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Salivary gland
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Salivary gland
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. Salivary glands can be classified as serous, mucous, or seromucous (mixed).
In serous secretions, the main type of protein secreted is alpha-amylase, an enzyme that breaks down starch into maltose and glucose, whereas in mucous secretions, the main protein secreted is mucin, which acts as a lubricant.
In humans, 1200 to 1500 ml of saliva are produced every day. The secretion of saliva (salivation) is mediated by parasympathetic stimulation; acetylcholine is the active neurotransmitter and binds to muscarinic receptors in the glands, leading to increased salivation.
A proposed fourth pair of salivary glands, the tubarial glands, were first identified in 2020. They are named for their location, being positioned in front of and over the torus tubarius. However, this finding from one study is yet to be confirmed.
The two parotid glands are major salivary glands wrapped around the mandibular ramus in humans. These are largest of the salivary glands, secreting saliva to facilitate mastication and swallowing, and amylase to begin the digestion of starches. It is the serous type of gland which secretes alpha-amylase (also known as ptyalin). It enters the oral cavity via the parotid duct. The glands are located posterior to the mandibular ramus and anterior to the mastoid process of the temporal bone. They are clinically relevant in dissections of facial nerve branches while exposing the different lobes, since any iatrogenic lesion will result in either loss of action or strength of muscles involved in facial expression. They produce 25% of the total salivary content in the oral cavity. Mumps is a viral infection, caused by infection in the parotid gland.
The submandibular glands (previously known as submaxillary glands) are a pair of major salivary glands located beneath the lower jaws, superior to the digastric muscles. The secretion produced is a mixture of both serous fluid and mucus, and enters the oral cavity via the submandibular duct or Wharton duct. Around 70% of saliva in the oral cavity is produced by the submandibular glands, though they are much smaller than the parotid glands. This gland can usually be felt via palpation of the neck, as it is in the superficial cervical region and feels like a rounded ball. It is located about two fingers above the Adam's apple (laryngeal prominence) and about two inches apart under the chin.
The sublingual glands are a pair of major salivary glands located inferior to the tongue, anterior to the submandibular glands. The secretion produced is mainly mucous in nature, but it is categorized as a mixed gland. Unlike the other two major glands, the ductal system of the sublingual glands does not have intercalated ducts and usually does not have striated ducts, either, so saliva exits directly from 8-20 excretory ducts known as the Rivinus ducts. About 5% of saliva entering the oral cavity comes from these glands.
The tubarial glands are suggested as a fourth pair of salivary glands situated posteriorly in the nasopharynx and nasal cavity, predominantly with mucous glands, and its ducts opening into the dorsolateral pharyngeal wall. The glands were unknown until September 2020, when they were discovered by a group of Dutch scientists using prostate-specific membrane antigen PET-CT. This discovery may explain mouth dryness after radiotherapy despite the avoidance of the three major glands. However, these findings from just one study need to be confirmed. On the other hand, an interdisciplinary group of scientists disagree with this new discovery. They believe that an accumulation of minor salivary glands has been described. The researchers examined the scans and confirmed the glandular tissue through dissection of cadavers, proposing that this structure could constitute a previously unrecognized major salivary gland. Their findings raised clinical interest, particularly in radiation oncology, as damage to these glands during radiotherapy for head and neck cancers might contribute to xerostomia (dry mouth), even when the known major salivary glands are spared.
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Salivary gland
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. Salivary glands can be classified as serous, mucous, or seromucous (mixed).
In serous secretions, the main type of protein secreted is alpha-amylase, an enzyme that breaks down starch into maltose and glucose, whereas in mucous secretions, the main protein secreted is mucin, which acts as a lubricant.
In humans, 1200 to 1500 ml of saliva are produced every day. The secretion of saliva (salivation) is mediated by parasympathetic stimulation; acetylcholine is the active neurotransmitter and binds to muscarinic receptors in the glands, leading to increased salivation.
A proposed fourth pair of salivary glands, the tubarial glands, were first identified in 2020. They are named for their location, being positioned in front of and over the torus tubarius. However, this finding from one study is yet to be confirmed.
The two parotid glands are major salivary glands wrapped around the mandibular ramus in humans. These are largest of the salivary glands, secreting saliva to facilitate mastication and swallowing, and amylase to begin the digestion of starches. It is the serous type of gland which secretes alpha-amylase (also known as ptyalin). It enters the oral cavity via the parotid duct. The glands are located posterior to the mandibular ramus and anterior to the mastoid process of the temporal bone. They are clinically relevant in dissections of facial nerve branches while exposing the different lobes, since any iatrogenic lesion will result in either loss of action or strength of muscles involved in facial expression. They produce 25% of the total salivary content in the oral cavity. Mumps is a viral infection, caused by infection in the parotid gland.
The submandibular glands (previously known as submaxillary glands) are a pair of major salivary glands located beneath the lower jaws, superior to the digastric muscles. The secretion produced is a mixture of both serous fluid and mucus, and enters the oral cavity via the submandibular duct or Wharton duct. Around 70% of saliva in the oral cavity is produced by the submandibular glands, though they are much smaller than the parotid glands. This gland can usually be felt via palpation of the neck, as it is in the superficial cervical region and feels like a rounded ball. It is located about two fingers above the Adam's apple (laryngeal prominence) and about two inches apart under the chin.
The sublingual glands are a pair of major salivary glands located inferior to the tongue, anterior to the submandibular glands. The secretion produced is mainly mucous in nature, but it is categorized as a mixed gland. Unlike the other two major glands, the ductal system of the sublingual glands does not have intercalated ducts and usually does not have striated ducts, either, so saliva exits directly from 8-20 excretory ducts known as the Rivinus ducts. About 5% of saliva entering the oral cavity comes from these glands.
The tubarial glands are suggested as a fourth pair of salivary glands situated posteriorly in the nasopharynx and nasal cavity, predominantly with mucous glands, and its ducts opening into the dorsolateral pharyngeal wall. The glands were unknown until September 2020, when they were discovered by a group of Dutch scientists using prostate-specific membrane antigen PET-CT. This discovery may explain mouth dryness after radiotherapy despite the avoidance of the three major glands. However, these findings from just one study need to be confirmed. On the other hand, an interdisciplinary group of scientists disagree with this new discovery. They believe that an accumulation of minor salivary glands has been described. The researchers examined the scans and confirmed the glandular tissue through dissection of cadavers, proposing that this structure could constitute a previously unrecognized major salivary gland. Their findings raised clinical interest, particularly in radiation oncology, as damage to these glands during radiotherapy for head and neck cancers might contribute to xerostomia (dry mouth), even when the known major salivary glands are spared.
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