482 



MUSCLE-NERVE PHYSIOLOGY 



Intrinsic Muscles. The intrinsic muscles of the larynx are so connected with the 

 laryngeal cartilages that by their contraction alterations in the condition of the vocal cords 

 and glottis are produced. They are usually divided into four classes according to their 

 action, viz., into abductors, adductors, sphincters, and tensors. The Abductors, the crico- 

 arytenoidei, widen the glottis, by separating the cords; the Adductors, consisting of the 

 thyro-ary-epiglottici, the arytenoideus posticus seu transversus, the thyro-arytenoidei externi, 



FIG. 344. The Cartilages and Ligaments of the Larynx, Viewed from the Front, a, Epiglottis; 

 b, hyoid bone; c, cartilage tritica; d, thyro-hyoid membrane; e, superior cornu of thyroid cartilage- 

 j, thyroid notch; g, pomum Adami; h, crico-thyroid membrane; i, inferior cornu of thyroid cartilage; 

 /, cricoid cartilage. (Cunningham.) 



the crico-arytenoidei later ales, and the thyro-arytenoidei interni, approximate the vocal cords, 

 diminish the rima glottidis, and act generally as sphincters and supporters of the glottis. 

 Finally, the tensors of the cords put the cords on the stretch, with or without elongating 

 them; the tensors are the crico-thyroidei and the thyro-arytenoidei interni. 



The attachments and the action of the muscles will be readily understood from the 

 following table. All the muscles are in pairs except the arytenoideus posticus. 



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



ATTACHMENTS. 



