LIVER

The liver is the largest gland in the body, and is responsible for numerous functions within. It weighs around 1.5 kg, and is situated below the diaphragm to the right hand side of the upper abdomen. It has a small left lobe and a large right lobe, separated by the falciform ligament.

There are approximately between 50,000 and 100,000 lobules in the liver. These are the basic functional units of the liver.

Blood is supplied to the liver by 2 vessels which are;

·        Hepatic artery, this carries 30% of blood to the liver that is rich in oxygenated blood from the aorta.

·        Hepatic portal vein, this carries 70% of blood to the liver that is rich in soluble digested food from the intestines.

 The liver has to be drained of its blood, and this is done by the hepatic vein. Bile ducts also drain bile that has been produced to the duodenum.

 

The liver has approximately 500 functions which are categorized into 12 main ones.  These are;

CARBOHYDRATE METABOLISM

The liver is responsible for regulating our blood sugar level. When we have eaten our blood sugar level increases. The liver converts the excess glucose that has been absorbed from the intestines into glycogen and stores it. When our blood sugar level drops (decreases) the liver reconverts the glycogen back to glucose. Glycogen is broken down between meal times back into glucose for respiration in the cells. This is controlled by hormones insulin and glucagons produced by islets of Langemans in the pancreas.

LIPID METABOLISM

Lipids entering the liver can be broken down or modified and transported elsewhere in the body for storage. When the glycogen store is full in the liver the excess carbohydrates are converted to fat.

This in turn is cholesterol. Too much cholesterol in the blood can be excreted by the liver into bile. The liver can synthesize the excess which has been absorbed by the intestines and is not needed in the body.

It could lead to serious consequences however if there was a build up of cholesterol in the body. Too much could cause a narrowing of the arteries, leading to thrombosis. Or even still, this could lead to gall stones when there is too much in the bile. This could lead to blockages in the bile ducts.

PROTIEN METABOLISM

DEAMINATION

Proteins can-not be stored by the body, so a process called deamination takes place. The liver breaks down the excess amino acids. This is the removal of amino group (-NH2) to form ammonia (NH3).

TRANSAMINATION

The liver can convert one amino acid to another amino acid. This is known as transamination.  All non-efficient amino acids may be synthesized this way especially if you had a deficiency in your diet. If your liver lost the ability to synthesize proteins, you would die within a few days.

SYNTHESIS OF PLASMA PROTEINS

The liver is responsible for the production of vital proteins found in blood plasma. Which are;

·        Albumins

·        Globulins

The liver is also responsible for the production of clotting factors. These are;

·        Prothrombin

·        Fibrinogen

PRODUCTION OF BILE

The liver produces bile salts (sodium hydrogencarbonate). These help the intestinal enzymes to operate efficiently by neutralizing the acid chyme in the stomach thus keeping the pH a natural balance.

It is also added to bile pigment bilirubin from the breakdown of red blood cells. This is stored in the gall bladder before going to the duodenum.

If the secretion of the bile became abnormal, bilirubin may accommodate inside the body. This will cause the skin to turn a yellowish colour, which is a condition know as jaundice.

STORAGE OF VITAMINS

The liver is also capable of storing certain vitamins. It releases them when there is a deficiency in the diet.

The vitamins it stores is mainly fat soluble ones which are;

·        VITAMIN A

·        VITAMIN D

·        VITAMIN E

·        VITAMIN K

 

It can also store some water soluble ones as well. These are;

 

·        VITAMIN B

·        VITAMIN C

STORAGE OF MINERALS

The liver also stores minerals making them nutritious in our diets. These minerals are;

·        Iron

·        Potassium

·        Copper

·        Zinc

FORMATION AND BREAKDOWN OF RED BLOOD CELLS

The fetus relies on the liver for the production of red blood cells. This however changes in life because the bone marrow is then responsible for this function. Red blood cells are broken down at the end of a 120 day cycle. The kupffer cells perform the breakdown, producing bilirubin, which is excreted in the bile. Iron that has been stored in the liver is used for the new blood cells by the bone marrow.

The liver produces haematinic principle which is needed for the red blood cells. If there wasn’t enough red blood cells produced this would cause a deficiency known as pernicious anaemia.

STORAGE OF BLOOD

The liver can store up to 1500cm3 of blood. This is very vital if a person was to haemorrhage. The blood is forced out of the liver and released into the bloodstream to compensate for the loss. This also helps to maintain a steady blood pressure.

HORMONE BREAKDOWN

The liver can break down hormone in the body. Some are broken down more rapidly than others. The hormones it does break down are as follows;

·        Testosterone – this is broken down rapidly

·        Insulin – this is broken down slowly

DETOXIFICATION

This is probably the most common function of the liver known. It is responsible for acting like a filter for our blood. The liver removes, renders harmless / toxic materials that have been absorbed by the intestines. The blood is then transported around the body to where it is needed.

Foreign materials and other substances are ingested by the kupffer cells. Toxic substances are engulfed and made safe by chemical conversion within the hepatocytes.

Alcohol and nicotine are dealt with in this way.

PRODUCTION OF HEAT

The liver can produce heat if there is a fall in body temperature. This is triggered off by HYPOTHALAMUS.

The liver also responds to adrenaline and thyroxine, which is a nervous stimulation.