Alimentary Canal – Class 11 | Chapter – 16 | Biology Short Notes Series PDF

Alimentary Canal: It is mainly referred to as the pathway by which food enters our body and moves out through the anus after digestion. It is a tube-like structure which starts from the mouth and ends in the anus. It plays a primary role in human digestion and is also termed as the digestive tract.


The primary function is to carry out the process of digestion of food and absorption of nutrients from it. Apart from these primary functions, there are other supplemental yet essential roles. They are as follows:

  • It acts as an immune barrier to various harmful microbes. This function is carried out by gut-associated lymphoid tissue (GALT) and variable pH conditions that are present throughout it.
  • The colonic bacteria also help in maintaining immune homeostasis.
  • The colonic bacterial colony also prevents the growth of harmful bacteria in our alimentary canal.
  • Drug metabolism also occurs in the alimentary canal wherein the drug molecule is metabolized into smaller fractions and eventually eliminated from the body. Metabolism of antigens also occurs in the alimentary canal thereby detoxifying the body of the antigens.

pH in different parts of the Alimentary Canal

Parts pH
Oral cavity 6.5-7.5
Stomach 1–2
Small intestine
Duodenum 6-6.5
Ileum 7.4-7.5
Large intestine
Cecum 5.7
Ascending colon 5.7
Transverse colon 6.6
Descending colon 7.0

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By Team Learning Mantras