Chapter 28

### Big Picture

The larynx forms the air passageway from the hyoid bone to the trachea. The larynx is continuous with the laryngopharynx superiorly and with the trachea inferiorly. The larynx provides a patent (open) airway and acts as a switching mechanism to route air and food into the proper channels. The larynx is commonly known as the voice box and provides the cartilaginous framework for vocal fold and muscle attachments, which vibrate to produce sound.

### Hyoid Bone

The hyoid bone consists of a body, two greater horns, and two lesser horns, and is the only bone that does not articulate with another bone. The hyoid bone is U-shaped and is suspended from the tips of the styloid processes of the temporal bones by the stylohyoid ligaments (Figure 28-1A and C). The hyoid bone is connected to the thyroid cartilage and supported by the suprahyoid and infrahyoid muscles and by the middle pharyngeal constrictor muscle. In addition, the hyoid bone supports the root of the tongue.

###### Figure 28-1

A. The cartilaginous skeleton B. Vocal ligament anatomy. C. Posterior view of the movements of the laryngeal cartilage joints.

### Laryngeal Cartilages

The framework of the larynx is an intricate arrangement of nine cartilages connected by membranes and ligaments (Figure 28-1A–C).

• Thyroid cartilage. The thyroid cartilage forms a median elevation, called the laryngeal prominence (“Adam's apple”), and lies inferior to the hyoid bone. The thyroid cartilage typically is larger in males than in females because the male sex hormones stimulate its growth during puberty. The superior horn of the laryngeal cartilage is attached to the tip of the greater horn of the hyoid bone, whereas its inferior horn articulates with the cricoid cartilage, forming the cricothyroid joint.
• The thyrohyoid membrane, as its name implies, stretches between the thyroid cartilage and the hyoid bone. The superior laryngeal vessels and the internal laryngeal nerve pierce the membrane en route to providing vascular supply and sensory information, respectively, to the mucosa superior to the vocal folds.
• Cricoid cartilage. The cricoid cartilage is shaped like a signet ring, with the broad part of the ring facing posteriorly. The lower border marks the inferior limits of the larynx and pharynx. The function of the cricoid cartilage is to provide attachments for laryngeal muscles, cartilages, and ligaments involved in opening and closing of the airway to produce sound.
• Epiglottis. The epiglottis is elastic cartilage, shaped like a spoon, that is posterior to the root of the tongue. The lower end of the epiglottis is attached to the deep surface of the thyroid cartilage. When only air is flowing into the larynx, the inlet to the larynx is open wide, with the free edge of the epiglottis projecting superiorly and anteriorly. During swallowing, ...

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