The parotid gland is the largest salivary gland in the human body and is one of the three major salivary glands found in humans. The other two major salivary glands are submandibular glands and the sublingual glands.
There are two parotid glands present in a normal person, one on each side of the mouth, in front of the ears. The name ‘parotid’ means ‘beside the ear’. It weighs around 15 to 30gms and is a uni-lobular gland.
The parotid secretes a fluid which can be categorized as ‘serous salivary gland’. Serous glands are the glands which contain serous acini. These are a group of serous cells which secrete serous fluid, which contains enzymes like alpha-amylase.
Parotid Gland Location And Structure
The parotid is situated in the ‘preauricular area’, which is the area in front of the ears and is pyramidal in shape. Anatomically it is said to be located in between the mandible and the sternocleidomastoid muscle. The external auditory meatus lies in a superior position to the parotid.
Structurally the parotid can be divided into two parts. The apex and the base. Both the apex and the base of this gland allows certain important structures to pass through them.
The important structures that pass through the apex of the parotid gland are
- Cervical branch of the facial nerve,
- The anterior division of the retromandibular vein
- Formation of the external jugular vein
The structures that pass through the base of the gland are
- The temporal branch of the facial nerve
- Superficial temporal vessels
- Auriculotemporal nerve
The facial nerve divides the gland of parotid into two lobes. A superficial lobe and a deep lobe. Both of these lobes are connected by a part called ‘isthmus’.
There is a layer of tissue that is connected with the superficial layer of “deep cervical fascia” which acts as a capsule for the parotid gland and is called ‘parotid capsule’. This layer is made up of fibrous tissue and is strongly adherent with the gland.
The parotid capsule has two layers. The superficial layer and the deep layer. The superficial layer is attached to the gland whereas the deep layer is attached to the styloid process and the tympanic plate.
The attachment of the deep layer of the parotid capsule with the styloid process and the tympanic plate forms a ligament named ‘stylomastoid ligament’ which separates the parotid gland from the submandibular salivary gland.
The Parotid Duct
The parotid duct arises from the anterior part of the gland and lies 1.5 cm inferior to the Zygomatic arch. The parotid duct is also called the ‘Stenson’s duct’.
The parotid duct is approximately 4-6 cm in length and 1–5 mm in diameter. This duct opens in the mouth on the buccal mucosa (inside of the cheek) opposite the maxillary second molar (upper second molar tooth).
Parotid Gland Salient Features and Clinical Significations
Following are some of the important features and the significations of the parotid gland.
- The inflammatory swellings of this gland are usually painful, which is due to the adherent fibrous fascia that covers the parotid.
- The facial nerve is closely associated with the gland of the parotid. This relation becomes very important for the doctor especially during the surgeries in this area.
- If a person is suffering from the parotid abscess, skin incisions are needed, for draining the abscess. The surgeon will have to take utmost care while giving an incision in this area for draining the abscess, to prevent injuries to the facial nerve branches. The incisions are usually vertical for skin incisions and are horizontal for deeper incisions.
- The parotid duct which opens in the mouth is slightly wider at some distance before opening in the mouth. This causes the storage of saliva in the area. If due to different reasons, epithelial cells and other organic matters get lodged in this area, these may cause obstruction to the salivary flow. This may lead to the formation of salivary stones.
- The right angle turn of the parotid duct is the other reason which facilitates the formation of stones in the salivary duct.
- Another significant feature associated with the parotid is about mumps or the viral parotitis. Pus is never produced in this condition. So if a person is suffering from mumps and has pus formation, secondary infection or some other condition may be suspected.
- Frey’s syndrome: This is a condition caused due to the damage to the auriculotemporal nerve because of a trauma to the parotid or somewhere near its location.
- During a procedure called parotidectomy, a process which involves the surgical excision of the parotid gland, the gland is removed in two parts, to preserve the facial nerve.
Parotid Gland Infection and Inflammation
Below are some of the important conditions that may cause inflammation and/or infection of the parotid gland.
This is one of the most common infections of the salivary glands occurring in humans that involves parotid gland. This is a viral infection caused by a virus called the paramyxovirus.
Mixed parotid tumor
This is a slow-growing tumor which is lobulated. This tumor presents itself as a painless mass without and doesn’t affect the facial nerve.
Occasionally this tumor may become malignant in which case the swelling becomes painful, and has a rapid increase in the size. Malignancy also involves the facial nerve and the person affected has enlarged cervical lymph nodes.
This is a condition where the salivary flow and the secretion are obstructed due to the formation of calcifications in the parotid gland and/or the duct. Due to the structure of the parotid duct, the chances of formation of parotid stones are high. These are also called ‘salivary stones’.
Parotitis is a condition which presents itself in the form of inflammation of one or both of the parotid glands. The most common cause of parotitis is viral parotitis or mumps. Bacterial infection and other infections are less common causes.
Parotid gland malignancies are rare but happen. Almost 80% of the parotid conditions are benign. Cancers that most commonly affect the parotid gland are the mucoepidermoid carcinoma and adenoid cystic carcinoma.