Structure and function of accessory organ-1

The Accessory Structures

Salivary Glands

A gland known as a salivary gland secretes saliva into ducts that connect to the mouth cavity. Saliva is combined with food when it is in the mouth, serving a variety of functions, including moistening the food to aid in chewing and deglutition. Saliva also inhibits bacterial development and keeps the mouth and teeth healthy. This watery concoction is made up of mucus and salivary amylase, an enzyme that kick-starts the digestive process by converting starch to sugar. It consists of three pairs of accessory glands that serve as organs:

• The Parotid Glands, the largest of the group, are located inferior and anterior to the ear between the skin and the masseter muscle. Each secretes saliva into oral cavity via a parotid ducts or stensen’s duct opposite to the upper 2nd molar teeth. They have serious type of cell which secretes watery secretion and which is 20% of total salivary secretion.
• The Submandibular Glands are located near the body of the lower jaw. Two submandibular open on the floor of the mouth, one on each side of the frenulum of the tongue. They have mixed type of cells which secretes moderately viscous secretion and it constitutes 70% total secretion.
• The Sublingual Glands are under the tongue and superior to the sub-mandibular glands. They opens at the floor of mouth. They have mucous cell and secretes viscous secretion. It constitutes about 5% of total salivary secretion.

Blood Supply of Salivary Gland

Arterial blood is supplied is by various branches from external carotid arteries and venous blood is drained into the external jugular vein.

Nerve Supply of Salivary Gland

All glands are supplied by sympathetic and parasympathetic nerve fibers.

Composition of Saliva

Chemically, Saliva is 99.5% water and 0.5% solutes such as sodium, potassium, chloride, bicarbonate, phosphate and, salivary amylase and digestive enzymes. Saliva also contains smaller amounts of lipase, nucleases, lysozyme, peroxidases, lactoferrin, immunoglobulin (IgA), blood clotting factors.

Secretion of Saliva

Saliva production and secretion are regulated by the autonomic nervous system. Every day, between 1000 and 1500 ml of saliva are released, typically at a flow rate of 0.5 mL/min, however this rate is significantly slower when you sleep. Typically, parasympathetic activation encourages the production of copious amounts of watery saliva, which contains few enzymes and other organic compounds. Small amounts of saliva rich in organic material are secreted as a result of sympathetic activation, particularly from the sub-mandibular glands. When there is food in the mouth, saliva is secreted reflexively. This reflex is readily trained such that the sight, smell, or even the concept of food will cause saliva to flow.

Functions of Saliva

• It moistens the mouth and tongue.
• It lubricates food so that it can be rolled into a soft mass or bolus which can be easily swallowed. Salivary enzyme ptyalin acts on the starch and breaks them up into dextrin and maltose.
• Saliva also dissolves the part of the food which stimulates taste buds.
• It has a cleansing action in the mouth.