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Functions
- Ingestion
- Mechanical processing
- Chemical digestion
- Absorption
- Excretion
- Defecation
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Accessory organs of digestive system
teeth, tongue, salivary glands, liver, pancreas
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Histological organization of digestive tract
- 1. Mucosa
- 2. Submucosa
- 3. Muscularis externa
- 4. Serosa
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Mucosa
Mucosa = mucous membrane- mucosal epithelium : simple or stratified; mucosa folds = plicae- Lamina propria: loose aerolar C.T- muscularis mucosae
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Submucosa
Submucosa - dense irregular C.T- exocrine glands - Brunner's glands = mucous; Peyer's patches= lymphoid- parasympathetic and sympathetic innervation - submucosal plexus
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Muscularis externa
- smooth muscle in circular and longitudinal layers
- myenteric nerve plexus - sympathetic and parasympathetic
- forms sphincters and valves
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Serosa
- Serous membrane
- none in oral cavity, pharynx, esophagus, rectum
- have adventitia - collagen fibers attach digestive tract to adjacent structures
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notes
- mucosa ends with muscularis mucosa
- muscularis externa - involuntary smooth muscle with gap junctions
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Peristalsis
alternate waves of contraction and relaxation of muscles in the organ walls; propels materials along the tract
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Segmentation
- no net movement
- fragment the materials in tract - smooth muscles - no sarcomeres, powerful gap junctions of sheet and layers
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serosa
visceral peritoneum
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greater omentum
pouch of fat, lymph nodes
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The Oral cavity
- Analysis, mechanical processing, lubrication, limited digestion - CHO
- lined by stratified squamous epithelium
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tongue
- manipulate food
- secretions aid in fat digestion (lipase)
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Salivary glands
- lubricates, moistens, dissolves chemicals, flushes mouth
- parotid - salivary amylase (CHO breakdown)
- sublingual - mucus (lubricates)
- submandibular (mixed)
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