Section VII. LARYNX
7-25. INTRODUCTION
The larynx (voice box; "Adams apple") is located in the lower anterior neck
region. In many respects, the larynx is different in men and women (sexual
dimorphism).
7-26. LARYNX AS A PART OF THE HYOID COMPLEX
The larynx is suspended from the hyoid bone by a membrane. The root of the
tongue is attached to the top anterior portion of the hyoid bone. These three
structures--the larynx, the hyoid bone, and the tongue--are together known as the hyoid
complex. They always move together as a unit.
7-27. GENERAL FUNCTIONS OF THE LARYNX
The larynx performs several functions in humans.
a. Its primary function is to control the volume of the air passing through the air
passageways, to and from the alveoli of the lungs (para 7-28).
b. The larynx also produces selected vibration frequencies in the moving column
of air (para 7-29).
c. During swallowing, the hyoid complex is raised into the oral cavity. As this
happens, the epiglottis of the larynx acts like a trap door, turning down to cover the
entrance of the larynx. This prevents swallowed items from entering the lower air
passageway, altogether forming the glottis.
7-28. CONTROL OF VOLUME OF AIR
A pair of folds is found at the bottom of the vestibule of the larynx. These are
called the vocal folds or true vocal cords. Extending from front to back, there is one
vocal fold on each side. With a special set of muscles, the vocal folds can be drawn
apart or pulled together, altogether forming the glottis.
a. Thus, the vocal folds are used to control the size of the opening between
them, which is called the rima glottidis. When the rima glottidis is wide, air can flow
easily between the upper and lower air passageways. When the vocal cords are drawn
so tightly that the rima glottidis is completely closed, no air can flow through.
b. In Valsalva's maneuver (para 7-9b(4), (5)), the lungs are filled with air and the
rima glottidis is closed tightly. The muscles of the trunk wall contract strongly to
increase the internal pressure of the trunk.
MD0007
7-13
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