Larynx

Overview

The larynx connects the pharynx to the trachea and can be found in the midline of the human body at the level of the third to the sixth cervical vertebrae.

Like the pharynx, the larynx is divided up into three regions:

• the vestibule
• the ventricle
• the infraglottic area

Cartilages

The larynx is composed of six individual cartilages of which three are paired and three are unpaired. The hyaline cartilages consist of: 

• thyroid cartilage (unpaired)
• cricoid cartilage (unpaired)
• arytenoid cartilage (paired)

The elastic cartilages are the following:

• epiglottis (unpaired)
• corniculate cartilage (paired)
• cuneiform cartilage (paired)

The thyroid cartilage is the largest of all the cartilages and it is linked to the hyoid bone via the thyrohyoid membrane, while the corniculate and the cuneiform cartilages are considered to be minor cartilages, due to their small size.

Membranes and ligaments

The membranes and ligaments of the larynx are categorized according to their function.

The major extrinsic ligaments include:

• the two lateral thyrohyoid ligaments
• the single median thyrohyoid ligament 
• the thyrohyoid membrane
• the median cricothyroid ligament 
• the cricotracheal ligament

The major intrinsic ligaments of the larynx include the:

• vocal ligament 
• the conus elasticus 
• the quadrangular membrane 
• the vestibular ligament

Muscles

The cricothyroid muscle is the only laryngeal muscle that is supplied by the external laryngeal nerve, whereas all the others are supplied by the recurrent laryngeal nerve. It increases the tension on the vocal ligaments because it stems from the arch of the cricoid cartilage and inserts into the lamina and inferior conu of the thyroid cartilage.

The thyroarytenoid muscle decreases the tension of the vocal ligaments because it originates in the angle of the thyroid cartilage and stretches across to the vocal process of the arytenoid cartilage.

The posterior cricoarytenoid muscle opens the rima glottidis, while the lateral cricoarytenoid muscle, the transverse arytenoid muscle and the oblique arytenoid muscle close it. It originates in the lamina of the cricoid cartilage and inserts into the muscular process of the arytenoid cartilage.

The lateral cricoarytenoid inserts itself just as the posterior cricoarytenoid muscle does. It stems from the lateral portion of the arch of the cricoid cartilage.

The transverse arytenoid muscle originates from the muscular process of the arytenoid cartilage and fastens itself to the muscular process of the opposing arytenoid cartilage.

The oblique arytenoid muscle seemingly has no origin as it stretches itself between the two arytenoid cartilages from the muscular process of one arytenoid cartilage to the apex of the opposite one.

The aryepiglotticus and the thyroepiglotticus are two muscles that help close the laryngopharyngeal opening by inserting themselves into the epiglottis. The first arises from the muscular process of the arytenoid cartilage and the second from the lamina of the thyroid cartilage.

Blood supply

The arterial supply of the larynx is provided by the superior laryngeal artery and the inferior laryngeal artery. The venous drainage is managed by the superior laryngeal vein and the inferior laryngeal vein.

Innervation

The motor and sensory innervation of the larynx in its entirety comes from the vagus nerve (CN X). The three branches which are contributed include the internal laryngeal nerve, the recurrent laryngeal nerve and the external laryngeal nerve.