This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
The parotid gland lies on the cheek, behind the jaw and below the ear. The limits (Fig. 60) of the gland are important because suppuration may occur in any portion of its structure. Its extent is as follows: above to the zygoma, lying below its posterior two-thirds; posteriorly, to the external auditory canal, the mastoid process, and digastric and sternomastoid muscles; below to a line joining the angle of the jaw and mastoid process; and in front about half the width of the masseter muscle. This latter is, however, quite variable.
Fig. 60. - Parotid gland and structures of the side of the face.
The parotid duct, also called Stensori's duct, leaves the upper anterior portion of the gland about a centimetre below the zygoma and runs on a line joining the lower edge of the cartilaginous portion of the ear with the middle of the upper lip. It opens on a papilla on the inside of the cheek opposite the second upper molar tooth. This papilla can readily be seen and a fine probe can be inserted from the mouth into the duct; thus the presence of a calculus may be detected. In operating on the cheek the line of this duct must be borne in mind, as wounding it may cause a salivary fistula. Wounds of the lobules of the gland are not nearly so liable to result in fistula as those of the duct itself.
The gland is covered by the parotid fascia. This fascia is moderately dense and is continuous with the fascia separating the lobules of the gland. Above it is attached to the zygoma; in front it is continuous with the masseteric fascia over the masseter muscle; and below and posteriorly it is continuous with the deep fascia of the neck. It stretches from the angle of the jaw to the sternomastoid muscle and somewhat deeper to the styloid process; the band running from the styloid process to the lower jaw is called the stylomandibular ligament. From thence it is continued over the internal carotid artery and the upper surface of the internal pterygoid muscle.
The gland has extentions in various directions (Fig. 61). A prolongation behind the articulation of the lower jaw, into the posterior portion of the glenoid cavity immediately in front of the external auditory canal, is called the glenoid lobe. Another extension winds around the posterior edge of the lower jaw on the lower surface of the internal pterygoid muscle and is called the pterygoid lobe. A prolongation inward, passing between the external carotid on the outside and the styloid process and the internal carotid artery on the inside, is called the carotid lobe. A separate portion of the gland, sometimes quite detached, lies at its upper anterior portion between the zygoma and the duct of Stenson; it is called the socia parotidis.
Fig. 61. - The lobes of the parotid gland.