Page 209 - My FlipBook
P. 209
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BLOOD-VESSEL SYSTEM OF THE HEAD, ETC. 219
the upper border of the thyroid cartilage. From this point it passes up
the neck between the pharynx and the muscles resting upon tlie vertebra
in this region, to a point opposite the surgical neck of the lower jaw,
where it divides into two terminal branches, the internal maxillary and
the superficial temporal. As it ascends the neck it decreases in size, the
reduction in calibre being due to the number of large branches it gives
off. In early life it is smaller than the internal carotid, but it gradually
increases until adult life, M'hen both arteries are of the same size.
Relations.—At its origin the external carotid artery is situated at the
median side of the internal carotid, but soon becomes superficial to that
artery. It is covered by the skin, the platysma myoides and stcrno-
cleido-mastoid muscles, and the deep fascia. The superior laryngeal
nerve passes behind the artery in this situation. Its deep relation at
its commencement is with the pharynx and hyoid bone. From this
position it passes up internally to the stylo-hyoicl and posterior belly of
the digastric muscle and part of the parotid gland, "which separates it
from the back part of the ramus of the jaw. The posterior belly of
the digastric muscle is a good guide in the ligation of the artery.
Throughout its upper portion it is separated from the internal carotid
by the stylo-glossus and stylo-pharyngeus muscles, the glosso-pharyn-
geal nerve, and part of the parotid gland.
The external carotid artery is usually unaccompanied by a vein,
although the temporo-maxillary vein crosses it within the parotid gland,
the anterior division of the temporo-maxillary vein passing downward
to the facial. The facial and lingual veins cross the artery below the
digastric muscle on their way to join the internal jugular. Higher up,
in the substance of the parotid gland, the artery is crossed by the facial
nerve, the hypoglossal nerve crossing it just below the posterior belly
of the digastric muscle.
Branches of the External Carotid Artery.—The external carotid artery
in its ascent through the neck gives off eight branches. Their names,
in great measure, indicate their distribution. Three of the branches
viz. the superior thyroid, lingual, and facial — pass anteriorly; two—viz.
the occipital and posterior auricular — pass posteriorly ; one, the ascend-
ing pharyngeal, passes internally : it terminates in two branches, the
superficial temporal and the internal maxillary.
Variations.—The general variations in the origin of the external
carotid artery have been mentioned under the head of the common
carotid. Other variations are caused by the manner in w^hich its
branches are given off. The external carotid may at times be entirely
M-anting. When this is the case the different branches which are usually
given off by it arise from a common trunk which represents the inter-
nal and external carotids. The superior thyroid and the lingual arteries
may arise from a single branch, instead of two separate branches, or
the" lingual and facial or the superior thyroid, lingual, and facial may
originate in a similar manner. The superior thyroid may also arise
from the common carotid. The external carotid artery occasionally
divides at the angle of the jaw, reuniting again near the neck of the
inferior maxilla to form the temporal artery.
The Superior Thyroid Artery is the first anterior branch of the
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC. 219
the upper border of the thyroid cartilage. From this point it passes up
the neck between the pharynx and the muscles resting upon tlie vertebra
in this region, to a point opposite the surgical neck of the lower jaw,
where it divides into two terminal branches, the internal maxillary and
the superficial temporal. As it ascends the neck it decreases in size, the
reduction in calibre being due to the number of large branches it gives
off. In early life it is smaller than the internal carotid, but it gradually
increases until adult life, M'hen both arteries are of the same size.
Relations.—At its origin the external carotid artery is situated at the
median side of the internal carotid, but soon becomes superficial to that
artery. It is covered by the skin, the platysma myoides and stcrno-
cleido-mastoid muscles, and the deep fascia. The superior laryngeal
nerve passes behind the artery in this situation. Its deep relation at
its commencement is with the pharynx and hyoid bone. From this
position it passes up internally to the stylo-hyoicl and posterior belly of
the digastric muscle and part of the parotid gland, "which separates it
from the back part of the ramus of the jaw. The posterior belly of
the digastric muscle is a good guide in the ligation of the artery.
Throughout its upper portion it is separated from the internal carotid
by the stylo-glossus and stylo-pharyngeus muscles, the glosso-pharyn-
geal nerve, and part of the parotid gland.
The external carotid artery is usually unaccompanied by a vein,
although the temporo-maxillary vein crosses it within the parotid gland,
the anterior division of the temporo-maxillary vein passing downward
to the facial. The facial and lingual veins cross the artery below the
digastric muscle on their way to join the internal jugular. Higher up,
in the substance of the parotid gland, the artery is crossed by the facial
nerve, the hypoglossal nerve crossing it just below the posterior belly
of the digastric muscle.
Branches of the External Carotid Artery.—The external carotid artery
in its ascent through the neck gives off eight branches. Their names,
in great measure, indicate their distribution. Three of the branches
viz. the superior thyroid, lingual, and facial — pass anteriorly; two—viz.
the occipital and posterior auricular — pass posteriorly ; one, the ascend-
ing pharyngeal, passes internally : it terminates in two branches, the
superficial temporal and the internal maxillary.
Variations.—The general variations in the origin of the external
carotid artery have been mentioned under the head of the common
carotid. Other variations are caused by the manner in w^hich its
branches are given off. The external carotid may at times be entirely
M-anting. When this is the case the different branches which are usually
given off by it arise from a common trunk which represents the inter-
nal and external carotids. The superior thyroid and the lingual arteries
may arise from a single branch, instead of two separate branches, or
the" lingual and facial or the superior thyroid, lingual, and facial may
originate in a similar manner. The superior thyroid may also arise
from the common carotid. The external carotid artery occasionally
divides at the angle of the jaw, reuniting again near the neck of the
inferior maxilla to form the temporal artery.
The Superior Thyroid Artery is the first anterior branch of the
