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Digestive System Notes
Digestive system functions
• Mechanical processing
• Secretion
• Digestion
• Absorption
• Elimination
Digestion
 The mechanical and chemical breakdown of foods and the absorption of the
resulting nutrients by cells
 Mechanical digestion: breaking down large pieces into smaller ones
 Chemical digestion: breaks food into simpler chemicals
Alimentary canal
 About 8 m long
 Extends from mouth to anus
 Includes: mouth, pharynx, esophagus, stomach, small intestine, large
intestine, rectum and anus
 4 layers: mucosa, submucosa, muscular layer, and serosa
 Moves food by peristalsis (wavelike muscle contractions)
Accessory organs
 Not part of the alimentary canal
 Food does not travel through these organs, but they help out with digestion
 Includes:
 salivary glands- secrete saliva into mouth
 Liver- aids in metabolism of carbs, lipids and proteins; stores nutrients,
secretes bile
 Gallbladder- stores bile; releases bile into small intestine
 Pancreas- secretes pancreatic juice into small intestine
Mouth
 Begins digestion by mechanically breaking down food and mixing it with saliva
 Includes: cheeks, lips, tongue, palate, pharyngeal tonsils, teeth
Esophagus
 Connects pharynx to stomach
 Joins to stomach at the lower esophageal sphincter or cardiac sphincter
Stomach
 Capacity of about 1L
 Mixes food with gastric juice, starts protein digestion, absorbs some nutrients
and moves food to small intestine.
 4 regions: cardiac, fundic, body and pyloric


Covered in folds called rugae
Chyme- paste of food and gastric juice
Small Intestine
 About 5.5-6 m long
 Mixes food with bile and pancreatic juice
 95% of nutrients absorbed here
 Regions: duodenum, jejunum, ileum
 Mesentery: membrane that attaches small intestine to abdominal wall;
contains blood vessels, nerves and lymphatic vessels
 Small intestine wall contains villi; tiny finger-like projections that increase the
surface area of the intestine for absorption
Large intestine
 about 1.5 m long
 Absorbs water and electrolytes
 Forms and stores feces
 Parts: cecum, colon, rectum, and anal canal
 Apendix is connected to the cecum; no known function
 No villi