The lips are two mobile muscular folds that surround the opening of the mouth. Each has an outer skin surface, a red vermilion zone where the skin is thin and very vascular, and an inner moist mucosal surface. Their core is the orbicularis oris muscle, and they meet at the corners of the mouth (the labial commissures).
| Location | Around the opening of the mouth (oral fissure), forming the anterior wall of the oral vestibule |
|---|---|
| Parts |
|
| Nerve Supply | Infraorbital nerve, CN V2 (upper lip sensation); Mental nerve, CN V3 (lower lip sensation); Buccal and marginal mandibular branches of the facial nerve (motor) |
| Blood Supply | Superior labial artery; Inferior labial artery |
| Venous drainage | |
| Lymphatic drainage |
|
Close the mouth, hold food and fluid in, form a seal for sucking and drinking and shape many speech sounds. They are also highly sensitive tactile organs and key to facial expression.
The vermilion border must be lined up exactly when a lip wound is repaired, since a step of even 1 mm is visible. The central lower lip drains to the submental nodes while the upper lip and lateral lower lip drain to the submandibular nodes, which guides neck examination in lip cancer. Numbness of the lower lip (numb chin) can be the first sign of a mental or inferior alveolar nerve lesion, including metastatic disease of the mandible.
Congenital failure of fusion of the maxillary and medial nasal processes, producing a gap in the upper lip that may extend into the nose and palate.
Usually squamous cell carcinoma of the sun-exposed lower lip, more common in fair-skinned outdoor workers and smokers.
Recurrent cold sores caused by reactivation of herpes simplex virus from the trigeminal ganglion, appearing as clusters of painful vesicles at the vermilion border.
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