Flashcards in Exam 4: Digestive System Deck (58)
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Gastrointestinal (GI) Tract
-tube that extends from mouth to anus
-mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus
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Functions of GI Tract
-digestion
-absorption
-elimination of wastes
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Digestion
-process of breaking down food into small fragments
-2 types mechanical and chemical
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Mechanical Digestion
-using forces/physically breaking down food
-Ex: stomach mechanically digests by muscle contraction
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Chemical Digestion
-uses enzymes (proteins) that speed up a chemical reaction
-Ex: stomach chemically digests with gastric juices
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Absorption
-water and food molecules pass through to GI lymphatics and blood vessels
-most nutrients absorbed in blood vessels
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Lacteals
-absorb lipids and lipid soluble vitamins in small intestine (A, D, E, K)
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Accessory Digestive Organs
-not part of GI tract but assist with digestion
-tongue, teeth, salivary glans, liver, gallbladder, pancreas
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Peritoneum
-serous membrane that lines the abdominal cavity
-parietal lines abdominal wall
-visceral covers abdominal organs
-peritoneal cavity is the space between the two, serous fluid secreted here
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Parasympathetic Innervation
-in general, it stimulates or increases activity of GI tract
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Sympathetic Innervation
-in general, it inhibits or decreases activity of GI tract
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Oral Cavity
-continuous posteriorly with oropharynx
-nonkeratinized stratified squamous epithelium
-upper part of the oral cavity: palate
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Hard Palate
-anterior 2/3 of palate, bony
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Soft Palate
-posterior 1/3 of palate, formed from skeletal muscle
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Uvula
-dangling muscle off soft palate
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Extra Credit Names
-Osmosis Jones and Drix
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Function of Soft Palate and Uvula
-close off opening to nasopharynx when you swallow
-these muscles move and that's why milk goes up your nose
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Teeth
-20 deciduous (baby) teeth replaced by 32 permanent teeth
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Tongue
-big skeletal muscle
-covered with stratified squamous epithelium
-function: perceives taste and mechanical digestion
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Salivary Glands
-3 pairs
-secrete saliva composed of water, mucus, amylase (digests carbs), lysozyme (antibacterial agent) and antibodies
-functions: dissolves food molecules so they can be tasted, moistens food and turns it into bolus, chemically digests carbs, cleanses mouth, lysozyme and antibodies inhibit bacterial growth
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Pharynx
-throat
-muscular tube that connects nasal cavity and mouth, to larynx and esophagus
-function: propel food and drink to esophagus and air to larynx
-only the oropharynx and laryngopharynx conduct both food and air
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GI Tract Layers
-4 layers, tunics
-mucosa, submucosa, muscularis, adventita/serosa
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Mucuosa
-innermost tunic
-esophagus has nonkeratinized stratified squamous epithelium
-stomach to anal canal has simple columnar epithelium
-areolar CT
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Muscularis Mucosae
-thin layer of smooth muscle
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Submucosa
-connective tissue
-contains major blood vessels
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Muscularis
-typically contains 2 layers of smooth muscle:
-exception: stomach (3 layers)
-inner circular layer
-outer longitudinal layer
-responsible for peristalsis: alternate waves of contraction and relaxation
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Serosa or Adventitia
- outermost layer
-serosa = visceral peritoneum + areolar CT
-adventitia = areolar CT only
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Esophagus Gross Anatomy
-muscular tube that connects pharynx to stomach
-function:propel food to stomach
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Esophagus Histology
-mucosa: nonkeratinized stratified squamous epithelium
-muscularis: 2 layers of muscle
-upper 1/3: skeletal muscle
-middle 1/3: skeletal + smooth
-lower 1/3: smooth muscle only
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