Thyroarytenoid Muscle

*UPDATE*
I have launched this discussion in a few voice teacher groups. It was very interesting to see that many colleagues – also the ones I consider to be “the smart ones” – were following the threads, because they were as confused as I was. The final conclusion is that the thyroarytenoid muscle consists of the medial thyroarytenoid muscle – also called vocalis – and the lateral thyroarytenoid.

It was dr. David Young , Resident Physician, Otolaryngology – Head & Neck Surgery at Vanderbilt University Medical Center, who has shed light on the issue of multiple terms, by clarifying that the other terms are archaic and more the domain of old anatomy textbooks. Thanks, David! 🙏

I’m leaving the original blog post here, as THIS is a very important reason of why I have created VocalDrawings.com. I want to contribute to clear and simple information that we can trust. There’s already enough confusion in the world of voice ;-)

Original blog post

Dear colleagues, I need your help.

It appears that there’s a lot of confusion around the terminology of the thyroarytenoid muscle. In my drawing of Larynx / Voice Box Transverse plane, I have named the outer part of the muscular part of the vocal folds thyroarytenoid muscle, and the inner part vocalis muscle.

I’m going to update those tags, as they are confusing. Maybe even wrong? But before I do so, I’d like to throw it in the group, in the hope we can end up with a definite conclusion. Because there are clearly different opinions on this matter.

Here’s some of the conflicting terminology I have found in trustworthy sources. I think you’ll get the confusion :-)

  1. The whole muscular part is called the thyroarytenoid AND vocalis muscle, so they are synonyms.
  2. The muscular part of the vocal folds consists of 2 parts. The external part is called the thyroarytenoid muscle and the internal part is called the vocalis muscle.
  3. The whole muscular part is called thyroarytenoid, which is divided into an internal part & an external part. Those parts are given various names:
    • The vocalis muscle & the lateral thyroarytenoid.
    • The thyrovocalis part & the thyromuscularis part.
    • The vocalis part & thyrovocalis part.

I have my own ideas on what is “wrong” and how certain terms could both be “right”, but as I said before,  I’m throwing this in the group.

So… Is there a terminology we can agree on? Which terms are being used in the latest research? And most of all: Which terms create the least confusion for our students, clients and patients?

4 replies
  1. Joanna Cazden says:

    Sarah: thanks for your diligence in this. A few comments:
    (1) Anatomy is full of wording conflicts like this. Do not feel that you need to fix/resolve the issue, nor that you’ll be judged badly if choose one labelling system over another! Anat labels develop over 1000 years, with personalities and language translations and so on shaping them. It is a human process like any other. Then, just as in singing pedagogy: authors tend to keep the terminology from their own teachers & “lineage.” Psychologically, singing students & teachers may expect medical science to be more perfectly logical or well-defined, BUT SOMETIMES IT’S NOT. and thats OK.
    (2): I just looked up Zemlin’s Speech and Hearing Science/ Anatomy and Physiology, which was my text in grad school (1980s) and he uses #3b of your label options: thyroarytenoid as the whole & vocalis/ muscularis as its sub-sections. If you want to be super-comprehensive, whichever one you pick, just indicate somewhere that “also sometimes called …..” and list alternatives. I did that in my VASTA article on nervous system: “Somato-sensory also sometimes called sensory-motor” .
    (3): Remember that anatomy is simply the name, and if there is a teensy amount of fascia around a group of muscle fibers, that can be dissected out under microscope, it gets a unique name. PHYSIOLOGY is how the muscles work, which is far more important. If the two parts of TA muscle work together in almost every way that’s relevant to phonation, functionally the two-part distinction is unimportant. (I always refer back to Thomas Hixon in “Respiratory Function in Singing” : that singing teachers know too much anatomy and not enough physiology. ) Body builders, physical therapists, and some athletes may need to isolate one portion of biceps from another, but the average person at the gym doesn’t care… I’m not immediately aware of any vocal action that engages vocalis & lateral TA differently, or that can preferentially train one or the other. This is one reason I lean toward using TA as an inclusive label. Students using your drawings may not need further detail. (But I could be wrong)
    do not lose sleep over this!

    Reply
    • Sarah says:

      Thank you so much for your thorough reply, Joanna, I appreciate it! I have to admit that I have lost some sleep over it, as my claim is that my drawings are “anatomically correct & reviewed by experts on the voice”. I have to walk the talk ;-)

      1) Indeed, it evolves over time. It was so interesting to see how much terminology has been used for these tiny parts of our bodies in just a few decades. David Young’s mentioning of the fact that some terms are archaic and more the domain of old anatomy textbooks made me understand that. It cleared up a lot of confusion when I put terminology next to date of publication.

      2) I agree with you. That’s why I have added ‘vocalis muscle’ tot the medial thyroarytenoid, because that term is being used a lot in the world of voice pedagogy.

      3) Actually, according to some people who have engaged in the discussion, there IS a distinction between the two parts, regarding function:

      Kenneth Wood Bozeman said that it might be that the contraction of the lateral TA shortens the VF, while allowing the more medial TA (vocalis) to remain loose. Along with the loosened cover, that would be an explanation of a free low chest voice, which requires some blend of short, thick, and loose folds.

      Dave Wilkinson has shared this literature review that researches the difference between the lateral TA & medial TA with regards to fast and slow twitch muscle fibers and their function in the voice. I haven’t had the time to read it thoroughly, but the short glance that I have been able to throw on it tells me it’s worth reading! http://www.scielo.br/scielo.php?pid=S1516-80342011000300020&script=sci_arttext&tlng=en&fbclid=IwAR2AIwOblrSl7mlZvSNGeFTot1aLXGgOLMX30WI9_wnFRL12gGP-L2H-VcQ

      And then David Young shared this: If you look at coronal slices you’ll see two distinct muscle bellies running within the vocal fold between the arytenoid and the thyroid cartilages. Taken together these are usually referred to as TA. If you want to get more detailed, the medial aspect of the muscle inserts on the vocal process of the arytenoid and is sometimes referred to as vocalis or thyrovocalis for this reason, though calling it the medial TA would also be appropriate. The lateral TA belly inserts on the muscular process of the arytenoid. A good axial slice can clearly show these different insertions. Most of the time people just call the whole thing TA. If we wanted to get deep in the weeds we could look at the rotational vectors of the arytenoid in 3D and say that the vocalis part does more to shorten and thicken the fold while the lateral part is more for adduction but that’s getting pretty deep. I think for an atlas you could show the divisions of the muscle bellies clearly delineating their distinct insertions and label the medial one Medial TA/Vocalis and the lateral one as Lateral TA. That’s about as thorough as you can get and should be clear to anyone reading it or reading current research. The other terms are archaic and more the domain of old anatomy textbooks.

      I fully understand using TA as an inclusive label. I do that too for most of my students :-) But I also teach teachers & SLP’s. And I did divide the muscular part of my drawing, so I should clarify what those 2 parts are in the version with tags. However, when I’m teaching non-teachers & non-SLP’s, I personally use the drawing without tags and refer to the whole pinkish thing as the vocal folds. This is actually why I provide several versions of the same drawing: So that teachers can choose which ones they want to use, according to the person they’re working with.

  2. Joanna Cazden says:

    Hats off to you for this thoroughness… it could be an essay or blog by itself (TA parts 1 & 2, whats the difference… )!!! BRAVA

    Reply
    • Sarah says:

      Thanks! I’m doing my best to offer more than just “Please, buy my drawings” on this website, hence the blog :-)

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