|
|
Digestive System
Carbohydrates
Based on a 2,000 calorie diet, it is recommended that 55 to 60 percent of total daily calories be from carbohydrates. Some of our most common foods contain mostly carbohydrates. Examples are bread, potatoes, legumes, rice, spaghetti, fruits, and vegetables. Many of these foods contain both starch and fiber. The digestible carbohydrates are broken into simpler molecules by enzymes in the saliva, in juice produced by the pancreas, and in the lining of the small intestine. Starch is digested in two steps: First, an enzyme in the saliva and pancreatic juice breaks the starch into molecules called maltose; then an enzyme in the lining of the small intestine (maltase) splits the maltose into glucose molecules that can be absorbed into the blood. Glucose is carried through the bloodstream to the liver, where it is stored or used to provide energy for the work of the body.
Table sugar is another carbohydrate that must be digested to be useful. An enzyme in the lining of the small intestine digests table sugar into glucose and fructose, each of which can be absorbed from the intestinal cavity into the blood. Milk contains yet another type of sugar, lactose, which is changed into absorbable molecules by an enzyme called lactase, also found in the intestinal lining.
Protein
Foods such as meat, eggs, and beans consist of giant molecules of protein that must be digested by enzymes before they can be used to build and repair body tissues. An enzyme in the juice of the stomach starts the digestion of swallowed protein. Further digestion of the protein is completed in the small intestine. Here, several enzymes from the pancreatic juice and the lining of the intestine carry out the breakdown of huge protein molecules into small molecules called amino acids. These small molecules can be absorbed from the hollow of the small intestine into the blood and then be carried to all parts of the body to build the walls and other parts of cells.
Fats
Fat molecules are a rich source of energy for the body. The first step in digestion of a fat such as butter is to dissolve it into the watery content of the intestinal cavity. The bile acids produced by the liver act as natural detergents to dissolve fat in water and allow the enzymes to break the large fat molecules into smaller molecules, some of which are fatty acids and cholesterol. The bile acids combine with the fatty acids and cholesterol and help these molecules to move into the cells of the mucosa. In these cells the small molecules are formed back into large molecules, most of which pass into vessels (called lymphatics) near the intestine. These small vessels carry the reformed fat to the veins of the chest, and the blood carries the fat to storage depots in different parts of the body.
Vitamins
Another vital part of our food that is absorbed from the small intestine is the class of chemicals called vitamins. The two different types of vitamins are classified by the fluid in which they can be dissolved: water soluble vitamins (all the B vitamins and vitamin C) and fat soluble vitamins (vitamins A, D, and K).
Water and Salt
Most of the material absorbed from the cavity of the small intestine is water in which salt is dissolved. The salt and water come from the food and liquid we swallow and the juices secreted by the many digestive glands.
Your Digestive System and How It Works
Movement of Food Through the System
Production of Digestive Juices
Carbohydrates
How the Digestive Process is Controlled
|
Nexium - Esomeprazole
Aciphex - Rabeprazole
Prevacid - Lansoprazole
Prilosec - Omeprazole
Prilosec OCT
Protonix - Pantoprazole
| GastroEsophageal Reflux Disease
|
GERD
Causes of GERD
Diet for GERD
Infant GERD
Children 1 - 11 Years Old
Medication for GERD
Symptoms of GERD
GERD Surgery
GERD Treatment
Heartburn
Causes of Heartburn
Symptoms of Heartburn
Heartburn Medications
Heartburn Remedy
Can Flatulence Be Controlled
Lump In Throat
Proton Pump Inhibitors
Remedies for GERD
Acne
Hair Removal
HGH
|