Larynx

Larynx Structure

• The larynx, also known as the voice box, is an organ in the neck involved in breathing, producing sound, and protecting the trachea against food aspiration.
• The larynx houses the vocal cords, which manipulate pitch and volume, essential for phonation.
• The larynx is situated just below where the tract of the pharynx splits into the trachea and esophagus.
• The word 'larynx' comes from the Ancient Greek word 'lárunx', meaning 'throat' or 'gullet'.

Larynx Components

• The larynx consists of cartilages attached to each other and surrounding structures by muscles or fibrous and elastic tissue components.
• The larynx is lined by a ciliated columnar epithelium, except for the vocal folds.
• The cavity of the larynx extends from its triangle-shaped inlet to the epiglottis and to the circular outlet at the lower border of the cricoid cartilage.

Folds and Cords

• The mucous membrane lining the larynx forms two pairs of lateral folds that project inward into its cavity.
• The upper folds are called the vestibular folds or false vocal cords, which play no part in vocalization.
• The lower pair of folds are known as the vocal cords, which produce sounds needed for speech and other vocalizations.
• The slit-like space between the left and right vocal cords is called the rima glottidis, the narrowest part of the larynx.

Location and Cartilages

• In adult humans, the larynx is found in the anterior neck at the level of the cervical vertebrae C3–C6.
• The larynx connects the inferior part of the pharynx (hypopharynx) with the trachea.
• The laryngeal skeleton consists of nine cartilages: three single (epiglottic, thyroid, and cricoid) and three paired (arytenoid, corniculate, and cuneiform).
• The hyoid bone is not part of the larynx, though the larynx is suspended from the hyoid.

Muscles

• The muscles of the larynx are divided into intrinsic and extrinsic muscles.
• Intrinsic muscles are responsible for controlling sound production, including respiratory and phonatory muscles.
• Extrinsic muscles support and position the larynx within the mid-cervical region.

Nerve Supply

• The larynx is innervated by branches of the vagus nerve on each side.
• Sensory innervation to the glottis and laryngeal vestibule is by the internal branch of the superior laryngeal nerve.
• Motor innervation to all other muscles of the larynx and sensory innervation to the subglottis is by the recurrent laryngeal nerve.

Development

• In newborn infants, the larynx is initially at the level of the C2–C3 vertebrae, and is further forward and higher relative to its position in the adult body.
• The larynx descends as the child grows.