The Process of Digestion 38-2

The digestive system A one way tube which includes the mouth, pharynx, esophagus, stomach, small intestine and large intestine Also there are accessory structures, with are salivary glands, the pancreas, and the liver Add secretions to digestive tract Function: to help convert foods into simpler molecules that can be absorbed and used by the cells of the body

The Mouth Teeth do the mechanical breaking down of food by cutting, tearing and crushing food into small pieces Saliva is released by salivary glands. It moistens food to make it easier to chew Saliva also contains amylase, an enzyme that breaks the chemical bonds in starches to release sugars.

The Esophagus The esophagus is the tube that connects the mouth to the stomach Food passes through the esophagus by contractions of smooth muscles, this process is know peristalsis

The Stomach The stomach is the large muscular sac that continues the mechanical and chemical digestion of food Chemical digestion start with millions of glands that releases mucus, hydrochloric acid and pepsin Pepsin breaks down proteins Mechanical digestion continues in the stomach as result of the stomach contracting to churn and mix the fluids and food Chyme is the mixture of fluid and food

The Small Intestine Most of the chemical digestion and absorption of the foods you eat occurs in the small intestine Pancreas has 3 important functions Produces hormones to regulate blood sugar levels Produces enzymes to break down carbohydrates, proteins, lipids and nucleic acids Produces sodium bicarbonate to neutralize stomach acids Liver is a large organ just above the stomach produces bile which helps with the digestions of fats

Absorption in the Small Intestine The small intestine is specially adapted for the absorption of nutrients The folded surfaces of the small intestine are covered with fingerlike projections called villi The villi provide a large amount of surface are to rapidly absorb nutrients By the time the food leaves the small intestine it is basically nutrient free and just consist of water, cellulose and other indigestible substances

The Large Intestine The large intestine removes water from the undigested material that is left After the water is removed the concentrated waste passes through the rectum and is eliminated from the body

Digestive System Disorders Sometimes the strong acids in the stomach damage the lining and produce a hole, this is know as a peptic ulcer Diarrhea is cause when not enough water is absorbed by the large intestine Constipation is caused when too much water is absorbed from the undigested materials