1. Digestive Systems

2. Heterotrophs need food!!
Filter feeders-Suspension feeder
Substrate feeders
Fluid feeders
Bulk feeder

3. What type of Food?
Macronutrients (elements): Needed in large quantity….Can you name some?
Micronutrients (elements): Can you name some?

4. Intracellular vs. Extracellular Digestion
Intracellular: Food taken into cells by phagocytosis with digestive enzymes being secreted into the phagocytic vesicles Ex:
Extracellular: digestion in the lumen (opening) of digestive system; nutrients are transferred to the blood or body fluid Ex:

5. One opening primitive digestive systems
Planaria

6. Simple Tube Digestive Systems
Nematode

7. Compartmentalized Digestive System
Horse

8. Digestion: Mechanical
Oral Cavity
food torn my mouth to increase surface area
Movement by tongue
Stomach
Smooth muscles of stomach contract to mix food with gastric juices
Wave like contractions

9. Digestion Oral Cavity (carbohydrate digestion only) Pharynx Esophogus
Salivary glands secrete salivary amylase
Mucous helps to moisten food
Pharynx Esophogus
No digestion or absorption occurs
Stomach (protein digestion only)
Chief cells secrete pepsinogen
Goblet cells secrete mucus
Perietal cells secrete HCl
Mixture of food and gastric juices called acid chyme

10. More Digestion Small Intestine Mucosa cells secrete
Peptidases (proteases)
Glycosidases
Lactase
Pancreas secretes into Duodenum of Small Intestine
Sodium bicarbonate
Lipase
Amylase
Trypsin
Gall Bladder
Secretes bile through bile duct

11. Digestion and Absorption
In mammals, absorption of nutrients occurs in the small intestine

12. Villi of small intestine

13. Absorption Small Intestine Large Intestine
Villi and microvilli absorb nutrients and transport into blood vessels and lymph
Jejunum and illeum
Large Intestine
Main function is absorption of water, minerals and important vitamins
Synthesis of vitamin K also takes place

14. Hormones regulate digestion
Gastrin: stimulates HCl secretion in the stomach
Secretin: stimulates pancreas to secrete bicarbonate
Cholecystokinin (CCK) stimulates contractions of the gall bladder
Insulin: lowers blood sugar
Many gut hormones also in brain: CCK induces feeling of satiety (feeling full)