Digestive System : Structure

Digestion is catabolic process which involves breakdown of large, complex and insoluble food molecules into small, simple and soluble food molecules with the help of enzymes present in the digestive juices.

Digestive system consists of alimentary canal and digestive glands.

The main parts of alimentary canal are: mouth, oral cavity, pharynx, oesophagus, stomach, small intestine and large intestine, rectum and anus.

There are two types of human teeth: temporary or milk teeth and permanent teeth. Structure of tooth consists of crown, neck and root.

Small intestine consists of three regions deudenum, jejunum and ileum.

Large intestine is composed of three parts; caecum, colon and rectum.

Wall of alimentary canal is made up of four layers: Serosa or adventitia, muscular layer, sub mucosa and mucosa.

Digestive glands secrete digestive juices which help in digestion of food.

Main digestive glands are salivary glands, gastric gland, intestinal gland, liver and pancreas.

Salivary glands are of three types that are parotid, sub lingual, sub maxillary glands.

Gastic glands are of three types cardiac, pyloric and fundic.

There are two types of intestinal glands; Crypts of lieberkuhn and Brunner’s glands.

Liver is the largest gland which is situated just below the diaphragm in abdominal cavity. Liver secretes bile which is yellowish or reddish brown in colour, alkaline in nature with pH 7- 8.6 and bitter in taste.

Pancreas is a compound gland which is 16 cm long and 2.5 cm broad.

Pancreatic juices help in lipid metabolism and also facilitate digestion of carbohydrates and proteins.

The two hormones insulin and glucagon regulate blood sugar level and work antagonistic to each other. Metabolism of glucose takes place by following three processes namely glycogenesis, glycogenolysis and glyconeogenesis . Synthesis and storage of fats can take place by lipogenesis and beta oxidation.

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  • Q1

    How many sets of teeth appear in mammals during its life?


    Mammalian teeth appear in two sets during its life.
    i) Temporary or deciduous teeth
    ii) Permanent teeth.

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  • Q2

    Name the three regions of the large intestine.


    The three regions of the large intestine are:
    i) Caecum
    ii) Colon
    iii) Rectum

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  • Q3

    How many teeth are normally present in adult human?


    Normally 32 teeth are present in adult human.

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  • Q4

    What is alimentary canal?


    Alimentary canal is a long muscular tube, which starts with the mouth and ends at the anus.

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  • Q5

    Name the glands associated with digestive system.


    The glands associated with digestive system are salivary glands, liver and pancreas.

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