The New Student's Reference Work/Liver
Liv′er, an important digestive organ found in many invertebrates and all vertebrates. It is the largest gland in the human body, weighing three or four pounds and measuring about 12 inches from side to side and six or seven from front to back. It is situated on the right side just below the diaphragm, and arches over a part of the stomach. It is divided into two unequal lobes, the right one being much the larger. The substance of the liver is divided into five-sided lobules, which, in turn, are made of cells. Running through its substance are blood-vessels, lymphatics, nerves and branches of the bile-duct. The latter collects the bile, and connects with the
in which the bile is stored. The bile-duct also opens into the small intestines not far from the stomach. The liver performs many offices. First it secretes bile, which is of use in helping the absorption of fats. Then it forms liver-sugar, as was shown in 1848 by Claude Bernard. Within its substance red blood-corpuscles are broken up, and it aids in removing urea from the blood in connection with the kidneys. Finally, the liver plays a part in food elaboration. Food does not pass by a single step from lifeless material into living protoplasm, but there are many steps by which it is changed a little and advanced on its way. The precise work of the liver in this direction is imperfectly understood, but it is believed to be considerable. The circulation in the liver is peculiar. There is, first, arterial blood coming directly from
the aorta through the hepatic artery, and this nourishes the liver. The other blood-supply is through the portal system. This is venous blood which has already passed through one set of capillaries in the stomach, intestines or spleen, and is carried in the portal vein to the liver. There it branches and breaks up into another set of capillaries within the liver. U
usually venous blood passes directly to the heart. It is altogether exceptional for it to be carried to another organ and there pass through another set of capillaries, but this occurs in the liver and is called the portal circulation.