Digestive system I

Department of Anatomy &Histology: Dr. Raja Ali
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Digestive SYSTEM:

• GENERALS TRUCTURE OF THE DIGESTIVET RACT
• ORAL CAVITY
• LIP
• Tongue
• HARD &SOFT PALATE
• Pharynx
• Teeth
• ESOPHAGUS
• STOMACH
• SMALL INTESTINE
• LARGE INTESTINE

2 groups of organs compose the digestive system
? Gastrointenstinal (GI) tract or alimentary canal – mouth, most of pharynx, esophagus, stomach, small intestine, and large intestine
? Accessory digestive organs – teeth, tongue, salivary glands, liver, gallbladder, and pancreas
Functions of the digestive system
1. Ingestion
2. Secretion of water, acid, buffers, and enzymes into lumen
3. Mixing and propulsion
4. Digestion
? Mechanical digestion churns food
? Chemical digestion – hydrolysis
5. Absorption – passing into blood or lymph
6. Defecation – elimination of feces
Layers of the GI tract
? Wall of GI tract from lower esophagus to anal canal has same basic 4 layers Fig. (1):
1. Mucosa – inner lining
? Epithelium protection, secretion, absorption
? Lamina propria – connective tissue with blood and lymphatic vessels and mucosa-associated lymphatic tissue (MALT)
? Muscularis mucosae – thin layer of smooth muscle making folds to increase surface area.
The main functions of the digestive tract epithelial lining
are to:
• . Provide a selectively permeable barrier between the contents
• of the tract and the tissues of the body,
• " Facilitate the transport and digestion of food,
• Promote the absorption of the products of this digestion,
• Produce hormones that affect the activity of the digestive
• system,
• Produce mucus for lubrication and protection.
2. Submucosa
? Connective tissue binding mucosa to muscularis
? Contains many blood and lymphatic vessels
? Submucosal plexus
3. Muscularis
? Voluntary skeletal muscle found in mouth, pharynx, upper 2/3 of esophagus, and anal sphincter
? Involuntary smooth muscle elsewhere
? Arranged in inner circular fibers and outer longitudinal fibers
? Myenteric plexus between muscle layers
4. Serosa
? Outermost covering of organs suspended in abdominopelvic cavity
? Also called visceral peritoneum
? The first two third of Esophagus lack serosa ( has adventitia)