The =crico-thyroid joints= (Articulationes crico-thyreoideæ) are
diarthroses formed by the apposition of the convex facets on the ends of
the posterior cornua of the thyroid cartilage with corresponding facets
on the sides of the cricoid cartilage. The =capsule= is thin, but is
strengthened by accessory bands dorsally, externally, and internally.
The movements are chiefly rotation around a transverse axis passing
through the centers of the two joints.
The =crico-arytenoid joints= (Articulationes crico-arytænoidea) are also
diarthrodial. They are formed by the apposition of the convex facets on
the anterior border of the cricoid cartilages with the concave facets on
the bases of the arytenoid cartilages. Each has a very thin, loose
=capsule=, strengthened by accessory bundles dorsally and internally.
The movements are gliding and rotation. In the former the arytenoid
cartilage glides inward or outward; in the latter it rotates around a
longitudinal axis, so that the vocal process swings outward or inward.
The =thyro-hyoid joints= (Articulationes hyo-thyreoideæ) are formed by
the anterior cornua of the thyroid cartilage and the extremities of the
thyroid cornua of the hyoid bone. They permit rotation around a
transverse axis passing through the two joints.
The =crico-thyroid membrane= (Ligamentum crico-thyreoideum) occupies the
thyroid notch and extends backward to the arch of the cricoid cartilage.
It is triangular in form, and is attached by its base to the anterior
border of the arch of the cricoid cartilage, while its borders are
attached to the margins of the thyroid notch. It is strong, tightly
stretched, and composed largely of elastic tissue. It is reinforced
ventrally by longitudinal fibers, dorsally by fibers which stretch
across the thyroid notch.
The =thyro-hyoid membrane= (Membrana hyo-thyreoidea) connects the
anterior border of the thyroid cartilage with the body and thyroid
cornua of the hyoid bone.
The =hyo-epiglottic ligament= (Ligamentum hyo-epiglotticum) attaches the
lower part of the oral surface of the epiglottis to the body of the
hyoid bone. It forms an elastic sheath for the hyo-epiglottic muscle.
Ventrally it blends with the thyro-hyoid membrane, and dorsally it is
not well defined.
The =thyro-epiglottic ligament= (Ligamentum thyreo-epiglotticum) is
strong and thick; it is composed chiefly of elastic tissue. It connects
the base of the epiglottis with the body and the adjacent inner surface
of the laminæ of the thyroid cartilage. Other fibers attach the
cuneiform processes somewhat loosely to the thyroid laminæ.
The =transverse arytenoid ligament= (Ligamentum arytænoideum
transversum) is a slender band which connects the inner angles of the
bases of the arytenoid cartilages.
The =vocal= (or inferior thyro-arytenoid) =ligament= (Ligamentum vocale)
forms the basis of the true vocal cord (Fig. 254). It is elastic and is
attached ventrally to the body of the thyroid cartilage and the
crico-thyroid membrane close to its fellow of the opposite side, and
ends dorsally on the processus vocalis of the arytenoid cartilage.
The =ventricular= (or superior thyro-arytenoid) =ligament= (Ligamentum
ventriculare) is included in the false vocal cord. It consists of
loosely arranged bundles which arise chiefly from the cuneiform process
and end on the outer surface of the processus vocalis and adjacent part
of the arytenoid cartilage.
The =crico-tracheal membrane= (Ligamentum crico-tracheale) connects the
cricoid cartilage with the first ring of the trachea.