The Digestive System

1. The Digestive System Anatomy & Physiology Mrs. Halkuff

2. Functions • Digestion • Absorption • Elimination

3. 2 Types of Digestion 1. Mechanical • Begins immediately after ingestion • Mastication (chewing) with teeth • Purpose is to break down food into smaller pieces • Peristalsis: Squeezing of food down the esophagus 2. Chemical • Accomplished by digestive enzymes • Enzymes break down large molecules (Fats, Carbohydrates, & Proteins)

4. Enzymes • Protease: Breaks down protein • Lipase: Breaks down fat • Amylase: Breaks down carbohydrates (starches down to sugars

5. Alimentary Canal • Canal connecting mouth to anus. • Mouth • Pharynx • Esophagus • Stomach • Small Intestines • Large Intestines • Colon • Rectum • Anus

6. Mouth • Hard Palate: Roof of mouth (front) • Soft Palate: Roof of mouth (back) • Uvula: Fleshy flap that keeps food from moving up into your nasal cavity when swallowed. • Epiglottis: Elastic cartilage attached to root of tongue that directs air into the trachea and food into the esophagus. • Tongue : Moves food around and allows for taste. • Teeth: Used to break down food into smaller pieces.

7. Coats • Beginning with the pharynx to the anus, the walls of the alimentary canal are composed of two coats: • Mucus Coat • Epithelial Goblet cells line the canal producing mucus. • Muscle Coat • Inner muscles: Circular • Outer muscles: Longitudinal • Both coats facilitate movement of food.

8. Pharynx • Throat • Air, Food, Liquid all mix here.

9. Esophagus • Connects the pharynx to the stomach • Pushes food down by peristalsis. • Bolus: Chewed food

10. Stomach • “C-shaped” organ that contains acid to break down food. • Food mixes with stomach acid to produce a thick cream called chyme. • Has 3 Regions: • Cardiac: Upper stomach region • Body: Mid stomach region • Pylorus: End stomach region

11. Stomach • Sphincters: Muscular valves that control opening & closing. • Cardioesphageal Sphincter: Valve connecting the esophagus to the stomach. • Pyloric Sphincter: Valve connecting the pylorus to the small intestines.

12. Stomach: Curvy & Wrinkly • Curvatures: • Fundus • Greater Curvature • Lesser Curvature • Rugae: Internal stomach wrinkles • Fewer rugae when full • More rugae when empty

13. Small Intestine • Main function is absorption of nutrients • Has 3 divisions: • Duodenum • Jejunum • Ileum

14. Duodenum • First segment of the small intestine • Connects to stomach • Receives chyme from stomach • Regulates gastric emptying • Continues digestion • Signals hunger cues • Stimulates the liver, gall bladder, & pancreas • In gastric bypass surgery, the duodenum is usually bypassed.

15. Jejunum • Second segment of the small intestine • Finalizes food digestion

16. Ileum • Third & final segment of the small intestine • Main function is to absorb nutrients • Returns bile back to liver • Connects to the large intestine by the ileocecal valve

17. Large Intestine • Watery waste is passed from the small intestine to large intestine. • Main function is to absorb any water or minerals from the waste. • Compresses waste into compact form for easy removal from the body. • Chyme combines with mucus and bacteria and is converted to feces.

18. Large Intestine • 4 divisions: 1. Cecum 2. Colon 3. Rectum 4. Anal Canal

19. Cecum • First segment of large intestine. • Connection at the small intestine at ileocecal valve.

20. Colon • 4 segments named for their relation to the pelvis: 1. Ascending colon 2. Transverse colon 3. Descending colon 4. Sigmoid colon

21. Rectum • Collects feces accumulated in the colon.

22. Anal Canal • Short tube (1.5”) • 2 muscular rings • Involuntary (Internal muscle) • Voluntary (External muscle) These muscles relax to allow for defecation.