Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

The Doctrine of Viscera (Splanchnology)
Respiratory System
Larynx

The larynx, which Functions as both a respiratory and phonatory organ, is situated in the anterior neck below the Hyoid bone at the level of the IV–VI cervical vertebrae. It is bounded anteriorly by the Superficial Neck Muscles and posteriorly by the laryngeal part of the Pharynx. The Thyroid Gland lies adjacent to the larynx anteriorly and laterally. The larynx is suspended superiorly from the hyoid bone and attached inferiorly to the Sternum via Ligaments and Muscles. During swallowing, speaking, and coughing, the larynx moves vertically. It communicates with the pharynx above and continues into the Trachea below.

The framework of the larynx is formed by cartilages interconnected by joints and ligaments. These include the unpaired thyroid and cricoid cartilages and the epiglottis. The paired components are the arytenoid cartilages, along with the smaller corniculate, cuneiform, and triticeal cartilages (Fig. 56). The thyroid Cartilage is the largest; it consists of two quadrilateral laminae that fuse anteriorly at a right angle. This angle projects forward to form a prominent landmark, which is particularly pronounced in males. Located inferior to the thyroid cartilage is the cricoid cartilage, which resembles a signet ring and articulates with the thyroid cartilage through two joints. Situated on the posterior lamina of the cricoid cartilage are two mobile arytenoid cartilages, surmounted by the paired corniculate and cuneiform cartilages, with the triticeal cartilages lying even higher. The laryngeal inlet from the pharynx is guarded by the epiglottis, which is composed of elastic cartilage. The internal surface of the larynx is lined with a mucous membrane.

Based on its shape and The Structure of its walls, the laryngeal cavity is divided into three sections: the vestibule, the ventricle (middle compartment), and the infraglottic cavity (Fig. 57). The upper section, which tapers inferiorly from the upper margin of the epiglottis to the vestibular folds, is called the laryngeal vestibule. The middle (ventricular) section lies between the vestibular folds superiorly and the vocal folds (true vocal cords) inferiorly. On both the right and left sides, between the vestibular and vocal folds, lie recesses known as the right and left laryngeal ventricles. The lower section of the larynx—the infraglottic cavity—is located inferior to the vocal cords. Widening as it descends, the infraglottic cavity transitions into the trachea at the level of the VI cervical vertebra.

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Fig. 56. Cartilages, ligaments, and JOINTS OF THE larynx:

A — anterior view: 1 — body of the hyoid bone; 2 — triticeal cartilage; 3 — superior horn of the thyroid cartilage; 4 — lamina of the thyroid cartilage; 5 — inferior horn of the thyroid cartilage; 6 — arch of the cricoid cartilage; 7 — tracheal cartilages; 8 — annular ligaments; 9 — cricothyroid joint; 10 — cricothyroid ligament; 11 — superior thyroid notch; 12 — thyrohyoid membrane; 13 — median thyrohyoid ligament; 14 — lateral thyrohyoid ligament.

B — posterior view: 1 — epiglottis; 2 — greater horn of the hyoid bone; 3 — triticeal cartilage; 4 — superior horn of the thyroid cartilage; 5 — lamina of the thyroid cartilage; 6 — arytenoid cartilage; 7 — right cricoarytenoid joint; 8 — right cricothyroid joint; 9 — tracheal cartilages; 10 — membranous wall of the trachea; 11 — lamina of the cricoid cartilage; 12 — left cricothyroid joint; 13 — inferior horn of the thyroid cartilage; 14 — left cricoarytenoid joint; 15 — muscular process of the arytenoid cartilage; 16 — vocal process of the arytenoid cartilage; 17 — thyroepiglottic ligament; 18 — corniculate cartilage; 19 — lateral thyrohyoid ligament; 20 — thyrohyoid membrane

Fig. 57. Laryngeal cavity (opened from behind):

1 — greater horn of the hyoid bone; 2 — triticeal cartilage; 3 — thyrohyoid membrane; 4 — superior horn of the thyroid cartilage; 5 — vestibular fold; 6 — laryngeal ventricle; 7 — vocal fold; 8 — cricoarytenoid joint; 9 — infraglottic cavity; 10 — lamina of the cricoid cartilage (partially removed); 11 — posterior cricoarytenoid Muscle; 12 — arytenoid cartilage; 13 — corniculate cartilage; 14 — laryngeal vestibule; 15 — lateral thyrohyoid ligament; 16 — epiglottis

The vocal folds are formed by the vocal ligaments covered by a mucous membrane. The narrow space between the right and left vocal folds is termed the rima glottidis (glottis). As exhaled air passes through the rima glottidis, the vocal cords oscillate and vibrate, producing sound.

During quiet breathing, the width of the glottis is approximately 5 mm. During phonation, and especially during forced breathing or shouting, the glottis widens to its maximum dimensions—up to 15 mm (Fig. 58). Vocal pitch depends on the length of the vocal cords. In males, the vocal cords are longer than in females, resulting in a deeper voice. In females, the cords are shorter, yielding a higher-pitched voice. The tension of the vocal cords and the width of the glottis during Respiration and phonation are regulated by the laryngeal muscles, which are divided into three groups: glottal openers (dilators), glottal closers (constrictors), and tensors of the vocal cords. The glottis is widened by the posterior cricoarytenoid muscles. It is narrowed by the lateral cricoarytenoid muscles, as well as the oblique and transverse arytenoid muscles. The vocal cords are tensioned by the cricothyroid and vocalis muscles.

The vocal cords merely generate sound; its volume and pitch depend on cord tension and the velocity of the airflow passing through the glottis. Articulate speech is shaped by the coordinated action of the Lips, Tongue, Teeth, Oral Cavity, and Nasal cavity with its Paranasal Sinuses.

Fig. 58. Position of the vocal cords under various functional states. The glottis is closed (I), open during quiet breathing (II), and maximally widened during phonation (III).

The arrows indicate the direction of muscular pull.

A — laryngoscopic view: 1 — epiglottis; 2 — epiglottic tubercle; 3 — vocal fold; 4 — corniculate tubercle; 5 — cuneiform tubercle; 6 — vestibular fold.

B — various positions of the vocal cords, glottis, and arytenoid cartilages: 1 — right lamina of the thyroid cartilage; 2 — vocal ligament and vocalis muscle; 3 — arytenoid cartilage; 4 — posterior cricoarytenoid muscle; 5 — lateral cricoarytenoid muscle; 6 — transverse arytenoid muscle; 7 — thyroarytenoid muscle