544 



THE BLOOD-VASCULAR SYSTEM 



posterior belly of the digastric, about the level of the tip of the styloid process. 

 Occasionally it arises under cover of the digastric, quite close to, or as a common 

 trunk with, or as a branch of, the occipital. It courses upward and backward in 

 the parotid gland to the notch between the margin of the external auditory meatus 

 and the mastoid process, where it divides into branches. In this course it rests 

 on the styloid process, crosses the spinal accessory nerve, and is crossed by the 

 facial nerve. 



Fig. 450. — Scheme of Left Occipital and Posterior Auricular Arteries. (Walsham.) 



Termination branch of pos 

 terior auricular 



Occipital branch of pos- 

 terior auricular 



Parotid gland 

 Sterno-mastoid, cut 



Auricular branch of 

 occipital 

 Post, auricular artery 

 Rectus capitis lateralis 



Spinal accessory nerve 



Occipital artery. 



Internal jugular vein ^M^^, 



Ext. maxillary artery _ _.^'^lr ' 



Hypoglossal n. , 



Lingual artery _ . ^^-^ ^rT" ITT / J//^]~~/ 



Vagus nerve .\J. |_ 1 (|///// /^ 



Superior thyreoid .^'^- | 



Common carotid % =; / 



Lateral branch of 

 occipital 



Medial branch of 

 occipital 



fj-T/T' Semi-spinalis capitis 

 %^____Descending branch of 

 ■j^ occipital 



^- -Superior oblique 



Longissimus capitis, cut 



Splenius capitis, cut 



Meningeal branches 



Sternocleidomastoid branch 

 of occipital 



Internal carotid 

 Sterno-mastoid 



External carotid 

 Trapezius 



I 



Branches of the Posterior Auricular Artery 



The branches of the posterior auricular artery are: — (1) the stylo-mastoid; (2) 

 the auricular; (3) the occipital (fig. 450). 



The posterior auricular also gives branches to the parotid gland and the adjacent muscles, 

 namely, the posterior belly of the digastric, the stylo-hyoid, and auricularis posterior (retrahens 

 aurem). 



(1) The stylo-mastoid artery [a. stylomastoidea] comes off from the posterior auricular 

 artery just before it reaches the notch between the margin of the external auditory meatus 

 and the mastoid process, and, following the facial nerve upward, enters the stylo-mastoid fora- 

 men in the temporal bone. In the facial canal (aqueduct of Fallopius) it gives off the following 

 named twigs: — (a) meatal, to the external auditory meatus; (fc) mastoid [rami mastoidei], to 

 the mastoid cells and tympanic antrum; (c) stapedic [ramus stapedius], which runs forward to 

 the stapedius muscle; {d) posterior tympanic [a. tympanica posterior], which anastomoses with 

 the anterior tympanic branch of the internal maxillary, forming with it in the foetus a vascular 

 circle around the membrana tympani; (e) vestibular, to the vestibule and semicircular canals; 

 and (j) terminal, a small twig which leaves the facial canal (by the hiatus) with the great super- 

 ficial petrosal nerve, and anastomoses with the superior petrosal branch of the middle meningeal 

 artery. 



(2) The auricular branch [ramus auricularis] passes upward behind the ear and beneath the 

 auricularis posterior (retrahens aurcm), supplying the medial surface of the pinna and adjacent 



