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Digestive system / Bio160

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DIGESTIVE SYSTEM
Five Basic Processes
Ingestion - eating
2. Movement of the food along the G.I. tract.
3. Digestion- chemical and mechanical breakdown of food.
4. Absorption of the breakdown products into the lymphatic and circulatory systems.
5. Defecation - elimination of undigested substances.
alimentary canal
The Gastrointestinal tract
- extends from the moth to the anus.
- 30 feet long (in the cadaver)
- accessory structures
- aid in digestion
- example: teeth, liver, pancreas
Histology
- 4 basic layers with subdivisions
Mucosa, Submucosa, Muscularis, Serosa
Epithelium
- in contact with the food
- varies from stratified squamous in esophagus and anal canal to simple columnar
in the small intestine
Mucosa
- mucous membrane
- lining of a tract
- has 3 sublayers
Epithelium, Lamina Propria, Muscularis mucosae
Lamina Propria
- areolar connective tissue
Muscularis mucosae
smooth muscle
Submucosa
- binds mucosa to underlining smooth muscle layer
- made of areolar connective tissue
- contains ANS supply to muscularis mucosae called Submucosal Plexus (Plexus
of Meissner)
Muscularis
- in mouth, pharynx and esophagus is skeletal muscle
- in the rest of the tract is smooth muscle.
- usually contains 2 sheets (stomach has 3)
- inner circular
- outer longitudinal
- contains the major nerve supply to the major nerve supply the Myenteric
Plexus (Plexus of auerbach) controls motility
Serosa
- serous membrane
- made of connective tissue and epithelium
Mouth
- oral or buccal cavity
- anatomy
cheeks, labial frenulum, lingual frenulum, fauces, hard palate, soft palate
cheeks
help hold food in place between molars
labial frenulum
- mucous membrane fold
- attaches lips to gums
lingual frenulum
attaches tongue to base of oral cavity
fauces
opening between the oral cavity and the oropharynx (throat)
hard palate - made from:
palatine processes of the maxilla and horizontal plates of the palatine bones
soft palate
arch between oral pharynx and nasal pharynx
Tongue
- holds food in place over molars (with cheeks) so food can be masticated
- moves food to back of mouth for swallowing and is involved in swallowing
- 2 sets of muscles
Extrinsic muscles, Intrinsic muscles
Extrinsic muscles
the origin of the muscle is outside of the tongue. Functions; aids in chewing and swallowing and moves tongue in and out and from side to side.
Intrinsic muscles
- origin and insertion of muscles is inside the tongue itself
- functions
- alters the shape of the tongue
- speech and swallowing
glands on the surface of the tongue secrete ________
Lingual Lipase
-digest triglycerides into fatty acids and monoglycerides
Salivary Glands
- buccal glands secrete some_______
- 3 pairs of major salivary glands
saliva
Salivary Glands
- 3 pairs of major salivary glands
Parotid Salivary glands, Submandibular Salivary glands, Sublingual Salivary gland
Parotid Salivary glands
- located anterior to the ears
- secrete through parotid duct into the oral cavity by upper second molar
- secrete a watery mucous with salivary amylase
Submandibular Salivary glands
- located under the mandible at sides of tongue
- secrete a thicker saliva with mucous and salivary amylase
- empty under the tongue
Sublingual Salivary gland
- located under the tongue
- secrete a thick mucous with little salivary amylase
- secrete into mouth under the tongue
saliva is composed of:
99.5% water, 0.5% solutes like: ions, gases, urea/uric aid, serum proteins,
lysozyme, salivary amylase
Secretion of Saliva
- 1000 to 1500 ml secreted daily from salivary glands
- under nervous system parasympathetic stimulation from the salivary nuclei in the brain stem
secretion of the saliva can be brought about by:
- food in the mouth
- thought, smell, sound, sight of food.
Teeth
- accessory structures
- aid in masticating food
- two dentitions:
Deciduous teeth, Permanent teeth

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