596
UNIT FOUR
border, they divide to form the internal and external carotid
arteries.
The
external carotid artery
courses upward on the side
of the head, giving off branches to structures in the neck,
face, jaw, scalp, and base of the skull. The main vessels that
originate from this artery include the following:
1.
Superior thyroid artery
to the hyoid bone, larynx, and
thyroid gland.
2.
Lingual artery
to the tongue, muscles of the tongue, and
salivary glands beneath the tongue.
blood supply. The circle is complete in only 20% to 30% of
the population.
The
thyrocervical
(thi
ro-ser
vı˘-kal)
arteries
are short
vessels that give off branches at the thyrocervical axis to the
thyroid gland, parathyroid glands, larynx, trachea, esopha-
gus, and pharynx, as well as to various muscles in the neck,
shoulder, and back. The
costocervical
(kos
to-ser
vı˘-kal)
arteries,
the third vessels to branch from the subclavians,
carry blood to muscles in the neck, back, and thoracic wall.
The left and right
common carotid arteries
ascend deeply
in the neck on either side. At the level of the upper laryngeal
Vertebral a.
Subclavian a. (cut)
External carotid a.
Common carotid a.
Internal carotid a.
Middle meningeal a.
to meninges of brain
Internal carotid a.
to arterial circle
and brain
Facial a.
Lingual a.
Thyroid a.
Brachiocephalic a.
FIGURE 15.45
An angiogram of the arteries associated with the head. (
a.
stands for artery.)
Anterior
cerebral a.
Internal
carotid a.
Pituitary
gland
Basilar a.
Anterior
cerebral a.
Middle
cerebral a.
Posterior
cerebral a.
Posterior
communicating a.
Anterior
communicating a.
Middle
cerebral a.
Basilar a.
Vertebral a.
Spinal cord
Spinal a.
FIGURE 15.46
View of inferior surface of the brain. The cerebral
arterial circle (circle of Willis) is formed by the anterior and posterior
cerebral arteries, which join the internal carotid arteries. (
a.
stands for
artery.)
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