Internal and external ligaments and membranes unite the cartilages and stabilise

the soft tissue covering. The thyroid cartilage is united by a joints to the

cricoid cartilage. Rocking and slight gliding movements occur at this joints.

The cricoid cartilage is united by a joints to arytenoid cartilages.

The muscles, ligaments, and membranes between the cartilage allow the

functionally important movements between different parts of the larynx.

The external ligaments and connective tissue membranes anchor the larynx to the

surrounding structures.

The most important membranes include (Fig. 32):

The thyrohyoid membrane has the opening for the superior laryngeal artery and

Vein and for the internal branch of the superior laryngeal nerve which supplies

sensation to the larynx above the vocal cords.

The cricothyroid (conical) membrane is the point where the airway comes closest

to the skin: it is the site of laryngotomy.

The cricotracheal ligament provides attachment to the trachea.

The internal ligaments and connective tissue membranes, e.g., the conus

elasticus, the thyroepiglottic ligament, the aryepiglottic ligament connect the

cartilaginous parts of the larynx to each other.

The external muscles of the larynx:

- sternohyoid muscle;

- sternothyroid muscle;

- thyrohyoid muscle.

The internal muscles act synergistically and antagonistically to control the

functions of the larynx (Fig. 33, 34). They open and close the glottis and put

the vocal cords under tension.

This interplay explains the different positions of the vocal cords in paralysis

of the recurrent laryngeal nerve or of the external branch of the superior

laryngeal nerve.

Functions of the Laryngeal Musculature

Opening of the glottis, abduction of the vocal cordsPosterior

cricoarytenoid muscle (posticus muscle)

Closure of the glottis, adduction of the vocal cordsLateral cricoarytenoid

muscle (lateralis muscle)

Transverse arytenoid muscle (transversus muscle)

Oblique arytenoid muscle

Thyroarytenoid muscle, lateral part

Tension of the vocal cords

Cricothyroid muscle (anticus muscle)

Thyroarytenoid muscle, medial part (vocalis muscle)

Movement of the

epiglottis Aryepiglottic muscle

Thyroepiglottic muscle

There is only one muscle which opens the glottis, the "posticus". The muscles

that close it are clearly in the majority. The ratio of their relative power is

1:3. Only the arytenoid muscle (pars transversa) is unpaired; all other muscles

are paired.

Laryngeal cavity (Fig. 35, 37). In the interior of the larynx two folds of

mucous membrane are stretched from front to back. They are rounded and pink in

colour, and are called the false cords (vestibular cords). Under the vestibular

cords there are vocal cords (true cords). The vocal cords are attached

anteriorly in the midline to the posterior surface of the thyroid cartilage.

Posteriorly they are attached to the arytenoid cartilages. The vocal cord

includes the vocal ligament, the vocalis muscle, and the mucosal covering. The

length of the vocal cord is 0,7 cm in the newborn, 1,6 to 2 cm in women, and 2

to 2,4 cm in men.

The laryngeal ventricle is the site of the primitive air sac and lies between

the vocal cord and vestibular cord.

The laryngeal cavity is divided for clinical purposes into three compartments:

Supraglottis, Glottis, Subglottis. The glottis is formed by the edges of the

true vocal cords, it is divided into an intermembranous part which lies between

the paired vocal ligaments and an intercartilaginous part which lies between the

arytenoid cartilages of each side.

Superiorly, the larynx is limited by the free edge of the epiglottis, the

aryepiglottic fold, and the interarytenoid notch. Inferiorly, the lower edge of

the cricoid cartilage marks the junction with the trachea.

The nerve supply of the laryngeal musculature is provided by the external branch

of the superior laryngeal nerve and by the recurrent laryngeal nerves that arise

from the vagus nerve.

The superior laryngeal nerve divides into a sensory internal branch, which

supplies the interior of the larynx down into the glottis, and an external

brunch, which provides the motor supply to the cricothyroid muscle.

The recurrent laryngeal nerve provides motor supply to the entire ipsilateral