1294 A MANUAL OF ANATOMY 



Development of the Larynx. — The larynx is developed from the upper 

 part of a median diverticulum from the ventral aspect of the fore-gut, which 

 diverticulum by its lower part gives rise to the trachea. The epiglottis, 

 arytenoid cartilages, and aryteno-epiglottidean folds are developed from the 

 furcula, which is an elevation, like a horseshoe, lying between the second, 

 third, and fourth visceral arches of either side (see Fig. 523). The front part 

 of the furcula gives origin to the epiglottis, the lateral parts to the aryteno- 

 epiglottidean folds, and the back part (extremities of the horseshoe bend) to 

 the arytenoid cartilages. The groove within the furcula represents the 

 superior aperture of the larynx. 



Prevertebral Muscles. 



Rectus Capitis Anticus Major — Origin. — By four short tendons 

 from the tubercles of the costal processes (anterior tubercles of the 

 transverse processes) of the third, fourth, fifth, and sixth cervical 

 vertebrae, where it coincides with the origin of the scalenus anticus. 



Insertion. — The inferior surface of the basilar process of the 

 occipital bone, from the pharyngeal tubercle obliquely outwards 

 and forwards for about ^ inch. 



Nerve-supply. — The cervical plexus. 



The muscle is directed upwards and inwards. 



Action. — ^To flex the head. 



Relations — Anterior. — ^The upper part of the common carotid, 

 and the internal carotid, arteries, the internal jugular vein, the 

 pneumogastric and sympathetic nerves, and the pharynx. Pos- 

 terior. — A part of the longus colli, and a large portion of the rectus 

 capitis anticus minor. 



Rectus Capitis Anticus Minor — Origin. — ^The front of the root of 

 the costal process of the atlas. 



Insertion. — The inferior surface of the basilar process of the 

 occipital bone, between the foramen magnum and the outer part of 

 the insertion of the rectus capitis anticus major. 



Nerve-supply. — ^The anterior primary division of the first cervical 

 nerve. 



The muscle is directed upwards and slightly inwards. 



Action. — To flex the head. 



Rectus Capitis Lateralis — Origin. — ^The upper aspect of the ex- 

 tremity of the transverse process of the atlas at its front part. 



Insertion. — ^The inferior surface of the jugular process of the 

 occipital bone. 



Nerve-supply. — The anterior primary division of the first cervical 

 nerve. 



The muscle passes vertically upwards. 



Action. — ^To flex the head to one side. 



Longus Colli. — ^This complex muscle consists of three parts — 

 upper oblique, vertical, and lower oblique. 



Upper Oblique Part — Origin. — ^The fronts of the tubercles of the i 

 costal processes (anterior tubercles of the transverse processes) of 1 

 the third, fourth, fifth, and sixth cervical vertebrae. 



Insertion. — ^The lateral aspect of the anterior tubercle of the !^ 

 atlas. i 



