SS2 Biology Lesson Note on Liver and Skin

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REGULATION OF INTERNAL ENVIRONMENT (LIVER AND SKIN)

 CONTENT:

1. The liver

• • Structure, functions and diseases of the liver, bile products
  • The effects of liver diseases and remedy.

2. The Skin

Structure of the liver

The liver is the largest gland in the body. It is located on the right side of the upper end of the abdomen, just below the diaphragm.

The liver is a reddish brown soft and well vascularised organ which consists of four lobes, two of which are very prominent. These are the right lobe which is the largest, the left lobe, the quadrate lobe and the candate lobe. The quadrate and candate lobes are small in size and lie behind the right lobe. Each lobe of the liver is made up of smaller units called lobules.

The liver is spongy in texture. Blood enters the liver through the portal vein. The gall bladder is found on the side of the right lobe.

LIVER

The liver has many functions, among them the synthesis of proteins, immune and clotting factors, and fat-carrying substances. Its chief digestive function is the secretion of bile, a solution critical to fat emulsion and absorption. The liver also filters drugs and poisons from the bloodstream, neutralizing them and excreting them in bile. When chronic liver disease leads to cirrhosis, all of these vital functions become impaired, causing complications throughout the body.

FUNCTIONS OF THE LIVER

The liver performs a number of functions and it is one of the most important organs concerned with metabolism, storage and detoxification.

Functions of the liver include the following:

1. Control of glucose level: the liver controls the amount of glucose in the blood stream. The optimum blood sugar level in man’s about 90mg/cm²/blood. Any amount in excess of this, the kidney first would attempt excreting it in urine and the liver follows by converting it to glycogen for storage. Any shortage from the optimum blood sugar level causes brain damage and the liver would again convert the store glycogen for release into the blood to prevent damage to brain cells. In the liver glucose is converted to glycogen is reconverted by glucagon (a hormone) to glucose when the body requires more glucose.
2. Protein metabolism (Deamination): deamination is the process by which the liver breaks down excess protein in the form of amino acids in the liver into ammonia to be excreted by the kidney. The liver is responsible for amino acids levels in homeostasis. When protein is in excess, the liver breaks down the excess nitrogen containing amino acids and then converts it to urea which is also excreted by the kidneys. Liver also converts keto acids to glucose, glycogen and fats.
3. Manufacturing of plasma and protein, globulins, fibrinogen and bile.
4. Liver is a storage organ for soluble vitamins such as A, D, E, K and water soluble vitamins such as B and C. Mineral ions of Zink, copper and potassium are stored in the liver.
5. Formation of red blood cells in foetus and lysis of red blood cells in adults. Haemoglobin released from worn-out red corpuscles destroyed in the bone marrow and the spleen is broken down by the formation of bile.
6. It is involved in the de-toxication of toxin, drugs and medicines, food preservations and additives as well as pollutants in air and water.
7. Production of heat: the liver produces heat which is distributed in the body through the circulatory system. The heat keeps the body warm.
8. Production of prothrombin: The enzyme ptothrombin, which takes part in blood clotting, is produced in the liver.
9. Removal of lactic acid: lactic acid, formed as a waste product by muscles during vigorous exercise is removed by the liver and converted into glycogen.
10. Action on fats: the liver acts on saturated fats and removes hydrogen, forming unsaturated fats. This is called desideration. The cell in tissues can use these unsaturated fats for their respiration.

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