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Mucosa
- Innermost layer
- all nutrients must cross the mucosa to enter the blood
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Submucosa
- layer of connective tissue containing blood vessels, lymph vessels, and nerves.
- components of food that are absorbed across the mucosa enter the blood and lymph vessels of this layer.
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muscularis
- responsible for motility or movement
- consists of two or three sublayers of smooth muscle
- inner sublayer oriented in circular fashion around the lumen
- outer sublayer arranged lengthwise.
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serosa
- outermost layer of the gastrointestinal tract wall
- thin connective tissue surrounds and protects the three layers
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sphincters
rings of circular smooth muscle that may be between organs
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Digestive System Processes
1) Mechanical Processing and Movement
Chewing, mixing, propelling
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Digestive System Processes
2) Secretion
fluid, digestive enzymes, acid, alkali, bile, and mucus are secreted into GI tract
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Digestive System Processes
3) Digestion
breakdown food to smallest absorbable units
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Digestive System Processes
4) Absorption
through mucosa into blood or lymph vessels
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Digestive System Processes
5) Elimination
undigested material is eliminated form the body
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Bolus
food that has been chewed into a mass
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Peristalsis
- Propels food down the GI tract by wave like muscle contractions
- mainly in esophagus
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segmentation
- mixes food by muscles contracting and relaxing
- mainly in small intestine
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The Mouth
- begins digestion
- -teeth
- -tongue
- -saliva
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swallowing
- delivers food to stomach
- -voluntary: tongue pushes bolus into pharynx
- -Involuntary: receptors stimulated by presence of food in pharynx
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epiglottis
closes opening to trachea when food is present
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pharynx
common passage way for air, food, and liquid
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