Excretion = the removal of metabolic waste from the body
1. BLOOD FLOW
There are two sources of blood for the liver.
- Oxygenated blood from the heart. Blood travels from aorta via hepatic artery into the liver. It supplies the oxygen needed for aerobic respiration. Hepatocytes are very active, they carry out lots of metabolic processes and so need lots of energy in the form of ATP.
- Deoxygenated blood from the digestive system. Enters the liver via the hepatic portal vein. Contains products of digestion, may contain toxic compounds absorbed in the intestine.
Blood leaves the liver via the hepatic vein.
Bile Duct - carries bile from the liver to the gallbladder where it is stored until it is used to help fat digestion in the small intestine.
2. ARRANGEMENT OF CELLS
- On entering the liver, the hepatic artery and hepatic portal vein split into smaller vessels
- Vessels run between lobules and are called inter-lobular vessels
- Branches from hepatic artery and hepatic portal vein enter the lobules
- Blood from the two vessels is mixed and passed along a chamber - the sinusoid
- Sinusoid is lined by liver cells - ensures close contact with liver cells so the can remove molecules from the blood and pass molecules…