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Anatomy and Function of the Alimentary Canal: From Mouth to Stomach, Study notes of Physiology

An in-depth exploration of the structure and functions of the alimentary canal, focusing on the mouth and stomach. It covers the layers of the alimentary canal, the roles of the muscles and mucosa, and the processes of mechanical and chemical digestion in the mouth. The document also discusses the importance of salivary glands and the swallowing mechanism.

Typology: Study notes

2009/2010

Uploaded on 12/07/2010

ephrayim921
ephrayim921 🇺🇸

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Chapter$14$Lecture
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The Digestive System

Chapter 14 Lecture

Digestion

‡ Digestion Ȃ mechanical and chemical breakdown of

foods

± Breakdown allows for absorption of nutrient molecules

‡ The digestive system consists of:

1) Alimentary canal

‡ Tube that runs from the mouth to the anus

2) Accessory organs

‡ Salivary glands, liver, gallbladder, and pancreas ‡ Food does NOT travel through the accessory organs!!

The Alimentary Canal

‡ Alimentary Canal

± Tube is ~8M in length

± Runs through the thoracic

& abdominopelvic cavities

The Alimentary Canal

‡ Structure

± Outermost layer = serosa (serous layer; composed of

visceral peritoneum)

‡ Secretes serous fluid ± Protects underlying tissues ± Lubrication of the tube prevents friction with organs in the abdominal cavity

± Middle layer = Muscle (two layers of smooth muscle)

‡ Moves food through the tube ± Contraction of circular fibers Ȃ decreases diameter ± Contraction of longitudinal fibers Ȃ shortens tube

The Alimentary Canal

‡ Movements of the tube

± Mixing movements

‡ Smooth muscles contract rhythmically in small sections of the tube

± Propelling movements

‡ Peristalsis Ȃ wavelike motion

‡ Waves of contraction and relaxation ± Contraction pushes food through the tube; relaxation allows food to move into the next segment of the tube

Mouth

‡ Mouth

± Receives food

± Both mechanical and chemical digestion occur in the

mouth:

‡ Mastication Ȃ mechanical breakdown of food ( chewing )

‡ Enzymes secreted in the saliva initiate chemical digestion

Mouth

‡ Cheeks and Lips

± Cheeks form the lateral walls of the mouth

‡ Composed of : skin, muscle, fat, and epithelium ± Do you remember the muscles that are located within the cheeks and are associated with chewing and facial expressions?

± Lips surround the mouth opening

‡ Composed of skeletal muscle ‡ Contain sensory receptors Ȃ detect food temperature and texture

Mouth

‡ Teeth

± Begin mechanical digestion Ȃ break food into smaller pieces

± Two sets of teeth:

‡ Deciduous (primary) teeth Ȃ develop between 6 months and 4 years of age ± 20 total Ȃ 10 in the maxilla and 10 in the mandible

‡ Permanent (secondary) teeth Ȃ develop between 6 years and 25 years of age ± 32 total Ȃ 16 in each jaw

Mouth

‡ Teeth

± Teeth are adapted to handle food in different ways

‡ Incisors (8) ± Bite off pieces of food ‡ Canines (4) ± Ž•‘”‡ˆ‡””‡†–‘ƒ•Dz —•’‹†•dz ± Grasp and tear food ‡ Premolars (8) ± Ž•‘”‡ˆ‡””‡†–‘ƒ•Dz„‹ —•’‹†•dz ± Grind food particles ‡ Molars (12) ± Grind food particles

*Numbers are representative of secondary teeth