Saliva : It is a viscous fluid which has pH value 6.7. It contains water, salts, mucin, ptyalin (salivary amylase) and maltase enzymes. It is produced by the salivary glands.

Goblet cells secrete mucus, but in gastric glands mucus neck cells secrete mucus.

Functions of mucus :

1. Mucus lubricates the food

2. Mucus dilutes the action of enzymes so that they may not affect wall of alimentary canal. In case of duodenum mucoid fluid also protects wall of duodenum form acidic chyme.

1. In this mode of nutrition the organisms cannot manufacture their own food and feed upon high energy organic molecules. It is of four types holozoic, saprozoic, parasitic and symbiotic nutrition. 

Nutrients : The chemical substances present in the food are called nutrients.

Nutrition : It is the use of nutrients by an organism for obtaining energy, building body, growth, development and providing resistance from diseases. 

Human dental formula for one side of buccal

Diphydont dentition : It is the dentition having two sets of teeth, first set is of milk teeth which are replaced by the second set of permanent teeth.