Renal Physiology - Quiz 2 Flashcards
Work unit of kidneys for excretion of wastes; purpose is to form an ultrafiltrate of plasma
Glomerulus
regulates flow through the glomerulus
afferent arteriole muscle tone
What is the charge of the basement membrane in the glomerulus? Why?
negative
because of the glycoproteins which compose it
What impact does the charge of the glomerular basement membrane have on filtration?
Proteins cannot be filtered through the membrane (unless the kidneys are injured)
define glomerular filtration rate (GFR)
total volume per unit time (mL/min) which leaves the capillaries and enters Bowman’s Space
what is normal GFR in mL/min and L/day?
120 mL/min
180 L/day
what % of CO is renal blood flow?
20 %
1200 mL/min
What is the only organ that gets a higher percentage of CO than the kidneys?
Liver
True or False. The vast majority of filtered blood/plasma is reabsorbed.
True
4 factors that determine GFR
- Ultrafiltration coefficient
- Oncotic pressure
- Net hydraulic pressure
- Capillary plasma flow rate
What 2 factors determine the ultrafiltration coefficient?
- capillary permeability
2. surface area available for filtration
Does oncotic pressure in Bowman’s Space favor or oppose filtration? Why?
Opposes filtration
b/c there should be no free protein in bowman space; all the proteins are in the blood.
where does net hydraulic pressure push fluid
into Bowman’s space from the capillaries
How does capillary plasma flow rate affect filtration?
Higher flow = greater filtration
Net filtration pressure (10 mmHg) = ______ - ______ - ______
Glomerular hydrostatic pressure (60 mmHg) - Bowman’s capsule pressure (18 mmHg) - Glomerular oncotic pressure (32 mmHg)
Why does filtration slow as plasma moves towards the end of the glomerular capillary?
increase in oncotic pressure within the capillaries
As fluid (but not proteins) is removed from the blood, the protein concentration increases in the blood, pulling water back into the blood
what drops significantly at the level of the efferent arteriole, resulting in maximal reabsorption into the vasa recta and peritubular plexi?
Capillary hydrostatic pressure
term that reflects the kidney’s ability to regulate GFR over a range of conditions
autoregulation
2 mechanisms that enable autoregulation in the kidneys
- constriction and dilation of pre capillary spinsters in the afferent and efferent arterioles (allow more or less fluid into the glomerulus)
- Increased Na delivery to the macula densa decreases GFR
part of the basement membrane of the distal tubule that lies against the afferent and efferent arterioles; senses Na levels/concentration and decreases GFR if Na levels are increased/more concentrated
Macula densa
Volume of plasma from which all of a given substance is removed per unit time in one pass through the kidney
renal clearance
if renal clearance > GFR, there must be net secretion or reabsorption?
secretion
IF renal clearance is < GFR, there must be net secretion or reabsorption?
reabsorption
if renal clearance = GFR, there must be net secretion or reabsorption?
neither
What is used clinically to estimate GFR?
Renal clearance of creatinine