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The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. [1] Salivary glands can be classified as serous, mucous, or seromucous (mixed).
Saliva on a baby's lips. Saliva (commonly referred to as spit or drool) is an extracellular fluid produced and secreted by salivary glands in the mouth.In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be extracted), enzymes (such as lipase and amylase), and antimicrobial agents (such as secretory IgA, and lysozymes).
The disease is characterised by inflammatory changes in the moisture-producing glands throughout the body, leading to reduced secretions from glands that produce saliva, tears and other secretions throughout the body. [8] Primary Sjögren's syndrome is the combination of dry eyes and xerostomia.
It has also been defined as increased amount of saliva in the mouth, which may also be caused by decreased clearance of saliva. [ 4 ] Hypersalivation can contribute to drooling if there is an inability to keep the mouth closed or difficulty in swallowing (dysphagia) the excess saliva, which can lead to excessive spitting.
Salivary gland dysfunction affects the flow, amount, or quality of saliva produced. A reduced salivation is termed hyposalivation . Hyposalivation often results in a dry mouth condition called xerostomia , and this can cause tooth decay due to the loss of the protective properties of saliva.
An unstimulated salivary flow rate of 0.1 to 0.2 ml/min and a stimulated flow rate of 0.7 ml/min or less is considered to be abnormally low flow rates indicative of salivary gland hypofunction. [61] Unstimulated saliva production reduces by 40 to 70% between the age of 20 and 80 years, but stimulated saliva production is not affected. [62]
Mucoepidermoid carcinoma is a common malignant tumour of the salivary glands and has a low incidence of 4–13%. [13] Adenoid cystic carcinoma is also a common malignant salivary gland lesion and has an incidence of 4–8%. This carcinoma tends to invade nerves and can re-occur post-treatment.
Saliva stagnates and forms a mucus plug behind the stricture during sleep when the salivary output of the parotid is reduced. Then, when salivary secretion is stimulated, the mucus plug becomes stuck in the stricture. [1] The backlog of saliva behind the blockage causes the swelling, and the increased pressure inside the gland causes the pain.