The threshold of the mouth

The vestibule of the mouth , vestibulum oris, is a slotted horseshoe-shaped space, bounded from the outside by lips and cheeks, and from the inside by gums and rows of teeth.

Lips of the mouth, labia oris, are basically two muscular folds: the upper lip, labium superius, and the lower lip, labium inferius. Being closed, they cover the oral opening and limit the transverse mouth slit, rima oris, whose ends are called the corners of the mouth, anguli oris. The visible surface of the lips is covered with skin, which passes into the mucous cover on their inner surface. The thickness of the lips is formed mainly by the circular muscle of the mouth, loose connective tissue, skin and mucous membrane. On the dermal surface of the upper lip along the median line there is an unpaired, labial groove bordered by skin dents, a philtrum, adjacent to the tubercle of the upper lip, tuberculum labii superioris.

The upper lip is separated from the cheeks by a nasolabial furrow. The lower lip is delimited from the chin by a horizontally running chin-labial furrow.

In the corners of the mouth, the upper and lower lips are joined by the lip adhesions, commissurae labiorum.

The surface of the lips, facing the teeth, is smooth, moist and passes into the mucous cover of the alveolar processes - into the gums, gingivae. In the gums, the gingival margin is distinguished, margo gingivalis, which rises around the tooth. A small groove between the rising edge of the gum and the tooth is called the gingival sulcus, sulcus gingivalis, and the mucosa at the edge of the gum, between the teeth, is called the gingival (interdental) papilla, papilla gingivalis (interdentalis).

In the cover of each lip, three parts are distinguished: dermal, intermediate (a segment of pink color, also having skin, but without the stratum corneum) and the mucous membrane occupying the inner surface of the lips.

When the mucous membrane of the lips (upper and lower) passes into the gums, two sagittally median folds are formed: the bridle of the upper lip, frenulum labii superioris, and the bridle of the lower lip, frenulum labii inferioris.

In the submucosal base of the lips lie in a large number of labial glands, glandulae labiales, reaching the size of a pea: the excretory ducts of these glands open on the surface of the mucous part of the lips.

Innervation: motor - n. Facialis; Sensitive: upper lip - n. Infraorbitalis, lower lip - n. Mentalis, corner of the mouth - nn. Buccalis, infraorbitalis, mentalis.

Blood supply: aa. Labiales superior et inferior, mentalis; Vv. Labialis superior et labiales inferiores.

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