Larynx and Pharynx - LO4
4. Describe the laryngeal cartilages, membranes, & muscles. Describe how the intrinsic muscles of the larynx affect either the positions of the vocal ligaments, or vocal pitch.
CARTILAGES:
The cartilaginous laryngeal skeleton is comprised of nine major cartilages. Three cartilages makeup the bulk of the laryngeal skeleton. They are the:
Thyroid cartilage:
Most prominent cartilage
Formed from two laminae, united anteriorly along the midline (posteriorly, the cartilage is incomplete)
Suspended from the hyoid bone by the thyrohyoid membrane
Superior horns loosely articulate with the greater horns of hyoid
Inferior horns form the cricothyroid joint with the cricoid cartilage
Cricothyroid joint allows for thyroid cartilage to ‘tip’ forwards
Cricoid cartilage:
Forms a complete ring around the airway
Most robust posteriorly
Epiglottic cartilage:
Leaf-shaped cartilage
Sits posterior to thyroid cartilage
Forms the epiglottis
Forms a lid to cover the laryngeal inlet during deglutition (swallowing)
Three pairs of cartilages also help to support the structure and function of the larynx. They are the:
Arytenoid cartilages:
Pyramid-shaped
Sit atop the cricoid laminae (posterior)
Vocal process (attaches to vocal ligament)
Muscular process (allows for muscle attachment)
Capable of either rotation or gliding
For either abduction, or adduction of vocal cords
Corniculate cartilages:
Sit atop the arytenoid cartilages
Extend the structure provided by the arytenoids posteromedially
Posterior portion of the laryngeal inlet
Cuneiform cartilages:
Within the ary-epiglottic fold
Lateral portions of laryngeal inlet
MEMBRANES:
Two sheets of fibro-elastic connective tissue help to give shape to the walls of the larynx and laryngeal features: the quadrangular membrane and the conus elasticus.
The quadrangular membrane is a poorly defined fibro-elastic sheet spanning the space between the lateral margins of the epiglottis and the arytenoid cartilages. The inferior-most extent of the quadrangular membrane forms the vestibular ligaments. The vestibular ligaments are covered by mucosa to form the vestibular (false vocal) folds. The vestibular folds play an important role in protecting the airway, and may also be used to produce harmonic tone in throat singing, and related activities. The quadrangular membrane is an important funnel of air that is inhaled.
The conus elasticus is a fibro-elastic sheet that shapes the walls of the larynx as a funnel between the thyroid and cricoid cartilages. The superior-most aspects of the conus elasticus are the vocal ligaments and the walls of the laryngeal ventricle. The vocal ligaments are covered by mucosa to form the (true) vocal folds (=vocal cords). The vocal folds vibrate with exhaled air (in a slightly adducted position) for phonation. The vocal folds may be abducted to allow for a more patent pathway for air to move. The anteromedial aspect of the conus elasticus is the (median) cricothyroid ligament, the connective tissue pierced during a cricothyrotomy. The conus elasticus is an important funnel of air that is exhaled.
INTRINSIC LARYNGEAL MM.:
Muscles that connect adjacent cartilages of the larynx are known as the intrinsic mm. of the larynx. These muscles either directly or indirectly affect the vocal ligaments, and therefore affect phonation (speech).
