Page 4 - 86 human physiology part-2

The Gastrointestinal System

• Lipase-lipid: digests fats.
• Amylase: digests carbohydrates.
• Endocrine functions: Hormone secretion.
• Somatostatin: inhibits the function of insulin. Produced if the body is getting too
much glucose.
• Glucagon: stimulates the stored glycogen in the liver to convert to glucose. Produced if the
body does not have enough glucose.
• Insulin: made in the beta cells of the Islets of Langerhans of the pancreas. Insulin is a
hormone that regulates blood glucose.

7. Vermiform appendix

The Digestive System

The first step in the digestive system can actually begin before the food is even in your mouth.
When you smell or see something that you just have to eat, you start to salivate in anticipation of
eating, thus beginning the digestive process.

Food is the body's source of fuel. Nutrients in food give the body's cells the energy they need to
operate. Before food can be used it has to be broken down into tiny little pieces so it can be absorbed
and used by the body. In humans, proteins need to be broken down into amino acids, starches into
sugars, and fats into fatty acids and glycerol.

During digestion two main processes occur at the same time.

• Mechanical digestion: larger pieces of food get broken down into smaller pieces while
being prepared for chemical digestion. Mechanical digestion starts in the mouth and continues
in to the stomach.
• Chemical digestion: several different enzymes break down macromolecules into smaller
molecules that can be more efficiently absorbed. Chemical digestion starts with saliva and
continues into the intestines.

The digestive system is made up by the alimentary canal, or the digestive tract, and other
abdominal organs that play a part in digestion such as the liver and the pancreas. The alimentary canal
is the long tube of organs that runs from the mouth (where the food enters) to the anus (where
indigestible waste leaves). The organs in the alimentary canal include the esophagus, stomach and the
intestines. The average adult digestive tract is about thirty feet (30') long. While in the digestive tract
the food is really passing through the body rather than being in the body. The smooth muscles of the
tubular digestive organs move the food efficiently along as it is broken down into absorbable atoms and
molecules. During absorption, the nutrients that come from food (such as proteins, fats, carbohydrates,
vitamins, and minerals) pass through the wall of the small intestine and into the bloodstream and
lymph. In this way nutrients can be distributed throughout the rest of the body. In the large intestine
there is reabsorption of water and absorption of some minerals as feces are formed. The parts of the
food that the body passes out through the anus is known as feces.

Mastication

Digestion begins in the mouth. A brain reflex triggers the flow of saliva when we see or even think

Wikibooks | 219