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Larynx


Larynx


         The larynx is connected with the laryngopharynx at the upper side and with the breathing tube at the lower side.  Hyoid bone and the lower portion of the tongue are present on it. There are neck muscles at the front side and and laryngopharynx and cervical vertebrae at the back side. It is the highest portion of the breathing tube which opens on the level of seventh cervical vertebrae in the breathing system or trachea. The sound is made by the larynx. There is a vibration in the vocal cords at the time of speaking and consequently the sound comes out. The complete larynx is made of several unequal cartilages which are connected to each other by the ligaments and membranes. These have been mentioned below-

Thyroid cartilage:

       It is made of two flat pieces or laminae of cartilage which make a acute angle by jointing altogether on the middle line at the frontal portion which appear in the form of larynx projections in the neck which is called Adam’s apple. Generally, it is called Tentua in Hindi language. There is a pit or notch at its upper edge in the form of ‘V’ which is called thyroid notch. The thyroid cartilage is incomplete at the back side and two cilia take birth by the back portion of each laminae which are called upper and lower cornua. The thyroid cartilage is bigger in men than the women and because of this reason it appears clearly in men. The upper portion is unstratified with stratified epithelium and the lower portion with ciliated epithelium.

Cricoid cartilage:

      Cricoid cartilage is situated under the thyroid cartilage. It is like signet ring in size of which broad portion is towards the back side. It makes lateral and posterior walls of larynx and it is unstrated with ciliated epithelium.

Arytennoid cartilages:

       These are the two small formations situated on the apex of the broad portion of cricoid cartilage in the shape of pyramid. The last walls of larynx are made of these arytennoid carilages. Ligaments of vocal cords are connected with them.

Epiglottis:

       It is a plate in the shape of a leaf made by yellow elastic cartilage which is attached to the internal surface of frontal wall just below the thyroid notch. It goes upwardly by becoming curved and remains present at the back side of tongue and upper portion of the larynx. It is unstratifed with the stratified with Scevamas epithelium.  Covering the opening of the larynx which is called glottis at the time of swallowing is the main function of it. Thus, the meal does not enter into the respiratory system. The work of covering to the pharynx or esophagus while breathing is done by this organ.

     Besides these, there is cuneiform cartilage and corniculate cartilage in the larynx. Both these are the minute formations. 

Vocal cords:

       On the base of larynx, the vocal cords start from the internal wall of the projections of the thyroid cartilage at the frontal side and extend to the arytenoid cartilages at the back side. These are the formations like string made by elastic connective tissues at the both sides which are called true vocal cords. There is a pair of vestibular folds above and close by the true vocal cords which is called false vocal cords. They have no special place in producing sound.

      When the muscles of larynx get contracted, aretinoid cartilages bring vocal cords close to each other and the place between the two vocal cords becomes narrow and the rima glottidis comes into existence. When the air goes through this rima glottidis during expiration, the vocal cords get vibrated and the sound originate. When the muscles of larynx become relaxed, the cartilages move outwardly and because of these reasons vocal cords get removed far from each other and the rima glottidis gets expanded of which no sound originates. The pitch of sound depends on the length and their traction because of which the vibration originates in the vocal cords. Excessive traction produces high sound and less traction produce low sound. The change of sound depends on the lip, tongue and muscle of soft palate.