Surgical Anatomy.—The parotid gland lies on the side of the face below and in front of the ear, and extends deeply behind the mandible reaching almost to the side wall of the pharynx. Its deeper part lies in close relation with the internal carotid artery, the internal jugular vein, and the vagus, glosso-pharyngeal, accessory, and hypoglossal nerves. The external carotid artery passes through the substance of the parotid, and bifurcates opposite the neck of the condyle into the temporal and internal maxillary arteries. It is accompanied by the venous trunk formed by the junction of the temporal and internal maxillary veins. The facial nerve and its branches traverse the lower third of the gland from behind forwards. The facial portion of the gland lies on the surface of the masseter muscle, and the parotid duct (Stenson's duct) emerges from its anterior border. After crossing the masseter, the duct pierces the buccinator muscle and the mucous membrane obliquely, and opens into the mouth opposite the second upper molar tooth. Its course is indicated by a line passing from the upper part of the lobule of the ear to a point midway between the ala of the nose and the margin of the upper lip—that is, at a higher level than the facial nerve. Several lymph glands—pre-auricular—lie inside the capsule of the parotid just in front of the ear.
The submaxillary gland lies under the integument and fascia in the triangle formed by the lower jaw and the two bellies of the digastric muscle. Its anterior part is crossed by the facial vessels, and several lymph glands lie inside its capsule. The submaxillary duct (Wharton's duct) opens into the mouth by the side of the frenum of the tongue.
The sublingual gland lies in the floor of the mouth just beneath the mucous membrane. It has numerous ducts, some of which open directly into the mouth, others into the submaxillary duct.
Injuries.—The parotid is frequently injured by accidental wounds and in the course of operations. If the blood vessels traversing the gland are divided, such wounds are liable to bleed freely, and if the facial and auriculo-temporal nerves are damaged, motor and sensory paralysis of the parts supplied by them ensues. Wounds of the parotid heal rapidly and without complications so long as infection is prevented, but if suppuration takes place they are liable to be followed by the escape of saliva, which may go on for weeks; in some cases a salivary fistula is thus established.
The parotid duct may be divided and a salivary fistula result. If the external wound heals rapidly, a salivary cyst may develop in the substance of the cheek, forming a swelling, which fills up at meals, and may be emptied by external pressure, the saliva escaping into the mouth.
In a wound implicating the whole thickness of the cheek the skin should be accurately sutured, care being taken that the stitches do not include the duct, but in order that the saliva may readily reach the mouth, the mucous membrane should not be stitched.
Fig. 261.—Series of Salivary Calculi.
Salivary Fistulæ.—A salivary fistula may occur in relation to the glandular substance of the parotid or in relation to the duct. Fistula in connection with the glandular substance—parotid fistula—seldom results from a wound, made, for example, in the removal of a tumour or in an operation on the ramus of the jaw, so long as it is aseptic; but as a sequel of suppuration in the gland, and particularly of an abscess developing around a concretion, it is not uncommon. The fistulous opening is usually small, and may occur at any point over the gland. The fistula may be dry between meals, or the saliva may escape in small transparent drops, but the quantity is always greatly increased when food is taken. A parotid fistula, although it may continue to discharge for weeks, or even for months, usually closes spontaneously.