THE COMMON 
CAROTID 
ARTERY 637 
superficially with the jugular vein, but further forward the omo-hyoideus muscle 
intervenes between the artery and vein. 
more deeply placed and is related laterally 
to the mandibular and parotid glands, medi- 
ally to the cesophagus. In some cases it is in 
contact ventrally with the lateral lobe of the 
thyroid gland, especially when the latter is 
more dorsally situated or larger than usual. 
The left common carotid artery (A. 
carotis communis sinistra) differs from the 
right one in that it is related deeply to the 
esophagus also, which usually separates it 
from the trachea in part of its course. 
The left carotid is commonly in contact with 
the trachea for a short distance (ca. 8-10 em.) at the 
root of the neck, but this contact may be even less 
when the cesophagus is more ventral than usual and 
the bicarotid trunk long. On the other hand, the re- 
lation to the trachea may be more extensive. 
The collateral branches of the common 
carotids are in the main small. They com- 
monly comprise the following: 
1. Muscular branches (Rami muscu- 
lares) of variable size go to the ventral 
muscles of the neck and the skin. 
2. Gsophageal and tracheal branches 
(Rami cesophagei et tracheales). Small 
twigs go to the cervical lymph glands also. 
3. The parotid artery (A. parotidea) 
comes off near the termination and enters 
the ventral part of the parotid gland. It 
also sends twigs to the adjacent lymph 
glands, and sometimes detaches a branch to 
the mandibular gland. It is inconstant. 
4. The anterior thyroid or thyro-laryn- 
geal artery (A. thyreoidea cranialis), the 
largest collateral branch of the carotid, 
arises from the latter two or three inches 
before it divides. It curves over the anterior 
end of the thyroid gland, into which it sends 
several branches. It gives off the laryngeal 
artery (A. laryngea), which sends branches 
to the external muscles of the larynx and the 
constrictors of the pharynx, passes between 
the cricoid and thyroid cartilages, and sup- 
plies the internal muscles and the mucous 
membrane of the larynx. A small pharyn- 
geal branch (A. pharyngea ascendens) runs 
upward and forward to the crico-pharyn- 
geus, and supplies twigs to the posterior 
part of the pharynx and the origin of the 
cesophagus. Small innominate twigs are 
Near its termination the artery becomes 
Fic. 557 —Cross-section oF Neck oF Horse, 
Passinc THROUGH FirrH CERVICAL VER- 
TEBRA; ANTERIOR VIEW. 
a, Branches of cervical nerves; a’, nuchal fat; 
b, intertransversalis muscle; c, longissimus mus- 
cle; d, vertebral artery; e, vertebral vein; /, ner- 
vus transversarius; g, spinal accessory nerve (dor- 
sal division); h, recurrent nerve; i, vago-sympa- 
thetic trunk; k, tracheal lymph duct; /, body of 
fifth cervical vertebra; J’, transverse process of 
same; m, common carotid artery; n, jugular vein; 
o, deep cervical artery; 0’, satellite vein of 0; 
Pp, spinal cord; g, dura mater; r, spinal vein; s, 
ligamentum nuchz; ¢, rhomboideus muscle; u, 
splenius; », complexus; w, multifidus; 2, serratus 
cervicis; y, brachiocephalicus; z, sterno-cephalicus; 
i, rectus capitis ventralis major; 2, omo-hyoideus; 
8, cutaneus; 4, sterno-thyro-hyoideus; 5, longus 
colli; 6, 7, longissimus capitis et atlantis; 8, trape- 
zius; 9, spinalis; 10, esophagus; 11, trachea, with 
eartilaginous ring (1/1’), mucous membrane (11”’), 
and muscular layer (/1’’). (After Ellenberger, 
in Leisering’s Atlas.) 
given off to the trachea, the cesophagus, and the sterno-thyro-hyoideus and omo- 
hyoideus muscles. 
