SCIE 22273 Chapter Notes - Chapter 15: Lingual Tonsils, Gastrointestinal Tract, Gastric Glands
12 Apr 2016
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Digestion: mechanical and chemical breakdown of foods and the absorption of the nutrients from it. Mechanical digestion breaks larger foods into smaller one. But it does not alter the chemical composition. Chemical digestion breaks foods into simpler form. The alimentary canal is a muscular tube that passes through the thoracic and abdominopelvic cavities. The alimentary canal consists of 4 distinct layers: mucosa/ mucous membrane: innermost layer. In some regions, it consists of lumen (lumen helps increase surface area) It protects tissues beneath it and carries on secretion and absorption: sub mucosa: Its vessels nourish tissues and carries away absorbed materials: muscular layer: Has 2 coats of smooth muscle tissue. When the circular fibers contract, the tube"s diameter decrease. When the longitudinal fiber contracts, it shortens: serous layer. Protects underlying tissues and secretes serous fluid, which moistens outer surface. Begins digestion by mechanically breaking food and mixes it up with saliva.
