DIGESTIVE SYSTEM

Digestive system includes the alimentary tract or canal and all the organs and glands associated with the digestion and assimilation of food in animals.
   



 Digestion is the breaking down of large molecules of food into simple and absorbable form for use by the animals.
   


A typical mammalian alimentary tract or canal includes the following parts: Mouth, pharynx, oesaphagus or gullet, stomach, small intestine or ileum, caecum, appendix, large intestine, rectum and anus. All these parts can be found in most vertebrates.





Digestion of food in man.
The alimentary canal of man includes the mouth, oesaphagus, stomach, duodenum, small intestine, caecum, appendix, large intestine, rectum and anus.




The description and importance of the parts are as follows:
1. Mouth: the mouth contains the teeth, salivary gland and tongue.


2. Teeth: the teeth are used to cut, grind or chew food into tiny particles.



3. The tongue: the tongue roll the food, it aid movement of the food in the mouth, it allows mixing of food with saliva or tyalin, it aids swallowing of food into the gullet or oesaphagus.

          Feeding habits




Organisms exhibit different feeding habits. These are:



1. Parasitic feeding: Parasitic feeding is found in both plant and animals. Animal parasites are tapeworm, roundworms, tick and guinea worm. Plant parasites are cassytha, dodder and mistle. Parasites are structurally modified organism that depends wholly or partially on other living organisms for their food and survival.


2. Fluid feeding: Animals which feed on any fluid materials are classified as fluid feeder's. Examples are bug, mosquito, butterfly, aphid, tsetse fly and housefly.



3. Saprophytic feeding: saprophytic are mainly non-green plants which do not have chloroplast and therefore cannot manufacture their own food. Examples are Rhizopus, mushroom, mucor. They feed on dead and decaying organic matter.


4. Filter feeding: Filter feeder's which are also called microphagous feeders, they feed on very tiny organisms. Filter feeders are mainly aquatic animals.

          Dentition


Dentition refers to the arrangements, number and confirmation of teeth in an organism.

Types of dentition
There are two types of dentition namely:


1. Homodont dentition: The organism have the same type of teeth. Examples are fishes, reptiles, amphibians.


2. Heterodont dentition: the organisms possess teeth of different shapes, sizes and functions. Examples of organisms having heterodont dentition are mammals e.g Rabbits, man,dog, cattle's etc.
     
       Types of teeth

i  Incisors
ii Canines
iv Premolars
iv Molars