The Digestive System and Nutrition 7th Grade Science Mrs. Christopherson Mrs. Goede
Important Vocabulary • Digestion: The process of breaking food down to be used by the body. • Why is digestion important? • Food must be broken down in order for our body to be able to absorb all of the substances important for daily functions. • Food must small enough to be absorbed into the blood and carried to the cells.
Important Vocabulary • Digestion cont: • Two types of digestion: • Mechanical Digestion: occurs in the mouth (chewing), and in the stomach (churning of stomach muscles) • Chemical Digestion: occurs through the use of enzymes (substances which chemically act on food to break it down) in saliva, the stomach, in the small intestine
Important Vocabulary: Organs of the Digestive System • Mouth: The first step in digestion is actually getting the food into your body. • Teeth: mechanically break food down into smaller pieces • Saliva: softens food and chemically breaks food down further • Tongue: moves food around the mouth, forms a bolus (ball of food)
Important Vocabulary: Organs of the Digestive System • Esophagus: a hollow tube at the back of the throat that connects to the stomach. • To prevent food from “going down the wrong pipe” a flap of skin called the epiglottis closes over the opening of the trachea (windpipe) when we swallow • Peristalsis: muscular contractions that move food down the esophagus into the stomach. • Imagine squeezing a tube of toothpaste…
Important Vocabulary: Organs of the Digestive System • Stomach: a hollow, J-shaped organ located below the esophagus and above the small intestine. • The stomach uses both mechanical and chemical digestion to break food particles down. • Mechanical digestion: 3 layers of muscles • Chemical digestion: digestive or gastric enzymes
Important Vocabulary: Organs of the Digestive System • Small Intestine: responsible for absorbing nutrients from food. • First 1/3 of the S.I. :Bile from the gall bladder and digestive enzymes from the pancreas and walls of the small intestine further break food down. • Second 1/3 of the S.I.: contains finger-like projections called villi
Important Vocabulary: Organs of the Digestive System • Small Intestine cont: • Villi: increase the surface area of the S.I. so that more nutrients can be absorbed into the blood stream
Important Vocabulary: Organs of the Digestive System • Large intestine: “large” because it is wider in diameter than the small intestine (about 3” vs. 1”). Responsible for absorbing water from undigested food. • Material found in the large intestine is mostly food that cannot be digested any further and water.
Important Vocabulary: Organs of the Digestive System • Large Intestine: 3 parts • Colon: Absorbs water and nutrients from food, as the material moves through the colon it gets harder and harder-turning into feces. • Rectum: Stores feces. Feces move to the anus by peristalsis. • Anus: Eliminates solid waste from the body
Other Organs • Liver: produces bile, is located to the right of the stomach. • Bile: responsible for breaking down fats • Pancreas: located behind the stomach, and above the small intestine. • Secretes digestive enzymes • Gall Bladder: stores and excretes bile