Renal

Question 1

Normal glomerular filtration rate?

Answer 1

120 mL/min

Question 2

Normal filtration fraction

Answer 2

20%

Question 3

Filtration fraction equation

Answer 3

FF = GFR (glomerular filtration rate) / RPF (renal plasma flow)

120/600

Question 4

The glomerulus is =

Answer 4

a ball of capillaries surrounded by the Bowman’s capsule

Question 5

3 main layers of the filtration barrier

Answer 5

Glomerular capillary endothelium

Specialised capillary basement membrane

Modified epithelial lining of the Bowman’s capsule

Question 6

How small do molecules need to be to fit through the filtration barrier?

Answer 6

<7000 Da

Question 7

What other molecular characteristic reduces it’s ability to pass through the filtration barrier?

Answer 7

If it’s negatively charged

Question 8

Clearance definition =

Equation =

Answer 8

volume of plasma that is cleared of a substance per unit time

Clearance = (Urine conc of a substance x urine flow rate) / plasma concentration

Question 9

Why is creatinine used for estimate eGFR?

Answer 9

It is freely filtered and not reabsorbed

Question 10

Primary vs secondary active transport

Answer 10

Primary - uses ATP directly as an energy source

or secondary which uses the concentration gradient created by primary

Question 11

Facilitated diffusion =

Answer 11

Rate of diffusion of specific substances enhanced by ion channels and uniporters

Question 12

Maximum tubular transport =

Answer 12

Limit to the rate at which any transporter can operate, therefore maximum rate of absorption / secretion can be reached

Question 13

Renal threshold concentration =

Answer 13

level at which transporters start to saturate and glucose appears in the urine

(varies across nephrons)

11 mmol/L

Question 14

Glucose tubular transport maximum

Answer 14

21 mmol/L

This is the level at which all the nephrons have become saturated

Question 15

Difference between the threshold and transport maximum =

Answer 15

splay

Question 16

Main function of the proximal tuble

Answer 16

Reabsorption

Glucose
Amino acids
Phosphate
Bicarb
Na+
K+
Ca2+
Cl-
Urea
Water

Question 17

Movement of Na+ in the proximal tubule

Answer 17

Moving down electrochemical gradient into the tubule cell

Then actively transported into the interstitial space

Only 20% diffuses into the capillaries due to back flux via paracellular pathways

Question 18

Movement of glucose in the proximal tubule e

Answer 18

Reabsorbed into the tuble cell by cotransport with Na2+

Diffuses out of the cells into the interstitium

Question 19

Tubular fluid is WHAT compared to plasma when it enters the loop of henle

Answer 19

Isotonic

Question 20

Tubular fluid is WHAT compared to plasma at the tip of the harpin

Answer 20

Hypertonic

Question 21

Tubular fluid is WHAT compared to plasma as it enters the distal nephron

Answer 21

Hypotonic

Question 22

Water and ion movements in the descending limb

Answer 22

Permeable to water so diffuses out of the lumen via passive transport (impermeable to solutes)

Question 23

Water and ion movements in the thin ascending limb

Answer 23

Passive movement of urea and NaCl out of the lumen

(nil water movement as impermeable)

Question 24

Water and ion movements in the thick ascending limb

Answer 24

Active reabsorption of NaCl out of the lumen

(nil water movement as impermeable)

Question 25

Countercurrent multiplier role

Answer 25

Creation of concentration via active transport in the ascending limb, increases interstitial fluid osmolality, therefore causes more passive movement of water down the osmotic gradient in the descending limb.

Question 26

Loop diuretics MOA

Answer 26

Inhibit the Na/Cl/K symporter on the apical membrane, preventing reabsorptin of NaCl and water

Question 27

What cells do both the distal tubule and collecting ducts contain?

Answer 27

Principle cells - respond to ADH

Intercalated cells - secrete H+

Question 28

Distal collecting system is WHAT to water?

Except in the presence of?

Answer 28

Impermeable

ADH

Question 29

Importance of urea in the distal collecting system

Answer 29

Provides osmolality in the medulla

Question 30

Action of aldosterone on K+ in the distal collecting system?

Answer 30

Increase K+ secretion, increased Na+ pump activity so more water retained

Question 31

W

Question 31

What regulated calcium reabsorption in the distal tubule?

Answer 31

PTH & activated Vit D