I. Aids to Understanding Words

Aliment – Food

Alimentary Canal Tube: Part of digestive system.

Chym – Juice

Chyme: Semifluid paste of food particles and gastric juice formed in the stomach.

Decidu – Falling off.

Deciduous Teeth: Teeth shed during childhood.

Gastr – Stomach

Gastic Gland: Part of the stomach that secretes gastric juice.

Hepat – Liver.

Hepatic Duct: Duct that carries bile from the liver o the bile duct.

Lingu – Tongue.

Lingual Tonsil: Mass of lymphatic tissue at root of the tongue.

Nutri – Nourish.

Nutrient: Substance needed to nourish cells.

Peri – Around.

Peristalsis: Wavelike ring of contraction that moves material along the alimentary canal.

Pyl – Gatekeeper.

Pyloric Sphincter: Muscle that serve as a valve between stomach ad small intestine.

Vill – Hair.

Villic: Tiny projections of mucuous membrane in small intestine.

15.1 Introduction

A. Define digestion.

Digestion is mechanical and chemical breakdown of food and absorption of nutrients by cell. Mechanical digestion breaks down large pieces into smaller pieces. Chemical digestion breaks down food into simple chemicals. The organs in the digestive system carries out the process of digestion.

15.2 General Characteristic of Alimentary Canal

A.

Name

Structure

Function

Mucous Membrane

Surface of epithelium, underlying connective tissue, small amount of smooth muscle.

Glands secrete mucus and digestive enzyme.

Protective tissue beneath it and carries on secretion and absorption.

Submucosa

Contains loose connective tissue, glands, blood vessels, and lymphatic vessels.

Vessels nourish surrounding tissues and carry absorbed material.

Muscular Layer

Consists of two coats of smooth muscle tissue.

Provides movements of tube.

Tubes diameter decreases when circular fibers contact.

When longitudinal fiber contracts, the tube shortens.

Serous Layer

Layer of epithelium on the outside.

Protect underlying tissue.

Secretes fluid which moistens the outer tube’s organs.

B. The two types of movement of the alimentary tube are mixing movements and propelling movement.

C. What is peristalsis?

Peristalsis is the propelling movement. Contractions occur within the tube. The muscular wall ahead of ring relaxes. The peristaltic wave moves along the tube, pushing the tubes contents ahead.

15.3 Mouth

A. What is the function of the mouth?

Mouth receives food and begins the digestion process by breaking up the solid into smaller pieces and mixing it with saliva. The process is known as mastication.

B. What is the function of the tongue?

The tongue fills oral cavity when the mouth is closed. Body of the tongue is skeletal muscle. Muscular actions mix food with saliva while chewing and moving food toward the pharynx while swallowing. Tongue also helps move food under the teeth while chewing.

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