Fundamentals of Anatomy and Physiology

Nutrition and the Digestive System 389

The functions of the pancreas are, therefore, twofold.
The acini secrete enzymes that continue the digestion of
food in the small intestine, and the alpha and beta cells
secrete the hormones glucagon and insulin that regulate and
control blood sugar levels.

The Liver

The liver is one of the largest organs of the digestive
system (Figure 16-11). The liver weighs approximately 4
pounds and is divided into two principal lobes: the right
lobe and the left lobe, each separated from one -another by
the falciform ligament. The lobes of the liver are made
up of numerous functional units called lobules.
The functions of the liver are so numerous and im-
portant that we cannot survive without it. The liver has six
major functions:

1.^ The liver manufactures the anticoagulant heparin^
and most of the other plasma proteins, such as
prothrombin and thrombin, that are involved in

the^ blood clotting mechanism.^

2. Kupffer cells of the liver phagocytose (eat)
   certain bacteria and old, worn-out white and red

blood cells.^

3. Liver cells contain various enzymes that either break
   down poisons or transform them into less harmful
   substances. If the body cannot break down and
   excrete certain poisons, it stores those poisons.

Right hepatic duct

Cystic

duct

Gallbladder

Common bile (^) Head of
duct^ pancreas^
Hepatopancreatic
ampulla
Duodenum
Figure 16- 11 The anatomy of the liver.
When we digest proteins into amino acids, the amino
acids go to the mitochondria to be converted into ATP.
This process produces ammonia as a waste product,
which is toxic to cells. The liver cells convert
ammonia to urea (harmless) that is then ex-creted by
the kidneys or the sweat glands.^

4.^ Excessive newly absorbed nutrients are collected^
in the liver. Excess glucose and other monosaccha-
rides can be stored as glycogen (animal starch) or
converted to fat. When needed, the liver can then
transform glycogen and fat into glucose.^
5. The liver stores glycogen, copper, and iron, as well
as vitamins A, D, E, and K.^
6. The liver produces bile salts that break down fats.
These bile salts are sent to the duodenum of the small
intestine for the emulsification (breakup) and
absorption of fats.

The Gallbladder

The gallbladder is a pear-shaped sac about 3 to 4 inches

long located in a depression of the surface of the liver. Its

lining, like the stomach, has rugae that allow it to expand-

and fill with stored bile. The gallbladder’s func-tion is to

store and concentrate the bile produced by the liver lobules

until it is needed in the small intestine. The bile enters the

duodenum through the common bile duct.

Left lobe of liver

Left hepatic duct

Common hepatic duct

Tail of

pancreas

Main pancreatic duct

(^) ®
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