Relations of Omo-hyoid 



THE DEPRESSORS OF THE HYOID BONE 



The sterno-hyoid arises from the back of the manubrium and the 

 adjacent part of the clavicle, and, sloping towards the middle line, is 

 inserted into the lower part of the body of the hyoid bone. 



The sterna-thyroid arises from the manubrium, just below the 

 sterno-hyoid, and, ascending under cover of that muscle, slopes slightly 

 backwards to its insertion in the oblique line on the thyroid cartilage. 

 This and the preceding muscle are often marked a little below their 

 insertion by a tendinous intersection. The net ye supply of these 

 two muscles is from the loop of the descendens and communicantes 

 noni. 



Relations. These muscles ascend from the anterior mediastinum, 

 and are under cover of the sterno-mastoid, the deep fascia, platysma, 

 and the anterior jugular vein. The omo-hyoid joins company with 

 them above on their outer side. They rest upon the trachea and the 

 lower part of the larynx ; the thyroid gland and its vessels ; the innomi- 

 nate, subclavian, and common carotid arteries, and the internal jugular, 

 subclavian, and innominate veins. 



The thyro-hyoid continues the sterno-thyroid up to the body and 

 great cornu of the hyoid bone. It hides the passage of the superior 

 laryngeal vessels and nerve through the thyro-hyoid membrane, and 

 is itself covered by the sterno-hyoid and omo-hyoid. Its motor nerve 

 is a special branch of the hypoglossal. 



The omo-hyoid ascends from the upper border of the shoulder- 

 blade (co/zo?) to the body of the hyoid bone, just external to the inser- 

 tion of the sterno-hyoid. It is a double-bellied muscle, the median 

 tendinous part being bound by a process of the deep cervical fascia, 

 beneath the sterno-mastoid, to the first rib. As the posterior belly 

 passes upwards and forwards to dip beneath the sterno-mastoid, it 

 forms the base of the occipital and the upper border of the subclavian 

 triangle ; in a thin person this belly may be seen at work in its 

 oblique position above the clavicle, especially when a deep inspiration 

 is taken. And as the anterior belly emerges from beneath the sterno- 

 mastoid and mounts to the hyoid bone it forms the upper boundary 

 of the inferior and the base of the superior carotid triangle. 



The nerve-stipply is from the loop of the descendens and com- 

 municantes noni. 



Relations. Coming up from the shoulder-blade, the omo-hyoid is 

 covered by the trapezius, clavicle and subclavius, the deep fascia, 

 platysma, and integument, and it lies above the subclavian vessels, 

 the lower cervical nerves, and the posterior and middle scalenes. It 

 then passes beneath the sterno-mastoid and over the scalenus anticus 

 and the phrenic nerve, and over the sheath of the common carotid 

 with the internal jugular vein and the vagus. It subsequently rests 



