1. Gastrointestinal System
Structure and Function

2. Gastrointestinal system

3. Where does digestion occur?
Begins in the mouth
Ends at the anus

4. Types of Digestion Mechanical digestion: mastication (teeth, tongue)
Chemical digestion: salivary glands secrete ptyalin; CHO digestion

5. The Mouth Mechanical: mastication
Chemical: saliva contains “ptyalin” that begins breakdown of carbohydrates

6. The Tongue Moves food around
Saliva that is produced coats and lubricates the food for easier chewing and swallowing.
Taste buds occur in different areas of tongue: bitter, sweet, salty, sour

7. The Teeth Chew and break food down into small morsels
The Gingivae (gum) support and protect the teeth

8. The Salivary Glands Located in and around the mouth and throat.
Saliva is secreted into the oral cavity by three pairs of salivary glands:
Parotid salivary glands – largest salivary gland, swell during an attack of mumps
Submandibular gland - about the size of a walnut, its secretions contain both mucin and ptyalin
Sublingual glands – the smallest, secrete mainly mucus and contain no ptyalin

9. The Pharynx Serves as a passageway for food (swallowing) and air
When a person swallows the back of the tongue helps close the epiglottis which directs food away from the larynx and into the esophagus.

10. The Peritoneum Two layered membrane Lines the abdominal cavity
Parietal layer: lines entire abdominal cavity
Visceral layer: covers the outside of each abdominal organ
Mesentary: attached to posterior abdominal wall; small intestines anchored here
Greater Omentum: 2 layers of peritoneum containing fat; hangs over abdominal organs

11. The Esophagus Connects the pharynx to the stomach
Carries food, liquids, and saliva from the mouth to the stomach
When food (bolus) is swallowed it enters the upper portion of the esophagus
The walls of the esophagus have four layers: the mucosa, submucosa, muscular, and external serous layer

12. The Stomach Muscular organ located in LUQ
Chemical and mechanical digestion continues; semisolid solution “chyme”
Secretes HCl: aids in protein breakdown, kills bacteria, & aids Fe absorption
Secretes intrinsic factor: vitamin B12 absorption
Secretes “lipase”: fat digestion
Rennin: infant stomachs – milk digestion
Contains rugae for expansion
Cardiac sphincter: separates esophagus and stomach
Pyloric sphincter: separates stomach and duodenum

13. The Stomach Continued…
Secretes “lipase”: fat digestion
Rennin: infant stomachs – milk digestion
Contains rugae for expansion
Cardiac sphincter: separates esophagus and stomach
Pyloric sphincter: separates stomach and duodenum

14. The Stomach

15. The Small Intestine Duodenum: first 10 inches Jejunum: middle section
Ileum: terminal section
Entire section is approximately 20 ft. in length and 1 inch in diameter
Absorption of nutrients (CHO, fats, proteins, vitamins, minerals)
Digestion completed

16. The Duodenum
Bile and pancreatic juices enter here; calcium, fat, and iron digestion/absorption begin

17. The Jejunum
Middle section
Fats, proteins, CHO absorption

18. The Ileum Terminal end of small intestine
Vitamin B12 and bile salts absorbed here
Separated from large intestine by ileocecal valve or cecum
Digestion is completed in small intestine
Villi and microvilli: fingerlike projections on inside of small intestine; increase surface area for absorption

19. The Villi and microvilli

20. Nutrient absorption
Villi contain blood capillaries to absorb sugars and proteins
Lacteals, in the villi, absorb fats

21. The Large Intestine Approximately 5 – 6 feet long
Separated from small intestine by ileocecal valve
Forms framework around small intestine
Absorbs water
Eliminates waste
Contains bacteria that produce vitamin K and B12

22. The Large intestine Ascending colon Transverse colon Descending colon
Sigmoid colon
Rectum: stores solid waste
Anus: terminal opening of GI tract

23. The Vermiform appendix
Small blind pouch located at ileocecal valve
Contains lymphatic type tissue
May aid in infection control

24. The Liver Located in RUQ Makes bile for fat breakdown
Stores sugar in form of glycogen
Stores Fe and fat soluble vitamins
Produces clotting factors
Detoxifies harmful substances

25. The Gallbladder
Located beneath liver
Stores bile and releases it when fat enters duodenum

26. The Pancreas Located behind stomach in LUQ
Produces enzymes for digestion
Amylase: breakdown sugar
Trypsin, chymotrypsin: breakdown protein
Lipase: breakdown fats
Produces hormone insulin
Insulin needed for sugar to enter cells

27. Digestive system GI tract Starts with mouth and ends with anus
Chemical and mechanical digestion