1. Digestive System

2. Organs

3. Digestive System Broken Down Into 2 Parts
1. Alimentary Canal – gastrointestinal (GI Tract) – Path that food travels
2. Accessory Organs

4. GI Tracts Accessory Organs Oral Cavity Pharynx Esophagus Stomach
Duodenum
Jejunum
Ileum
Cecum
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid Colon
Rectum
Anus
Tongue
Liver
Parotid Gland
Sublingual Gland
Submandibular Gland
Uvula
Lingual Frenulum
Pancreas
Gallbladder
Appendix

5. Mouth
Palate:
Hard
Soft
Uvula
Tongue

6. Salivary Glands Cleanses Mouth Important for Taste Moistens food
Contains Enzymes

7. Major Salivary Glands Parotid gland Submandibular gland
Sublingual gland
The average person produces ml a day

8. 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 Muscles  Peristalsis
Peristalsis - is a radially symmetrical contraction and relaxation of muscles that propagates in a wave down a tube

10. Esophagus
Propels food using muscles (Peristalsis)

11. Stomach Mostly Protein Digestion No Absorption***
Mechanically & Chemically Digested Into Chyme
Gastric glands produce gastric juice: acidic
Walls of Stomach lined with mucus so the acid doesn’t “digest itself”

12. Chyme
Substance in the stomach that is formed from food and enzymes

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

14. Small Intestine

15. Sm. Intestine
Chemical digestion of carbohydrates, proteins, nucleic acids, & fats
Done with enzymes from pancreas and bile (formed in liver)
Pancreatic duct and bile duct empty into duodenum – where enzymes empty into.

16. Large Intestine Function: Role of Bacteria: To absorb water
Eliminate residue as feces
Absorb vitamins produced by bacteria
Role of Bacteria:
Digest some nutrients
Produce vitamins
Produce gas

17. Action of L. Intestine Peristalsis
Mass Peristalsis: a strong wave that pushes contents towards rectum
Problems:
Diarrhea
Constipation

18. Accessory Organs - Pancreas
Releases enzymes into duodenum
Has an endocrine function

19. Accessory Organs - liver
Produces bile; leaves through common hepatic duct
Bile: part waste produce, part digestive secretion (mechanical digestion of lipids)

20. Other Liver Functions Metabolism of carbs, lipids, and proteins
Processing of drugs and hormones
Excretion of bilirubin (from hemoglobin of old RBCs)

21. Accessory Organs - Gallbladder
Releases bile in response to fatty food entering duodenum
Location: underside of liver
Gallstones

22. Steps of Digestion

23. Digestion
Major functions of the digestive tract are digestion and absorption

24. Essential Activities of the Gi Tract
Ingestion
Propulsion
Food Breakdown – mechanical digestion
Food Breakdown – chemical digestion
Absorption
Defecation

25. 1. Ingestion
Food must be placed into the mouth before it can be acted on.
Active, voluntary process

26. 2. Propulsion
In order for food to be processed by different organs, they must be propelled from one organ to the next.
Example:
Swallowing – depends on the propulsive process called peristalsis
Peristalsis – involuntary and involves alternating waves of contraction and relaxation of the muscles in the organ walls

27. 3. Food Breakdown – Mechanical Digestion
Mixing of food in the mouth by the tongue
Churning food in stomach
Segmentation – propels foodstuffs through the small intestine
Prepares food for further degradation by enzymes

28. 4. Food Breakdown – Chemical Digestion
Sequence of steps which large food molecules are broken down to their building blocks by enzymes

29. 5. Absorption
Transport of digested end products from the lumen of the GI tract to the blood or lymph
For absorption to occur, digested foods must first enter the mucosal cells by active or passive transport processes
Small intestine is major site of absorption

30. 6. Defecation
Elimination of indigestible residues from the GI tract via the anus to form feces

31. Neural & Hormonal Control

32. Cephalic Phase
Occurs before food enters the stomach, especially while it is being eaten
Brain is activated by smell, sight, thought, and taste of food
Neurons to salivary glands and gastric glands/stomach muscles
Autonomic Nervous System

33. Gastric Phase Stimulus: Food in stomach
Neural:
Stretch receptors activated. Impulse to neurons in submucosa
Triggers:
Gastric gland production and causes peristalsis
Hormonal:
Food triggers release of gastrin. Goes in the blood.
Triggers:
Gastric gland juices
Sphincter to prevent acid- reflux
Stomach muscles
Relaxes lower stomach sphincter

34. Intestinal Phase Stimulus: Food in Intestine
Neural:
Stretch receptors to medulla oblongata
Sympathetic nerves to stomach cause:
Decreased stomach movement & increase contraction of pyloric – bottom – sphincter (delays stomach emptying)
Hormonal:
Cholecytokinin (CCK): stimulates pancreatic juice/squeezes gallbladder