1. Digestive System: pp
Pre-Movie:
Major structures:
Mouth
Throat
Esophagus
Stomach
Liver
Pancreas
Small and large intestines

2. Digestive System Key Functions
Extracts and absorbs nutrients from food
Removes wastes
Maintains water and chemical balances

3. Key terms
Nutrient – a substance required by the body for energy, growth, repair, and maintenance. Nutrients in food and beverages include:
Carbohydrates
Lipids
Proteins
Vitamins
Minerals
Digestion – the process of breaking down food into molecules the body can use
calorie – a unit by which the energy available in food is measured
It is the amount of heat energy required to raise the temperature of 1g of water 1oC
A calorie is actually a very small amount of energy so nutritionists use a unit called the Calorie (with a capital C) which is equal 1,000 calories

5. Terms Cont’d Carbohydrates – sugars Proteins – amino acids
Lipids – fats
Vitamins – organic substances that occur in many foods in small amounts and are necessary in trace amounts for the normal metabolic functioning of the body (e.x. fat-soluble vitamins – A, D, E, K; water-soluble vitamins – C and B)
Minerals – naturally occurring inorganic substances that are used to make certain body structures and substances, for normal nerve and muscle function, and to maintain osmotic balance. Your body doesn’t produce them, rather you need to intake them.
Teeth and bones require calcium and phosphorus
Iron is needed for the transportation of oxygen
Magnesium, calcium, sodium, potassium, and zinc help regulate function of the nerves and muscles

6. From Mouth to Anus
Food travels more than 26 feet through your digestive tract, which consists of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and rectum
The liver and pancreas are not part of the tract, but they deliver secretions into the tract through tubes called ducts

7. Pathway Cont’d
In your mouth, teeth rip and chew food. Also, saliva contains enzymes (amylases) that begin to help breakdown carbohydrates
Esophagus connects the mouth to the stomach through a valve called a sphincter
Stomach is just beneath the diaphragm
Stomach: temporarily stores food and also breaks it down
Gastric juice is secreted by the cells that line the inside of the stomach, and it is made up of hydrochloric acid and pepsin

8. Pathway Cont’d
Food passes from the stomach into the small intestine with a sphincter
Digestion and absorption of nutrients
The first part of the small intestine (duodenum) receives secretions from the pancreas, liver, and gallbladder
Liver produces bile (helps break down fats) which is stored in the gallbladder and released to the small intestine
Most absorption, or passage of nutrients to the blood or lymph, occurs in the small intestine

9. Pathway Cont’d
Food wastes move into the large intestine (colon); no digestion takes place here
Mostly mineral ions and water are absorbed through the wall of the large intestine
Bacteria in your colon help make compounds your body needs (ex. vitamin K and several B vitamins) but also help transform and compact the undigested materials into feces
The final segment of the large intestine is called the rectum and from the rectum the solid feces are eliminated from the body through the anus

11. Diarrhea
When wastes are rushed through the large intestine before the remaining water is absorbed = watery feces

12. Constipation (hard feces)
When food remains in the colon for long periods of time, which causes much water to be absorbed

13. More about your liver
Open and read “The Liver’s Role in Digestion” and “The Liver’s Role in Metabolism” on pages

14. Modeling the Function of Bile
Quick Lab Activity, p. 911 DEMO

15. Digestive System Practice
Do all three activities at
Building Your System
Inside Story
Food Path