1. Why a Digestive System ?
Kingdom Animalia
Heterotrophism

2. Digestive System General Function
The digestive system is responsible for the …
Intake and breakdown of complex foods into two categories:
Useable materials (nutrients)
Non-useable materials (wastes)

3. Six Major Digestive Processes
INGESTION
PROPULSION
MECHANICAL DIGESTION
CHEMICAL DIGESTION
ABSORPTION (of nutrients)
DEFECATION (of wastes)

4. GI Accessory Tract Organs
Oral Cavity
Esophagus
Stomach
Small Intestine
Large Intestine
Anus
Teeth
Tongue
Gall Bladder
Glands
Liver
Pancreas
Salivary

5. GI Tract and Accessory Organs

6. Digestive Processes of the Oral Cavity
INGESTION
MECHANICAL DIGESTION
CHEMICAL DIGESTION

7. Oral Cavity Borders: Anterior  Lips Lateral  Cheeks
Superior  Palate (Hard/soft)
Inferior  Tongue
Tongue:
Accessory Organ for:
mixing, taste buds
***

8. THE ESOPHAGUS carries bolus from oral cavity to stomach. PERISTALSIS
the automatic, involuntary, continuous propulsion of food through the GI tract.

9. P E R I S T A L S I S

10. Functional Anatomy cont
PART II
The STOMACH

11. Digestive Processes of the Stomach
Storage tank
Chemical digestion of proteins
Mechanical digestion
Bolus  Chyme
Volume— 50 ml  4 liters
Rugae allow for expansion
Enervated by ANS

12. Gastric Sphincters Cardiac Sphincter Pyloric Sphincter Functions:
Regulates/controls propulsion of food into/out of the stomach

13. Cardiac sphincter
Pyloric sphincter

15. PART III SMALL INTESTINE ACCESSORY STRUCTURES LIVER GALL BLADDER
PANCREAS

16. Small Intestine Three Regions: Duodenum Jejunum Ileum ~1 ft ~8 ft

17. Digestive Processes of the Small Intestine
CHEMICAL DIGESTION OF…
CARBOHYDRATES
PROTEINS
LIPIDS
NUTRIENT ABSORPTION!!

18. Microscopic Anatomy of the Small Intestine
Mucosa
Circular folds (“plicae circulares”)
Slow propulsion of chyme
Villi
Finger-like projections w/ capillaries in center
Microvilli
Small projections of cells that absorb nutrients (aka absorptive cells)

22. Before Nutrient Absorption occurs…
CHEMICAL DIGESTION MUST BE COMPLETED IN THE SMALL INTESTINE THROUGH ENZYMATIC ACTIVITY!

23. But There’s a Problem…
THE SMALL INTESTINE LACKS CELLS THAT PRODUCE/SECRETE DIGESTIVE ENZYMES!

24. Accessory Structures to the Rescue

25. LIVER Largest internal organ of the body Over 500 metabolic functions
Digestive Function:
Produces BILE for chemical digestion of LIPIDS

26. GALL BLADDER
Small sac embedded in liver
Stores bile produced by liver

27. PANCREAS Embedded within outer duodenum
Produces PANCREATIC JUICE containing:
Secretes PJ into duodenum via common bile duct
amylases
proteases
lipases
Nucleases

29. PART IV
THE LARGE INTESTINE (aka COLON)

30. Digestive Processes of the Large Intestine
ABSORPTION OF:
WATER
VITAMINS
PRODUCTION OF VITAMIN K
E. coli; bacterial flora
PROPULSION OF FECES FOR DEFECATION