The Digestive System

Do Now: 1. Can you remember why starch and other organic molecules (proteins, carbohydrates, lipids) cannot make it into the cell? 2. What would we need to do with these molecules to make them fit through the semi-permeable membrane of every cell in your body? (Hint…only small molecules can fit through) 3. Some molecules can fit through the membrane in their original form while others need to be broken down.

Digestion: the breakdown of large food molecules into smaller, more-usable ones. Mechanical digestion: the physical breakdown of food. Chemical digestion: the chemical breakdown of food molecules into smaller, simpler molecules.

The Digestive System Salivary Glands Mouth Epiglottis Esophagus Tongue Liver Stomach Liver Stomach Pancreas Large Intestine Small Intestine Appendix Pancreas Anus Rectum Gall bladder

The Food Pathway Mouth: mechanical (teeth and tongue) and chemical (saliva) breakdown of food. Esophagus: muscular tube that pushes food along with wavelike contractions (peristalsis). Stomach: mechanical digestion (churning of food) and chemical digestion of protein begins.

Small Intestine: Bile made from the liver and digestive enzymes made in the pancreas complete digestion. Nutrients are absorbed into the bloodstream. Millions of tiny, finger-like projections, called villi, line the small intestine. Villi increase the small intestine’s surface area so that most nutrients are absorbed by the time the food reaches the large intestine.

Large intestine: undigested material enters water, some vitamins, and minerals are absorbed into the bloodstream remaining materials exit through the anus

Diseases of the Digestive System:

Diarrhea Excess release of water caused by: Decreased absorption of water by large intestine. Increase in indigestible material. Increased rate of peristalsis. *** Dehydration due to diarrhea is the main cause of infant death in many Countries of the world.

Colon Cancer