Glomerular Filtration Rate & Tubular Function Flashcards
The nephron is composed of what main structures?
renal corpuscle and renal tubules
The renal corpuscle is composed of what?
glomerulus and Bowman’s capsule
The renal tubule is composed of what?
Loop of Henle; Distal convoluted tubules, connecting tubules
What are the different vessels of the nephron?
afferent arteriole, glomerulus, efferent arteriole, peritubular capillary
What is the capillary network in which large amount of fluid is filtered from blood? This will be collected in a capsular space before flowing to renal/urinary tubule.
glomerulus
At the tubes of the nephron, filtered fluid will eventually be converted to urine. What are the 5 tubes?
Bowman’s capsule, Proximal convoluted tubes, loop of Henle, Distal convoluted tubules, connecting tubule
By order after the glomerulus, enumerate parts of the tubule.
- Bowman’s capsule
- Proximal convoluted tubules
- Loop of Henle
- Distal convoluted tubules
- Collecting tubule
What is the difference between the proximal and distal convoluted tubule?
proximal = has microvilli and mitochondria
distal = no microvilli (because function is more on reabsorption)
What are the 2 cell types found at the collecting tubules?
intercalated cells & principal cells
What is the function of intercalated cells?
has microvilli + maintains the acid-base balance of the body
What is the function of principal cells?
no microvilli + maintains the water-salt balance of the body
What are the 2 capillary beds of the nephron?
glomerulus + peritubular capillaries
What are the low-pressure and porous capillaries adapted for absorption that arises from arterioles and adheres adjacent to the renal tubules?
peritubular beds
What are the 2 types of nephrons?
cortical nephron (85%) & juxtamedullary nephrons (15%)
What is the main difference between cortical and juxtamedullary nephrons?
cortical = short loops of Henle
juxtamedullary = long loops of Henle (more abundant in camels for reabsorption)
Afferent and efferent offer ___________ resistance to blood flow.
high
What are the benefits of a high pressure vascular bed?
good for filtration
What are the benefits of a low pressure vascular bed?
good for reabsorption
When afferent arterioles constrict because of sympathetic stimulation, the pressure of the glomerular capillary (PGC) decreases. What is the impaction to the GFR?
decreases
What happens when the efferent arteriole constricts? What happens to the GFR?
fluid can’t go out. GFR increases
Why can’t NSAIDs be given in certain situations (hint: related to the arterioles)?
NSAIDs inhibit prostaglandin which keeps afferent arterioles dilated. Taking them would lead to the arterioles to constrict and worsen kidney function.
Severe constriction at the efferent arteriole leads to what?
lower GFR
What are the 3 cells found at the juxtaglomerular apparatus?
Juxtaglomerular cells, Macula densa, Mesangial cells
What cell contains renin and acts as mechanoreceptors?
Juxtaglomerular Cells
What is the function of macula densa?
functions as chemoreceptors/osmoreceptors + produce signals to promote renin secretion by juxtaglomerular cells
What is the function of mesangial cells?
has phagocytic and contractile properties + influences capillary filtration
(note: can influence blood flow of glomerular capillaries + provide structure support)
What is the normal GFR at the first step of urine formation (glomerular filtration)?
125ml/min
What is glomerular filtration rate?
rate of production of filtrate at the glomeruli from plasma
99% of filtrate is reabsorbed, how much urine is normally excreted in a day?
1-2L
What is the filer that lies between the blood and the interior of the glomerular capsule?
filtration membrane
What are the three layers of the filtration membrane?
- fenestrated endothelium of the glomerular capillaries
- visceral membrane of the glomerular capsule
- basement membrane composed of fused laminae of other layers
What are the factors that control the passage of molecules through the glomerular membrane?
negative charge + size
What is the force responsible for the passage of filtrate through the glomerular membrane?
Starling’s forces
The net filtration pressure (NFP) is the sum of q
- pGC - hydrostatic pressure at glomerulus (promote)
- pBS - hydrostatic pressure at Bowman’s capsule (oppose)
- colloid osmotic pressure of glomerular plasma protein (oppose)
- colloid osmotic pressure of Bowman’s proteins (promote) = 0mmHg
GFR = Kf [(pGC + BS) - (pBS + GC)
Increased glomerular hydrostatic pressure _____ GFR.
Increases
Increased colloid osmotic pressure ________ GFR.
Decreases
In urinary obstructions, Pb increases/decreases GFR? (e.g. stones, tumors)
decreases
How do you compute for the filtration fraction?
GFR/RPF
note: RPF = renal plasma flow
What innervates the kidney?
renal artery
What are the steps to renal filtration (glomerular capillaries to renal tubules)?
- glomerular filtration
- tubular reabsorption
- tubular secretion
- excretion
At what stage of urine filtration does useful solutes from the filtrate return to the blood?
tubular reabsorption
At what stage of urine filtration does additional wastes from the blood added to the filtrate?
tubular secretion
At what stage of urine formation is water removed from the urine and returned to the blood (hint: concentration)?
water conservation
Tubular reabsorption is carried by what to the venous system?
peri-tubular capillaries
What is the volume of filtrate produced by both kidneys per minute? (give average)
Glomerular Filtration Rate (average =125 ml/min)
What is the average GFR per day?
180L per/day
If the GFR is too high, what happends?
fluid flows through tubules too quickly to be absorbed. causes dehydration and electrolyte depletion
If the GFR is too low, what happends?
fluid flows through tubules too slow = tubules reabsorb wastes that should’ve been eliminated.
can lead to azotemia
What factors at the capillary bed govern the filtration rate?
Total surface area for filtration (DP), Filtration membrane permeability (DP), Net filtration rated (DP)
What polymer of fructose is the best marker in measuring GFR in RESEARCH?
Inulin
CLINICALLY, what is the best marker in measuring GFR?
Creatine
Autoregulation of the kidney is achieved by which 2 major mechanisms?
myogenic auto-regulation and tubulo-glomerular feedback
GFR and renal plasma flow is almost always _________.
constant
The macula densa is sensitive to what?
salt
What hormones cause renal vasoconstrictions and net result of a decrease in RBF and GFR?
epinephrine, norepinephrine, angiotensin II
During fight or flight, blood is _____ away from the kidney.
shunted
What are factors that increase GFR and RBF?
high protein diet, hyperglycemia, fever
What factor decreases RBF?
Angiotensin II