Carbon Dioxide and Hydrogen Carbonate Ions Essay

1381 Words Jan 17th, 2011 6 Pages
Excretion.
a) excretion is the removal or metabolic waste from the body.
Metabolic waste consists of waste substances that may be toxic or are produced n excess by reactions inside cells.

b) Explain the importance of removing metabolic wastes, including carbon dioxide and nitrogenous waste, from the body.

The are many substances that need to be excreted - almost any cell product that is formed in excess by the chemical process occurring in the cells must be excreted. However there are two products that are produced in very large amounts.
Carbon dioxide from respiration.
Nitrogen containing compounds such as urea.

Where are these substances produced.
Carbon dioxide is produced by every living cell in the body as a result of
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Blood flow to and from the liver.
Usually the liver is supplied blood from two sources.
Oxygenated blood from the heart. Blood travels from the aorta via the hepatic artery into the liver. This supplies oxygen that is essential for aerobic respiration. The liver cells are active as they carry out metabolic processes. Many of these processes require ATP, so important that there is a good supply of oxygen.
Deoxygenated blood from the digestive system. This enters the blood via the hepatic portal vein, The blood is rich in products from digestion. The concentrations fof various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed in the intestine.

Blood leaves the liver via the hepatic vein this rejoins the vena cava and the blood returns to normal circulation.

A fourth vessel connects to the liver is not a blood vessel. It is the bile duct,
Bile duct carries bile from the liver to the gall bladder where it is stored until required to aid the digestion of fats in the small intestine.

The arrangement of cells inside the liver.
The liver is divided into lobes, which are further divided into cylindrical lobules.
As the hepatic portal vein and artery enter the liver they split into smaller and smaller vessels. These run between and parallel to lobules, and are known as interlobular vessels.
Now and again vessels lead into the lobules from the hepatic portal vein and artery -

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