Exam 4 Renal Physio Flashcards
what is the main function of the kidneys
excretion of metabolic waste product and foreign chemical (urea, creatine, bilirubin)
what are some other functions of the kidneys
regulation of water and electrolytes, regulate body fluid osmolarity, regulate BP, acid/base balance, RBC production (EPO), its an endocrine gland and is also does gluconeogenesis
the kidneys receive __% of CO
22%
what are the three regions of the kidney
the cortex (outer region) the medulla (central region and it is divides into the outer and inner medulla) the papilla (innermost tip of the inner medulla)
nephrons and aging
they are not regenerated, after the age of 40, the number of nephrons decrease by 10% every 10 years. Leads to HTN and HBP as age increases.
what are the two kinds of nephrons and where are they located
juxtamedullary nephrons are deep in the cortex near the medulla (20-30%
cortical nephrons are in the outer cortex (70-80%)
which nephrons have the vasa recta
the juxtamedullary
what are the four processes of urine formation
- glomerular filtration
- reabsorption
- secretion
- excretion
describe the loop of Henle
there is a thick and thin acceding limb, and the descending limb is all thin
describe the process of urine formation
the blood enters Bowman’s capsule and the glomerulus through the afferent arterioles, where glomerular filtration happens. This is where we get rid of things we do not want. the blood leaves the capsule in the efferent arterioles, and goes to the peritubular capillaries where reabsorption of things like water happen, and where further secretion continues to happen. Then, the blood goes to the renal vein and the stuff in the nephron can be excreted.
urinary filtration rate
= filtration - reabsorption + secretion
not all substances are reabsorbed or excreted. Describe that happens to things like
- creatine
- Na and Cl
- AA and Glucose
- organic acids and bases
- creatine (filtration only)
- Na and Cl (filtration and partial reabsorption)
- AA and Glucose (filtration first, then complete reabsorption)
- organic acids and bases (filtration and then secretion. Whatever was missed during filtration was then secreted in the peritubular capillaries)
Glomerular filtration is the first step in urine formation. blood from the ___ arteriole is filtered and exits Bowman’s capsule via ____ arterioles
afferent arterioles, exits in efferent.
FF =
FF = GFR/RPF
FF= filtration fraction GFR= glomerular filtration rate RPF= rate of plasma flow
what is normal GFR
125ml/min or 180 L/day
what is normal FF
0.2 (20% filtered)
the glomerular capillary membrane is the most permeable in the body, and has three layers. what are they
endothelium (with fenestrations), basement membrane and podocytes (part of the epithelium that has food processes with slit pores that allow movement through the membrane)
how are podocytes important with the rate of filtration
podocytes can change the distance between them and change the size of the slit pores, and therefore change the amount of filtration that occurs
what happens if a podocyte is damaged or broken away from the basement membrane
proteins can leak out and there can be protein int he urine, which would be a sign of disease or pathology
negatively charged molecules are filtered more/less easily then positively charged ones
less easily
how does the charge of a molecule help with regard to it being filtered
well, albumin has a radius of about 6nm, and the diameter of the glomerular membrane pores are about 8nm, which should mean that is can be filtered readily. However, albumin is not filtered. The electrical charge of albumin keeps it inside. The negative charge comes from the proteoglycans on the glycocalyx of the glomerular endothelium
what is proteinuria and what is its clinical significance
protein in the urine
means that there is renal disease, usually from another disease. from HTN, diabetes, pregnancy. must always be checking. why you pee in a cup
what are the two main factors that determine GFR
hydraulic conductance (Kf) and net filtration pressure.
what is hydraulic conductance (Kf). what happens to it in disease
a measure of the product of the hydraulic conductivity and the SA of the glomerular capillaries. in disease like HTN and DM, there is a decrease in Kf due to an increase in thickness of the glomerular capillary basement membrane
what is the net filtration pressure
the sum of the hydrostatic and colloid osmotic pressures across the membrane (Pg -Pb -piG - piB)
GRF = ?
Kf x net filtration pressure (Pg -Pb -piG - piB)
if you increase the hydrostatic pressure in the bowman capsule what happens to GFR
it decreases
what happens to GFR when you increase glomerular capillary colloid osmotic pressure
you decrease GFR.
what are two factors that influence glomerular capillary colloid osmotic pressure
- arterial plasma colloid osmotic pressure
2. FF of glomerular capillaries
what happens to colloid osmotic pressure as you go down the capillary. why?
the colloid osmotic pressure will increase because in the first half of the capillary, you filter out plasma and the fluid concentration decreases, but the proteins are still there, so the PRO concentration is relatively increased, meaning there is an increase in colloid osmotic pressure.
why does net filtration pressure decrease along the glomerulus
increased glomerular colloid osmotic pressure! as you move down the glomerulus, there is an increase in the colloid pressure because there is more fluid being filtered out, and relatively more stuff left behind.
what is the primary means for physiologic regulation of the GFR
the Pg
when you increase Pg (hydrostatic P of the glomerulus), what happens to GFR
it increases.
Pg is determined by three things. what are they
- arterial P
- afferent arteriole resistance, when the afferent arteriole is resisted, closed, then the Pg will decrease, and the GFR will decrease.
- efferent arteriole resistance, this causes an increase in the Pg, and therefore an increase in GFR
describe the biphasic effect that efferent arteriole constriction has on GFR
when you increase efferent arteriole resistance, you increase the Pg which will increase the GFR. but blocking that exiting pathway, you increase RBF and you therefore increase the colloid osmotic pressure of the glomerulus, which will cause a decrease in the GFR.
you would need severe constriction of the efferent arteriole to cause a decrease in GFR.
what is the effect of afferent arteriole constriction on the GFR
afferent arterial restriction will cause a decrease in Pg and therefore a decrease in GFR, unlike the biphasic effects of constricting the efferent arteriole.
what are the determinants of RBF
change in pressure between the renal artery and vein / the resistance.
as oxygen consumption increases, what happens to sodium reabsorption
it also increases
how does SNS and catecholamines like NE and epi affect GFR and RBF. give an example of when this happens
these cause an increase in resistance in the afferent and efferent arterioles, which will cause a decrease in GFR and a great decrease in RBF. hemorrhage
how does angiotensin II affect GFR and RBF
this increases resistance int he efferent arteriole which causes GFR to remain the same, and prevents it from decreasing, but will decrease the RBF
what does the decrease in RBF from the angiotensin II cause. when does this happen
the decreases the flow through the peritubular capillaries and this increases water and sodium reabsorption. the blood has more time to absorb all the nutrients. happens with a low sodium diet or volume depletion
how do prostaglandins affect the GFR and RBF
its a vasodilator, so this will greatly decrease the resistance of the afferent arteriole and decrease the resistance of the efferent, which will increase GFR and greatly increase RBF `
if you block prostaglandin synthesis, what happens to GFR
it decreases.
how does endothelial derived nitric oxide (EDRF) affect GFR and RBF
this is a vasodilator, so it will cause a duress in resistance of the afferent and efferent arteriole, and will cause an increase in GFR and a large increase in RBF.
how does endothelin affect GFR and RBF. in what kinds of conditions do we see this
it is a vasoconstrictor, so it causes an increase in resistance of the afferent and efferent arterioles which will decrease GFR and RBF.
renal failure, cirrhosis or even liver disease
what are the three things that help wth local control of GFR and RBF
- myogenic mechanism
- macula densa feedback (tubuloglomerular feedback)
- angiotensin II (contributed to GFR, not RBF)
what is the purpose of renal auto-regulation
when there is an increase or decrease in renal arterial pressure, there will be a respective increase or decree in GFR and RBF, but then there will be an autoregulatory reflex to bring them slowly back to normal.
why is autoregulation important
if you don’t have this, and there is no change in tubular reabsorption, you will pee out your entire plasma volume.
what do you need to maintain the amount of urine you are putting out
you need a good autoregulation as well as adaptive increases and reabsorption. Neither can work without the other.
what is the myogenic autoregulation
when you increase arterial pressure,e you have an increase in blood flow and GFR. but you also stretch the vessels which will increase the calcium entry into the cell, increasing the intercellular calcium and therefore increasing vascular resistance, which will cause a decrease in RBF and GFR.
what happens to GFR and RBF when renal artery BP increases
both the RBF and the GFR increases.
with an increase in GFR, there is an increased delivery of water and solutes to the macula densa. what happens now
this increase of things to the macula densa causes the MD to secrete vasoactive substances that will constrict the afferent arterioles, and therefore there will be a decrease in the RBF and GFR, bringing it back to normal
how is GFR regulated by angiotensin II
a decrease in GFR means a decrease in macula densa NaCl, which will increase renin and angiotensin II which will increase efferent arteriole resistance, and increase GFR. angiotensin II also increases BP which will increase RBF and GFR
what does fever do to GFR
increases it
what do glucocorticoids do to GFR
increase it
what does aging do to GFR
decreases it
what does hyperglycemia do to GFR
increases it
what do dietary proteins, high protein do to GFR
increases it (low protein will decrease it)
for a substance to be reabsorbed, two things need to happen…
- it needs to be transported acrosss the tubular epithelium to the renal ISF
- it needs to be transported through the peritubular capillary membrane into the blood
what is the difference between a paracellular path and a transcellular path
the paracellular path goes thought the paratubular spaces, and the transcellular path needs the substance to enter the cell and then exit it.
what are some of the primary active transports through the tubular lumen
the Na/K ATPase
the H ATPase
the H/K ATPase
the Ca ATPase
what are some additional provisions that help with Na transport
a brush border makes the surface area 20x larger, which is a good thing because it can increase the chance of sodium reabsorption. also, carrier proteins on the luminal surface for facilitated diffusion
