b. Rami musculares.—Muscular branches pass to the digastric and to the hyoid muscles. A small branch ([Fig. 119], h), which may arise either from the external carotid or from the common carotid near the beginning of the external carotid, passes to the larynx and supplies the thyroarytenoid and lateral cricoarytenoid muscles of the larynx.

c. A. maxillaris externa ([Fig. 119], j).—The external maxillary artery leaves the external carotid (m) opposite the angle of the jaw and at about the dorsal border of the digastric muscle (8). It passes craniad, lying at first beneath the digastric muscle and sending a branch to the submaxillary gland. Opposite the caudal border of the mylohyoid muscle it gives off the submental artery, turns dorsad, emerges from beneath the digastric, and passes along the cranial border of the masseter onto the face. Here it divides into superior (k) and inferior (l) labial branches, which pass along the upper and lower lips, respectively, giving off numerous branches.

The submental artery passes to the symphysis menti between the digastric and mylohyoid muscles, giving off on its course collateral branches to the muscles of this region.

d. A. auricularis posterior ([Fig. 119], o).—The posterior auricular leaves the external carotid (m) opposite the middle of the bulla tympani and beneath the submaxillary gland. It passes about the base of the ear on its caudal and dorsal sides outside of the deep muscles of the occipital region, but beneath the auricular muscles, and sends several branches to the muscles of the external ear, passing onto the caudal surface of the concha. It sends also a large branch mediad to the muscles of the occiput, especially to the temporal muscle, within which it ramifies. A large branch (anterior auricular, [Fig. 131], u) passes from the caudal side of the concha craniodorsad, and appears on the cranial side of the external ear, running along the cranial margin of the auditory opening.

e. A. temporalis superficialis ([Fig. 119], p; [Fig. 120], h).—The superficial temporal artery arises from the external carotid as the latter lies between the cartilaginous auditory meatus and the caudal border of the masseter muscle. It passes dorsad and gives off soon after its origin a muscular branch to the masseter, and an auricular branch which passes distad along the concha auris and ramifies over its cranial surface. The superficial temporal itself passes onto the surface of the temporal muscle ([Fig. 120], 11), to which it gives numerous branches. It extends to the caudal angle of the eye ([Fig. 131], s), where it divides. One branch passes into the lower eyelid; the larger branch passes along the dorsal side of the eye, sending a branch into the orbit and small branches onto the dorsal surface of the nose.

f. A. maxillaris interna ([Fig. 119], n; [Fig. 120], i).—The internal maxillary artery is the continuation of the external carotid. It turns caudad at the caudal end of the mandible, then passes craniad, lying dorsad of the pterygoid muscles ([Fig. 120], 10), and against the medial surface of the mandible. It gives off the inferior alveolar artery ([Fig. 120], j), then the middle meningeal (k), and then continuing mediad divides into three or four branches. The branches redivide, and the twigs form a complicated plexus, the carotid plexus ([Fig. 120], l), which surrounds the maxillary division of the fifth nerve near its exit from the foramen rotundum. One of the larger branches of the plexus enters the skull through the orbital fissure, lying beside the hypophysis; it divides in the manner [described] below.

[Fig. 120].—Branches of External Carotid Artery.

a, common carotid; b, branch to larynx; c, internal carotid; d, lingual; e, external carotid; f, posterior auricular; g, external maxillary; h, superficial temporal; i, internal maxillary; j, inferior alveolar; k, middle meningeal; l, carotid plexus; m, branch to temporal muscle; n, ophthalmic; o, infraorbital; p, lesser palatine. 1, M. constrictor pharyngis inferior; 2, M. sternothyreoideus; 3, M. sternohyoideus; 4, M. thyreohyoideus; 5, M. constrictor pharyngis medius; 6, M. hyoglossus; 7, M. geniohyoideus; 8, M. genioglossus; 9, M. digastricus; 10, Mm. pterygoidei externus and internus (cut); 11, M. temporalis (cut).

Beyond the carotid plexus a main trunk which may be considered the continuation of the internal maxillary passes craniad, lying on the dorsal surface of the external pterygoid muscle; nearly opposite the molar tooth it divides into the infraorbital ([Fig. 120], o) and the sphenopalatine arteries.