The lips are formed mainly by the orbicularis oris muscle with its subdivisions and the accessory facial muscles (buccinator, levator and depressor anguli oris, levator labii superioris, levator labii superioris alaeque nasi, the zygomaticus major and minor, and the depressor labii inferioris). The orbicularis oris is attached to the superior maxilla in the incisor fossa above the second incisor tooth and also above to the septum. In the lower lip it is attached to the mandible beneath the second incisor tooth. The lips contain, beside muscular tissue, some areolar tissue, arteries, veins, and lymphatics. The muscular fibres are inserted into the skin. The mucous membrane lining the lips has lying beneath it some mucous glands. They sometimes become enlarged and form small, shot-like, cystic tumors containing mucus.

Affections Of The Lips

The lips are affected by wounds, angioma or blood tumor, cancer (epithelioma), and clefts (harelip). Wounds of the lip when properly approximated heal readily on account of the free blood supply. The arteries supplying the lips are the superior and inferior coronary branches of the facial. They are given off about opposite the angle of the mouth and pierce the muscle to run beneath the mucous membrane about midway betwen the edge of the lip and its attachment to the gums or nearer the free border of the lip. Therefore, in operating on the lip, the artery should be looked for in this situation and not toward the skin surface or in the substance of the lip. The superior coronary sends a branch to the nasal septum, called the inferior artery of the septum. In the sulcus between the lower lip and chin lies the inferior labial artery. The bleeding from this branch is not so free as that from the coronary arteries, because the anastomosis across the median line is not so marked.

Fig. 127.   Superficial dissection, showing the muscles of the head and face. (Piersol).

Fig. 127. - Superficial dissection, showing the muscles of the head and face. (Piersol).

Angioma

The blood-vessels, mainly the veins, of the lips sometimes become enlarged, forming a large protrusion. This may be noticed at or soon after birth as a dusky blue, slightly swollen spot on the lip. As the child grows the swelling enlarges. Sometimes it enlarges rapidly and operation is necessary to check its growth; otherwise it may involve a large portion of the face and prove incurable. It is composed of dilated veins with thin walls and large lumen. It does not pulsate and disappears under pressure, only to return when this is. removed. It is treated by excision. The thin skin is dissected off and the growth cut away from the tissues beneath, the bleeding being controlled by pressure, haemostats, and ligatures. In the case figured, the facial vein, as it crossed the mandible, and the transverse facial vein were obliterated by means of acupressure pins passed beneath them, and the growth was excised.

Cancer or epithelioma of the lip almost always affects the lower and not the upper lip. The disease extends through the lymphatics. These pass down and out from the lips to the submaxillary lymph-nodes and then to the nodes along the great vessels of the neck. It is in these regions that lymphatic infection is usually seen. The middle of the lower lip is drained into a node in the submental region in front of the submaxillary nodes. This also is sometimes involved. In operating for cancerous growths it is advisable to remove all nodes from both the submental and submaxillary triangles.

Fig. 128.   Angioma involving the right half of the upper lip in a child. (Personal sketch).

Fig. 128. - Angioma involving the right half of the upper lip in a child. (Personal sketch).

Fig. 129.   Single harelip.

Fig. 129. - Single harelip.

Cleft or harelip is so named from its resemblance to the lip of a hare. It is a deformity due to lack of development, in which the lip is cleft or split from the mouth up into the nostril, and sometimes even back through the hard and the soft palate. When the cleft is slight, it may not reach the nostril. It is practically always to one side of the middle, going toward one nostril. Sometimes the harelip is double, involving both sides. In such cases the bone between the two clefts may protrude. In the development of the face, the frontonasal process comes down from above to form the middle portion of the nose, upper lip, and upper jaw. It forms a bone known as the premaxilla and bears the incisor teeth. From the sides spring the nasal and maxillary processes. These join together as one process and grow toward the premaxilla. If this process fails to reach the premaxillary bone, a cleft is left constituting harelip. If both processes fail to reach the premaxilla, a double harelip is formed; the cleft may extend through the hard and the soft palate the cleft palate may alone be present as seen in Fig. 139 (see page 112). In operating for harelip, the two sides of the cleft are freshened and sewed together, thus closing the cleft.

Fig. 130.   Double harelip, showing the projecting premaxilla.

Fig. 130. - Double harelip, showing the projecting premaxilla.

Fig. 131.   Frontal view of human foetus about four weeks old. (After His).

Fig. 131. - Frontal view of human foetus about four weeks old. (After His).

Fig. 132.   Paralysis of depressor labii inferioris from section of the lower filament of the facial nerve. (McDowd).

Fig. 132. - Paralysis of depressor labii inferioris from section of the lower filament of the facial nerve. (McDowd).

Paralysis of the lips is due to interference with the functions of the seventh nerve. The muscles of the face and lip are supplied by the seventh or facial nerve. This is frequently paralyzed, for owing to its tortuous passage through the temporal bone in the canal of Fallopius it is injured in fractures of the base of the skull and becomes affected from middle ear disease or neuritis. When paralyzed, the muscles of the lips, both upper and lower, on the affected side, droop. The drooping of the lower lip may allow the saliva to run out of the mouth. It is also impossible for the patient to pucker his mouth, as in whistling. If the lesion of the facial nerve is inside the skull and not in the Fallopian canal, the great petrosal nerve and some of the palatal muscles will be paralyzed, the voice will be altered and swallowing interfered with.

The depressor labii inferioris instead of receiving its nerve supply from the supra-mandibular branch of the facial, frequently is supplied by the inframandibular branch; pressure or injury of this branch in enlargements of or operations on the submandibular lymph-nodes has produced paralysis of the muscle with a peculiar alteration of the facial expression, well shown (see Fig. 132) by a case of Dr. McDowd {Annals of Surgery, July, 1905).