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Digestive System Function: to obtain nutrients. Digestive System Function: obtaining nutrients. Activities of Digestion system: Ingestion – taking food or liquid into the mouth (eating or drinking). Movements Peristaltic and Segmentation Digestion Mechanical mastication - PowerPoint PPT Presentation
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Digestive SystemFunction:
to obtain nutrients
Digestive SystemFunction: obtaining nutrients
Activities of Digestion system:• Ingestion – taking food or liquid into the mouth (eating or drinking).• Movements
•Peristaltic and Segmentation• Digestion
•Mechanical• mastication• churning
• Chemical•Enzymes and acids
•Absorption – movement of substances into the body (across epithelium).• Elimination – involves compaction to eliminate waste from body
The Digestive System
Layers of Gastrointestinal Tract
• Four layers:– Know layers and their composition
• Tunic mucosa– Epithelial– Propria– Muscularis mucosae
• Tunic submucosa• Tunica muscularis externa• Tunica serosa-visceral peritoneum
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•Lines digestive tract•Moistened by glandular secretions•Simple or stratified depending on area of tract•Pleated for expansion (Surface Area)
Tunic Mucosa
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A Mucous membrane1) Epithelium2) Lamina propria 3) Muscularis mucosae
2. Tunic Submucosa
1. Tunic Mucosa
•Areolar Connective Tissue •Innervation•May have glands
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Smooth muscle layer capable of plasticityAbility to tolerate stretching
Visceral smooth muscle
Muscularis Mucosa
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3. Tunica Muscularis Externa
4. Tunica Serosa (or Adventitia*)
Smooth muscle layers
1) Inner Circular Layer 2) Outer Longitudinal Layer
Serous membrane – visceral peritoneum
* Name depends on location:a) Inside peritoneal cavity = serosab) Outside peritoneal cavity = adventitia
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Histology of the G.I. Tract
The Peritoneum: Two layersVisceral peritoneum (a.k.a serosa)Parietal peritoneum
Lines inner surfaces of body wall
Mesenteries: Fused double sheets of peritoneal membrane – to suspend portions of digestive tract:
Greater omentumLesser omentumMesentery properTransverse mesocolonSigmoid mesocolon
Serous Membranes
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Retroperitoneal Structures – these are attached to posterior abdominal wall
Ascending colonDescending colonDuodenumPancreas
Salivary glands
• Parotid• Sublingual• Submandibular
– Slightly different secretions– Release enzymes - amylase– Lubrication oral cavity
Fig
25.6
Fig
25.7
Only example of gomphosis joint
Incisors -clipping/cutting
Canines -tearing/slashing
Premolars - mashing/grinding
Molars mashing/grinding
Teeth
Regions:CrownNeckRoot
Layers:EnamelDentinPulp Cavity with Pulp
CementumApical foramenRoot canalPeriodontal membrane
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Pharynx and Esophagus
Deglutition
Swallowing
Epiglottis closes over larynx
Voluntary control
Fig
25.11
Tunica muscularis has three layers of muscle
Tunica mucosa has folds, rugae when empty
Secretin and cholecystokininInhibit gastric secretion
Histology of Gastric glandsChief - Pepsinogen; Parietal - HCl; Neck/Mucous Cells
Lacteal (terminal lymphatic) for lipid absorption
Small IntestineDuodenum
Jejunum
Ileum
Increase Surface Area for Absorption
Intestinal glandsGoblet cellsStem cells
Plicae CircularesIntestinal villiMicrovilli
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Diagrammatic view highlighting the distinguishing features of each region of the small intestine.
Duodenum:Duodenal (Brunner’s) glands produce:
•secretin •CCK•Alkaline mucus
Ilieum: lymphatic aggregations (Peyer’s patches)
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Secretin
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CCK
Large intestine
Functions of large intestineReabsorb water and compact fecesAbsorb vitaminsStore fecal matter
CecumIleocecal valveCollects material from small intestineVermiform appendix
Colon - ascending, transverse, descending and sigmoidRectum
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Histology of Large Intestine
Large Intestine:Lack of villiAbundance of goblet cellsMucous-secreting intestinal glandsMuscularis reduced to Taenia coliFatty appendices
Rectum and Anal canal
Horizontal section through the upper abdomen showing the position of the liver relative to other visceral organs.
Other digestive organs
Liver
Bile Ducts
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Diagrammatic view of lobular organization.
Pancreas
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EtOH on Liver
Pancreas
Exocrine: acini
Endocrine:
Pancreatic islets
Isles of Langerhans
Pancreas