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The liver (hepar) is an extremely important organ in the body of mammals and vertebrates as it provides functions essential for life. It is the largest internal organ and has numerous functions including production of bile and protein, fat and carbohydrate metabolism. During foetal development, the liver has an important haemopoetic function, producing red and white blood cells from tissue between the hepatic cells and vessel walls.

The liver (hepar) is an extremely important organ in the body of mammals and vertebrates as it provides functions essential for life. It is the largest internal organ and has numerous functions including production of bile and protein, fat and carbohydrate metabolism. During foetal development, the liver has an important haemopoetic function, producing red and white blood cells from tissue between the hepatic cells and vessel walls.

The size of the liver varies due to its role in metabolism. In carnivores the liver weighs about 3-5% of body weight, in omnivores 2-3% and in herbivores 1.5%. the liver is much heavier in young animals than older animals as it atropies with age.

The size of the liver varies due to its role in metabolism. In carnivores the liver weighs about 3-5% of body weight, in omnivores 2-3% and in herbivores 1.5%. the liver is much heavier in young animals than older animals as it atrophies with age.

The liver is derived from an outpocketing of endoderm epithelium on the ventral duodenum from the caudal part of the foregut. The connection to the gut narrows to become the bile duct. The parenchymal tissue of the liver is formed from proliferating epithelial cords or strands which integrate with the blood sinuses of the umbilical and vitelline veins.

The liver is derived from an outpocketing of endoderm epithelium on the ventral duodenum from the caudal part of the foregut. The connection to the gut narrows to become the bile duct. The parenchymal tissue of the liver is formed from proliferating epithelial cords or strands which integrate with the blood sinuses of the umbilical and vitelline veins.

==Bile Acids==

==Bile Acids==

Bile acids are composed of cholesterol, bile acids and steroids. The main bile acid is '''cholic acid''' (C24). Conjugated to taurine or glycine in the liver to reduce pKa so they exist in an ionised form as bile salts. Bile salts conjugate with cholesterol and phospholipids and are then secreted into the bile. 95% are recycled in enterohepatic circulation. They emulsify fats which helps absorb fat soluble vitamins. In aqueous solution, they form micelles which are amphiphilic and can transport free fatty acids across the brush border.

Bile acids are composed of cholesterol, bile acids and steroids. The main bile acid is '''cholic acid''' (C24). Conjugated to taurine or glycine in the liver to reduce pKa so they exist in an ionised form as bile salts. Bile salts conjugate with cholesterol and phospholipids and are then secreted into the bile. They emulsify fats which helps absorb fat soluble vitamins. In aqueous solution, they form micelles which are amphiphilic and can transport free fatty acids across the brush border.

 

==Species Differences==

==Species Differences==

[[Image:Canine Liver Topography.jpg|thumb|right|250px|Liver Topography (Dog) - Copyright Nottingham 2008]]

[[Image:Canine Liver Topography.jpg|thumb|right|250px|Liver Topography (Dog) - Copyright Nottingham 2008]]

[[Image:Portal Triad Histology.jpg|thumb|right|250px|Portal Triad Histology in a Lobule- from [[Gastrointestinal Tract Histology resource|GIT-2 tutorial]] ]]

[[Image:Portal Triad Histology.jpg|thumb|right|250px|Portal Triad Histology in a Lobule- from [[Gastrointestinal Tract Histology resource|GIT-2 tutorial]] ]]

'''Hepatocytes''' are the smaller liver cells in the lobules. They contain glycogen granules and have a spherical nucleus. They form cords called '''branching plates''' (lamellae). The upper and lower margins are tight junctions. They have 3 functioning surfaces. '''Kupfer macrophages''' are present near the lining of the sinusoids. The hepatocytes tain pink as they are '''eosinophilic'''.

'''Hepatocytes''' are the smaller liver cells in the lobules. They contain glycogen granules and have a spherical nucleus. They form cords called '''branching plates''' (lamellae). The upper and lower margins are tight junctions. They have 3 functioning surfaces. '''Kupfer macrophages''' are present near the lining of the sinusoids. The hepatocytes stain pink as they are '''eosinophilic'''.

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[[Category:Liver and Gall Bladder - Anatomy & Physiology]]

[[Category:Liver and Gall Bladder - Anatomy & Physiology]]

[[Category:To Do - AimeeHicks]]

[[Category:To Do - AimeeHicks]]