Salivary glands : There are three pairs of salivary glands in man. They secrete about 1 to 1.5 litres of saliva in 24 hours. Three pairs of salivary glands are :
1 .Parotid salivary glands : They are present on the sides of the face below and in front of ears. These are the largest salivary glands. They secrete saliva into the vestibule just opposite to the upper second molar teeth.
Human salivary glands
2. Sublingual glands : These glands lie under the front part of the tongue. These secrete the saliva under the tongue by sublingual ducts.
3. Submaxillary glands : These glands are present at the angles of the lower jaw. These also secrete saliva below the tongue.
Diphyodont is the condition of having two set of teeth during the life of an organism. For example : humans are diphyodont as they have two set of teeth namely temporary milk or deciduous teeth which are replaced by permanent or adult teeth.