_a_, Aortic arch; _a′_, thoracic aorta; _b_, brachiocephalic artery;
_c_, left brachial artery; _d_, _d_, common carotid arteries; _e_,
vertebral artery; _f_, dorsal artery; _g_, deep or superior cervical
artery (usually given off from a common trunk with _f_); _h_,
extrathoracic part of _f_; _i_, subcostal artery; _k_, inferior
cervical artery; _l_, descending branch of _k_; _m_, ascending
branch of _k_; _n_, internal scapular; _o_, acromial; _p_,
superficial cervical; _q_, _s_, extrathoracic part of left brachial;
_r_, external thoracic; _t_, internal thoracic; _t′_, asternal;
_t″_, anterior abdominal; _u_, perforating branch of _t_; _v_,
anterior mediastinal (thymic); _w_, ventral intercostals; _x_,
bronchial; _y_, œsophageal; _y′_, dorsal intercostals; _z_,
descending branch of left coronary artery; _z′_, circumflex branch
of same; _1_, œsophagus; _2_, trachea; _2′_, bronchi; _3_, first rib
(sawn off); _4_, right ventricle; _5_, left ventricle; _5′_, left
auricle; _5″_, pulmonary artery (cut off); _6_, diaphragm; _7_, _8_,
_9_, last three cervical vertebræ; _10_, thymus. (After Ellenberger,
in Leisering’s Atlas.)
]
The =vertebral artery= may arise either in front of or behind the trunk
above mentioned; in the latter case it crosses the inner face of the
trunk. It passes along the neck in typical fashion to the third cervical
vertebra and divides into three branches. The largest of these supplies
the muscles in this region, compensating for the absence of branches of
the superior cervical artery. The second passes between the second and
third cervical vertebræ into the vertebral canal and unites with the
opposite artery and a branch of the occipital artery to form the
basilar. The third branch is the small continuation of the parent trunk;
it passes to the wing of the atlas and anastomoses with the occipital.
The =inferior cervical artery= gives off the superficial cervical which
ascends in front of the supraspinatus.
The =internal thoracic artery= is large and sends perforating branches
to the pectoral mammary glands.
The =external thoracic artery= arises outside of the thorax and sends
branches to the mammary glands.
The =common carotid arteries=, left and right, arise in that order from
the brachiocephalic. In the neck the right one lies on the trachea, the
left on the œsophagus. Collateral branches are the posterior thyroid
(which may, however, arise from the right or left brachial or the
inferior cervical), pharyngeal, thyro-laryngeal muscular, tracheal, and
glandular (to the submaxillary gland). Each carotid divides under the
wing of the atlas into occipital and internal and external carotid
branches.
[Illustration: