1/2 Filtration and quantitation of Transport

Question 1

How much of the cardiac output do the kidneys receive?

Answer 1

25% of the Cardiac Output

Question 2

What is the difference between cortical and juxtamedullary nephrons?

Answer 2

Cortical nephrons (90%):
-have short loops
-efferent arterioles form peritubular caps
Juxtamedullary nephrons (10%):
-long loops of henle
-Efferent arterioles form peritubular caps. and vasa recta

Question 3

How much of the entering afferent plasma is filtered into Bowman’s space?

Answer 3

20% of the plasma entering the afferent arteriole is filtered

Question 4

Explain the structure of the kidneys capillary membrane

Answer 4

(blood vessel)

1. capillary endothelial cells (700 angstrom holes)
2. Basement Membrane
   - allows water and small molecules less than 15 A to pass
   - contains fixed negative charged that selectively filter small proteins
3. podocytes
   - foot processes form filtration slits 250 angstroms in diameter
   - diaphragms have pores of 40X140 angstroms

Question 5

Where is the juxtaglomerular apparatus?

What are the two most important cells in this region?

Answer 5

• JG apparatus: region where DT of nephron comes in close contact with afferent and efferent arterioles
• macula densa (in DT) and Juxtaglomerular Cells (afferent/efferent)

Question 6

What is the function of macula densa cells?

Answer 6

• monitor renal fluid composition, in particular the NaCl concentration
• located in distal tubule

Question 7

What is the function of Juxtaglomerular cells?

Answer 7

• Produce renin and help to control constriction of the afferent and efferent arterioles
• they line the afferent and efferent arterioles

Question 8

What expression are all kidney calculations derived from?

Answer 8

Excretion rate = filtration rate - reabsorption rate + secretion rate

Question 9

What is defined as the excretion rate of any compound, x?

Answer 9

UxV

Ux= [x in urine] mg/ml
V=urine flow rate (ml/min)

Question 10

GFR corresponds to the clearance of the a compound with what properties?

Answer 10

1. freely filtered
2. not reabsorbed or secreted
3. not metabolized or produced by the kidney
4. Does not alter GFR

-inulin and creatinine are two examples of compounds like this

Question 11

RPF can be measured using a compound with what properties?

Answer 11

1. Freely filtered
2. very efficiently (ideally completely) secreted
3. not reabsorbed

eg, PAH

Question 12

What is defined as the filtration rate for any compound?

Answer 12

(GFR X Px) = filtration rate of x (mg/min)

Px = [x in the plasma] (mg/ml)

Question 13

What is a typical Glomerular Filtration Rate? (GFR)

Answer 13

-120 ml/min (he said remember this)