1. Digestive System
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2. Digestive System Oral Cavity Ingestion Mechanical breakdown
Chemical breakdown
Propulsion (swallowing)

3. Digestive System Oral Cavity Salivary glands 1st Accessory Organ
Parotid
Sublingual
Submandibular

4. Digestive System
Oral cavity -> Pharynx -> Esophagus -> Stomach
Stomach
Mechanical breakdown
Chemical breakdown
Rugae: folds on the inside of the wall of the stomach
Allows the stomach to stretch
Empty stomach: approx 50ml
Full stomach: approx 2 liters

5. Digestive System
Stomach
3 layers
pH of 1.5 – 2.5

6. Digestive System Small Intestine 3 segments
Duodenum: first and shortest
Jejunum
Ileum

7. Digestive System Duodenum
Where liver, gallbladder and pancreas secretions enter

8. Digestive System
Jejunum:
Follows duodenum, about 8 feet long

9. Digestive System Small intestine lining Villi
Microvilli : “brush border”

10. Digestive System
Ileum
3-5 feet long

11. Digestive System Small intestine:
Major site for absorption for the end products of digestion

12. Digestive System A few more notes about enzymes and hormones.
The gallbladder releases bile into the small intestine. The hormone that stimulates this release is called cholecystokinin-pancreozymin.
The pancreas can release a bicarbonate into the small intestine, in addition to its digestive enzymes. The hormone that stimulates the release of bicarbonate is secretin.

13. Digestive System
Proteins are broken down by enzymes in gastric and intestinal juices.
Fats are broken down by lipase enzyme in the small intestine.
Carbohydrates are broken down by enzymes in the mouth and small intestine.
The major final product that results from the digestion of carbohydrates is glucose.

14. Digestive System
A chemical digestion process called enzymatic hydrolysis can break the bonds holding the molecular ‘building blocks’ within the food together.
Water splits larger compounds into smaller ones.
Hydrochloric acid converts pepsinogen into pepsin.

15. Digestive System
Enzymes are very specific, they fit their substrates like a “key-in-a-lock.”
Enzymes are pH sensitive because changes in hydrogen ion concentrations can affect the shape of the protein molecule.

16. Digestive System
A wavelike muscle contraction that moves food along the digestive system is called perstalsis