Thyroid cartilage

The thyroid cartilage is a hyaline cartilage structure that sits in front of the larynx and above the thyroid gland. The cartilage is composed of two halves, which meet in the middle at a peak called the laryngeal prominence, also called the Adam's apple, which is more prominent in males. In the midline above the prominence is the superior thyroid notch. A counterpart notch at the bottom of the cartilage is called the inferior thyroid notch. The two halves of the cartilage that make out the outer surfaces extend obliquely to cover the sides of the trachea. The posterior edge of each half articulates with the cricoid cartilage inferiorly at a joint called the cricothyroid joint. The most posterior part of the cartilage also has two projections upwards and downwards. The upper projection is called the superior horn (), and the lower is called the inferior horn. The superior horn is long and narrow, backward, and medialward, and ends in a conical extremity, which gives attachment to the lateral thyrohyoid ligament. The inferior horn is short and thick; it is directed downward, with a slight inclination forward and medialward, and presents, on the medial side of its tip, a small oval articular facet for articulation with the side of the cricoid cartilage. The entire superior edge of the thyroid cartilage is attached to the hyoid bone by the thyrohyoid membrane. The thyroid cartilage is found between the levels of the C4 to C5 vertebrae. The oblique line is a line on the thyroid cartilage. It marks the upper lateral borders of the thyroid gland. Two muscles originate along the line, the thyrohyoid muscle and the inferior pharyngeal constrictor. The sternothyroid inserts along the line. Movement of the cartilage at this joint produces a change in tension at the vocal folds, which in turn produces variation in voice. Variations The thyroid cartilage may contain a variant foramen, known as thyroid foramen, in up to 39% of individuals. ==Function==

The thyroid cartilage forms the bulk of the front wall of the larynx. It protects the vocal folds ("vocal cords"), which are located directly behind it. When the angle of the thyroid cartilage changes relative to the cricoid cartilage, this changes the pitch of voice. The cartilage also serves as an attachment for several muscles. ==Etymology==

Shield-like The English term thyroid cartilage is derived from the Latin expression . The latter is a translation of Ancient Greek , attested in the writings of the Greek physician Galen. while the ancient Greek word means shield-like or shield-shaped. The ancient Greek word can be found in the Odyssey of Homer, and represented a large square stone that was put against the door to keep it shut. cartilago parmalis, were coined for the thyroid cartilage. In 16th-century Italian anatomist Realdo Colombo's De re anatomica, while the name of the shield itself, i.e. scutum, is still being mentioned as a synonym for the thyroid cartilage. Spelling In the various editions of the official Latin nomenclature (Nomina Anatomica, in 1998 rebaptized as Terminologia Anatomica), three different spellings can be found, i.e. cartilago thyreoidea. cartilago thyroidea and the previously mentioned ''. The variant with the adjective thyreoidea'' (with the ending -ea) would be a faulty rendering of Ancient Greek in Latin. Greek compounds ending in -, when imported into Latin as a loanword, ended in -ides. In the 17th century the non-classical Latin form -ideus/-idea/ideum for Greek -/- came into use, mostly by French anatomist Jean Riolan the Younger. but after a list of recommendations/corrections was made forcing a greater resemblance between Latin and English orthography. Dorland's medical dictionary from 1948 but earlier works preferred the etymologically correct thyreoid cartilage. The official Latin veterinary nomenclature, Nomina Anatomica Veterinaria, has the form '', in common with the human Nomina Anatomica/Terminologia Anatomica, but allows (in contrast to the latter) cartilago thyreoidea'' as an alternative spelling. ====== A mishap is the resemblance between Latin thyroidea and English thyroid on the one side and Ancient Greek on the other side, as the latter does not mean shield-like, but actually means like a door, derived from , door. is however used in anatomic nomenclature in the expression ( = hole, perforation, aperture), coined by the Greek physician Galen. Ancient Greek can be translated, besides the aforementioned door, as gate, entrance and opening. The Greek name for this opening between the os pubis and the os ischii, currently called obturator foramen, clearly originates from its being an opening (), while bearing no resemblance to a shield (). The Latin translation foramen thyreoideum for by the 18th–19th-century German physician and anatomist Samuel Thomas von Sömmerring is clearly mistaken. The current foramen thyroideum of the Terminologia Anatomica is not a Latin translation of Galen's , but an orthographic revision of what was previously known in the Nomina Anatomica as foramen thyreoideum, an inconstantly present opening in the lamina of the thyroid cartilage. ==See also==