Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/72

58 origin cephalad to the occipital artery, then posteriorly, sending branches to the thyroid gland, and one small branch to the larynx.

(3) The lingual artery leaves the external carotid anterior to the superior thyroid artery, enters the posterior region of the tongue, and follows a sinuous course nearly to the tip in the ventral part of that organ.

(4) The external maxillary or facial artery leaves the external carotid a short distance anterior to the lingual artery, and passes anteroventrally along the medial surface of the masseter muscle. Anteriorly it occupies the groove between the masseter and digastric muscles. It bifurcates about half a centimeter back of the angle between the upper and lower lips. The dorsal ramus supplies the snout and lateral wall of the mouth. The ventral ramus supplies the lower lip. This artery sends vessels to the lymph and salivary glands of the neck region, to the masseter muscle, the ventral musculature of the lower jaw, and the floor of the posterior region of the buccal cavity.

(5) Posterior auricular artery. The external carotid artery turns abruptly dorsally immediately after giving off the external maxillary. It turns anteriorly again ventrolateral to the tympanic bulla. The posterior auricular artery arises at the latter turn. It courses dorsally along the posterior surface of the external auditory meatus to the pinna of the ear, to which it sends branches. It also supplies the muscles adjoining the pinna. Trace the terminal branches of the external carotid.

The innominate artery is the first arterial trunk leaving the aortic arch. A short distance from its origin the innominate divides into the right common carotid and the right subclavian arteries. The subclavian passes anterolaterally to the anterior surface of the first rib, where, in company with the nerves of the brachial plexus, it leaves