1. Generalities, the Mouth and Salivary Glands
The Digestive System
Generalities, the Mouth and Salivary Glands

2. Human Digestive System
Digestion – the breakdown of food and absorption of resulting nutrients by cells
Structures
Alimentary canal (mouth, pharynx, esophagus, stomach, small intestine, large intestine, anal canal)
Accessory (teeth, tongue, salivary glands, liver, gall bladder, pancreas)
Basics: tube, open at both ends, 186 m2

3. mouth
pharynx

5. Structure of Wall
Mucosa – mucous membrane of surface epithelium, underlying CT, and small amount of smooth muscle tissue
Folded in some regions to increase surface area in lumen (digestive tube)

6. Movements of the Tube Two main types of movement
Mixing – smooth muscles in small segments of tube contract rhythmically
Propelling – wavelike motion called peristalsis
Ring of contraction appears in wall of tube and wall ahead of ring relaxes
Pushes tubular contents ahead of wave

7. Mouth – primary site of digestion
Reduces size of food particles (mechanical digestion)
Mixes with saliva (chemical digestion)
Lips, cheeks, tongue, and palate
Oral cavity – between palate and tongue
Vestibule – narrow space between teeth and cheeks

8. Mouth cont. Tongue – nearly fills oral cavity when mouth is closed
Frenulum – connects midline of tongue to floor of mouth
Skeletal muscle helps mix food w/ saliva and moves toward pharynx during swallowing
Papillae – rough projects providing friction and taste buds

9. Mouth cont. Palate – roof of oral cavity Anterior (hard palate)
Posterior (soft palate) – muscular arch that extends posteriorly and downward as a cone shaped projection  uvula
During swallowing muscles draw uvula upward to close opening between nasal cavity and pharynx  you may squirt food out your nose if this action isn’t completed fully before swallowing

11. Teeth Two sets during development
Primary (baby teeth) – shed in same order they appear  root reabsorbed before pressure from secondary teeth pushes out
Secondary (permanent) – 32 total (16 in each jaw)
Break down food into smaller pieces thus increasing surface area of particles

12. Teeth cont. Incisors – 4 central, 4 lateral Cuspids – 4
Biting off pieces
Cuspids – 4
Grasping and tearing food
Bicuspids – 4 first, 4 second
Grinding
Molars – 4 first, 4 second, 4 third

13. Teeth cont. Crown – portion of tooth above gum
White enamel covering – calcium salts (hardest substance in the body)
Cannot be replaced if damaged
Dentin – bone like substance surrounds central cavity (pulp cavity that extends into root)

14. Teeth cont. Root – portion below gum
Pulp cavity – contains blood vessels, nerves and a CT called pulp
Cementum – thin layer of bonelike material encloses root
Periodontal ligament – surrounds cementum with dense CT attaching tooth to jaw

15. Salivary Glands
Secrete saliva – moistens food particles, binds them, and begins chemical digestion of carbohydrates
Two types of cells
Serous cells – produce watery fluid that contains digestive enzyme amylase
Amylase splits starch and glycogen into disaccharides
Mucous cells – secrete thick mucus
Binds food particles and lubricates during swallowing

16. Salivary Glands cont. Three major pairs
Parotid glands – largest, lying anterior and somewhat inferior to each ear
Secretions rich in amylase
Submandibular glands – floor of mouth, on inside surface of lower jaw
Predominately serous, with a few mucous cells
Sublingual glands – smallest, floor of mouth, inferior to tongue
Mainly mucous, secretions thick and stringy

17. Salivary Glands