Liver


Liver


          It is the biggest gland of human body. Its weight is about 1.5 kg in an adult. It is situated below dyframe in the upper left side of abdominal cavity and surrounds the whole right part of hypochondria. Its upper surface is convex and lower surface is concave. Stomach, first part of duodenum and the right part of colon (large intestine are situated below it. Its left part is little pointed and right part is blunt. It is the biggest gland of human body. Its weight is about 1.5 kg in an adult. It is situated below dyframe in the upper left side of abdominal cavity and surrounds the whole right part of hypochondria.

Structure- The liver is being covered with a layer of connective tissue, called Glisson’s capsule. It is divided in to two main lobes by a mesentery connected with the front middle wall of stomach. It is called falciform ligament. Its right lobe is about 6 times bigger than left lobe and situated above right kidney and right colic flexor (hepatic) of colon (large intestine). Left lobe is situated above stomach. The right love of the liver is divided in to two lobes on its ventral surface- quadrate lobe at above and caudate lobe at below. There is a transversal gap found in between quadrate love and caudate lobe, called portal hepatic or liver door. Through which, blood vessels, nerves, lymphatic ducts and ducts pass.

  • Hepatic artery- It is the branch of abdominal aorta and sub-branch of celiac artery. It carries oxygenated blood to liver. About 20% of total blood reached in the liver, is done by it. 
  • Portal vein- It is made up of splenic vein and intestinal vein and carries blood from stomach, small and large intestines, pancreas and spleen to the liver. Remain 80% blood reaches in the liver through it. Nutritive element (nutrients) absorbed by small intestine presents in it.
  • Hepatic vein- It carries blood come in liver to inferior vena cava. 
  • Hepatic ducts- Bile ducts are called bile canaliculi. It is made up of bile capillaries and keeps store after collecting bile from liver cells. The bile secreted by liver reaches in tiny bile duct from where, it reaches in right and left hepatic ducts. Both these ducts form common bile duct on a point of cystic duct coming from gall bladder. Common bile duct is connected with main pancreatic duct and then opens in the other section of duodenum.

Micro-structure- The lobes of liver are made up of many small lobules. They are pentagonal or hexagonal in shape. Most of the lobe is about 1 ml in diameter and has central vein. Inside the lobes, heptocytes is arranged in unicellular layer and expand from central vein to lobe’s edge. In the corner of each lobe, there is a portal area that is made up of portal vein, hepatic artery, bile duct and the branches of nerve.

        Sinusoids are present in between the rows of liver cells that carry blood from the portal vein and the branches of liver artery. The blood flows in shiranalabh from the artery of portal area and vein and then it reaches in central vein from where it reaches in liver vein from lobe. The walls of shiranalabh are layered with endothelial cells. Fagositic stilate reticuloandochhilian cells are attached with these layered cells that digest red and white blood cells, micro bacteria and other outer substances passing through liver. 

Functions of the liver- Liver makes nutrients (nutritive elements of food) as useful for tissues by chemical actions as well as keeps store till need. In this way, functions of the liver can be divided into three phases- metabolic, storage and secretory. Besides them, the liver also involves in excretion.

Metabolic functions-

  1. It separates amino acids from carbonic compound.
  2. It produces urea from proteins and converts extra amino acids into urea.
  3. Mostly it produces plasma proteins.
  4. It produces metabolic heparin and helps in the synthesis of prothrombin and fibrinogen.
  5. It separates bilirubin from blood.
  6. It converts metabolic galactose and fructose into glucose.
  7. It oxidizes fatty acids.
  8. It separates erythrocytes from blood and stores hematin.
  9. It produces lipoproteins, cholesterol and phospholipids necessary for metabolic plasma membrane. 
  10. It converts carbohydrates and proteins in to lipid.
  11. It does detoxification of medicines and poisonous substances.
  12. It synthesizes vitamin A from carotene.
  13. It produces antibodies and antitoxins.
  14. It maintains body temperate. Many metabolic reactions go on taking place in it, resulting the blood goes in other organs from it, temperature is increased in that and in this way, it keeps the body’s temperature as maintained.  

Storage functions- The liver is the main storage center of the body. It keeps store glucose in the form of glycogen and converts this glycogen into glucose again with the help of enzymes at the time of need.

        Vitamins A, D, E and K soluble in fat, anti-anemic factor (vitamin B12), amino acids obtained from foods, etc. are also present in it. 

Secretory functions- Among important functions of the liver as digestive organs, one function of it is to secrete bile. The bile secreted from the liver’s cells is a thick yellowish green fluid. It is alkaline and has water, sodium carbonate, bile salts, bile pigments, cholesterol, musin, lecithin and bilirubin. Liver secretes about 1 litter bile daily that remains stored in gall bladder. When food reaches in duodenum from stomach, gall bladder secretes bile in duodenum where it imlasikrit fats and helps in their absorption. Secretion of bile is increased also by the actions of chemicals, hormones and nervous system.