VAN 221: Veterinary Splanchnology and Applied Anatomy (1+1)

CARTILAGES OF LARYNX

Cricoid cartilage

• The cricoid cartilage is a ring shaped cartilage
• It consists of a dorsal part- the lamina and ventral and lateral parts -the arches
• The lamina is broad and thick and is marked by a large median ridge
• On either side of this ridge are two facets, the cranial of which articulates with the arytenoids and the caudal with the caudal cornua of thyroid cartilage
• Both the articulations are syndesmoses. The arches are curved and each presents a groove on the lateral surface for the crico-thyroid muscle
•  The cranial border gives attachment to thyroid cartilage by the cricothyroid membrane while the caudal border gives attachment to first ring of trachea by the crico-tracheal membrane
• The internal surface is lined by mucous membrane

Thyroid cartilage

• The thyroid cartilage is a shield-shaped cartilage
• It consists of a central part, the body and two lateral parts- the laminae
• The body is attached to the base of the epiglottis by the thyro-epiglottic ligament
•  The body shows a prominence ventrally, the laryngeal prominence
• The laminae form the sides of larynx and unite completely on the ventral aspect to form a long plate, which is notched in front, and behind
• It presents two cornua on either side: the cranial and caudal cornua
• The cranial cornua articulates with the thyroid cornua of the hyoid bone by syndesmoses and the caudal cornu with the facet on the caudal part of the lamina of the cricoid cartilage again by syndesmoses
• The cranial cornua presents below its upper border a thyroid notch or foramen for the passage of the cranial laryngeal nerve

Arytenoid cartilages

• The arytenoid cartilages are paired and each is situated dorsally, in front of the cricoid, partly medial and dorsal to the lamina of the thyroid cartilage
• It is pyramidal in form and presents three surfaces (medial, dorsal and lateral) three borders (cranial, caudal and lateral), a base and an apex
• The base faces backward and articulates with cricoid. The apex is in front and curves upwards and backwards
• The cranial and caudal borders converge ventrally to form the vocal process. The process is so named because it furnishes attachment to vocal ligament
• The medial angle of the base is attached to its fellow by a transverse arytenoid ligament

Epiglottis

• The epiglottis is short, leaf-like plate of cartilage placed above the body of the thyroid. It presents two surfaces, two borders, a base and an apex
• The surfaces are oral and pharyngeal surface. The borders are thin, irregular and somewhat everted. The base is caudal, attached to the thyroid cartilage
• The apex is cranial and the tip is free rounded and curves towards the root of the tongue. The surfaces are lined by mucous membrane.
• The cricoid and thyroid cartilages and the greater part of the arytenoid cartilages are hyaline in nature
• The apices, vocal processes of the arytenoid and the epiglottis consist of elastic cartilage. They show no tendency towards ossification at any age