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 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
Surgery to correct the problem
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

11. Part III: Liver, Pancreas, Intestines
Digestive System
Part III: Liver, Pancreas, Intestines

12. Small Intestine

13. Small intestine ~ 6 meters long 3 parts: DUODENUM -25 cm JEJUNUM-2.5 m
ILEUM-3.5 m

14. Small intestine Major site of digestion and absorption of food
Large surface area due to 3 modifications :
Circular folds
Villi
Microvilli
Mucosa and submucosa form circular folds
Fingerlike projections of mucosa = villi
Cytoplasmic extensions = microvilli
Blood capillary network and lacteal (lymphatic) inside each villi = important for trasnport of nutrients

16. Small intestine Mucosa and submucosa form circular folds
Fingerlike projections of mucosa = VILLI
Cytoplasmic extensions = MICROVILLI
Blood capillary network and LACTEALS(lymphatic) inside each villi = important for transport of nutrients
Mucosa and submucosa form circular folds
Fingerlike projections of mucosa = villi
Cytoplasmic extensions = microvilli
Blood capillary network and lacteal (lymphatic) inside each villi = important for trasnport of nutrients

17. Cells of small intestine
Absorptive cells: have microvilli, produce enzymes, absorb digested nutrients
Goblet cells: produce a protective mucus
Endocrine cells: regulatory hormones
Granular cells (Paneth’s cells): may help protect against bacteria

18. Secretions of small intestine
Peptidases: enzyme to break down proteins
Disaccharidases: enzyme to break down sugar
Lactase: specific disaccharidase that breaks down the sugar in dairy (lactose).
Most mammal species experience a sharp decrease in lactase production after infancy.
Worldwide, 60% of adults are lactose intolerant
In some Asian countries, 90% of adults have lactose intolerance; in Americans, 10% of adults; in Spain & France, 50% of adults.

19. Duodenum
Common bile duct (from liver) and Pancreatic duct (from pancreas) empty into this section of the small intestine

20. Liver

21. Liver 2 major lobes 2 major sources of blood
Hepatic artery: brings oxygen rich blood from heart to liver
Hepatic portal vein: brings oxygen poor but nutrient rich blood to liver from digestive tract

22. Liver: Bile Bile: produced by hepatocytes
Transported by hepatic ducts out of liver
Secretes 700 mL bile daily
Dilutes & neutralizes stomach acid
Bile salts: emulsify lipid globules
Gallbladder:
Small sac
Inferior surface of liver
Stores & concentrates bile

23. Liver: Detoxification
Alters structure of harmful substances
Example:
Ammonia : a byproduct of amino acid metabolism
Alcohol: removed from blood at a rate of ½ oz pure alcohol per hour
How your Body processes Alcohol:

24. Disorders of Liver Cirrhosis Viral Hepatitis
Damage to liver causes scarring
Inflammation of liver by 7 distinct viruses
Most common
A: poor sanitation
B: body fluids
C: chronic disease and possible cancer

25. Pancreas

26. EnZymes Of the Pancreas
HCO3 neutralizes acidic chyme from stomach
Protein Digestive enzymes:
Trypsin
Chymotrypsin
Carboxypeptidase
Lipid digestive enzymes:
Lipases