The Human Digestive System

1. The Human Digestive System

2. Cells, Tissues, Organs & Systems • The basic structure in the human body is the CELL • There are over 200 different types of cells in the human body • Cells of the same type combine to form TISSUES • Different tissues combine to form organs (structures that work towards a common goal)

3. Cells, Tissues, Organs & Systems • Groups of organs working together towards a common goal are called SYSTEMS

4. The Digestive System

5. Digestion • The transformation of food into smaller molecules that can be used by the body • Two ways: • Physical Transformation: breaking food down physically and moving it along through the tube • Chemical Transformation: enzymes produced by the body break apart different molecules

6. Anatomy of the Digestive System • Digestive Tract • Mouth • Esophagus • Stomach • Small Intestine • Large Intestine (Colon)

7. Anatomy of the Digestive System • Digestive Glands • Salivary glands • Pancreas • Liver • Gastric glands • Intestinal glands

8. The Mouth

9. The Mouth • The Tongue • Responsible for moving food around to different parts of the mouth • Teeth • Incisors: four front teeth (top & bottom); used to cut pieces of food • Canines: pointy teeth beside incisors; used to shred food (especially meat) • Premolars: towards the back from canines; used to grind and crush food • Molars: at the very back; used to grind and crush food

10. The Mouth

11. The Mouth • The Pharynx (throat) • Cavity at the back of the mouth • Place where digestive and respiratory tubes meet • Salivary glands • Produce saliva • Saliva is used to kill bacteria and begin the digestion of starch molecules • Three sets: parotid glands, sublingual glands and submandibular glands

12. The Mouth

13. The Esophagus • A tube, roughly 25 cm long and 3 cm in diameter • Peristaltic contractions of the walls of the esophagus push food down to the stomach

14. The Esophagus

15. The Stomach • The stomach has valves at both ends • The cardiac sphincter (entrance) • The pyloric sphincter (exit) • The gastric glands produce gastric juice (a mix of enzymes, hydrochloric acid and mucus) • Function: mixes food with gastric juice to begin digesting protein and sugars

16. The Stomach

17. The Small Intestine • About 7 m long and 3 cm in diameter • Three sections • The Duodenum: first 25 cm at the exit of the stomach • The Jejunum: next 2 m • The Ileum: the final 5 m ending at the colon • Intestinal Glands: produce intestinal juice (a mix of enzymes used to digest protein and carbohydrates)

18. The Small Intestine

19. The Liver • The largest gland of the human body • Produces BILE, a liquid that is stored in the GALL BLADDER • Bile drains down to the duodenum when needed and is used to break fats into smaller droplets

20. The Liver

21. The Pancreas • A long, leaf-shaped gland below and behind the stomach • Produces PANCREATIC JUICE, a liquid that drains to the duodenum and is used to digest protein • Also produces INSULIN, a hormone used to help sugars leave the blood and enter cells

22. The Pancreas

23. Absorption • At the end of the digestive process (in the small intestine), simple nutrients are ready to enter the bloodstream • Carbohydrates: simple sugars (glucose, galactose and fructose) • Protein: amino acids • Fat: fatty acids and glycerol • Vitamins • Minerals

24. Absorption • Simple nutrients pass through VILLA in the walls of the small intestine

25. The Large Intestine (Colon) • About 2 m long and 8 cm in diameter • Begins with the cecum and the appendix • Ends with the rectum and the anus • Divided into three sections: • Ascending colon • Transverse colon • Descending colon

26. The Large Intestine (Colon) • Water is absorbed into the blood • Some vitamins are produced by bacteria living in the colon and then absorbed

27. The Large Intestine (Colon)

28. All together now… • http://kitses.com/animation/swfs/digestion.swf