Tag: digestion and absorption

The glucose stored in the liver serves as a buffer for blood glucose levels. Therefore, if the blood glucose levels start to get low because person has not consumed food for a period of time, the liver is able to release glucose into the bloodstream to maintain healthy levels. If the body reserves of glucose deplete, a process called gluconeogenesis will take place. During gluconeogenesis, glucose is synthesized from molecules that are not carbohydrates. 

Liver is the largest gland of the body weighing about 1.2 to 1.5 kg in an adult human. It is situated in the abdominal cavity, just below the diaphragm and has two lobes. The hepatic lobules are the structural and functional units of liver containing hepatic cells arranged in the form of cords. Each lobule is covered by a thin connective tissue sheath called the Glissons capsule. The bile secreted by the hepatic cells passes through the hepatic ducts and is stored and concentrated in a thin muscular sac called the gall bladder. The duct of gall bladder (cystic duct) along with the hepatic duct from the liver forms the common bile duct. The bile, pancreatic juice and the intestinal juice are the secretions released into the small intestine. The bile released into the duodenum contains bile pigments (bilirubin and biliverdin), bile salts, cholesterol and phospholipids but no enzymes. Bile helps in emulsification of fats, i.e., breaking down of the fats into very small micelles. Bile also activates lipases. Fats are broken down by lipases with the help of bile into di-and monoglycerides.

Liver is the largest gland of human body that accomplishes a diverse set of functions. Liver is known as chemical factory of the body. Most of the biochemical functions of the body are done by the liver. Detoxification is a major function of liver. Thus, conversion of toxic substances into non-toxic substances is done by liver. The toxic substances include xenobiotic compounds or may be formed by metabolic activities of the body. e.g., Prussic acid is converted into Potassium sulfocyanide (it is a non-toxic salt) by the liver.

Steroids like cholesterol are crystallisable lipids having four hydrocarbon rings, consisting of three cyclohexane and one cyclopentane ring and a long hydrocarbon side chain. In animals,  liver is the major site of cholesterol production. Cholesterol is an important constituent of bile produced in liver.

One of the most important biochemical roles of liver is detoxification i.e., conversion of toxic substances into non-toxic substance. The toxic substances cab be foreign or xenobiotic compounds or are formed by metabolic activities of the body. One of the detoxification strategies of liver is to make the xenobiotic and harmful chemicals water soluble by hydroxylating them. Once hydroxyl group is added, the chemicals become water soluble and can be easily excreted through urine route.

Glycogenesis is the conversion and storage of extra amount of glucose into glycogen from the digested food. In human body glycogen is strored in liver and muscles.

The main centre of carbohydrate metabolism is liver. Following steps are related with carbohydrate metabolism-
(i) Glycogenesis- The conversion and storage of extra amount of glucose into glycogen. The main stored food in the liver is glycogen.
(ii) Glycogenolysis- The conversion of glycogen into glucose back when glucose level in blood falls down is called glycogenolysis.
(iii) Gluconeogenesis- At the time of need, liver converts non carbohydrate compounds (e.g., amino acids, fatty acids) into glucose. This conversion is called as gluconeogenesis. This is the neo-formative process of glucose. 

Deamination and urea formation is a major function of liver. Deamination of amino acids is mainly done by liver (separation of amino group of amino acid and its conversion to ammonia). Preparation of urea from the amino acids is done by the liver. Liver converts ammonia (obtained from deamination) into urea through ornithine cycle. So, after the damage or spoilage of liver, the ammonia level in the animal body is increased and the animal dies.

Stool that is pale or whitish grey colour may be caused by insufficient bile output. Bile salts from the liver give stool its brownish color. If there is decreased bile output, stool is much lighter in color. Thus whitish grey colour stool is due to malfunctioning of liver.