1. A journey of nutrition p. 454-485 Part II
Ch. 16 Digestive System
A journey of nutrition p
Part II

2. Getting & Using Food Ingest Digest Absorb Eliminate
taking in food
Digest
mechanical digestion
breaking up food into smaller pieces
chemical digestion
breaking down food into molecules small enough to be absorbed into cells
enzymes
Absorb
absorb nutrients across cell membranes
diffusion
active transport
Eliminate
undigested material passes out of body
intracellular digestion
extracellular digestion

3. Human digestive system
After chewing and swallowing, it takes 5 to 10 seconds for food to pass down the esophagus to the stomach, where it spends 2 to 6 hours being partially digested.
Final digestion and nutrient absorption occur in the small intestine over a period of 5 to 6 hours.
In 12 to 24 hours, any undigested material passes through the large intestine, and feces are expelled through the anus.

4. Stomach Lesser Curve, Greater Curve Fundus Three layers of muscle
Rugae
Cardiac
Phyloric

5. Gastric Glands
Gastric pits : openings for glands along the mucosal surface of stomach
5 groups:
Surface Mucous cells
Mucous Neck cells
Parietal cells: HCl and Intrinsic Factor
Endocrine cells: regulatory hormones
Chief cells: pepsinogen
Surface Mucous Cells: mucus coating to protect stomach
Neck cells: produce mucus
Parietal cells: HCl and intrinsic factor (absorbs vitamin B12 in small intestine)
Chief cells: pepsinogen (protein digesting enzyme)

6. Gastric Glands
Gastric pits : openings for glands along the mucosal surface of stomach
5 groups:
Surface Mucous cells
Mucous Neck cells
Parietal cells: HCl and Intrinsic Factor
Endocrine cells: regulatory hormones
Chief cells: pepsinogen
Surface Mucous Cells: mucus coating to protect stomach
Neck cells: produce mucus
Parietal cells: HCl and intrinsic factor (absorbs vitamin B12 in small intestine)
Chief cells: pepsinogen (protein digesting enzyme)

7. Hypertrophic Pyloric Stenosis
Defect of stomach
Thickened pylorus
Food cannot enter small intestine
Results in projectile vomiting, reduces nutrient uptake, infant fails to gain weight
Possible connection to an antibiotic used by mother? ethromycin

8. Gastric Bypass Roux-en-Y: most common
Small stomach pouch by stapling stomach together or by vertical banding
Y-shaped section of small intestine

9. Phases of Stomach Secretion Regulation
Cephalic phase: sensation of taste, smell, process of chew/swallow stimulate medulla oblongata
Gastric secretions: mucus, HCl, pepsinogen, intrinsic factor
Gastric Phase: Presence of food in stomach
Greatest amount of secretion
Distention in stomach stimulates
Intestinal Phase: controlled by chyme entering intestine
Secretin: inhibits gastric secretions

10. Movement in stomach
Every 20 seconds contractions occur in stomach wall
Mixing waves: mix food with stomach secretions, more solid food moves to center while fluid food towards pyloric sphincter
Peristaltic waves: push chyme toward and through pyloric sphincter