion
minor calyces
drain pyramids at papillae
major calyces
collect urine from minor calyces
empty urine into renal pelvis
urine flow
renal pyramid->minor calyx->major calyx->renal pelvis->ureter
nephron
structural and functional units that form urine
contains renal corpuscle and tubule
mostly found in renal cortex
renal corpuscle
contains glomerulus and Bowman’s capsule
Bowman’s capsule
parietal layer=simple squamous epithelium
visceral layer= podocytes
podocytes
foot processes that cling to BM and allow filtrate to pass into capsular space
PCT
cuboidal cells w/ dense microvilli and large mitochondria
secretion and absorption
site of most reabsorption (glucose, AA, Na+, water, ions, uric acid, urea)
secrete H+ into filtrate
distal descending limb of loop of henle
aka thin limb
simple squamous epithelium
water can leave, solutes cannot
higher osmolarity
ascending limb of loop of henle
thick and thin limb
cuboidal to columnar cells
water cannot leave, solutes can
more dilute
DCT
cuboidal cells
secretion
in cortex
principal cells
in collecting ducts
sparse
short microvilli
maintain water and Na+ balance
intercalated cells
in collecting ducts
cuboidal cells
abundant microvilli
A and B cells that both help maintain acid-base balance
collecting ducts
receive filtration from many nephrons
run through pyramids
fuse together to deliver urine through papillae into minor calyces
reabsorption hormonally regulated (ADH, aldosterone, ANP, PTH)
cortical nephrons
85% of nephrons
mostly in cortex
juxtamedullary nephrons
long nephron loops deeply invade medulla
important in production of concentrated urine
glomerulus
specialized for filtration
blood goes into afferent arteriole->glomerulus->efferent arteriole
high BP due to large diameter of afferent arterioles
Bowman’s capsule receives filtrate from glomerulus
peritubular capillaries
low BP
porous
absorption of water and solutes
empty into venules
cling to adjacent renal tubules in cortex
vasa recta
long, thin-walled vessels parallel to long nephron loops of juxtamedullary nephrons
arise from efferent arterioles serving juxtamedullary nephrons
formation of concentrated urine
macula densa
tall, closely packed cells of ascending limb
chemoreceptors sense NaCl content of filtrate
granular cells
aka juxtaglomerular cells
enlarged, SM cells
contain enzyme renin
mechanoreceptors sense BP in afferent arteriole
extraglomerular mesangial cells
in juxtaglomerular complex
b/w arteriole and tubal cells
interconnected w/ gap junctions
pass signals b/w macula densa and granular cells
glomerular filtration
no metabolic energy required
hydrostatic pressure forces fluids and solutes through filtration membrane
filtration membrane
porous membrane b/w blood and interior or glomerular capsule (water and solutes smaller than plasma proteins)
made up of fenestrated endothelium, BM, and podocytes
hydrostatic pressure in glomerular capillaries
glomerular BP
chief force pushing water and solutes out of blood
55 mmHg due to efferent arteriole being high resistance
promote filtrate formation (outward force)
hydrostatic pressure in capsular space
inhibit filtrate formation (inward force)
pressure of filtrate in capsules
15 mmHg
colloid osmotic pressure in capillaries
inhibit filtrate formation (inward force)
pull of proteins in blood
30 mmHg
net filtration pressure
sum of forces
55 mmHg forcing out
45 mmHg opposing=net outward force of 10 mmHg
GFR
volume of filtrate formed per min by both kidneys (120-125 mL/min)
directly proportional to NFP, total surface area available for filtration (controlled by glomerular mesangial cells), filtration membrane permeability
decreased GFR triggers renin release in order to increase GFR
intrinsic controls
maintain GFR of kidneys when MAP in range of 80-180 mmHg
act locally within kidney
myogenic and tubuloglomerular (involves macula densa cells) mechanism
extrinsic controls
maintain systemic BP
nervous and endocrine mechanisms that maintain BP
take over if BP <80 or >180 mmHg
decreased BP->release of NE by SNS and E by adrenal medulla->vasoconstriction->increase BP
OR decreased BP->constriction of afferent arterioles-> decreased GFR->increase BV and BP
myogenic mechanism
intrinsic control
increased BP->constriction of afferent arterioles-> restricts BF into glomerulus (protects glomerulus from damaging high BP)
decreased BP->dilation of afferent arterioles
RAAS
extrinsic control
stimulate renin release via granular cells by SNS, macula densa cells when NaCl filtrate concentration is low, or reduced stretch of granular cells
other extrinsic controls
adenosine
prostaglandin E2
intrinsic angiotensin II
form concentrated urine
juxtamedullary nephrons and vasa recta
juxtaglomerular apparatus
macula densa cells
juxtaglomerular cells
extraglomerular mesangial cells
osmosis
reabsorption of water aided by aquaporins present in PCT (obligatory water reabsorption)
aquaporins present in collecting ducts only if ADH present (facultative water reabsorption)
solute concentration
increases in filtrate as more water is reabsorbed
transport maximum
reflects number of carriers in renal tubules available for every reabsorbed substance
when carriers saturated, excess excreted in urine (glucose)
ADH
causes principal cells of collecting ducts to insert aquaporins in apical membranes (aids in water reabsorption)
aldosterone
targets principal cells and DCT
promotes synthesis of apical Na+ and K+ channels and basolateral Na+-K+ ATPase for water reabsorption (water follows)
increases BP and decreases K+
ANP
decreases Na+ (decreases BV and BP)
PTH
acts on DCT to increase Ca2+ reabsorption