Digestive Systems

1. Digestive Systems Before food can be used for energy, it must be broken down (digested) and absorbed into the body.

2. 2 types of digestive systems: • Intracellular digestion – food is digested inside the cell. intra extra • Extracellular digestion – food is broken down outside the cell in a digestive tract or cavity, then absorbed into the body.

3. Intracellular digestion Extracellular digestion both Mollusks, annelids, Arthropods, echinoderms, All chordates Sponges Cnidaria Flatworms

4. Extracellular digestion: • Single opening – cnidarians & flatworms (gastrovascular cavity) • Digestive tract – one way tube from mouth  anus

5. Invertebrate digestive tracts • Roundworms, annelids, mollusks, echinoderms • Specialized regions (stomach, intestines) • Allows food to be processed more efficiently

6. Non-vertebrate chordates • Filter feeders – feed by straining suspended matter and food particles from water

7. Vertebrate digestive tracts • Organs are adapted to different feeding habits: carnivores – shorter digestive tracts herbivores – longer digestive tracts to help with digesting the plant material

8. Parts of the digestive system: • Mouth – mechanical digestion and the beginning of chemical digestion • Esophagus – tube leading from mouth to stomach – helps move the food with peristalsis • Stomach – mechanical and chemical digestion • Small intestine – most of the chemical digestion • Large intestine (colon) – removes water from the undigested material • Rectum – holds the wastes until the body is ready get rid of it

9. In some animals: • Crop – stores food • Gizzard – grinds the food (mechanical digestion) gizzard crop Found in annelids, insects, mollusks, birds, reptiles, and some fish.

10. More parts: (accessory organs) • Liver – produces bile which helps to digest fats • Gall bladder – stores the bile and releases it to the small intestine • Pancreas – produces digestive enzymes that help to digest fats, proteins, and carbohydrates in the small intestine

11. Liver Gall bladder

12. Small intestine: • Folded surface, forming finger-like projections called villi • Villi are covered by thousands of smaller projections called microvilli • Villi and microvilli increase surface area for absorption of nutrients.

13. Animation: Organs of Digestion • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html • View the animation • Answer the 5 question quiz • Click submit • Email your score to : ichaney@crosbyisd.org

14. Class work • Label and color the human digestive system (use different colors for each part). • Write a poem or letter about the digestive system