LIVER AND BILIARY SYSTEM

Irawan Yusuf

Department of Physiology

ANATOMI OF THE LIVER• The liver is the largest organ

in the body - 1,200 ~ 1,500 gm. – It comprises about 1/50 of the

total adult body weight, and it is relatively larger in infancy, comprising about 1/18 of the birth weight.

– It is a complex organ that performs many vital functions, from regulating the levels of chemicals in the body to producing important substances including blood coagulation factors.

• The liver has two lobes, the right and the left. The right lobe is about six times the size of the left.

PHYSIOLOGY OF THE LIVER

• The liver consists of four systems:

1.Hepatocyte ( liver cell) system

2.Biliary tract system

3.Blood circulatory system

4.Reticulo-endothelial system

Histology of the Liver Cells

Blood Circulatory System

• Dual blood circulatory system:– Systemic circulation– Portal circulation

• Blood flow of the liver: 1,300 cc of blood flow into the liver every minute, it is about 1/4 of the cardiac output.

• 3/4 of the blood in the liver is supplied by the portal system, and the remaining 1/4 is supplied by hepatic artery from systemic circulation.

• The liver receives blood from both the intestine and the heart. The blood then flows through a latticework of tiny channels inside the liver. Blood from the intestine and heart then mix together and flow back to the heart through the hepatic vein.

• The portal system includes all the veins which drain the blood from the abdominal part of the digestive tube (with the exception of the lower part of the rectum) and from the spleen, pancreas, and gall-bladder. From these viscera the blood is conveyed to the liver by the portal vein.

• The portal vein (vena portæ) is about 8 cm. in length, The right branch of the portal vein enters the right lobe of the liver, but before doing so generally receives the cystic vein. The left branch, longer but of smaller caliber than the right, crosses the left sagittal fossa, gives branches to the caudate lobe, and then enters the left lobe of the liver.

Reticulo-endothelial System

• Kupffer cells: highly mobile macrophages, attached to the endothelium, phagocytic

• Lipocytes (Ito cells): fat-storing cells in the sinusoids

• Pit cells: highly mobile, natural killer lymphocytes attached to the endothelium

• Endothelial cells:

Function of The Liver• Formation and secretion of bile• Nutrient and vitamin metabolism

– Carbohydrate– Protein – Lipids– Vitamins– Drugs

• Inactivation of various substances– Toxins– Steroids and other hormones

• Synthesis of plasma proteins– Albumin– Clotting factors– Binding proteins

• Immunity– Kupffer cells

BILIARY SECRETIONS

• General Feature of Bile– Function. Bile is required for the digestion and

absorption of fats and for the excretion water-insoluble substances such as cholesterol and bilirubin

– Formation. Bile is formed by the hepatocyte and ductal cells. Between 250-1100 ml of bile secreted daily

– Storage. Bile is stored in the gall bladder

– Release. Bile is released during digestive period after chyme has triggered the release of CCK, which then produces contraction of the gallbladder and relaxation of the sphincter Oddi

Composition of Bile

• Water 97.0%• Bile salts 0.7%• Bile pigments 0.2%• Cholesterol 0.06%• Inorganic salts 0.7%• Fatty acids 0.15%• Lecithin 0.1%• Fat 0.1%• Alkaline phosphatase ----