744 HUMAN ANATOMY. 



the integument upon the aponeurosis of the occipito-frontalis. The artery pierces 

 the deeper structures, accompanied by the great occipital nerve, a short distance 

 lateral to and a little below the external occipital protuberance. 



Branches. — In addition to its terminal branches, the occipital artery gives off : 



(a) A superior sterno-mastoid branch which supplies the upper part of the sterno-cleido- 

 mastoid. 



{b) Posterior meningeal branches, one or more slender vessels which pass upward along 

 the internal jugular vein and, entering the skull by the jugular foramen, are supplied to the 

 dura mater of the posterior fossa. 



{c) An auricular branch (ramus auricularis) which passes upward over the mastoid process 

 to supply the pinna of the ear. 



{d) A mastoid branch (ramus mastoideus) which enters the skull by the mastoid foramen 

 and supplies the mucous membrane lining the mastoid cells, the diploe, and the dura mater. 



{e) An arteria princeps cervicis (ramus descendens) which arises from the artery, just as it 

 passes out from beneath the splenius and descends the neck, supplying the adjacent muscles and 

 anastomosing with the superficial cervical branch of the transversalis colli and with the pro- 

 funda cervicis from the superior intercostal. 



{/) Muscular branches (rami musculares) which are given off all along the course of the 

 artery to the neighboring muscles. 



Anastomoses. — The occipital artery makes comparatively large and abundant 

 anastomoses in the scalp with the stylo-mastoid and temporal arteries, and also, 

 by means of its art. princeps cervicis, with branches of the transversalis colli and 

 superior profunda arteries, which arise from the subclavian. These latter anastomoses 

 are of considerable importance in the development of a collateral circulation after 

 ligation of either the common carotid or the subclavian arteries. 



Variations. — The occipital artery occasionally passes superficial to the sterno-cleido-mas- 

 toid muscle instead of beneath it, and it not infrequently gives origin to the ascending pharyn- 

 geal artery or to the stylo-mastoid. 



Practical Considerations. — The occipital artery is rarely formally ligated. 

 The cervical portio7i may be reached through an incision along the anterior border 

 of the sterno-mastoid, beginning midway between the ramus of the mandible and the 

 lobe of the ear and extending downward two and a half inches. The deep fascia at 

 the upper angle of the wound (parotid fascia) is spared oh account of the risk of 

 salivary fistula. At the lower angle it is divided, the parotid and sterno-mastoid 

 are separated, and the digastric and stylo-hyoid muscles recognized and drawn 

 upward. The occipital artery, near its origin, will then be seen crossing the internal 

 carotid artery and internal jugular vein and in contact with the curve of the hypo- 

 glossal nerve where it turns to cross the neck. The artery may be ligated close 

 behind the nerve, the needle being passed from without inward to avoid the jugular 

 vein. The occipital portion is approached through an almost horizontal incision two 

 inches in length, beginning at the tip of the mastoid apophysis and extending back- 

 'vard and a little upward. The outer fibres of the sterno-mastoid and its aponeu- 

 rotic expansion, the splenius, and often the complexus, must then be divided and 

 the pulsation of the artery sought for in the space between the mastoid and the 

 transverse process of the atlas, whence the vessel may be traced outward. If it is 

 isolated near to the mastoid, great care must be taken not to injure the important 

 mastoid venous tributaries of the occipital vein which in this region connect it with 

 the lateral sinus. 



8. The Posterior Auricular Artery. — The posterior auricular artery (a. 

 auricularis posterior) (Fig. 693) arises from the external carotid after it has passed 

 beneath the posterior belly of the digastric. It passes upward and backward, cov- 

 ered at first by the parotid gland, which it supplies, and divides in the angle between 

 the pinna and the mastoid process into terminal branches, some of which supply the 

 pinna, while others anastomose with branches from the occipital and superficial 

 temporal. 



