"oo A MANUAL OF ANATOMY 



The carotid triangle (superior carotid) is bounded inferiorly by 

 the anterior belly of the omo-hyoid ; superiorly by the posterior 

 belly of the digastric and stylo-hyoid ; and posteriorly by the anterior 

 border of the sterno-cleido-mastoid. 



The digastric or submaxillary triangle is bounded postero-inferiorly 

 by the posterior belly of the digastric and stylo-hyoid ; antero- 

 inferiorly by the anterior belly of the digastric ; and superiorly by 

 one half of the base of the inferior maxilla, and a line drawn from 

 the angle of that bone to the mastoid process. 



Contents of the Triangles — Muscular Triangle. — ^The area of this 

 triangle is occupied by the sterno-hyoid and sterno-thyroid muscles ; 

 hence the name muscular triangle. Under cover of these muscles 

 there are the carotid sheath with its contents, the lateral lobe of 

 the thyroid body, the trachea, and the larynx. The oesophagus 

 lies behind the trachea, with a slight inclination towards the left 

 side at the root of the neck, and the inferior or recurrent laryngeal 

 nerve lies in the groove between the trachea and the oesophagus. 

 The inferior thyroid artery pursues a tortuous course inwards 

 behind the lower part of the carotid sheath, and the gangliated 

 cord of the sympathetic descends behind the sheath. 



Carotid Triangle. — ^This triangle contains the upper part of the 

 common carotid, and the commencements of the external and 

 internal carotid, arteries, all of these being overlapped by the 

 anterior border of the sterno-cleido-mastoid, when the deep fascia 

 which ensheathes that muscle is undisturbed. The common 

 carotid and internal carotid arteries, together with the pneumo- 

 gastric nerve, are contained within the carotid sheath, and the 

 descendens cervicis nerve lies upon the sheath, or within it, being 

 situated in either case over the common carotid artery. The 

 sterno-cleido-mastoid artery and the superior thyroid vein cross 

 the sheath near the bifurcation of the common carotid artery, 

 and the carotid body lies behind the vessel about the same level. 

 The deep cervical glands lie along the course of the internal jugular 

 vein. The origins of the superior thyroid, lingual, facial, and 

 occipital arteries are contained in this triangle, and the ascending 

 pharyngeal branch of the external carotid lies deeply between that 

 vessel and the internal carotid. The internal jugular vein in this 

 triangle receives the common facial, lingual, and superior thyroid 

 veins. The hypoglossal nerve lies along the lower border of the 

 posterior belly of the digastric muscle, and it here gives off, from 

 behind forwards, the descendens cervicis and thyro-hyoid nerves, 

 the former passing downwards over, or within, the carotid sheath, 

 and the latter passing forwards and downwards at an acute angle 

 with the parent trunk. The internal branch of the superior 

 laryngeal nerve lies deeply behind the bloodvessels, and the ex- 

 ternal laryngeal branch of that nerve descends internal to them, 

 and passes beneath the depressor muscles of the hyoid bone. The 

 pneumogastric nerve is within the carotid sheath, and the gangli- 

 ated cord of the sympathetic is behind it. The spinal portion of 

 the spinal accessory nerve lies deeply, its course being downwards 



