1. Mammalian Digestive System

2. Oral Cavity, Pharynx, & Esophagus
Digestion Starts in the Oral Cavity
Mechanical digestion occurs here
Increased surface area and makes easier to swallow
Salivary glands secret saliva
Saliva begins chemical digestion
Composed of enzymes, buffers, & antibacterial agents
Tongue distinctions food and pushes bolus
Bolus- ‘ball’ of food swallowed

3. Oral Cavity, Pharynx, & Esophagus
Food is pushed to the Pharynx (a.k.a. throat)
Composed of the esophagus and trachea
Separated by the Epiglottis
Moves down the esophagus via peristalsis movement
Rhythmic movement off the muscles

4. Digestion in the Stomach
Stomach- pouch where food is stored and digested
Secrets fluid called gastric fluid which aids in digestion of the food
Mixture of juice and food called Chyme
Fluid is composed of two components:
Hydrochloric Acid (HCl)
2ph environment in the stomach
Kills bacteria and denatures protein to expose petite bonds

5. Digestion in the Stomach
Fluid is composed of two components:
Protease (pepsin)
Breaks peptide bond, cleaving proteins into small polypeptides
Fluid created by the gastric glands
Parietal cells release H & Cl ions
Chief cells release pepsin in inactive form of pepsinogen
Stomach protected from fluid via mucus and lining replacement

6. Digestion in the Small Intestine
Small intestine- 6m long tube where most hydrolysis of molecules occurs
First 25cm forms the duodenum
Chyme mixes with additional digestive juices
Juices secreted by the liver, pancreas, and gallbladder
Pancreas secretion
Alkaline solution containing enzymes
Acts as a buffer

7. Digestion in the Small Intestine
Liver secretion
Called bile
Stored and concentrated in the gallbladder
Breaks down fats and other lipids
Absorption
Nutrients absorbed and distributed throughout the body
Increased surface area increases absorption
Aided by villi and mircovilli

8. Digestion in the Small Intestine
Absorption
Can be active or passive
When absorbed, it is transported to the liver via blood
Transported to the liver for two reasons:
Detoxification
Nutrient balance

9. Large Intestine Large intestine- consists of colon, cecum, and rectum
Connected to small intestine via T junction
One arm of junction is colon
Leads rectum and anus
Major function water recovery
Other arm leads to cecum
Pouch for fermenting ingested material

10. Large Intestine Feces forms in large intestine
Feces stored in rectum until elimination