Page 217 - My FlipBook

BLOOD-VESSEL SYSTEM OF THE HEAD, ETC. 227
trachelo-mastoid ; a branch somewhat hirger tlian the rest supplies the
sterno-cleido-mastoid muscle. This branch usually arises a little above
the origin of the occipital artery, though it may arise from the external
carotid.
The Auricular Artery is a small branch which supplies the auricle and
the tissues near the mastoid process. This branch is not ahvavs present.
The Descending Cervical, or Ramus Cerricularis Princeps Artery, is
of large size, and arises beneath the splenius capitis muscle. Soon after
its origin it divides into two branches, superficial and deep. The super-
ficial branch perforates the splenius muscle, supplying it and the trape-
zius. The deep branch passes beneath the com})lexus and semi-sj)inalis
colli, and inosculates with the vertebral and the deep branch of the
superior intercostal. Through the anastomoses of these arteries a col-
lateral circulation is maintained after the ligation of either the common
carotid, external carotid, or subclavian arteries.
The Posterior or Meningeal Branch arises from the occipital, passes
up along the internal jugular vein, and enters the brain-case through
the jugular foramen it supplies the posterior portion of the dura mater.
;
This artery is not always present.
The 3Iastoid Artery is a small branch from the occipital, which enters
the mastoid foramen of the temporal bone ; it supplies the diploe, walls
of the mastoid cells and lateral sinus, and the dura mater in the occip-
ital fossa.
The Superficial or Cranial Arteries are terminal branches of the
occipital, and pass between the integument and the occipital muscle,
supplying the structures in this region. They anastomose freely with
each other, with the corresponding artery of the opposite side, and the
posterior auricular and superficial temporal arteries.
Variations.—The occipital occasionally arises from the internal
carotid or in conjunction with the facial or from the cervical Vn'anch
of the inferior thyroid. Its direction also may vary : instead of pass-
ing to the median side of the trachelo-mastoid muscle, it may extend
laterally. It occasionally divides into a larger and smaller branch, the
smaller assuming the usual direction of the artery, whik the larger
passes superficially to the sterno-cleido-mastoid muscle. The stylo-
mastoid artery occasionally arises from the occipital instead of the pos-
terior auricular artery.

The Posterior Auricular Artery,
The posterior auricular artery arises from the external carotid nearly
opposite the apex of the styloid process of the temporal bone, above the
digastric and stylo-hyoid muscles. It is about 2 mm. (J^ i"<^"h) in cali-
it extends obliquely upward and backAvard beneath the ]3arotid
bre ;
gland, and passes up the styloid process, where it is crossed by the
facial nerve. It then ascends between the cartilage of the ear and the
mastoid process of the temporal bone, becomes superficial, and divides
into two terminals, the auricular and the mastoid.
The branches of the posterior auricular artery are the stylo-mastoid
and the auricular.