Contents -SUBJECT INDEX -BIBLIOGRAPHIC RECORD -ILLUSTRATION INDEX

Henry Gray (1825–1861). Anatomy of the Human Body. 1918.

pages 387

inserted into a depression in front of the neck of the condyle of the mandible, and into the front margin of the articular disk of the temporomandibular articulation.

The Pterygoideus internus (Internal pterygoid muscle) (Fig. 383) is a thick, quadrilateral muscle. It arises from the medial surface of the lateral pterygoid plate and the grooved surface of the pyramidal process of the palatine bone; it has a second slip of origin from the lateral surfaces of the pyramidal process of the palatine and tuberosity of the maxilla. Its fibers pass downward, lateralward, and backward, and are inserted, by a strong tendinous lamina, into the lower and back part of the medial surface of the ramus and angle of the mandible, as high as the mandibular foramen.

FIG. 383– The Pterygoidei; the zygomatic arch and a portion of the ramus of the mandible have been removed. (See enlarged image)

Nerves.—The muscles of mastication are supplied by the mandibular nerve.

Actions.—The Temporalis, Masseter, and Pterygoideus internus raise the mandible against the maxillæ with great force. The Pterygoideus externus assists in opening the mouth, but its main action is to draw forward the condyle and articular disk so that the mandible is protruded and the inferior incisors projected in front of the upper; in this action it is assisted by the Pterygoideus internus. The mandible is retracted by the posterior fibers of the Temporalis. If the Pterygoidei internus and externus of one side act, the corresponding side of the mandible is drawn forward while the opposite condyle remains comparatively fixed, and side-to-side movements. Such as occur during the trituration of food, take place.

5. The Fasciæ and Muscles of the Anterolateral Region of the Neck. a. The Superficial Cervical Muscle

The antero-lateral muscles of the neck may be arranged into the following groups:

I. Superficial Cervical. III. Supra- and Infrahyoid.  II. Lateral Cervical. IV. Anterior Vertebral. V. Lateral Vertebral.

The Superficial Cervical Muscle Platysma. The Superficial Fascia of the neck is a thin lamina investing the Platysma, and is hardly demonstrable as a separate membrane.