Academic journal article Alcohol Health & Research World

Overview of Liver Structure and Function

Academic journal article Alcohol Health & Research World

Overview of Liver Structure and Function

Article excerpt

Occupying the upper right quadrant of the abdomen and extending into the upper left quadrant, the liver is one of the largest organs in the human body. Structurally, this 3 1/2-pound organ consists of 50,000 to 100,000 functional units, called lobules, situated within an extensive network of blood vessels and bile ducts known as the portal triad (see figure). Each cylindrical lobule is typically several millimeters (mm) in length and up to 2 mm in diameter.

Small branches of the hepatic artery and portal vein running along each lobule's outer edge supply blood, which flows into the lobule through tiny channels called sinusoids. Like spokes of a wheel, the sinusoids converge in the core of the lobule to form a central "drainage" vein or outflow region.

Sinusoids serve as the liver's microcirculatory system. The endothelial cells composing the sinusoid walls contain large pore openings. These openings allow oxygenated blood from the hepatic artery and nutrientladen blood flowing from the intestine via the portal vein to bathe the liver's principal cells (i.e., hepatocytes), which are arranged in clusters between the sinusoids. Stacks of thin hepatocyte clusters just one or two cells thick (i.e., hepatic cellular plates) circle the lobule's central vein (see figure).

Relatively large and metabolically very active, the hepatocytes are the workhorses that perform the varied and vital functions of the liver. These cells process and store nutrients, manufacture proteins, and remove toxins from the blood before it enters general circulation. Hepatocytes also produce bile, which collects between adjacent cells and drains into bile ducts for transport to the gallbladder. Thick, liquid bile stored in the gallbladder is released intermittently into the small intestine, where it aids in fat digestion. …

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