Digestion: The process by which food is broken down into absorbable units. To take apart.

GI Tract: Gastrointestinal: Stomach / intestines
 

1. Mouth - chews and mixes food, salivary glands secrete saliva with starch-digesting enzymes

Epiglottis √ protects airway
Trachea √ passage for air to the lungs

2. Esophagus √ passes food from mouth to stomach

Cardiac sphincter √ allows passage from esophagus to stomach; prevents backflow
Food passes as a BOLUS to stomach

3. Stomach √ adds acid, enzymes, fluid.  Churns, mixes, grinds food to a liquid mass.

Pyloric sphincter √ allows passage to small intestine; prevents backflow
Food passes as CHYME to duodenum

4. Small Intestine √ secretes enzymes that digest all energy-yielding nutrients to smaller particles.  Cells of wall absorb nutrients into blood and lymph

Duodenum, Jejunum, Ileum
Illeocecal sphincter √ allows passage to large intestine; prevents backflow

5. Large Intestine (colon) √ reabsorbs water and minerals. Passes waste (fiber, bacteria, unabsorbed nutrients) along with water to rectum

6. Rectum √ stores water prior to elimination

7. Anus √ holds rectum closed
 

Liver √ makes bile and is the first to receive nutrients from the intestines

Gallbladder √ stores and concentrates bile: excretes bile into the duodenum when fat is present.

Pancreas √ secretes enzymes into duodenum

Appendix √ a narrow blind sac extending from the beginning of the colon that stores lymph cells
 

1. Peristalsis: wavelike contractions of the GI tract that push contents along
2. Stomach action: churns by muscular contractions
3. Segmentation: periodic squeezing or partitioning of the intestine at intervals by circular muscles
4. Sphincter contractions
 

1. Salivary Glands (in mouth): secrete saliva (secretes carbohydrase enzyme to act on carbohydrates)

2. Gastric Glands (stomach): secrete gastric juice; hydrolysis of proteins

Water, enzymes, and hydrochloric acid
Hydrochloric acid (HCl) √ very strong acid √ stomach protected by mucus

3. Pancreas-Intestinal:  Pancreatic Juices and Intestinal Enzymes

Digestion of Carbohydrates, Protein, Fat

4. Liver-Gallbladder-small intestine: Bile

Emulsifies fat: into a suspension

Homeostasis: maintenance of constant conditions (chemistry, temperature, blood pressure).  Stomach pH 1.5-1.7

Hormones

Gastrin: tells stomach to secret gastric juices

Gastric-peptide: Produced in intestine; tells stomach to slow secretion of gastric juices

Secretin: Produced in duodenum; tells pancreas to secrete bicarbonate-rich pancreatic juice

Cholecystokinin / CCK: Produced in intestine; tells gallbladder to release bile