Part 16

Shape.—Triangular, fan-shape.

Relations.—Superiorly with the skin.

Action.—Controls the skin in this region. The anterior end being fixed, the muscles are raised; and the posterior end acting as the fixed point, the feathers are caused to lie close to the body.

=Dermo-pectoralis.= Location.—On each side of the chest, lying in a longitudinal manner.

Origin and Insertion.—Attached to the skin on either side of the thorax corresponding to the dermo-dorsalis. Anteriorly it disappears over the region of the origin of the cleido-trachealis, and posteriorly just behind the tips of the post-pubic parts of the pelvis.

Shape.—Thin, delicate.

Relations.—Superiorly with the skin.

Action.—The anterior part acting as the fixed point, the feathers of the chest are raised; and the posterior end acting as the fixed point, the feathers are made to lie flat.

THE DERMO-OSSEOUS MUSCLES

Dermo-temporalis Platysma myoides Dermo-cleido dorsalis Cleido-trachealis Dermo-spinalis Dermo-iliacus Dermo-ulnaris

=Dermo-temporalis= (Fig. 18, No. 1). Location.—From the temporal region down the side of the neck to the anterior part of the thoracic region.

Origin.—By a broad tendinous attachment from a small depression above and anterior to the temporal fossa. From here the fibers pass upward and backward and then downward.

Insertion.—A few fibers blend with those of the cleido-trachealis. The fibers are then lost upon the skin in front and opposite the shoulder-joint. Some of the fibers blend with those of the dermo-tensor patagii.

Shape.—Long, flat, and ribbon-shaped. The lower portion consists of delicate fibers.

Relations.—Superior to the temporal muscle and sphenotic process. Superior to the cleido-trachealis and inferiorly to the shoulder-joint. The superior portion touches the skin throughout its entire length.

Action.—A tensor of the lateral cervical integument. It is an auxiliary to the tensor patagii.

=Platysma Myoides.= Location.—The inferior portion of the throat.

Origin.—From the lower margin of the rami of the jaw. Just inferior to the attachment of the masseter.

FIG. 18.—Muscles of the upper neck region, 1, Dermo-temporalis. 2, Cornu of the os hyoideum. 3, Carotid artery. 4, Jugular vein. 5, Pneumogastric nerve. 6, Esophagus. 7, Trachea. ]

Insertion.—From the point of origin it spreads out into a thin fan-like layer and meets its fellow in the median raphe. It is attached to the skin in this region.

Shape.—A very thin fan-shaped muscle.

Relations.—Closely adherent to the skin.

Action.—Assists in supporting the lingual apparatus and superior larynx. Compresses and elevates the part.

=Dermo-cleido Dorsalis.= Location.—Anterior shoulder region.

Origin.—From the upper mesial part of the clavicular bone.

Insertion.—Three fasciculi forming a fan-like arrangement attached to the skin in the shoulder-joint and scapular region. The extremities of the fasciculi may meet in the median line of the dorsal region and merge with the dermo-dorsalis.

Shape.—Three fasciculi forming a fan-shaped radiation.

Relations.—Superiorly with the skin. Inferiorly with the shoulder-joint.