Parotid gland
Encyclopedia
The paired parotid glands are the largest of the salivary gland
s. They are each found wrapped around the mandibular ramus, and secrete saliva through Stensen's ducts into the oral cavity, to facilitate mastication
and swallowing and to begin the digestion of starches.
to the angle of the mandible. This gland is effectively palpated (can be felt) bilaterally by starting anterior to each ear, moving to the cheek area and then inferiorly to the angle of the mandible.
Above the parotid gland lies the external auditory meatus and temporomandibular joint
. Below, the parotid overlaps the posterior belly of the digastric muscle. Medially lies the styloid process
. Posteriorly, the parotid overflows the sternocleidomastoid and anteriorly it overlies the mandible with the overlying masseter.
The parotid gland resembles a three sided pyramid. The apex of the pyramid is directed downwards. the gland has four surfaces:
(1) superior
(2) superficial
(3) anteromedial &
(4) posteromedial.
The surfaces are separated by three borders:
(1) anterior
(2) posterior &
(3) medial
Structures which pass through the parotid gland:
traverse the glandular tissue and supply the parotid gland with oxygenated blood. The main branch to supply the gland is the transverse facial artery
, whereas numerous local veins drain the organ. These veins drain into tributaries of external and internal jugular vein
s.
The maxillary vein and superficial temporal vein meet to form the retromandibular vein within the parotid gland, but are not responsible for draining it.
Lymphatics mainly comprise pre-auricular lymph nodes.
arising from the otic ganglion
.
. The most common cause of parotitis is mumps
. Widespread vaccination against mumps has markedly reduced the incidence of mumps parotitis. Other infections such as bacterial infections can cause parotitis as may blockage of the duct, whether from salivary duct calculi or external compression. Stones mainly occur within the main confluence of the ducts and within the main parotid duct. The patient usually complains of intense pain
when salivating and tends to avoid foods which produce this symptom. In addition, the parotid gland may become enlarged upon trying to eat. The pain can be reproduced in clinic by squirting lemon juice into the patient's mouth. Surgery depends upon the site of the stone: if within the anterior aspect of the duct a simple incision into the buccal mucosa with sphinterotomy may allow removal; however, if situated more posteriorly within the main duct, complete gland excision may be necessary.
Swelling of the parotid gland may also indicate the eating disorder bulimia nervosa, creating the look of a heavy jaw line.
Eighty percent of tumors of the parotid gland are benign. The most common of these include pleomorphic adenoma
and Warthin's tumor
. Their importance is in relation to their anatomical position and tendency to grow over time. The tumorous growth can also change the consistency of the gland and cause facial pain on the involved side since the facial nerve travels through the gland.
Twenty percent of parotid tumors are malignant with the most common tumors being mucoepidermoid carcinoma
and adenoid cystic carcinoma
. Critically, the relationship of the tumor to the branches of the facial nerve
(CN VII) must be defined because resection may damage the nerves, resulting in paralysis of the muscles of facial expression. If the tumor is deep within the gland, the patient should give consent with specific regard to potential damage of the facial nerve.
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...
s. They are each found wrapped around the mandibular ramus, and secrete saliva through Stensen's ducts into the oral cavity, to facilitate mastication
Mastication
Mastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion and it increases the surface area of foods to allow more efficient break down by enzymes. During the mastication process, the food is positioned between the teeth for grinding by...
and swallowing and to begin the digestion of starches.
Location
The parotid glands are found overlying the mandibular ramus and anterior and inferior to the external ear. The glands occupy the parotid fascial spaces, an area posterior to the mandibular ramus, anterior and inferior to the ear on each side of the head. Each gland extends irregularly from the zygomatic archZygomatic arch
The zygomatic arch or cheek bone is formed by the zygomatic process of temporal bone and the temporal process of the zygomatic bone , the two being united by an oblique suture; the tendon of the Temporalis passes medial to the arch to gain insertion into the coronoid process...
to the angle of the mandible. This gland is effectively palpated (can be felt) bilaterally by starting anterior to each ear, moving to the cheek area and then inferiorly to the angle of the mandible.
Above the parotid gland lies the external auditory meatus and temporomandibular joint
Temporomandibular joint
The temporomandibular joint is the joint of the jaw and is frequently referred to as TMJ. There are two TMJs, one on either side, working in unison. The name is derived from the two bones which form the joint: the upper temporal bone which is part of the cranium , and the lower jaw bone called the...
. Below, the parotid overlaps the posterior belly of the digastric muscle. Medially lies the styloid process
Styloid process
In anatomy, a styloid process , usually serving as points of attachment for muscles, refers to the slender, pointed process of :* temporal bone of the skull - Temporal styloid process...
. Posteriorly, the parotid overflows the sternocleidomastoid and anteriorly it overlies the mandible with the overlying masseter.
The parotid gland resembles a three sided pyramid. The apex of the pyramid is directed downwards. the gland has four surfaces:
(1) superior
(2) superficial
(3) anteromedial &
(4) posteromedial.
The surfaces are separated by three borders:
(1) anterior
(2) posterior &
(3) medial
Structures which pass through the parotid gland:
- The facial nerveFacial nerveThe facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
and its branches run through the gland superficial to the retromandibular vein - The external carotid arteryExternal carotid arteryIn human anatomy, the external carotid artery is a major artery of the head and neck. It arises from the common carotid artery when it bifurcates into the external and internal carotid artery.-Course:...
, which gives off its two terminal branches, the maxillary artery and the superficial temporal arterySuperficial temporal arteryIn human anatomy, the superficial temporal artery is a major artery of the head. It arises from the external carotid artery when it bifurcates into the superficial temporal artery and maxillary artery....
, inside the gland - The retromandibular vein
Vascularization
Branches of the external carotid arteryExternal carotid artery
In human anatomy, the external carotid artery is a major artery of the head and neck. It arises from the common carotid artery when it bifurcates into the external and internal carotid artery.-Course:...
traverse the glandular tissue and supply the parotid gland with oxygenated blood. The main branch to supply the gland is the transverse facial artery
Transverse facial artery
The transverse facial artery is an artery that branches from the superficial temporal artery and runs across the face.-Course:The transverse facial artery is given off from the superficial temporal artery before that vessel leaves the parotid gland; running forward through the substance of the...
, whereas numerous local veins drain the organ. These veins drain into tributaries of external and internal jugular vein
Internal jugular vein
The two internal jugular veins collect the blood from the brain, the superficial parts of the face, and the neck.-Path:On both sides and at the base of the brain, the inferior petrosal sinus and the sigmoid sinus join to form the internal jugular vein...
s.
The maxillary vein and superficial temporal vein meet to form the retromandibular vein within the parotid gland, but are not responsible for draining it.
Lymphatics mainly comprise pre-auricular lymph nodes.
Innervation
Although the facial nerve passes through the parotid gland it does not receive innervation from it. Instead, the parotid gland is innervated by parasympathetic fibers of the glossopharyngeal nerveGlossopharyngeal nerve
The glossopharyngeal nerve is the ninth of twelve pairs of cranial nerves . It exits the brainstem out from the sides of the upper medulla, just rostral to the vagus nerve...
arising from the otic ganglion
Otic ganglion
The otic ganglion is a small, oval shaped, flattened parasympathetic ganglion of a reddish-gray color, located immediately below the foramen ovale in the infratemporal fossa. It gives innervation to the parotid gland for salivation....
.
Pathology
Inflammation of one or both parotid glands is known as parotitisParotitis
Parotitis is an inflammation of one or both parotid glands, the major salivary glands located on either side of the face, in humans. The parotid gland is the salivary gland most commonly affected by inflammation.-Infectious parotitis:...
. The most common cause of parotitis is mumps
Mumps
Mumps is a viral disease of the human species, caused by the mumps virus. Before the development of vaccination and the introduction of a vaccine, it was a common childhood disease worldwide...
. Widespread vaccination against mumps has markedly reduced the incidence of mumps parotitis. Other infections such as bacterial infections can cause parotitis as may blockage of the duct, whether from salivary duct calculi or external compression. Stones mainly occur within the main confluence of the ducts and within the main parotid duct. The patient usually complains of intense pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
when salivating and tends to avoid foods which produce this symptom. In addition, the parotid gland may become enlarged upon trying to eat. The pain can be reproduced in clinic by squirting lemon juice into the patient's mouth. Surgery depends upon the site of the stone: if within the anterior aspect of the duct a simple incision into the buccal mucosa with sphinterotomy may allow removal; however, if situated more posteriorly within the main duct, complete gland excision may be necessary.
Swelling of the parotid gland may also indicate the eating disorder bulimia nervosa, creating the look of a heavy jaw line.
Eighty percent of tumors of the parotid gland are benign. The most common of these include pleomorphic adenoma
Pleomorphic adenoma
Pleomorphic adenoma is a common benign salivary gland neoplasm characterised by neoplastic proliferation of parenchymatous glandular cells along with myoepithelial components, having a malignant potentiality. It is the most common type of salivary gland tumor and the most common tumor of the...
and Warthin's tumor
Warthin's tumor
Warthin's tumor or Warthin tumour, also known as papillary cystadenoma lymphomatosum or adenolymphoma, is a type of benign tumor of the salivary glands.-Etiology:Its etiology is unknown, but there is a strong association with cigarette smoking...
. Their importance is in relation to their anatomical position and tendency to grow over time. The tumorous growth can also change the consistency of the gland and cause facial pain on the involved side since the facial nerve travels through the gland.
Twenty percent of parotid tumors are malignant with the most common tumors being mucoepidermoid carcinoma
Mucoepidermoid carcinoma
Mucoepidermoid carcinoma is the most common type of salivary gland malignancy in children. Mucoepidermoid carcinoma can also be found in other organs, as bronchi, lacrimal sac and thyroid.Mucicarmine staining is one stain used by pathologist for detection....
and adenoid cystic carcinoma
Adenoid cystic carcinoma
Adenoid cystic cancer is a rare type of cancer that can exist in many different body sites. It most often occurs in the areas of the head and neck, in particular the salivary glands; but has also been reported in the breast, lacrimal gland of the eye, lung, brain, bartholin gland, trachea, and...
. Critically, the relationship of the tumor to the branches of the facial nerve
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
(CN VII) must be defined because resection may damage the nerves, resulting in paralysis of the muscles of facial expression. If the tumor is deep within the gland, the patient should give consent with specific regard to potential damage of the facial nerve.
