Liver

Question 1

What is the difference between excretion and defection.

Answer 1

Excretion is the removal of waste products of metabolisms from the body, they become toxic if they build up too much in the body, damaging cells. The main excretory products in mammals are carbon dioxide, urea and bile pigments from the break down of RBC. Defection or egestion is the removal of undigested food that has not entered the bloodstream.

Question 2

What is the name given to a liver cell.

Answer 2

A hepatocyte

Question 3

Describe how blood enters and leaves the liver.

Answer 3

Hepatic arteries supply the liver with oxygenated blood from the vena cava. The hepatic portal vein carries blood from the small intestine that are rich in digested foods, the liver filters out any harmful substances. The hepatic vein carries deoxygenated blood away from the liver via the aorta.

Question 4

Describe the structure of the livers cells

Answer 4

lobules made up of rows of hepatocytes. Oxygenated blood and digested food are carried in via HA and HPV sinusoids are specialised capillaries which connect to the central vein which carries the deoxygenated blood away from the cell.

Question 5

how are sinusoids adapted for their function

Answer 5

they have a thin cell surface membrane which means they have a short diffusion pathway. they have a fenestrated membrane which means they have lots of little pores to increase permeability.

Question 6

give 3 reasons why birds don’t excrete ammonia, but guanine instead.

Answer 6

ammonia is more toxic than guanine
2 urea is more soluble in water than guanine
3 guanine has a high proportion of nitrogen