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The root of the neck | Main Anatomy Index | Neck Index
| The thyroid gland
Last updated 1 April 2006
- This is between the pharynx and the trachea. It communicates with the mouth and the nose
though the laryngeal and oral parts of the pharynx.
- Although it is part of the air passages, the larynx normally acts as a valve for
preventing swallowed food and foreign bodies from entering the lower respiratory passages.
- The larynx is the phonating mechanism that is
specifically designed for voice production.
- The larynx is located in the anterior portion of the neck.
- In adult males it is about 5 cm in length and is related posteriorly to the bodies of C3
to C6 vertebrae.
- The larynx is shorter in women and children and is situated slightly more superiorly in
The Skeleton of the
- The laryngeal skeleton comprises nine cartilages that are joined by various ligaments
- Three of the cartilages are single (thyroid, cricoid and epiglottis), and three are
paired (arytenoid, corniculate, and cuneiform).
The Thyroid Cartilage (p. 838)
- This is the largest of the laryngeal cartilages.
- It is composed of two laminae (L. thin plates).
- The inferior 2/3 of these laminae are fused anteriorly in the medial plane to form a
projection called the laryngeal prominence.
- The larynx is more prominent in postpubertal males than in females because the angle at
which the thyroid laminae meet is smaller in males. Also the anteroposterior diameter of
the laminae is greater.
- Immediately superior to the laryngeal prominence is a V-shaped
- The posterior border of each lamina projects superiorly as the superior
horn and inferior as the inferior horn (L. cornua).
- The superior border of the thyroid cartilage is attached to the hyoid
bone by the thyrohyoid membrane.
- An oblique line marks the lateral surface of each
lamina. It provides attachment for the inferior constrictor muscle of the pharynx and the
sternothyroid and thyrohyoid muscles.
- The inferior horns of the thyroid cartilage articulate with the cricoid cartilage at
special facets that allow the thyroid cartilage to tilt or glide anteriorly or posteriorly
in a visor-like manner.
The Cricoid Cartilage (p. 838)
- The cricoid (G. ring) is shaped like a signet ring with
its band facing anteriorly.
- The posterior (signet) part of the cricoid is called the lamina
and the anterior (band) part is termed the arch.
- Although it is much smaller than the thyroid cartilage, the cricoid is thicker and
- It is located at the level of C6 vertebra.
- It is the most inferior of the cartilages of the larynx.
- The cricoid forms the inferior parts of the anterior and lateral walls and most of the
posterior wall of the larynx.
- The cricoid cartilage is attached to the inferior margin of the thyroid cartilage by the
cricothyroid ligaments and to the first tracheal ring by
the cricotracheal ligament.
The Arytenoid Cartilages
- These paired cartilages are shaped like three-side pyramids.
- They articulate with the lateral parts of the superior border of the lamina of the
- Each cartilage has an apex superiorly, a vocal process anteriorly, and a muscular
- The apex is attached to the aryepiglottic fold, the vocal process to the vocal ligament,
and the muscular process to the posterior and lateral cricoarytenoid muscles.
Corniculate and Cuneiform Cartilages (pp. 838, 841)
- These are small cartilaginous nodules.
- They are in the posterior part of the aryepiglottic folds.
- These cartilages are attached to the apices of the arytenoid cartilages.
- The cuneiform (L. wedge-shaped) cartilages lie in the aryepiglottic folds and are
approximated to the tubercle of the epiglottis when the inlet of the larynx is closed
The Epiglottic Cartilage
- This is a thin piece of cartilage that is shaped like a leaf or a bicycle saddle.
- It gives flexibility to the epiglottis.
- It is situated posterior to the root of the tongue and hyoid bone and anterior to the
inlet of the larynx.
- The epiglottic cartilage forms the superior part of the anterior wall and the supe