Digestive System Basic Divisions – Digestive tract – Accessory organs: various exocrine glands.
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Transcript of Digestive System Basic Divisions – Digestive tract – Accessory organs: various exocrine glands.
• Digestive Processes
– Ingestion
– Mechanical Processing
– Motility
•Peristalsis
•Segmentation movements
• Digestive Processes, continued
– Chemical digestion
– Secretion
– Absorption
– Excretion and defecation
• Layers of the digestive tract– Mucosa
• Epithelium• Lamina propria (areolar CT)
• Muscularis mucosae
• Layers of the digestive tract, continued
– Muscularis externa:
responsible for peristalsis and segmentation movements
• longitudinal layer
• circular layer
• myenteric plexus
• Layers of the digestive tract, continued– Serosa (the visceral
peritoneum is an example)• Simple squamous epithelium
• Areolar CT Within peritoneal cavity
only
• Layers of the digestive tract, continued
– Adventitia
• Dense irregular CT Oral cavity, pharynx,
esophagus, rectum
• The mesenteries
– Mesentery proper
– Mesocolon
– Greater omentum
– Lesser omentum
– Falciform ligament
• Accessory structures of the oral (buccal) cavity– Teeth: will cover in lab– Tongue: read textbook– Salivary glands
• buccal glands• lingual glands
• Oral (buccal) cavity– Salivary Glands
• buccal glands• lingual glands• major salivary glands
– parotid
• Oral (buccal) cavity– Salivary Glands
• buccal glands• lingual glands• major salivary glands
– parotid– sublingual– submandibular
– Functions of saliva
• lubrication for swallowing, speaking
• re-mineralizes tooth enamel
• buffer
• antibodies (IgA)
• dissolves food molecules
• some chemical digestion
• Esophagus
– Structural features
• muscular tube about 25 cm long
• posterior to larynx, trachea
• pierces diaphragm through esophageal hiatus
• Histology highlights
– mucosa
– submucosa: lots of mucous glands
– muscularis externa
– adventitia (no serosa)
• Stomach Histology
– mucosa: location of gastric glands
• gastric gland cells
– mucous cells
– parietal cells
– chief cells
– endocrine cells
• Stomach Functions– food reservoir– formation of chyme– some chemical digestion– regulation of chyme entry into
S.I.– intrinsic factor production– some absorption
Digestive System, review
• Basic Divisions
– Digestive tract
– Accessory organs: various exocrine glands
– Liver Functions
• Maintains blood glucose levels
• Cholesterol synthesis
• HDL and LDL synthesis
• Plasma protein synthesis
– Liver Functions, continued
• Hormone and drug removal
• Phagocytosis
• Vitamin storage
• Iron storage
• Bilirubin excretion
– Liver Functions, continued
• Hormone and drug removal
• Phagocytosis
• Vitamin storage
• Iron storage
• Bilirubin excretion
– Liver Functions, continued
• Hormone and drug removal
• Phagocytosis
• Vitamin storage
• Iron storage
• Bilirubin excretion
• Bile salt secretion
• Gross Structural Features of Gall Bladder
– Muscular sac
– Mucosa folded into rugae
– Bile enters and leaves through cystic duct
• Gall Bladder Function
– Stores and concentrates bile
– Contracts during meals to force bile into SI
• Small Intestine
– 1 inch diameter
– 10-20 ft. in length
• duodenum (10 in)
• jejunum (3-6 ft.)
• ileum (6-12 ft)
• Features of SI mucosa, cont’d
–Epithelial cell types:
•absorptive cells
•Goblet cells
•Endocrine cells
•Paneth cells
• Functions of small intestine
– Completion of chemical digestion
• “brush-border” enzymes required
– Absorption
– Endocrine control of some digestive processes
• Features of LI mucosa– no villi– numerous
intestinal glands– goblet and
absorptive cells in epithelium
– MALT in lamina propria
• Other Structural Features
– Vermiform appendix
– Ileocecal valve
– Stretch receptors in rectum
• initiate defecation reflex
• Other Structural Features
– Vermiform appendix
– Ileocecal valve
– Stretch receptors in rectum
• initiate defecation reflex
– Anal sphincters of anal canal
• Motility of Large Intestine
– From cecum to transverse colon:
• peristalsis
– From transverse colon to rectum:
• mass movements
• Large Intestinal Bacteria
– Coat surface of mucosa
– Examples: E. coli
– Keep out pathogenic bacteria