Mike McCullough, age 14, of Milwaukee, Wisconsin, for his question:
What are the major functions of the liver?
A list of all the liver's functions would fill several pages. Even, so, some would be omitted because medical scientists are still mystified by them. Fortunately, today's question requests only the liver's major functions.
The liver is the body's largest internal vital organ and certainly the most complex. When its major functions fail, the body can survive no longer than a day. It is shaped somewhat like an oversized mushroom and is located at the right side of the chest cavity. This two to four pounds of soft, reddish browm tissue is tucked under the heart and lungs, folded around the stomach, the spleen and gall bladder and rests on top of the coiled intestines. The liver's location, packed amid so many key organs, is a clue to its importance.
The liver's numerous functions are diverse, to say the least. It performs most of its "miracles" on the circulating blood stream. The blood enters from the digestive tract through the portal vein, swishes through the liver in a few seconds, and exits through the hepatic artery on its way to the heart.
The liver's main functions operate in four general departments. It is a digestive gland and a detoxifier, it is a chemical builder and a storehouse of essential ingredients. As a gland, every day it manufactures bile which dribbles, into the intestine to break down fats. As a detoxifier, it remodels or disposes of wastes, certain poisons and harmful chemicals taken in from the outside. As a chemical builder it constructs antibodies proteins and enzymes for various cellular activities and makes many other substances needed throughout the body. Also every second it filters out millions of worn out blood cells. It stores the iron for re use, and also stores certain vitamins, plus a reserve supply of the body's vital chemical fuel glucose.
The liver is actually the sorting house and general headquarters of the digestive system. The first stages of digestion break down food into simple chemicals. The liver sifts out the trash and builds the broken down fragments into chemicals that the body can use. The blood from the digestive tract brings it sugar and assorted amino acids. The liver builds the amino acids into a variety of usable blood proteins and then releases them into the blood stream. It converts the sugar into usable glucose, releasing enough of this chemical fuel into the blood. Since glucose is hard to store, the liver converts the surplus into starchy glycogen which does not require so much space. Later glycogen is converted back to glucose and released as needed. This steady regulation of fuel into the blood stream helps our body to function at a constant rate.
Fortunately, the liver works automatically, day and night. It also works fast and economically. But naturally such a complex chemical plant produces waste materials. The disposal system sends harmful and useless materials into the kidneys, from where they drain out of the body.