Structure of the Alimentary Canal in relation to digestion and absorption

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Structure of the Alimentary Canal

in relation to digestion and absorption

There are two stages in human digestion:

  1. Mechanical breakdown-the large particles of ingested food are broken down into smaller pieces by the teeth in the mouth.

  1. Chemical breakdown – the large molecules of food are hydrolysed (broken down) by digestive enzymes into smaller, soluble molecules.

The alimentary canal (human gut) has the same general structure along its whole length but in some areas, it is specialised to carry out various roles. It extends as a tube from the mouth to the anus and along its length, the wall is composed of four layers:

  1. Mucosa- This is the innermost lining of the gut wall. It lubricates the passage of food with mucus and also protects it from the digestive action of enzymes. The mucosa surrounds the lumen which is made up of glandular epithelium and connective tissue containing blood vessels and lymph vessels.

  1. Submucosa- This is a layer of connective tissue that contains nerves, blood vessels and lymph vessels together with elastic fibres and collagen.

  1. Muscularis Externa- This is made up of circular and longitudinal layers of smooth muscle fibres which control the shape and movement of the gut.
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  1. Serosa- This is the outermost layer and is made up of loose connective tissue which provides protection from friction against other organs.

Different parts of the alimentary canal play a role in the journey of food from when it enters the mouth to when the leaves the body as waste:

  1. Mouth: This is where mastication happens. Mastication is the process of breaking down food into smaller pieces by the teeth. This provides a larger surface area so that enzyme action during chemical breakdown is more effective. The saliva in the mouth lubricates the smaller pieces of food and the tongue and cheek muscles help to make the lubricated food into a ...

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