Page 12 - 86 human physiology part-2

The Gastrointestinal System

Pancreatic secretions accumulate in intralobular ducts that drain the main pancreatic duct, which
drains directly into the duodenum.

Due to the importance of its enzyme contents, injuring the pancreas is a very dangerous situation.
A puncture of the pancreas tends to require careful medical intervention.

• Endocrine

Scattered among the acini are the endocrine cells of the pancreas, in groups called the islets of
Langerhans. They are:

• Insulin-producing beta cells (50-80% of the islet cells)
• Glucagon-releasing alpha cells (15-20%)
• Somatostatin-producing delta cells (3-10%)
• Pancreatic polypeptide-containing PP cells (remaining %)

The islets are a compact collection of endocrine cells arranged in clusters and cords and are
crisscrossed by a dense network of capillaries. The capillaries of the islets are lined by layers of
endocrine cells in direct contact with vessels, and most endocrine cells are in direct contact with blood
vessels, by either cytoplasmic processes or by direct apposition.

Liver

The liver is an organ in vertebrates, including human. It plays a major role in metabolism and has a
number of functions in the body including glycogen storage, plasma protein synthesis, and drug
detoxification. It also produces bile, which is important in digestion. It performs and regulates a wide
variety of high-volume biochemical reaction requiring specialized tissues.

The liver normally weighs between 1.3 - 3.0 kilograms and is a soft, pinkish-brown "boomerang
shaped" organ. It is the second largest organ (the largest being the skin) and the largest gland within the
human body. its anatomical position in the body is immediately under the diaphragm on the right side
of the upper abdomen, The liver lies on the right side of the stomach and makes a kind of bed for the
gallbladder.

The liver is supplied by two main blood vessels on its right lobe: the hepatic artery and the portal
vein. The hepatic artery normally comes off the celiac trunk. The portal vein brings venous blood from
the spleen, pancreas, and small intestine, so that the liver can process the nutrients and byproducts of
food digestion. The hepatic veins drain directly into the inferior vena cava.

The bile produced in the liver is collected in bile canaliculi, which merge from bile ducts. These
eventually drain into the right and left hepatic ducts, which in turn merge to form the common hepatic
duct. The cystic duct (from the gallbladder) joins with the common hepatic duct to form the common
bile duct. Bile can either drain directly into the duodenum via the common bile duct or be temporarily
stored in the gallbladder via the cystic duct. The common bile duct and the pancreatic duct enter the
duodenum together at the ampulla of Vater. The branching's of the bile ducts resemble those of a tree,
and indeed term "biliary tree" is commonly used in this setting.

The liver is among the few internal human organs capable of natural regeneration of lost tissue: as
little as 25% of remaining liver can regenerate into a whole liver again. This is predominantly due to

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