1. Layers of Alimentary Canal Organs
Four layers
Mucosa
Submucosa
Muscularis externa
Serosa

2. Structural Plan of the Digestive Tube
Wall Layer
Subdivision of the layer
Major Functions
Mucosa
Surface epithelium
Lamina propria: (connective tissue)
Smooth muscle layer
Secretion of enzymes, mucus, hormones, etc.
Absorption of digested foodstuffs
Protection against bacterial invasion
Submucosa
Connective tissue
Lymph nodules
Nerve Fibers
Protection
Muscularis externa
Circular muscular layer
Longitudinal muscle layer
Regulates GI Motility
Serosa
Visceral peritoneum
Reduces friction as the GI tract organs work

3. Organs of the Alimentary Canal
continuous coiled hollow tube
From mouth to anus
Figure 14.1

4. Stomach
Muscularis externa has a third oblique layer in the stomach in addition to the longitudinal layer and the circular layer.
The stomach is able to churn, mix, and pummel the food, physically breaking it down into smaller pieces.

5. Digestive System Terms
Appendix: a narrow, blind tube protruding from the cecum, having no known useful function, in humans being 3 to 4 inches (8 to 10 cm) long and situated in the lower right-hand part of the abdomen.
Anus: the distal end of the alimentary canal.
Esophagus: the part of the alimentary canal between the pharynx and the stomach; no digestive or absorptive role
Frendulum: membrane securing the tongue to the floor of the mouth
Greater omentum: a two-layered serous membrane attached to the greater curvature of the stomach
Hard palate :the anterior portion of the palate, separating the oral and nasal cavities, consisting of the bony framework and covering membranes.
Haustra: the small pouches caused by sacculation, which give the colon its segmented appearance
Ileocecal valve: physiological sphincter muscle situated at the junction of the small intestine (ileum) and the large intestine, with recent evidence indicating an anatomical sphincter may also be present in humans) Its critical function is to limit the reflux of colonic contents into the ileum
Large intestine: organ distal to the small intestine
Lesser omentum: a peritoneal fold joining the lesser curvature of the stomach and the first part of the duodenum to the porta hepatis.
Mesentry: refers to the peritoneum responsible for connecting the jejunum and ileum (parts of the small intestine) to the back wall of the abdomen.
Microvilli: surface projections of a mucosal epithelial cell; increases absorption
Oral Cavity= another name for “mouth”; the first portion of the alimentary canal that receives food and saliva; Mastication (chewing) of food; Mixing masticated food with saliva; Initiation of swallowing by the tongue; break down food mechanically
Parietal peritoneum: the portion of the largest serous membrane in the body that lines the abdominal wall
Peyer’s patches: one of a group of solitary nodules or groups of lymph nodes forming a single layer in the mucous membrane of the small intestine
Pharynx: is the part of the throat situated immediately posterior to (behind) the mouth and nasal cavity, and superior to the esophagus and larynx. Common passage for food and air
Plicae circulares: the numerous permanent crescentic deep folds of mucous membrane found in the small intestine especially in the lower part of the duodenum and the jejunum; increases absorption
Pyloric sphincter (valve): The pyloric sphincter, or valve, is a strong ring of smooth muscle at the end of the pyloric canal which lets food pass from the stomach to the duodenum.
Rugae: large folds in the mucous membrane of the stomach.
Small Intestine: part of the gastrointestinal tract following the stomach; bile produced by the liver and stored in the gallbladder, is secreted in the small intestine to assist in the absorption of fats; digestion is completed and nutrients and water are absorbed by the blood; pancreatic juice is secreted via the pancreatic duct into duodenum.
Soft palate: the fleshy part of the palate, extending from the posterior edge of the hard palate; the uvula projects from its free inferior border
Stomach: Mechanically, the stomach churns and grinds the food into smaller and smaller pieces, turning it into a substance of nutrients and gastric juices known as chyme.
Tongue: rolls the food into balls or boli (singular: 'bolus') and pushes them to the back of the mouth cavity for swallowing
Vestibule: the portion of the oral cavity bounded on one side by the teeth and on the other side by the lips and cheeks.
Villi: one of the minute fingerlike processes which more or less thickly cover and give a velvety appearance to the surface of the mucous membrane of the small intestine and serve in the absorption of nutriment and of which each has a central blindly ending lacteal surrounded by blood capillaries and covered with epithelium; increases absorption
Visceral peritoneum: That portion of the peritoneum covering the organs of the abdominal cavity

6. Digestive Structures

10. Teeth Function is to masticate (chew) food
Humans have two sets of teeth
Deciduous (baby or “milk”) teeth
20 teeth are fully formed by age two

11. Teeth
Permanent teeth
Replace deciduous teeth between the ages of 6 and 12
A full set is 32 teeth, but some people do not have wisdom teeth (third molars)
If they do emerge, the wisdom teeth appear between ages of 17 and 25

12. Classification of Teeth
Incisors—cutting
Canines—tearing or piercing
Premolars—grinding
Molars—grinding

13. Human Deciduous and Permanent Teeth
Figure 14.9

14. Regions of a Tooth Crown—exposed part
Enamel—hardest substance in the body
Dentin—found deep to the enamel and forms the bulk of the tooth
Pulp cavity—contains connective tissue, blood vessels, and nerve fibers
Root canal—where the pulp cavity extends into the root

15. Regions of a Tooth Neck Region in contact with the gum
Connects crown to root
Root
Cementum—covers outer surface and attaches the tooth to the periodontal membrane

16. Regions of a Tooth
Figure 14.10

17. The Digestive System Functions
Ingestion—taking in food
Digestion—breaking food down both physically and chemically
Absorption—movement of nutrients into the bloodstream
Defecation—rids the body of indigestible waste

18. Organs of the Digestive System
Two main groups
Alimentary canal (gastrointestinal or GI tract)—continuous coiled hollow tube
Accessory digestive organs

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

20. 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 projection of the soft palate

21. Mouth (Oral Cavity) Anatomy
Vestibule—space between lips externally and teeth and gums internally
Oral cavity proper—area contained by the teeth
Tongue—attached at hyoid bone and styloid processes of the skull, and by the lingual frenulum to the floor of the mouth
Tonsils
Palatine
Lingual

22. Mouth (Oral Cavity) Anatomy
Figure 14.2a

23. Mouth (Oral Cavity) Anatomy
Figure 14.2b

24. Mouth Physiology Mastication (chewing) of food
Mixing masticated food with saliva
Initiation of swallowing by the tongue
Allows for the sense of taste

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

26. Pharynx Anatomy
Figure 14.2a

27. Pharynx Physiology Serves as a passageway for air and food
Food is propelled to the esophagus by two muscle layers
Longitudinal inner layer
Circular outer layer
Food movement is by alternating contractions of the muscle layers (peristalsis)

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

29. Layers of Alimentary Canal Organs
Mucosa
Innermost, moist membrane consisting of
Surface epithelium
Small amount of connective tissue (lamina propria)
Small smooth muscle layer

30. Layers of Alimentary Canal Organs
Figure 14.3

31. Layers of Alimentary Canal Organs
Submucosa
Just beneath the mucosa
Soft connective tissue with blood vessels, nerve endings, and lymphatics

32. Layers of Alimentary Canal Organs
Figure 14.3

33. Layers of Alimentary Canal Organs
Muscularis externa—smooth muscle
Inner circular layer
Outer longitudinal layer
Serosa—outermost layer of the wall contains fluid-producing cells
Visceral peritoneum—outermost layer that is continuous with the innermost layer
Parietal peritoneum—innermost layer that lines the abdominopelvic cavity

34. Layers of Alimentary Canal Organs
Figure 14.3

35. Alimentary Canal Nerve Plexuses
Two important nerve plexuses serve the alimentary canal
Both are part of the autonomic nervous system
Submucosal nerve plexus
Myenteric nerve plexus
Function is to regulate mobility and secretory activity of the GI tract organs