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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
to it is the trachea, which it crosses obliquely. On the right side are the right innominate vein, the superior vena cava, the right phrenic nerve, and the pleura; and on the left side, the remains of the thymus, the origin of the left common carotid artery, the inferior thyroid veins, and the trachea.

Branches.—The innominate artery usually gives off no branches; but occasionally a small branch, the thyreoidea ima, arises from it. Sometimes it gives off a thymic or bronchial branch.
  The thyreoidea ima (a. thyreoidea ima) ascends in front of the trachea to the lower part of the thyroid gland, which it supplies. It varies greatly in size, and appears to compensate for deficiency or absence of one of the other thyroid vessels. It occasionally arises from the aorta, the right common carotid, the subclavian or the internal mammary.

Point of Division.—The innominate artery sometimes divides above the level of the sternoclavicular joint, less frequently below it.

Position.—When the aortic arch is on the right side, the innominate is directed to the left side of the neck.

Collateral Circulation.—Allan Burns demonstrated, on the dead subject, the possibility of the establishment of the collateral circulation after ligature of the innominate artery, by tying and dividing that artery. He then found that “Even coarse injection, impelled into the aorta, passed freely by the anastomosing branches into the arteries of the right arm, filling them and all the vessels of the head completely.” 1 The branches by which this circulation would be carried on are very numerous; thus, all the communications across the middle line between the branches of the carotid arteries of opposite sides would be available for the supply of blood to the right side of the head and neck; while the anastomosis between the costocervical of the subclavian and the first aortic intercostal (see infra on the collateral circulation after obliteration of the thoracic aorta) would bring the blood, by a free and direct course, into the right subclavian. The numerous connections, also, between the intercostal arteries and the branches of the axillary and internal mammary arteries would, doubtless, assist in the supply of blood to the right arm, while the inferior epigastric from the external iliac would, by means of its anastomosis with the internal mammary, compensate for any deficiency in the vascularity of the wall of the chest.
 
3. The Arteries of the Head and Neck. a. The Common Carotid Artery
 
  The principal arteries of supply to the head and neck are the two common carotids; they ascend in the neck and each divides into two branches, viz., (1) the external carotid, supplying the exterior of the head, the face, and the greater part of the neck; (2) the internal carotid, supplying to a great extent the parts within the cranial and orbital cavities.

The Common Carotid Artery (A. Carotis Communis)—The common carotid arteries differ in length and in their mode of origin. The right begins at the bifurcation of the innominate artery behind the sternoclavicular joint and is confined to the neck. The left springs from the highest part of the arch of the aorta to the left of, and on a plane posterior to the innominate artery, and therefore consists of a thoracic and a cervical portion.
  The thoracic portion of the left common carotid artery ascends from the arch of the aorta through the superior mediastinum to the level of the left sternoclavicular joint, where it is continuous with the cervical portion.

1. Relations.In front, it is separated from the manubrium sterni by the Sternohyoideus and Sternothyreoideus, the anterior portions of the left pleura and lung, the left innominate vein, and the remains of the thymus; behind, it lies on the trachea, esophagus, left recurrent nerve, and thoracic duct. To its right side below is the innominate artery, and above, the trachea, the inferior thyroid veins, and the remains of the thymus; to its left side are the left vagus and phrenic nerves, left pleura, and lung. The left subclavian artery is posterior and slightly lateral to it.
Note 1.  Surgical Anatomy of the Head and Neck, p. 62. [back]

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