Unit 1, Module 2 - Kidney

Question 0

What are the three regions of the kidney?

Answer 0

The outer region - cortex.
The inner region - medulla.
In the centre is the pelvis which leads into the ureter.

Question 1

Where are kidneys positioned?

Answer 1

On each side of the spine just below the lowest rib.

Question 2

What are the four parts of the nephron?

Answer 2

Proximal convoluted tubule.
Loop of Henle.
Distal convoluted tubule.
Collecting duct.

Question 3

What are the three layers between the blood in the capillary and the lumen of the Bowman’s capsule?

Answer 3

The endothelium of the capillary.
A basement membrane.
The epithelial cells of the Bowman’s capsule.

Question 4

How is the endothelium of the capillaries adapted to allow ultrafiltration?

Answer 4

It has narrow gaps between its cells that blood plasma and the substances dissolved in it, can pass through.

Question 5

How is the basement membrane adapted to allow ultrafiltration?

Answer 5

It consists of a fine mech of collagen fibres and glycoproteins.
They act as a filter to prevent the passage of molecules with a relative molecular mass of greater than 69000.
This means that most proteins are held in the capillaries of the glomerulus.

Question 6

How is the epithelial cells of the Bowman’s capsule, adapted to allow ultrafiltration?

Answer 6

Podocytes, have a very specialised shape.
Podocytes have many finger-like projections called major processes.
These ensure that there are gaps between the cells.
Fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowman’s capsule.

Question 7

What substances are pushed into the lumen of the Bowman’s capsule?

Answer 7

Water.
Amino acids.
Glucose. 
Urea.
Inorganic acids.

Question 8

Why does the water potential become lower as the fluid in the tubule descends deeper into the medulla?

Answer 8

Loss of water by osmosis to the surrounding tissue fluid.

Diffusion of sodium and chloride ions into the tubule from th surrounding tissue fluid.

Question 9

Why does the water potential become higher as the fluid ascends back up towards the cortex?

Answer 9

At the base of the tubule, sodium and chloride ions diffuse out of the tubule into the tissue fluid.
Higher up the tubule, sodium and chloride ions are actively transported out into the tissue fluid.
The wall of the ascending limb is impermeable to water, so water cannot leave the tubule.
The fluid loses salts but not water as it moves up the ascending limb.