The digestive system breaks down food into absorbable components through a long muscular tube called the alimentary canal, with accessory organs that secrete enzymes. The alimentary canal runs from the mouth through the esophagus, stomach, small and large intestines, and anus. Accessory organs include the salivary glands, liver, gallbladder and pancreas, which release secretions like bile and enzymes to further break down food. Peristalsis and sphincter muscles help move food through the system for digestion and absorption of nutrients.

1. Digestive system Food substances are changed into forms that can be absorbed through cell membranes

2. Basic divisions Alimentary canal - extends from mouth to anus Accessory organs - release secretions into canal

3. Alimentary Canal muscular tube, 9 meters long Substances move through it by peristalsis Sphincter muscles – circular muscles that control movement of food from one section to another

4. Mouth – mechanically reduces size of solid particles, mixes them with saliva a. Cheeks – muscular b. Lips – muscular, have sensory receptors c. Tongue – muscular, mix food particles, taste, move to back of pharynx d. Palate – roof of oral cavity, hard anterior, soft posterior e. Uvula – structure that hangs down in the back of the throat, seals nasopharynx while swallowing Teeth – primary; 20(deciduous) permanent; 32

5. Pharynx – connects nasal and oral cavities with larynx and esophagus Esophagus – straight, collapsible tube 25cm long, provides a passageway for substances between pharynx and stomach Stomach – J-shaped; can hold 1 liter of food; inner lining is folded until distended. Functions to receive food, mix it with gastric juices , begin digestion of proteins, do a little bit of absorption, and move food into small intestine

6. Small Intestine – Completes digestion, absorbs products, and transports leftovers to large intestine. Lined with villi – small fingerlike projections that increase surface area. Large Intestine – reabsorbs water and electrolytes; forms and stores feces until defecation. Includes the colon, rectum, and anus Feces – materials that were not digested or absorbed, together with water, electrolytes, and bacteria. 75% water; color is due to bile pigments; odor due to bacteria and their products Appendix – near the beginning of the colon

7. Accessory Organs Salivary Glands – secrete saliva ; moistens food particles, holds them together, and begins digestion of carbohydrates Pancreas – secretes digestive enzymes that digest carbohydrates, fats, proteins and nucleic acids (exocrine function)

8. Liver – located below diaphragm, mostly on the right side Metabolism of carbs, lipids, & proteins Storage of substances (glycogen) Filtering of blood – esp. from intestines Destruction of toxic chemicals Secretion of bile (emulsifies fats) Gall Bladder – pear shaped green sac attached to liver Stores bile between meals Concentrates bile by reabsorbing water Releases bile into small intestine

9. Sphincters Esophageal – between esophagus and stomach Pyloric – between stomach and sm. Int. Ileocecal – between large and sm. Int. Anal – 2 sets between rectum and anus