• SALIVARY GLANDS
    BIOLOGY

    SALIVARY GLANDS

    Three pairs of salivary glands exist in man while in rabbit they are four pairs. In man, the three pairs are parotid, submaxillary and sublingual glands. They all have ducts leading to the mouth cavity. They secrete digestive juice called saliva. Saliva contains an enzyme called ptyalin, mucin and water. The smell, sight and taste of food stimulate the secretion of saliva.   Functions Saliva protects the soft lining of the mouth from drying up. The watery parts of the saliva help to dissolve dry food substances. The mucin lubricates the chewed food and makes the food particles stick together to form bolus for easy swallowing. It helps in cleaning…

  • FEEDING MECHANISMS IN HOLOZOIC ORGANISMS
    BIOLOGY

    FEEDING MECHANISMS IN HOLOZOIC ORGANISMS

    There are five modifications and mechanisms of feeding associated with someorganisms. These feeding mechanisms include: 1) Absorbing mechanisms, e.g. tapeworm The tapeworm is an endoparasite which carries out parasitic feeding on its host i.e ., the man. It has no mouth but absorbs digested food from the intestine of its host. The body of the tapeworm is modified and adapted for parasitic feeding as follows: The alimentary canal is absent, hence food is absorbed through its entire body surface. The tapeworm has hooks and suckers which are used for attachment to the intestine of the host to avoid dislodgement. The body has thick cuticle which resists digestive enzymes of the…

  • THE ALIMENTARY CANAL AND DIGESTION OF FOOD IN MAN
    BIOLOGY

    THE ALIMENTARY CANAL AND DIGESTION OF FOOD IN MAN

    The alimentary canal of man includes the mouth, oesophagus, stomach, duodenum, small intestine or ileum, caecum, appendix, large intestine or colon, rectum and anus. The description and importance of the parts are as follows: Mouth: The alimentary canal of man starts from the mouth. The mouth contains the teeth, salivary gland and tongue.   The teeth The teeth are used to cut, grind or chew food into tiny particles. They expose large area of food for the action of enzymes.   The tongue The tongue rolls the food into bolus. It aids movement of food in the mouth. It allows mixing of food with saliva or ptyalin. It aids swallowing…

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