About how much saliva does a person produce each day?
A. 100 ml
B. 1 to 2 litre
C. 500 ml
D. 250 ml

Hint: Saliva is secreted by the salivary gland present in the mouth or the oral cavity. In the mouth, the space between the lips and teeth is called a vestibule where the saliva is secreted in humans and other animals.

Complete answer:
Saliva is formed of 99.5% water, 0.2% minerals like Na+, K+, Cl-, HCO3-, thiocyanate ions and an amylolytic salivary amylase, also called ptyalin. It hydrolyses about 30-40% of starch into maltose, isomaltose and limits dextrin 6.8 pH and presence of chloride ions.
The various types of salivary glands present in the mouthy are:
-Parotid gland- It is the largest gland present at the base of pinna. Its duct, Stenson’s duct, opens behind the upper second molar.
-Submandibular or submaxillary gland- It is situated below the tongue.
-Infra-orbital or zygomatic glands- It is situated below the eye orbit, its duct opens near the upper molars. These are absent in humans.
Approximately 1-2 litre of saliva is produced each day by all the salivary glands present in our mouth. The saliva secretion is stimulated more by the chewing of food.
The function of saliva are:
-It moistens and softens the food which helps in lubricating its passage.
-It facilitates speaking and free movement of tongue by keeping it moist.
-The lysosomes kill the bacteria and the amylase in the saliva breaks down the starch into dextrin and maltose.
After the treatment in mouth the food called bolus passes into the stomach.
So, the correct answer is “Option B”.

Note:
Saliva secretion is purely a reflex action and is under only nervous control. It is regulated by salivary centres located in the medulla oblongata which operate through vagal nerve fibres and acetylcholine. These salivary centres are stimulated by olfactory (smell), gustatory (taste), visual (sight), auditory (sound) and tactile (touch) stimuli.