1. Chapter 14 – Part 1 The Digestive System

2. The Digestive System and Body Metabolism
Digestion
Takes in food (ingests it)
Breaks it down physically and chemically into nutrient molecules (digests it)
Absorbs the nutrients into the bloodstream
Then, it rids the body of the indigestible remains (defecates)

3. Organs of the Digestive System
The organs of the digestive system can be separated into two main groups:
Alimentary canal – continuous coiled hollow tube
Performs the whole menu of digestive functions (ingests, digests, absorbs, and defecates)
Accessory digestive organs
Assists the process of digestive breakdown in various ways
Includes the teeth, tongue, and several large digestive glands

4. Organs of the Digestive System

5. The Alimentary Canal
The alimentary canal is also called the gastrointestinal (GI) tract.
Continuous, coiled, hollow, muscular tube that winds through the ventral body cavity
Is open at both ends
Is about 30 feet long in a cadaver

6. Organs of the Alimentary Canal
Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Anus

7. Mouth (Oral Cavity) Anatomy
Lips (labia) – protect the anterior opening
Cheeks – form the lateral walls
Hard palate – forms the anterior roof
Soft palate – forms the posterior roof
Uvula – fleshy fingerlike projection of the soft palate

8. Mouth (Oral Cavity) Anatomy
Vestibule – space between lips and cheeks externally and the teeth and gums internally
Oral cavity proper – area contained by the teeth
Tongue – muscle that occupies the floor of the mouth

9. Mouth (Oral Cavity) Anatomy
Tonsils
Palatine tonsils
Lingual tonsil

10. Processes of the Mouth Mastication (chewing) of food
Mixing masticated food with saliva
Initiation of swallowing by the tongue
Allowing for the sense of taste

11. Pharynx Anatomy Nasopharynx – not part of the digestive system
Oropharynx – posterior to oral cavity
Laryngopharynx – below the oropharynx and connected to the esophagus

12. Pharynx Function
Serves as a passageway for air and food (oropharynx and laryngopharynx only)
Food is propelled to the esophagus by two muscle layers
Longitudinal inner layer
Circular outer layer (constrictor muscles)
Food movement is by alternating contractions of the muscle layers
This propelling mechanism is called peristalsis

13. Esophagus Runs from pharynx to stomach through the diaphragm
Conducts food by peristalsis (slow rhythmic squeezing)
Passageway for food only (respiratory system branches off after the pharynx)
About 10 inches long

14. Layers of Alimentary Canal Organs
Mucosa
Innermost layer
Moist membrane
Consists primarily of:
Surface epithelium
Plus a small amount of connective tissue (lamina propria)
Small smooth muscle layer

15. Layers of Alimentary Canal Organs
Submucosa
Found just beneath the mucosa
Soft connective tissue layer containing blood vessels, nerve endings, lymph nodules, and lymphatic vessels

16. Layers of Alimentary Canal Organs
Muscularis externa –
Smooth muscle layer made up of:
Inner circular layer
Outer longitudinal layer
Serosa
Outermost layer – visceral peritoneum
Layer of serous fluid-producing cells

17. Layers of Alimentary Canal Organs
Serosa
Outermost layer
Consists of a single layer of flat serous fluid-producing cells

18. Layers of Alimentary Canal Organs