1. The digestive system
“ The digestive system takes in food, breaks it down into nutrient molecules and absorbs them into the bloodstream, and then rids the body of the indigestible remains.”
-E. Marieb

2. Consists of 2 “parts”
1. Alimentary canal (gastrointestinal - GI- tract) – path that food travels
2. Accessory organs

3. Digestive processes (disassembly)
Ingestion
Propulsion
a. Swallowing
b. peristalsis
Mechanical digestion
Chemical digestion
Absorption
Defecation

4. MOUTH (oral cavity)
Palate:
hard
Soft
uvula
Tongue

5. Salivary glands Cleanses mouth Important for taste Moistens food
Contains enzymes

6. Major salivary glands Parotid gland Submandibular gland
Sublingual gland
The average person produces ml a day

7. Teeth Masticate = to chew Baby teeth (deciduous)
Full set = 20 teeth
Permanent teeth = 32 teeth
Incisors
Canines
Premolars/molars

9. pharynx
Longitudinal & circular layers of muscle  peristalsis

10. esophagus
Propels food using muscles (peristalsis)

11. stomach

12. Mostly protein digestion
No absorption**
Mechanically and chemically digested into chyme
Gastric glands produce gastric juice: acidic
Walls of stomach lined with mucus so the acid doesn’t “digest itself”

13. Problems of the stomach
Ulcers: a hole in the mucus lining of the stomach
Heartburn (acid reflux): contents of stomach move into esophagus

15. Small Intestine

16. Small intestine
Chemical digestion of carbohydrates, proteins, nucleic acids, and fats
Done with enzymes from pancreas and bile (formed in liver).
Pancreatic duct and bile duct empty into duodenum

18. Absorption by small intestine
Increased surface area: villi, microvilli

19. Almost all food absorption
All structures increase surface area; decrease in # toward the end.
What’s left at end: some water, indigestible food material and large amounts of bacteria

20. DON’T WRITE:
Appendix C (A-5,6) – vitamins and minerals

21. (DON’T WRITE) 5 basic food groups and their major nutrients
FRUITS: carbohydrate, water (vitamins A, C, folic acid, iron, potassium, fiber)
VEGETABLES: carbohydrate, water (Vitamins A, C, E, K, B calcium, magnesium, iodine, manganese, phosphorus)
GRAINS: carbohydrate, protein, thiamin, niacin (water, fiber, iron, magnesium, selenium)
MILK PRODUCTS: protein, fat, riboflavin, B12, calcium, phosphorus, water
MEATS/MEAT ALTERNATIVES (eggs, seeds, nuts, soybeans, legumes): protein, niacin, B6, iron, zinc (carbohydrate, fat, B12, B1, water, fiber)

22. Large Intestine

23. Function of large intestine:
to absorb water
eliminate residue as feces
Absorb vitamins produced by bacteria
Role of bacteria:
Digest some nutrients
Produce vitamins
Produce gas

24. Problems: diarrhea and constipation
Action of L. intestine:
Peristalsis
Mass peristalsis: a strong wave that pushes contents towards rectum
Problems: diarrhea and constipation

25. PANCREAS
Releases enzymes into
duodenum
has an endocrine function

26. Don’t write: What is bile?
Bile is a yellow, brown, or green, watery solution containing bile salts, bile pigments, cholesterol, phospholipids and a variety of electrolytes. pH of 7.6 – 8.6

27. Liver Produces bile; leaves through common hepatic duct
Bile: part waste product, part digestive secretion (mechanical digestion of lipids)

28. Other liver functions Metabolism of carbs, lipids, and proteins
Processing of drugs and hormones
Excretion of bilirubin (from heme of old RBCs)

29. Gallbladder Releases bile in response to fatty food entering duodenum
Location: underside of liver
gallstones

30. liver summary…
Blood from stomach and intestines passes through liver. When the liver has broken down harmful substances, they are excreted into the bile or blood. Bile by-products enter the intestine and ultimately leave the body in the feces. Blood by-products are filtered out by the kidneys and leave the body in the form of urine.