A&P II: chap 26/Urinary System/Glomerulus
glomerulus
a tangled ball of capillary network in the Bowman's capsule, originating from a afferent arteriole, and leaving the capsule as a efferent arteriole
renal autoregulation: myogenic mechanism
as blood pressure rises, afferent arterioles stretch and the vessel constricts to decrease GFR.
Hormone regulation: Atrial natriuretic peptide (ANP)
atria in heart is stretched due to increased blood volume and releases ANP, ANP relaxs mesangial cells in glomerulus, increasing surface area available for filtration (increases GFR)
why is the glomerular capillary BP so high?
because efferent arteriole is smaller than the afferent arteriole --->resistance to outflow is high (BP helps here)
glomerulus capillaries are unique in what way?
because they are positioned between 2 arterioles, instead of between an arteriole and venule
BCOP
blood colloid osmotic pressure
afferent arterioles
bring blood to be filtered
the afferent and efferent arterioles regulate glomerular capillary pressure how?
by dilating or constricting
CHP
capsular hydrostatic pressure
glomerulus are considered part of what 2 systems?
cardiovascular and urinary
Hormone regulation: Angiotensin II
decreased blood volume or BP stimulates it's secretion: it constricts both afferent and efferent arterioles (decreases GFR)
blood colloid osmotic pressure (BCOP)
due to the presence of proteins (albumen, globulins, fibrinogen) in the blood plasma---->opposes filtration
main function of the renal corpuscle
filtering blood
GBHP
glomerular blood hydrostatic pressure
capsular hydrostatic pressure (CHP)
hydrostatic pressure exerted against the filtration membrane by fluid already in the space and renal tubule--->opposes filtration via "back pressure"
the differentiation of afferent/efferent arteriole responsiveness does what?
maintains a steady glomerular filtration rate (GFR)
renal autoregulation: tubuloglomerular feedback
mascula densa cells of JGA provides feedback to glomerulus. detection of increase NA+, CI- and water leads to decreased secretion of nitric oxide which then leads to vasoconstiction of arterioles (decreased GFR)
which of the two forms of renal autoregulation is quicker?
myogenic mechanism
what are two types of renal regulation of the GFR?
myogenic mechanism tubuloglomerular feedback
Angiotensin
potent vasoconstrictor: narrows afferent and efferent arterioles-->reducing GFR by reducing renal blood flow.
neural regulation of GFR
regulated by the sympathetic division, which releases EPI/NE (decreases GFR)
glomerular blood hydrostatic pressure (GBHP)
the blood pressure of the glomerular capillaries--->promotes filtration by forcing H2O + solutes in plasma through the filtration membrane
glomerular filtrate
the filtered fluid that enters into the capsular space
glomerular filtration is?
the first step in urine production; water and solutes pass from plasma into capsular space
net filtration pressure (NFP)
total pressure that promotes filtration GBHP-CHP-BCOP = NFP
net filtration pressure must be positive for you to do what?
urinate
filtration
use of pressure to force fluids + solutes through a membrane
efferent and afferent are responsive to signals how?
differentially: you can constrict the afferent arteriole without effecting the smooth muscle in the efferent arteriole.
efferent arterioles
exit the filtered blood
what are the two consequences of greatly decreasing GFR via renal autoregulation?
(like hemorrhage or intense exercise): 1) reduces urine output (conserves blood volume) 2) permits greater blood flow to other body tissues
renal corpuscle
Consists of glomerulus capillaries enclosed within Bowman's capsule
which pressures oppose filtration?
CHP BCOP
how does glomerular filtration work?
1) H2O + solutes in plasma move across the wall of the glomerular capillaries; 2) there they are filtered out and move into the Bowman's capsule; 3) then the H2O + solutes travel into the renal tubule
glomerular filtration depends on what three pressures?
1) glomerular blood hydrostatic pressure (GBHP) 2) capsular hydrostatic pressure (CHP) 3) blood colloid osmotic pressure (BCOP)
Factors that effect GFR (glomerular filtration rate)
1) large surface area = higher GFR 2) high or low BP--> high BP = high GFR 3) fenestrations size --> large fenestrations = high GFR
why is the volume of fluid filtered in the renal corpuscle higher than other capillaries?
1) larger surface area of glomerular capillaries 2) filtration membrane is thin/leaky (fenestrated) 3) glomerular capillary BP is high
what two hormones regulate the GRF?
Angiotensen II Atrial natriuretic peptide (ANP)
Out of the ways of regulating GRF, which is the only one increases the GFR?
Atrial natriuretic peptide (ANP)
how does neural regulation of GFR work?
EPI/NE hormone is released and bind to alpha-1 receptors of the afferent arterioles, causing them to constrict (decreases GFR)/ (causing an increased release of renin)
which pressure promotes filtration?
GBHP
renal autoregulation
Process the kidney uses to maintain a nearly constant glomerular filtration rate despite fluctuations in systemic blood pressure.
what are the three ways of regulating the GFR?
Renal Regulation Neural regulation Hormone regulation
