Digestive System
Function:
to obtain nutrients
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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
• 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 QuickTime™ and a
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– Epithelial
– Propria
– Muscularis mucosae
• Tunic submucosa
• Tunica muscularis externa
• Tunica serosa-visceral peritoneum
Tunic Mucosa
•Lines digestive tract
•Moistened by glandular secretions
•Simple or stratified depending on area of tract
•Pleated for expansion (Surface Area)
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1. Tunic Mucosa
A Mucous membrane QuickTime™ and a
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1) Epithelium
2) Lamina propria
3) Muscularis mucosae
2. Tunic Submucosa
•Areolar Connective Tissue QuickTime™ and a
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•May have glands
Muscularis Mucosa
Smooth muscle layer capable of plasticity
Ability to tolerate stretching
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Visceral smooth muscle
3. Tunica Muscularis Externa
Smooth muscle layers
1) Inner Circular Layer QuickTime™ and a
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2) Outer Longitudinal Layer
4. Tunica Serosa (or Adventitia*)
Serous membrane – visceral peritoneum
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a) Inside peritoneal cavity = serosa
b) Outside peritoneal cavity = adventitia
Histology of the G.I. Tract
Serous Membranes
The Peritoneum: Two layers
Visceral peritoneum (a.k.a serosa)
Parietal peritoneum
Lines inner surfaces of body wall
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Mesenteries: Fused double sheets of
peritoneal membrane – to suspend portions of
digestive tract:
Greater omentum
Lesser omentum
Mesentery proper
Transverse mesocolon
Sigmoid mesocolon
Retroperitoneal Structures – these are attached to posterior abdominal wall
Ascending colon
Descending colon
Duodenum
Pancreas
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:
Crown
Neck QuickTime™ and a
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Layers:
Enamel
Dentin
Pulp Cavity with Pulp
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Apical foramen
Root canal
Periodontal membrane
Voluntary
control
Pharynx and
Esophagus
Deglutition
Swallowing
Epiglottis
closes over
larynx
Tunica Fig
muscularis 25.11
has three Tunica
layers of mucosa
muscle has folds,
rugae
when
empty
Histology of Gastric glands
Chief - Pepsinogen; Parietal - HCl; Neck/Mucous Cells
Secretin and cholecystokinin
Inhibit gastric secretion
Small Intestine
Duodenum
Jejunum
Ileum
Increase Surface Area for Absorption
Plicae Circulares
Intestinal villi
Microvilli
Lacteal (terminal lymphatic)
for lipid absorption
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Goblet cells
Stem cells
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)
Secretin
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CCK
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Large intestine
Functions of large intestine
Reabsorb water and compact feces
Absorb vitamins
Store fecal matter
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Cecum
Ileocecal valve
Collects material from small intestine
Vermiform appendix
Colon - ascending, transverse, descending and sigmoid
Rectum
Histology of Large Intestine
Large Intestine:
Lack of villi
Abundance of goblet cells
Mucous-secreting intestinal glands
Muscularis reduced to Taenia coli
Fatty appendices
Rectum and Anal canal
Other digestive organs
Horizontal section through the upper abdomen showing the position of the liver relative to other
visceral organs.
Liver
Bile Ducts
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Diagrammatic view of lobular organization.
Pancreas
EtOH on Liver
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Pancreas
Pancreas
Exocrine: acini
Endocrine:
Pancreatic islets
Isles of Langerhans