Lecture 29

Question 1

Hydrostatic Pressure (Ph)

Answer 1

blood pressure from the glomerulus (55mm Hg)

Question 2

Colloid osmotic pressure (π)

Answer 2

osmotic pressure due to the gradient of proteins in the plasma (against the filter) (30mm Hg)

Question 3

Fluid Pressure (Pfluid)

Answer 3

fluid pressure created by the fluid in the bowman’s capsule (against the filter) (15mm Hg)

Question 4

Glomerular Filtration Rate /Net Filtration Pressure

Answer 4

Hydrostatic Pressure - Colloid Osmotic Pressure - Fluid Pressure

Ph- π - Pfluid = Net filtration pressure

Question 5

Why is GFR constant over a wide range of blood pressures?

Answer 5

it is maintained by regulating the renal blood flow
it will remain constant over MAP from 80-180mmHg

Question 6

How is renal blood flow regulated if renal blood flow deceases?

Answer 6

Vasoconstriction of efferent arteriole due to paracrines increases the GFR by increasing the hydrostatic pressure of glomerulus

Question 7

How is renal blood flow regulated if renal blood flow increases?

Answer 7

Vasoconstriction of afferent arteriole due to paracrines decreases the GFR by decreasing the hydrostatic pressure of glomerulus

Question 8

How is change in renal blood flow detected in arterioles?

Answer 8

by stretch receptors in the smooth muscles of the juxtaglomerular apparatus

Question 9

What is the juxtaglomerular apparatus and how does it detect blood flow?

Answer 9

it is where the ascending loop of henle passes the afferent and efferent arterioles. it detects the change in GFR by the Macula Densa cells.

Question 10

What do the macula dense cells do?

Answer 10

They release paracrines when they detect flow change to vasoconstrict the efferent or afferent arterioles

Question 11

What is reabsorption and where does it occur?

Answer 11

Movement from tubule lumen to blood. It mainly occurs in the proximal tubule.

Question 12

What substances use transepithelial transport?

Answer 12

Na+ and Glucose move across the membrane

Question 13

What substances use paracellular transport?

Answer 13

Cl- moves in between the cells using tight junctions

Question 14

How does the movement of Na affect the movement of reabsorption?

Answer 14

1) Na+ moves by active transport
2) It causes an electrochemical gradient for the anion to move
3) The movement of the anion causes water to follow (osmosis)
4) The last solutes like K+, ca2+ and urea diffuse by paracellular or transepithelial transport

Question 15

How is Na reabsorbed?

Answer 15

1) Apical side into the membrane by the epithelial Na channel ENac
2) Membrane to Basolateral side by sodium potsssium pump

Question 16

How is Glucose reabsorbed?

Answer 16

1) Secondary transport by the sodium glucose linked transport from apical into membrane
2) Glucose is facilitately diffused out of the membrane to basolateral side by GLUT protein

Question 17

Why does reabsorption occur in the proximal tubule?

Answer 17

The pressure gradient favours reabsorption as the hydrostatic pressure drops

Question 18

What is secretion used for?

Answer 18

• to remove organic compounds from body (creatinine, urea, NH4+)
• homeostatic regulation (H+ and K+)

Question 19

What is excretion used for?

Answer 19

to remove all the secretions and filtrates from the body
- should not contain blood cells, amino acids or glucose