1. The Digestive System Ch. 30.3

2. Feed Me! Digestive system uses mechanical and chemical energy to break organic material Digestive system uses mechanical and chemical energy to break organic material Material is absorbed into the cells of our bodies; used to make energy or other molecules Material is absorbed into the cells of our bodies; used to make energy or other molecules Mechanical: Mechanical: – Grinding, smashing tearing, crushing Chemical: Chemical: – Enzymes and Acidic solutions

3. The Mouth: Mechanical Chewing: Chewing: – Tearing and grinding food into small lumps; increase surface area for enzyme activity Teeth: Teeth: – Strongest bones in the body – Incisors; cutting food – Cuspids; tearing food – Molars; grinding food Tongue: Tongue: – Strongest muscle in the body – Pushes food down esophagus

4. The Mouth: Chemical Amylase: Amylase: – Enzyme that breaks down starch into di and monosaccharaides Taste buds: Taste buds: – Alert us to nutrients we need to consume – Sugar  Sweet – Acids  Sour – Toxins  Bitter – Salts  Salty – Protein  Umami Tonsils: Tonsils: – Protect body from bacteria take in through the mouth and nose

5. The Esophagus Swallowing pushes food down the esophagus to the stomach Swallowing pushes food down the esophagus to the stomach Peristalsis: Peristalsis: – Contractions of muscle waves move food in one direction Food has to pass by the trachea (entrance to the lungs) so a small cartilage cover (epiglottis) blocks the opening Food has to pass by the trachea (entrance to the lungs) so a small cartilage cover (epiglottis) blocks the opening Eating too fast can send food “Down the Wrong Pipe” Eating too fast can send food “Down the Wrong Pipe”

6. The Stomach: Mechanical Walls of stomach contract to crush food and help mix food with digestive juices Walls of stomach contract to crush food and help mix food with digestive juices

7. The Stomach: Chemical Glands in stomach release Pepsin and HCl Glands in stomach release Pepsin and HCl Pepsin breaks down proteins into amino acids Pepsin breaks down proteins into amino acids HCl keeps the stomach at a pH 2! HCl keeps the stomach at a pH 2! Food can take up to 4 hours to digest Food can take up to 4 hours to digest Why doesn’t HCl eat through the stomach? Why doesn’t HCl eat through the stomach? – Lining of stomach makes protective mucus

8. Heart Burn and Stomach Ulcers “Heart Burn” is when stomach acid gets into the esophagus and causes a burning feeling in the chest “Heart Burn” is when stomach acid gets into the esophagus and causes a burning feeling in the chest Caused by spicy food Caused by spicy food Stomach Ulcer is a hole in the stomach lining which can cause major health problems Stomach Ulcer is a hole in the stomach lining which can cause major health problems Caused by high acidic levels Caused by high acidic levels

9. The Small Intestine: Mechanical 6 m long but only 2.5 cm wide 6 m long but only 2.5 cm wide Peristaltic contractions move food through intestine and continue to break down food Peristaltic contractions move food through intestine and continue to break down food Food is absorbed into the blood through villus Food is absorbed into the blood through villus Liver and Gallbladder release bile which physically breaks globs of fat into smaller units Liver and Gallbladder release bile which physically breaks globs of fat into smaller units

10. The Small Intestine: Chemical 3 pronged attack in the Duodenum (first 25cm) 3 pronged attack in the Duodenum (first 25cm) – Pancreas releases enzymes to break down carbohydrates, proteins, fats, and nucleic acids; also NaHCO 3 to neutralize stomach acid – Liver releases enzymes to break down organic material – Gallbladder release mild acids to help enzyme activity

11. The Large Intestine Only 1.5m long but 6.5cm wide Only 1.5m long but 6.5cm wide Indigestible material is compacted as much water as possible is absorbed back into the body Indigestible material is compacted as much water as possible is absorbed back into the body Anaerobic bacteria produce vitamins B and K for us while digesting the material Anaerobic bacteria produce vitamins B and K for us while digesting the material After 18-24 hours, waste is removed from the body as feces After 18-24 hours, waste is removed from the body as feces Passes through the last part of the digestive system, the rectum (the butt) Passes through the last part of the digestive system, the rectum (the butt)