Thyroid cartilage

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Thyroid cartilage
The cartilages of the larynx.
Details
Precursor4th and 6th branchial arch
Identifiers
LatinCartilago thyreoidea
MeSHD013957
TA98A06.2.02.002
TA2967
FMA55099
Anatomical terminology

The thyroid cartilage is the largest of the nine cartilages that make up the laryngeal skeleton, the cartilage structure in and around the trachea that contains the larynx.

Structure

It is composed of two plate-like laminae that fuse on the anterior side of the cartilage to form a peak, called the laryngeal prominence. This prominence is often referred to as the "pomus Adami"[1] or "Adam's apple". The laryngeal prominence is more prominent in adult male than female because of the difference in the size of the angle: 90° in male and 120° in female.

The lip of the thyroid cartilage just superior to the laryngeal prominence is called the superior thyroid notch, while the notch inferior to the thyroid angle is called the inferior thyroid notch.

Its posterior border is elongated both inferiorly and superiorly to form the superior horn of thyroid cartilage and inferior horn of thyroid cartilage.

Thyroid cartilage

Layers and articulations

The two laminae that make up the main lateral, surfaces of the thyroid cartilage extend obliquely to cover either side of the trachea. The oblique line marks the superior lateral borders of the thyroid gland.

The posterior edge of each lamina articulates with the cricoid cartilage inferiorly at a joint called the cricothyroid joint.

Movement of the cartilage at this joint produces a change in tension at the vocal folds, which in turn produces variation in voice.

The entire superior edge of the thyroid cartilage is attached to the hyoid bone by the thyrohyoid membrane.

Function

The thyroid cartilage forms the bulk of the anterior wall of the larynx, and serves to protect the vocal folds ("vocal cords"), which are located directly behind it.

Changing the angle of the thyroid cartilage relative to the cricoid cartilage changes the pitch.

It also serves as an attachment for several laryngeal muscles.

Etymology

Shield-like

The English term thyroid cartilage is derived from the Latin expression cartilago thyreoides.[2][3] The latter is a translation of Ancient Greek χόνδρος θυρεοειδής,[4] attested in the writings of the Greek physician Galen.[4] The Latin word cartilago, as well as the Ancient Greek word χόνδρος, both mean cartilage,[4][5] while the ancient Greek word θυρεοειδής means shield-like or shield-shaped.[2][4] The latter compound is composed of Ancient Greek θυρεός, shield [2][4] and εἶδος, form/shape.[4] The Greeks used εἶδος in compounds to indicate a resemblance with the first part of the word.[6]

The ancient Greek word θυρεός can be found in the Odyssey of Homer,[4][7] and represented a large square stone that was put against the door to keep it shut.[4][7] Those θυρεοί were eventually used by the Greek army as shields to protect themselves.[7] This shield was adapted by Roman legions and referred to by them as a scutum.[7] The Roman scutum was an oblong shield with an oval shape.[4][7] Numerous shields were used by the Roman soldiers, such as the pelta, parma and clypeus.[7] In contrast to the scutum, these shields were round.[7] Despite these latter shields bearing a clear round shape, coinages like petalis cartilago,[8] cartilago parmalis,[7] and cartilago clypealis[9] were coined for the thyroid cartilage. In 16th-century Italian anatomist Realdo Colombo's De re anatomica,[8] besides the aforementioned incorrect petalis cartilago, correct forms like scutalis cartilago and scutiformis cartilago can be found, as the scutum is the real Roman pendant of the Greek θυρεός. The latter Latin expression can be found in its English form in medical dictionaries as scutiform cartilage,[10] while the name of the shield itself, i.e. scutum, is still being mentioned as a synonym for the thyroid cartilage.[11][12]

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.[13] cartilago thyroidea [14][15][16][17][18][19] and the previously mentioned cartilago thyreoides.[3][20] The variant with the adjective thyreoidea (with the ending -ea) would be a faulty rendering[6][21] of Ancient Greek θυρεοειδής in Latin. Greek compounds ending on -ειδής, when imported into Latin as loanword, ended on -ides.[6][22] In the 17th-century the non-classical Latin form on -ideus/-idea/ideum for Greek -ειδής/-ειδές became into use, mostly by French anatomist Jean Riolan the Younger.[7] No Greek loanwords (originally on -ειδής/-ειδές) ending on -ideus/-idea/-ideum exist in classical Latin,[5][22] thereby making the form on -ideus/-idea/-ideum non-Latinate in character.[22] The first edition of the Jena Nomina Anatomica (JNA) contained the incorrect cartilago thyreoidea,[23] but after a list of recommendations/corrections was made[23] this was corrected in subsequent editions of the JNA.[3][20]

The variant with thyroidea (omitting e after thyr) would be some kind of compromise to English-speaking anatomists, as they have difficulties in pronouncing that specific combination of letters,[24] forcing a greater resemblance between Latin and English orthography. Dorland's medical dictionary from 1948[11] already adopted this incorrect spelling with the erroneous reference to the official Basle Nomina Anatomica even before the nomenclature committee of the Nomina Anatomica officially approved this orthographic revision in its edition of 1961.[14] The spelling without an e is commonly accepted in English[12][25] but earlier works preferred the etymologically correct thyreoid cartilage.[10][26] The official Latin veterinary nomenclature, Nomina Anatomica Veterinaria has the form cartilago thyroidea [27] in common with the human Nomina Anatomica/Terminologia Anatomica, but allows in contrast to the latter, to use cartilago thyreoidea [27] as alternative spelling.

Shield versus door

An unfortunate mishap is the resemblance between Latin thyroidea and English thyroid on the one side and Ancient Greek θυροειδής on the other side, as the latter does not mean shield-like, but actually means like a door,[4] derived from θύρα, door.[4] Θυροειδής is however used in anatomic nomenclature in the expression θυροειδές τρῆμα (τρῆμα = hole, perforation, aperture[4]), coined by the Greek physician Galen.[7] Ancient Greek θύρα can be translated, besides the earlier mentioned door, as gate,[4][7] entrance[4][7] and opening.[7] The Greek name θυροειδές τρῆμα for this opening between the os pubis and the os ischii, currently called obturator foramen,[12] clearly originates for being an opening (θύρα), while bearing no resemblance to a shield (θυρεός).[7] The Latin translation foramen thyreoideum for θυροειδές τρῆμα of the 18th–19th-century German physician and anatomist Samuel Thomas von Sömmerring is clearly mistaken.[7] The current foramen thyroideum of the Terminologia Anatomica is not a Latin translation of Galen's θυροειδές τρῆμα, but an orthographic revision of what was previously known in the Nomina Anatomica as foramen thyreoideum,[3][13] an inconstantly present opening in the lamina of the thyroid cartilage.[12]

Additional images

  • Muscles of the pharynx and cheek.
    Muscles of the pharynx and cheek.
  • The cartilages of the larynx. Posterior view.
    The cartilages of the larynx. Posterior view.
  • Ligaments of the larynx. Posterior view.
    Ligaments of the larynx. Posterior view.
  • Sagittal section of the larynx and upper part of the trachea.
    Sagittal section of the larynx and upper part of the trachea.
  • Coronal section of larynx and upper part of trachea.
    Coronal section of larynx and upper part of trachea.
  • The entrance to the larynx, viewed from behind.
    The entrance to the larynx, viewed from behind.
  • Muscles of larynx. Side view. Right lamina of thyroid cartilage removed.
    Muscles of larynx. Side view. Right lamina of thyroid cartilage removed.
  • Front view of neck.
    Front view of neck.

See also

This article uses anatomical terminology.

References

  1. ^ Medical literature
  2. ^ a b c Triepel, H. (1910). Die anatomischen Namen. Ihre Ableitung und Aussprache. Mit einem Anhang: Biographische Notizen.(Dritte Auflage). Wiesbaden: Verlag J.F. Bergmann. Template:De icon
  3. ^ a b c d Kopsch, F. (1941). Die Nomina anatomica des Jahres 1895 (B.N.A.) nach der Buchstabenreihe geordnet und gegenübergestellt den Nomina anatomica des Jahres 1935 (I.N.A.) (3. Auflage). Leipzig: Georg Thieme Verlag. Template:De icon
  4. ^ a b c d e f g h i j k l m n Liddell, H.G. & Scott, R. (1940). A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with the assistance of. Roderick McKenzie. Oxford: Clarendon Press.
  5. ^ a b Lewis, C.T. & Short, C. (1879). A Latin dictionary. founded on Andrews' edition of Freund's Latin dictionary.Oxford: Clarendon Press.
  6. ^ a b c Triepel, H. (1927). Die anatomischen Namen. Ihre Ableitung und Aussprache. Anhang: Biographische Notizen.(Elfte Auflage). München: Verlag von J.F. Bergmann.
  7. ^ a b c d e f g h i j k l m n o Hyrtl, J. (1880). Onomatologia Anatomica. Geschichte und Kritik der anatomischen Sprache der Gegenwart. Wien: Wilhelm Braumüller. K.K. Hof- und Unversitätsbuchhändler.
  8. ^ a b Columbo, R. (1559). De re anatomica. Libri XV. Venice: Nicola Beviliacqua.
  9. ^ Schreger, C.H.Th. (1805). Synonymia anatomica. Synonymik der anatomischen Nomenclatur. Fürth: im Bureau für Literatur.
  10. ^ a b Foster, F.D. (1891–1893). An illustrated medical dictionary. Being a dictionary of the technical terms used by writers on medicine and the collateral sciences, in the Latin, English, French, and German languages. New York: D. Appleton and Company.
  11. ^ a b Dorland, W.A.N. & Miller, E.C.L. (1948). The American illustrated medical dictionary.’’ (21st edition). Philadelphia/London: W.B. Saunders Company.
  12. ^ a b c d Anderson, D.M. (2000). Dorland’s illustrated medical dictionary (29th edition). Philadelphia/London/Toronto/Montreal/Sydney/Tokyo: W.B. Saunders Company.
  13. ^ a b His, W. (1895). Die anatomische Nomenclatur. Nomina Anatomica. Der von der Anatomischen Gesellschaft auf ihrer IX. Versammlung in Basel angenommenen Namen. Leipzig: Verlag Veit & Comp.
  14. ^ a b Donáth, T. & Crawford, G.C.N. (1969). Anatomical dictionary with nomenclature and explanatory notes. Oxford/London/Edinburgh/New York/Toronto/Syney/Paris/Braunschweig: Pergamon Press.
  15. ^ International Anatomical Nomenclature Committee (1966). Nomina Anatomica . Amsterdam: Excerpta Medica Foundation.
  16. ^ International Anatomical Nomenclature Committee (1977). Nomina Anatomica, together with Nomina Histologica and Nomina Embryologica. Amsterdam-Oxford: Excerpta Medica.
  17. ^ International Anatomical Nomenclature Committee (1983). Nomina Anatomica, together with Nomina Histologica and Nomina Embryologica. Baltimore/London: Williams & Wilkins
  18. ^ International Anatomical Nomenclature Committee (1989). Nomina Anatomica, together with Nomina Histologica and Nomina Embryologica. Edinburgh: Churchill Livingstone.
  19. ^ Federative Committee on Anatomical Terminology (FCAT) (1998). Terminologia Anatomica. Stuttgart: Thieme
  20. ^ a b Stieve, H. (1949). Nomina Anatomica. Zusammengestellt von der im Jahre 1923 gewählten Nomenklatur-Kommission, unter Berücksichtigung der Vorschläge der Mitglieder der Anatomischen Gesellschaft, der Anatomical Society of Great Britain and Ireland, sowie der American Association of Anatomists, überprüft und durch Beschluß der Anatomischen Gesellschaft auf der Tagung in Jena 1935 endgúltig angenommen. (4th edition). Jena: Verlag Gustav Fischer.
  21. ^ Triepel, H. (1908). Memorial on the anatomical nomenclature of the anatomical society. In A. Rose (Ed.), Medical Greek. Collection of papers on medical onomatology and a grammatical guide to learn modern Greek (pp. 176-193). New York: Peri Hellados publication office.
  22. ^ a b c Kossmann, R. (1903). Allgemeine Gynaecologie. Berlin: Verlag von August Hirschwald.
  23. ^ a b Suzuki, S., Katsumata, T., Ura, R. Fujita, T., Niizima, M. & Suzuki, H. (1936). Über die Nomina Anatomica Nova. 'Folia Anatomica Japonica, 14, 507-536.
  24. ^ Drukker, J, & Walvoort, H.C. (2000). Terminologia anatomica: een nieuw anatomisch referentiewerk. Nederlands Tijdschrift voor Geneeskunde, 144, 890-891.
  25. ^ Dirckx, J.H. (Ed.) (1997).Stedman’s concise medical dictionary for the health professions. (3rd edition). Baltimore: Williams & Wilkins.
  26. ^ Barker, L.W. (1907). Anatomical terminology with special reference to the [BNA]. With vocabularies in Latin and English and illustrations. Philadelphia: P. Blakiston’s Son & Co.
  27. ^ a b International Committees on Veterinary Gross Anatomical Nomenclature, Veterinary Histological Nomenclature, & Veterinary Embryological Nomenclature (1994). Nomina Anatomica Veterinaria together with Nomina Histologica and Nomina Embryologica Veterinaria. Zürich/Ithaca/New York.

External links

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