Salivary Glands are group of organs present in our mouth that secretes saliva. It is found in mammals only. It is an exocrine gland which secretes substances outside the body or within a body cavity. Saliva contains various chemicals with water including mucus, salts, antibacterial substances, enzymes and chemicals that control the pH in the mouth. Do you know that the quantity of saliva increases when we taste, smell, or even think of food? It decreases when we go to sleep. Basically, saliva is a watery substance and is a part of Digestive System. Salivary Glands secrete 1 to 1.5 litres of saliva in 24 hours. In fact over 99% of saliva is water. It keeps mouth moist and clean, facilitates chewing , swallowing and helps in the digestion process. This article deals with the types of salivary glands and their functions.
Functions of Salivary Gland
Saliva is a mixture of water, mucus, antibacterial substance and digestive enzymes. Therefore, saliva has many uses. One of the digestive enzyme alpha-amylase helps to break down the starch present in our food in to simpler one like glucose and maltose. Whenever we chew, we activate these glands to secrete an enzyme to breakdown the food. Saliva has lubricating properties. It protect the inside cavity of our mouth, teeth and throats as we begin to swallow the food bolus. It also cleanses the mouth after the meal and dissolves it into chemicals that we perceive as taste.
Types of Salivary Gland
According to the size and functional importance it is of two types: minor and major salivary glands.
1. Minor salivary gland
The mucosa of the mouth, lips, tongue, and palate is filled with many small salivary glands that moisten these surfaces. Do you know that around 800 or 1000 minor salivary glands are located throughout the mouth? They secrete saliva directly into the mouth.
Ductless Glands present in the Human Body
2. Major salivary glands
There are three pairs of glands through which most of the saliva is secreted and symmetrically located on both sides of the jaw. They secrete saliva through ducts. These glands are parotid, submandibular and sublingual.
Parotid glands are the largest salivary gland. Each gland is approximately 6 cm long and 3-4 cm wide and can weigh up to 30 grams. They are located within each of our cheeks. In our oral cavity they are responsible for the secretion of about 20% of saliva. This saliva is known as serous i.e. more liquid and fluid. It helps in the first phase of the digestion of food, facilitate mastication "chewing". These glands secrete protein-rich fluid which is a suspension of alpha-amylase enzyme. Do you know why alcohol abuse is directly related to the lack of saliva? Because intake of alcohol or some drugs can affect the sympathetic nervous system and produces vasoconstriction of the parotid gland and reduces the secretion of saliva.
These glands are located beneath the lower jaw, outside the oral cavity. This is the movable part of our jaw. It is the second largest salivary gland and produces approx. 65-70% of saliva. It is a mixture of serous and mucus gland and released through submandibular ducts. Its saliva is more viscous as compare to the secretion of parotid gland.
It is the smallest of the major salivary glands. They are located under the tongue. Approximately 5% of the saliva comes from these glands. The saliva that comes out is mostly mucus, having viscous texture and flows in to the mouth through sublingual ducts. Sometimes, sialoliths also termed as salivary calculi, or salivary stones form in the ducts of salivary glands which block the flow of saliva and causes pain, swelling in the affected gland. Mostly, salivary stones affect submandibular glands and sometimes parotid too.
From the above article we have learnt about salivary glands, its types, functions and where they are located.