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 external carotid artery enters the gland to divide opposite the neck of the lower jaw into the temporal and internal maxillary. The temporal, before it leaves the gland, gives off the transverse facial artery which runs forward on the face between the zygoma and parotid duct. It is usually small but at times may be quite large and even go over to the angle of the mouth and form the two coronary arteries (as shown in M'Clellan's "Regional Anatomy"). The temporal vein, as it descends into the gland, is joined by the internal maxillary vein to form the temporomaxillary vein, which, after it receives the posterior auricular vein, goes to form the external jugular.
The facial nerve emerges from behind the jaw just below the lobe of the ear and divides into its various branches while still in the gland. There is usually a large branch passing parallel to the duct of Stenson and below it. The auriculotemporal nerve follows the temporal artery, emerging from the gland a little posterior to the artery. It is not of much surgical moment. The auricularis magnus from the second and third cervical supplies the skin over the gland.
Lymphatic nodes are found both on the gland and in its substance. These maybe involved in general disease of the cervical lymphatics.
The duct may be affected with calculus, as already mentioned. As the opening of the duct at the papilla is smaller than the lumen of the canal farther back, calculi are apt to lodge close to the anterior extremity. They are, therefore, readily felt and removed by incision on the inside of the mouth. The gland proper is subject to inflammations and tumors.
Simple parotiditis or mumps really is an infectious inflammation, nevertheless, it rarely suppurates. Suppurative parotiditis may occur from infected wounds or arise in the course of the eruptive fevers, etc. In. inflammation of the gland, pain and swelling are important symptoms. The pain, which is considerable, is not due so much to the so-called dense parotid fascia covering the gland, for this is only moderately thick, as it is to the fact that the gland is of a racemose type and the fibrous septa between the lobules are abundant and prevent free expansion of the contained lobules. Expansion is also hindered by the peculiar location of the various parts of the gland. Swelling of the glenoid lobe produces pain in the ear and also in the temporomaxillary articulation. Swelling of the carotid and pterygoid lobes causes pain and fulness in the throat. Opening the lower jaw reduces the space posterior to it in which the gland lies and pinches it against the bony meatus and mastoid process, so that it is impossible to open the jaw widely.
Fig. 62. - Structures in relation with the parotid gland.
If suppuration occurs it is liable to progress from one lobule to another; when this is the case comparatively small abscesses may appear in different parts of the gland with unaffected tissue between them. As an abscess heals in one lobule, suppuration is apt to occur in another, consequently the disease may persist for a long time. More rarely in the course of or following infectious diseases, particularly in debilitated patients, considerable portions of the gland may slough. This form is apt to be fatal. If the suppurating focus is confined to lobules which are deeply placed, the diagnosis may be obscure because it is difficult to localize the affected spot. If, however, it is near the surface of the gland, the pus does not tend to extend sideways, the fibrous septa prevent this, but it tends to work its way up and perforate the skin. If the glenoid lobe is affected, the pus may find an exit through the external auditory meatus or even involve the temporomaxillary joint. If the carotid or pterygoid lobes are affected, the pus may go between the pterygoid muscles, or around the internal carotid artery and project and open into the pharynx. It may also break into the carotid artery or jugular vein, or perforate through the fascia below and go down the neck. Large abscesses and sloughs may be followed by a parotid fistula.