This article is on Salivary Gland Anatomy. It is intended to help inform patients, relatives of patients and health professionals. The information in the grey boxes is more technical and intended more for Health professionals that are reading this article
What are the Salivary Glands?
The salivary glands contain tissues that produce saliva. Saliva is important to the body because it, helps keep the mouth moist, contains enzymes that break down food and it helps prevent infections of the mouth and throat. There are 3 major clusters of salivary glands.
1) Parotid Glands
2) Submandibular Glands (70% of saliva production)
3) Sublingual Glands
4) Minor salivary glands: (widely distributed including the nasal cavity, pharynx, larynx, trachea)
How do the Salivary glands work?
Saliva is produced in and secreted from salivary glands. The cells of salivary glands are in clusters called acini. These cells produce a secretion that contains water, electrolytes, mucus and enzymes, all of which flow out of the acinus into collecting ducts.
Within the collecting ducts, the composition of this secretion is altered. Most of the sodium (Na+) is actively reabsorbed in exchange potassium (k+) is secreted, and large quantities of bicarbonate (HCo3) are secreted this end product is Saliva! Bicarbonate secretion is of tremendous importance because it, along with phosphate helps neutralizing the stomach acids.
The Lysozymes, IgA & lactoferrin contained are protective in destruction of disease causing organisms
What nerves are responsible?
Salivation is stimulated by Thought, Sight , Smell and Taste , while it is inhibited by Sleep , Dehydration , fatigue and Fear. The rest and digestion are controlled by the Parasympathetic Nervous system located in the Brain stem by the Pons and Medulla.
Salivation is controlled by the Superior Salivatory and Inferior Salivatory Nucleii located in the Pons and Medulla respectively through, via the Facial Nerves ( CN 7) and Glossopharyngeal Nerve (CN9) .
Superior Salivatory nuclei > CN7 > via Parotid gland > Submandibular Ganglion > Sublingual /Submandibular glands
Inferior Salivatory Nuclei > CN9 > Octic Ganglion > Parotid Gland
It is worth noting these parasympathetic nerves CN7 and CN9 work via producing Acetylcholine which act on Muscarinic receptors M3 and M1 located on the Acinar Cells (cells of the salivary glands) to release of NaCl / H2o into the collecting duct system (Salivation), ergo Anticholinergic drugs inhibit this.
What are some complications?
There are generally no major complications associated with Parotid gland Surgery (parotidectomy). but a common mention is ;
- Damage/ injury to CN7 which passes through the parotid gland , causing weakness of the muscles of facial expression.
- Damage to Auriculotemporal Nerve (branch of the Trigeminal nerve CN5), which results in Frey’s Syndrome : Gustatory sweating profuse flushing and sweating over the parotid area when eating
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Author + Affiliation:
Dr Tonye Onyemelukwe, Department of Otolaryngology, Waikato Hospital.
Reviewed by Dr James Sanders, Otolaryngology, Waikato Hospital.
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