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Anatomy Atlases: Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: C: Cricothyroideus

Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: C


Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD

Peer Review Status: Internally Peer Reviewed

The right and left cricothyroid may cross the midline and interdigitate before inserting onto the cricoid cartilage. A very small band of muscle may be found on the inferior lateral aspect of the thyroid cartilage. It does not have any association with the cricoid, hence its function in this location is difficult to understand. It has, however, the elegant name of incisurae mediae obliquus (Gruber), and it may be found unilaterally or bilaterally.

Another small muscle, depressor thyroideae, arises from the lower border of the first tracheal ring and passes vertically upward, over the cricoid muscle to be inserted into the lower border of the thyroid cartilage. An associated muscle band is keratocricoideus, a stout small band that extends at an angle, from the lateral inferior border of the thyroid cartilage, to the medial inferior border of the cricoid cartilage.

Image 91

Varieties of Muscle Associated with the Cricoid and Thyroid Cartilages
Muscles Thyroidei Marginales Inferior: Incisurae Mediae Obliquus, B1 a unpaired, b unusual course of cricothyroidei; B2 a unpaired, left side, Incisurae Mediae Obliquus Bicaudatus, alpha, supernumerary inferior bundle of the same muscle, beta, unusual bundle of right thyrohyoid muscle; B3 a,a paired Incisurae Mediae Obliquus; C a Keratoarytenoideus; D a Thyrotrachealis Biceps, b c d Levator Glandulae Thyroideae; A a Ligamentum hyothyroideum accessorium.
from Gruber, 1868a, b, c, d.

Image 26

Depressor Thyroideae (near midline) and Keratocricoideus (angulated muscle)
from Bradley


Anson, B.J., Ed. (1966) Morris' Human Anatomy, 12th ed., The Blakiston Division, McGraw-Hill BooK Company, New York.

Bradley, S.M. (1872) Notes on myological pecularities. J. Anat. Physiol. 6:420-421.

Gruber, W. (1868a) Über das Zungenbein- Schildknorpel-Hilfs- band (Ligamentum hyothyreoideum accessorium). Arch. Anat. Physiol. Wissen. Med. 1868:633-634.

Gruber, W. (1868b) Über die Muskeln des unteren Schildknorpelrandes- Musculi thyroidei marginales inferiores. Arch. Anat. Physiol. Wissen. Med. 1868:635-639.

Gruber, W. (1868c) Über den seltenen Schildknorpelhorn- Giessbeckenknorpelmuskel (Musculus kerato-arytenoideus). Arch. Anat. Physiol. Wissen. Med. 1868:640-641.

Gruber, W. (1868d) Über eine neue Variante des Musculus thyreotrachealis und über den Musculus hyo-trachealis. Arch. Anat. Physiol. Wissen. Med. 1868:642-645.

Macalister, A. (1875) Additional observations on muscular anomalies in human anatomy (third series), with a catalogue of the principal muscular variations hitherto published. Trans. Roy. Irish Acad. Sci. 25:1-134.

Williams, P.L., Warwick, R., Dyson, M., and L.H. Bannister., Eds. (1989) Gray's Anatomy,37th ed. Churchill Livingstone, Edinburgh.

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