Sound producing muscles

We speak with the help of our voice box, the larynx. The voice box is situated below the pharynx and forms upper part of the trachea. The larynx is made up of muscles and in all nine cartilages. The "Adam's apple" seen prominently in men is the thyroid cartilage, a part of larynx.

Larynx is important in breathing and speech. At larynx the air is directed to wind pipe i.e. trachea and food into the food pipe, i.e. esophagus.

The larger laryngeal cartilages are - the thyroid (shield shaped), cricoid (ring like) and arytenoid (pitcher shaped) cartilages. The smaller cartilage are - epiglottis, cuneiform, corniculate and tips of arytenoids. They are moved by several muscles and the position of cartilages is quite important in all modes of phonation.

The muscles of the larynx are skeletal and show striations. They are - intrinsic muscles that interconnect various cartilages of the larynx, and extrinsic muscles connecting larynx to other structures around the larynx. Intrinsic muscles move the vocal cords. Extrinsic muscles raise and lower the entire larynx, which helps in swallowing.

Many of these muscles are named by the parts they connect, like - cricothyroid muscle, joining cricoid and the thyroid cartilage. Cricoarytenoid muscles (connect cricoid and arytenoid cartilages), interarytenoid muscles (connect two arytenoid cartilages).

The larynx has below the epiglottis, a pair of false vocal cords (the vestibular folds). They are called as false, since they do not take part in production of sounds. In the center of the lower part of larynx are the two true vocal cords or vocal folds. They are made of muscles (thyroarytenoids) and form a "V" when seen from above. Parallel to the vocal folds are the bundles of skeletal muscles, called the vocalis. They regulate tension of the vocal cords responsible for producing sounds of different frequencies.

The vocal cords are between 1 and 2 cms in length and are elastic on account of the elastin fibers they contain.

When air passes by the vocal cords they open and close producing sound. The Broca's area in frontal lobe of our brain, stores information required for speech production. Broca's area is responsible for movement of the tongue, lips and speech muscles to articulate words. The Wernick's area (gnostic area) on parietal lobe of the cerebrum is for understanding language and putting thoughts into words. Lesions (wounds) in the Wernick's area is known to cause defects in comprehension as well as expression of a patient.

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