Anatomy and Physiology Resource Site

13.6 - Salivary Glands

The salivary glands produce saliva; a watery mixture of several secretions that aids in the first stages of digestion.

Saliva contains:

Salivary amylase - hydrolyzes starch into disaccharides
A mixture of mucus and serous fluid - lubricates the food and protects the oral epithelium from abrasive food
Lysozyme - an antibacterial enzyme
Water - acts as a solvent for tastant molecules; provides water for hydrolysis
Bicarbonate ions - neutralizes food

Salivary reflexes

Saliva is continually produced to keep the oral cavity lubricated for speech and the potential ingestion of food. Secretion of saliva can be increased by both simple salivary reflexes and conditioned salivary reflexes.

Simple salivary reflex

Pressure receptors and chemoreceptors in the mouth are activated
Sensory signals are sent to the salivary centre in the medulla
Motor signals are sent to the salivary glands to increase salivary secretion

Conditioned salivary reflex

Inputs external to the mouth (thoughts, emotions, smells) are processed by the cerebral cortex
Signals are sent from the cortex to the salivary centre in the medulla
Motor signals are sent to the salivary glands to increase salivary secretion

Autonomic control of the salivary reflexes

Both branches of the ANS increase salivation, but the saliva produced under the stimulation of each branch is different.

Parasympathetic - Large volume of watery saliva rich in digestive enzymes; the most commonly produced saliva
Sympathetic - Small volume of thick saliva rich in mucus