THE MUSCLES AND FASCIAE. 



of the Sterno-thyroid. It arises from the oblique line on the side of the thyroid 

 cartilage, and passes vertically upward to be inserted into the lower border of the 

 body and greater cornu of the hyoid bone. 



Relations. By its external surface, with the Sterno-hyoid and Omo-hyoid 

 muscles ; by its internal surface, with the thyroid cartilage, the thyro-hyoid 

 membrane, and the superior laryngeal vessels and nerve. 



The Omo-hyoid passes across the side of the neck, from the scapula to the 



Symphysis 

 of jaw. 



Sternum. 

 FIG. 277. Muscles of the neck. Anterior view. 



hyoid bone. It consists of two fleshy bellies, united by a central tendon. It 

 arises from the upper border of the scapula close to, and occasionally from the 

 transverse ligament which crosses, the suprascapular notch ; its extent of attach- 

 ment varying from a few lines to an inch. From this origin the posterior belly 

 forms a flat, narrow fasciculus, which inclines forward and slightly upward 

 across the lower part of the neck, behind the Sterno-mastoid muscle, where it 

 becomes tendinous ; it then changes its direction, forming an obtuse angle, and 

 terminates in the anterior belly, which passes almost vertically upward, close to 

 the outer border of the Sterno-hyoid, to be inserted into the lower border of the 

 body of the os hyoides, just external to the insertion of the Sterno-hyoid. The central 

 tendon of this muscle, which varies much in length and form, is held in position 

 by a process of the deep cervical fascia, which includes it in a sheath. This 

 process is prolonged down, to be attached to the cartilage of the first rib* and the 

 sternum. It is by this means that the angular form of the muscle is main- 

 tained. 



This muscle subdivides each of the two large triangles at the side of the neck 

 into two smaller triangles ; the two posterior ones being the posterior superior or 

 occipital, and the posterior inferior or subclavian ; the two anterior, the anterior 

 superior or superior carotid, and the anterior inferior or inferior carotid triangle. 



Relations. By its superficial surface, with the Trapezius, the Sterno-mastoid, 

 deep cervical fascia, Platysma, and integument ; by its deep surface, with the 

 Scaleni muscles, phrenic nerve, lower cervical nerves, Avhich go to form the brachial 



