NERVES AND VESSELS OF SCALP 157 



The motor nerve distributed posterior to the auricle is the 

 posterior auricular branch of the facial nerve. 



The arteries distributed to the scalp are five in number on 

 each side ; they anastomose freely, and are derived, either 

 indirectly or directly, from the internal and external carotid 

 arteries. Three are distributed mainly anterior to, and two 

 posterior to the region of the auricle. The three anterior to 

 the auricle are the frontal and supra-orbital branches of the 

 ophthalmic branch of the internal carotid, which accompany 

 the supra-trochlear and supra-orbital nerves, and the superficial 

 temporal branch of the external carotid. This branch divides 

 into two main branches, an anterior, which accompanies the 

 temporal branches of the facial nerve, and is usually a very 

 tortuous vessel, and a posterior branch, which accompanies the 

 auriculo-temporal nerve, as it ascends anterior to the auricle 

 towards the vertex of the cranium. The two arteries posterior 

 to the auricle are both branches of the external carotid. They 

 are the posterior auricular, which accompanies the posterior 

 auricular branch of the facial nerve to the mastoid region 

 and the posterior part of the parietal region, and the occipital, 

 which is distributed to the occipital area and posterior part 

 of the parietal area. 



The terminations of the veins which drain the blood from 

 the scalp are as follows. The frontal and supra-orbital veins 

 unite, at the medial border of the orbit, to form the angular 

 vein, which is the commencement of the anterior facial vein 

 already dissected (p. 131). The blood it conveys passes 

 eventually to the internal jugular vein. The superficial 

 temporal vein accompanies the corresponding artery. It unites, 

 immediately above the posterior root of the zygoma, with the 

 middle temporal vein, which pierces the temporal fascia at 

 that point. The trunk formed by the union of the superficial 

 and middle temporal veins is the posterior facial vein, which 

 descends through the parotid gland, emerges from under 

 cover of its lower end and terminates immediately below the 

 angle of the mandible by joining with the anterior facial vein 

 to form the common facial vein. Whilst in the gland, it gives 

 off the commencement of the external jugular vein. The 

 posterior auricular vein descends posterior to the external 

 meatus and terminates in the external jugular vein. The 

 occipital vein accompanies the occipital artery into the sub- 

 occipital region, and ends in the sub-occipital venous plexus. 



