Relations.—Outer (lateral) surface in the thoracic region with the external oblique ([Fig. 68], p), the pectoralis minor ([Fig. 65], o), and in part with the serratus anterior ([Fig. 73], i); in the cervical region with the sternomastoid ([Fig. 65], g). Inner (medial) surface with the serratus anterior ([Fig. 73], i), the levator scapulæ ([Fig. 73], h), the longus atlantis, the transverse processes of the cervical vertebræ, and the longus capitis ([Fig. 73], e).
Action.—Flexes the neck and draws the ribs craniad.
M. longus capitis (or rectus capitis anterior major) ([Fig. 72], a; [Fig. 73], e).—This is a long muscle lying on the ventral aspect of the cervical vertebræ. With the muscle of the opposite side and the underlying longus colli ([Fig. 72], g′) it forms a trough in which lie the œsophagus, pharynx, and trachea.
Origin by five (or six) heads from the ventral margins of the transverse processes of the cervical vertebræ from the second to the sixth inclusive. The heads unite into a common belly, the lateral border of which is united with the levator scapulæ ventralis ([Fig. 72], c) near its insertion.
Insertion into the body of the sphenoid bone between the bulla and the middle line. The insertion extends craniad onto the basisphenoid.
Relations.—Ventral surface with the sternomastoid ([Fig. 65], g) and the large lymphatic gland ventrad of the external ear. Lateral surface with the scalenus ([Fig. 72], h) and craniad with the levator scapulæ ventralis ([Fig. 72], c-c″). Medial surface with the carotid artery, the trachea, œsophagus, and pharynx. Dorsal edge with the vertebræ, the longus colli ([Fig. 72], g′), and the rectus capitis anterior minor ([Fig. 72], b).
Action.—Lowers the snout.
M. rectus capitis anterior minor ([Fig. 72], b).—This is a flat band beneath (dorsad of) the longus capitis (a).
Origin from the ventral surface of the inferior arch (body) of the atlas (3) for about five millimeters laterad of the middle line.
Insertion into a deep depression on the basioccipital caudad of the insertion of the longus capitis (a) and between the caudal end of the bulla (1) and the median line.