The Digestive System The function of the digestive system is to convert foods into simpler molecules that can be absorbed and used by the cells of the body.

Two Types of Digestion Occur Mechanical Mouth (chewing) Stomach (squashing) Chemical Mouth (saliva) Stomach (HCl) Small Intestine (enzymes)

Mechanical (physical) Digestion Mechanical (or physical) digestion is the process of breaking the food into smaller pieces but not changing its chemical properties. How about now, is it still an apple? This is an apple. Is it still an apple?

Chemical Digestion Foods interact with hydrochloric acid (HCl) and enzymes to breakdown into molecules the body can use for energy, such as sugars, proteins and lipids (fats).

The Mouth The teeth tear and crush food into amounts small enough to be swallowed. Chewing begins the process of mechanical digestion. As you chew, the food gets mixed with a liquid called saliva. Saliva contains an enzyme that begins the chemical digestion process.

Esophagus Once the food becomes mush, it is pushed down into the throat by the tongue. This leads into a long tube called the esophagus, which leads to the stomach. Food does not travel down by gravity but rather by muscle contractions called peristalsis (per uh STAHL sis).

This new soupy mush is called chyme (kiem), Stomach Food from the esophagus empties into a large muscular sac called the stomach. The stomach continues both mechanical and chemical digestion. The stomach continues to squeeze food – mechanical digestion. While glands secrete enzymes (Pepsin) and acids (Hydrochloric Acids) – chemical digestion. This new soupy mush is called chyme (kiem),

Small Intestine The chyme is slowly released into the small intestine. Most of the chemical digestion occurs here, nutrients are absorbed into the bloodstream. The small intestine is lined with finger like extensions called villi (villus – singular).

Villi Finger-like projections that line the small intestine. They are covered in capillaries that pass nutrients on to the bloodstream.

Digestion Helpers Pancreas: Liver: Stores nutrients Food does not pass through these organs. They produce fluids that help breakdown foods. Pancreas: Bicarbonates to neutralize acids Insulin helps regulate blood sugar level Liver: Stores nutrients Breaks down toxins in the blood Makes cholesterol for cell membranes Makes green liquid (bile) used in to digest fats. Bile is stored in the gallbladder.

Large Intestine Stores, compacts and eliminates materials that cannot be digested; water is absorbed out of wastes. “Good” bacteria are present in the large intestine. These help prevent disease, produce some key vitamins, aid in digestion. When the doctor prescribes antibiotics to cure an ear infection or respiratory infection, how can this have a negative affect on our digestive system? What can be done to help?

The purpose of the digestive system is to: Review The purpose of the digestive system is to: Convert foods into molecules that can be used by the body Mechanical digestion takes place in these two places: Mouth and Stomach Where does chemical digestion takes place? Mouth, stomach and small intestines True or False: Food enters the esophagus then gravity forces it down into the stomach False How does the villi in the small intestine compare to the alveoli in the respiratory system?