Boundaries and fascial layers
The topographical boundaries of the parotideomasseteric region (regio parotideomasseterica) are determined by the following landmarks:
- Superiorly: zygomatic arch.
- Inferiorly: inferior border of the mandible.
- Anteriorly: a line drawn along the anterior border of the masseter muscle.
- Posteriorly: mastoid process and sternocleidomastoid muscle (SCM).
The skin in this area is thin (covered with hair in men). The subcutaneous adipose tissue is permeated by dense connective tissue strands that firmly bind the skin to the superficial fascia — fascia parotideomasseterica. This fascia forms a strong sheath (capsule) for the salivary gland.
Important anatomical structures run transversely on the outer surface of the masseter muscle (m. masseter). Initially located within the fascial splitting, they subsequently emerge into the subcutaneous tissue. This complex includes the parotid duct (ductus parotideus), transverse facial artery and vein (a. et v. transversa faciei), and buccal branches of the facial nerve (rr. buccales n. facialis).
Parotid salivary gland
The parotid salivary gland (glandula parotis) is a massive structure filling the retromandibular fossa (fossa retromandibularis).
Its deep part extends medially to the adipose tissue of the anterior parapharyngeal space, reaching the pharyngeal wall. The inferior process descends toward the inner surface of the mandibular angle, where it is separated from the submandibular salivary gland by a strong fascial septum. The superficial part of the gland is triangular in shape, with its base directed toward the zygomatic arch. It lies directly on the lateral side of the masseter muscle.
The parotid duct (ductus parotideus) runs transversely 1.5–2.0 cm below the zygomatic arch. It pierces the buccinator muscle (m. buccinator) and opens onto the buccal mucosa in the oral vestibule. The surface landmark for the opening is the level of the interdental space between the first and second upper molars.
Fascial capsule and spread of pus
The capsule of the gland is formed by the splitting of the superficial fascia of the lateral face. Clinically, it is crucial that it is unevenly developed:
- Dense (well-developed) areas: lateral surface, anterior side (adjoining the mandibular ramus, m. masseter, and m. pterygoideus medialis), posterior side, and inferior surface.
- Weak (poorly developed) areas: superior surface (adjoining the external acoustic meatus) and medial side (pars profunda, facing the anterior parapharyngeal space).
Clinical significance: in purulent inflammation (parotitis), pus takes the path of least resistance. It breaks through the weak spots of the capsule into the parapharyngeal space (toward the pharyngeal wall) or into the external acoustic meatus. According to statistics, pus breakthrough into these deep spaces occurs 4 times more often than outwardly through the dense part of the capsule.
Deep structures and masticatory-mandibular space
A complex array of vessels and nerves passes through the substance of the parotid gland itself. Here lie the facial nerve (n. facialis), forming a plexus, and the auriculotemporal nerve (n. auriculotemporalis). Among the vessels are the external carotid artery (a. carotis externa) with its terminal branches and the retromandibular vein (v. retromandibularis). Deep and superficial lymph nodes are also located within and on the fascia of the gland.
Deeper to the gland lies the masticatory-mandibular space (spatium masticatoriomandibulare). It is located between the masseter muscle and the mandibular ramus. The space is filled with loose connective tissue and contains the masseteric artery, vein, and nerve (a., v. et n. massetericae) coming from the deep facial region. Superiorly, this space communicates with the lateral surface of the temporalis muscle (under the zygomatic arch).
Posterior to the mandibular ramus, the retromandibular vein is formed. It is formed by the confluence of the glandular veins, the superficial, middle, and deep temporal veins, as well as the maxillary and transverse facial veins. Deeper than the venous trunk, the external carotid artery runs obliquely and vertically. At the level of the neck of the articular process, it divides into the superficial temporal and maxillary arteries.
To memorize the structures within the parotid gland, the acronym P.A.V.E.N. is used, which helps remember the passing nerves (facial, auriculotemporal), the external carotid artery with its branches, the retromandibular vein, and the lymph nodes.
Class and exam questions
Where does the parotid salivary duct open?
The duct (ductus parotideus) pierces the buccinator muscle and opens onto the mucosa in the oral vestibule at the level of the interdental space between the first and second upper molars.
Why does pus rarely escape outward during parotitis?
The lateral wall of the fascial capsule is very dense. Pus breaks through the weak areas of the capsule 4 times more often — upward into the external acoustic meatus or inward into the parapharyngeal space.
What is located in the masticatory-mandibular space?
The space between the masseter muscle and the mandibular ramus is filled with loose connective tissue through which the masseteric artery, vein, and nerve (a., v. et n. massetericae) run.
What else to study on this topic
- Topography and branching of the facial nerve within the parotid salivary gland.
- Formation and tributaries of the retromandibular vein (v. retromandibularis).
- Bifurcation of the external carotid artery and the course of its terminal branches.
- Connection of the masticatory-mandibular space with the fascial spaces of the temporal region.
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