MUSCLE-NERVE PHYSIOLOGY 



TABLE OF THE SEVERAL GROUPS OF THE INTRINSIC MUSCLES OF THE LARYNX AND 

 THEIR ATTACHMENTS. Continued. 



Group Muscle 



IV. 



Tensors. 



Attachments 



iii. Crico- A pair of muscles. They arise on either 

 arytenoi- side from the middle third of the upper 

 dei later- border of the cricoid cartilage and are 

 ales. inserted into the whole anterior margin 



of the base of the arytenoid cartilage. 



Some of their fibers join the thyroid- 



aryepiglottici. 



Action 



Approximate the vocal 

 cords by drawing the 

 processus muscularis 

 of the arytenoid car- 

 tilages forward and 

 downward and so 

 rotate the processus 

 vocalis inward. 



c. Inner- A pair of muscles. They arise on either Render the vocal cords 



most layer, side, internally from the angle of the! 

 Thyro- thyroid cartilage, internal to the last 



tense and rotate the 

 arytenoid cartilages 



arytenoi- described muscle, b. iii., and, running and approximate the 



dei in -I parallel to and in the substance of the 

 terni. vocal cords, are attached posteriorly to 



the processus vocalis and to the outer 

 surface of the arytenoid cartilages. 



Crico-thy-i A pair of fan-shaped muscles attached on 



processus vocalis. 



roidei. 



Thyro-ary- 

 tenoidei 

 interni. 



either side to the cricoid cartilage below; 

 from the mesial line in front for nearly 

 one-half of its lateral circumferencej 

 backward the fibers pass upward and 

 outward to be attached to the lower 

 border of the thyroid cartilage and to 

 the front border of its lower cornea. 



The most posterior part is almost a dis- 

 tinct muscle and its fibers are all but 

 horizontal: sometimes this muscle is 

 described as consisting of two layers, 

 superficial with cortical fibers, deep 

 with oblique fibers, described under 

 Group III. 



The thyroid cartilage 

 being fixed by its 

 extrinsic muscles, the 

 front of the cricoid 

 cartilage is drawn 

 upward, and its back, 

 with the arvtenoids 

 attached, is drawn 

 down. Hence the 

 vocal cords are elon- 

 gated antero-poste- 

 riorly and put upon 

 the stretch. Paral- 

 ysis of these muscles 

 causes an inability 

 to produce high 

 notes. 



Nerve Supply. The sensory filaments of the superior laryngeal branch of 

 the vagus supply the epithelial lining of the larynx, giving it that acute sensi- 

 bility by which the glottis is guarded against the ingress of foreign bodies, 

 or of irrespirable gases. The contact of these stimulates the nerve endings; 

 and the sensory nerve impulse conveyed to the medulla oblongata, whether 

 accompanied by sensation or not, arouses motor impulses through the fila- 

 ments of the recurrent or inferior laryngeal branch, which excite contraction of 



