1I04 



A MANUAL OF ANATOMY 



the hyoid bone; and (2) the basal half of the great cornu of that 

 bone. 



Nerve- supply. — ^The thyro-hyoid nerve, which is a special branch 

 of the hypoglossal. The nerve enters the deep surface of the muscle 

 close to its posterior border. 



The muscle is quadrilateral. Its superficial surface supports the 

 anterior belly of the omo-hyoid and the sterno-hyoid muscles, 

 and its deep surface is related to the ala of the thyroid cartilage, 

 the thyro-hyoid membrane, the internal branch of the superior 

 laryngeal nerve, and the superior laryngeal artery. 



The nerves which supply the infrahyoid group of muscles are regarded as 

 being of spinal origin. 



Action of the Infrahyoid Muscles — Omo-hyoid. — (i) To depress 

 the hyoid bone ; and (2) to render tense the deep cervical fascia in 

 the lower part of the neck. 



Sterno-hyoid. — To depress the hyoid bone. 



Sterno-thyroid. — To depress the thyroid cartilage. 



Thyro-hyoid. — (i) To depress the hyoid bone ; arid (2) to elevate 

 the thyroid cartilage, as in the production of high notes, or in 

 deglutition. 



Structures in the Median Line of the Neck.— The median line of 

 the neck is divisible into two regions, suprahyoid and infrahyoid. 



Great Corau 



Small Cornu 



- - Hyo-glossus 



Body 



- • Chondro-glossus 



Genio-hyo-glossus 

 Digastric 

 Stylo-hyoid 



Omo-hyoid (Ant. Belly) 



Thyro-hyoid 

 Mylo-hyoid 



Sterno-hyoid 



Genio-hyoid 



Fig. 448. — The Hyoid Bone, showing its Muscular Attachments. 



Suprahyoid Region. — The innermost fibres of the two platysma 

 myoides muscles decussate at the median line for a short distance 

 below the chin. On either side of the median line, under cover 0/ 

 the platysma myoides, is the anterior belly of the digastric muscle. 

 The anterior bellies of opposite sides are near each other at the chin, 

 but, as they descend with an inclination outward:, they diverge 



