Saliva (Digestive Juice)

Saliva is a watery alkaline secretion delivered into the mouth from salivary glands. Parotid, mandibular and sublingual glands are the major glands whereas labial, lingual palatine and buccal gland are the minor glands.

Composition of saliva:

Water (98.5-99%)

Dry matter (1-1.5%)

Gases (O2, N2 and CO2)

Cellular constituents Inorganic substances (Na, K, Ca, Cl, HCO3)

Organic substances

(yeast cell, bacteria, protozoa)

Enzyme Other organics

Ptyaline Mucin

Carbonic anhydrase Glucose

Phosphatase Protein

Lysozymes Cholesterol

Functions of saliva:

Food can be digested in the absence of saliva, but saliva is present, it does contribute. It also has several other functions.

a. Digestion: Saliva helps the food to be digested in the mouth and then partially digested specially starch by ptyalin. As the foods do not remain in the mouth for long time, the activities of saliva may continuesin the stomach for awhile upto the pH 4.5 deactivated by HCl in the stomach.

b. Deglutition: Swallowing, termed deglutition is impossible in the absence of

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Factors of Digestion

There are several factors of digestion. These are as follows:
1. Mechanical factors:
a. Prehension: Prehension means to grasp or to hold off and taken into mouth. Different species has different prehensile techniques and prehensile organs as well. These includes lips, teeth, tongue, forelimb, snout, claws etc.


b. Mastication (Chewing): Mastication means to make particles into smaller pieces. During mastication salivation is increased which helps to make bolus formation for easy swallowing.


c. Deglutition: deglutition is the process of swallowing of boluses to the stomach through the pharynx and esophagus. It is a complex reflex act.


d. Regurgitation:
The return of undigested material from the stomach to the mouth called regurgitation. Regurgitation is noted in ruminants and in certain birds such as

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