Kidney

Question 1

How is urea formed?

Answer 1

1. Amino acids are filtered into the liver along with the rest of the blood via the hepatic artery and hepatic portal vein.
2. excess amino acids cannot be stored and need to be broken down so they can be excreted. They are broken down into carbohydrates and ammonia.
3. Ammonia is very toxic and must be converted into a slightly less toxic chemical called urea
4. Amino acids that are needed and the urea are released back into the blood stream via the hepatic vein.

Question 2

What are the three main sections of the kidney?

Answer 2

cortex - around the outside
medulla - triangular shaped
pelvis - yellowy section

Question 3

Describe what happens in ultrafiltration.

Answer 3

1. blood from the renal artery flows through the glomerulus
2. a high pressure is built up which squeezes water, urea, ions, and glucose out of the blood and into the bowman’s capsule
3. larger molecules like proteins or red blood cells are too big to fit across capillary walls and therefore stay in the blood.

Question 4

What happens in water reabsorption stage?

Answer 4

The loop of Henle and the collecting duct are both involved in reabsorbing water if needed.
The Loop of Henle concentrates the urine by transporting salt into the blood by active transport which causes water to diffuse in the blood by osmosis.
The collecting duct responds to a hormone called ADH to vary how much water is reabsorbed.

Question 4

What is the function of the proximal convoluted tubule?

Answer 4

the cells lining it are specialised for movement of molecules - they have a folded membrane to increase surface area and many mitochondria to provide ATP for active transport.

Question 5

What happens in selective reabsorption?

Answer 5

1. The filtrate travels to the PCT. However it contains a lot of useful materials such as glucose which would be wasted unless they were recovered.
2. The specialised cells in the PCT move the useful materials back into the blood stream, initially by diffusion but some are also moved against the concentration gradient using ATP. This is active transport.

Question 6

What is absorbed in the stage of selective reabsorption?

Answer 6

All of the glucose and amino acids are reabsorbed along with some salts and 80% of the water

Question 7

What is osmoregulation?

Answer 7

The regulation of water levels within the body to keep to it rising or falling too much.

Question 8

How can water levels be changed?

Answer 8

By adjusting the permeability of the collecting duct in the nephron.

Question 9

What area of the brain monitors the levels of water in your blood?

Answer 9

The hypothalamus

Question 10

How does osmoregulation work?

Answer 10

If you need to reabsorb more water, the hypothalamus tells the pituitary gland to release more ADH.
The ADH diffuses out of the blood and binds with receptors on the surface of the collecting duct cells.
If ADH binds this triggers the wall of the collecting duct to become more permeable to water.
Therefore more water is reabsorbed into the blood. Less urine is produced and it is more concentrated with a darker colour