Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 153

The larynx or voice box (Figure 4.3) is formed from nine pieces of fused cartilage and is connected superiorly to the laryngopharynx and inferiorly to the trachea or wind pipe. The largest of the laryngeal cartilages is the shield-shaped thyroid cartilage which is so-named because of its close proximity to the thyroid gland. The thyroid cartilage is also known as Adam’s apple since in males it usually undergoes rapid expansion during puberty and becomes more prominent.

This expansion corresponds to a general enlargement of the larynx, which usually results in the ‘breaking’ and deepening of the voice characteristic of adolescent males. Probably the most well known of the laryngeal cartilages is the epiglottis; a piece of flexible elastic cartilage which functions like a ‘trap door’ to close over the airway during swallowing to prevent aspiration of food and fluids into the lungs (Chapter 10).

Figure 4.3 Structure of the larynx

The cricoid cartilage lies inferior to and is separated from the thyroid cartilage by the cricothyroid membrane. If the airway is occluded and the patient cannot breathe, an incision can be made in the cricothyroid membrane and a tube inserted to allow artificial ventilation to be established; this procedure is an example of intubation. Inside the larynx are the vocal cords; these are tiny ligaments that vibrate when air is passed over them to generate sound. The tension of the vocal cords can be varied by muscles to alter the pitch of sound produced; this effect is similar to what happens when tightening and loosening a guitar string.