Anatomy and Physiology Series: Laryngeal cartilages (and hyoid bone too)

Now we get to the fun stuff...okay maybe not quite yet.  This is more like the dry anatomy build-up to the fun stuff (laryngeal physiology).  Much of what I say here can be found in pretty much any vocal pedagogy book out there, but I think it's still important to go over.  Even if you feel you know this from a pedagogy course you took in school, the information is worth reviewing, and who knows...you might find there's something new in here as well.

Let's start with the 5 main cartilages (and hyoid bone) of the larynx.  These cartilages and one bone make up the internal structure of the larynx and serve as attachment points to the intrinsic laryngeal musculature.  The 5 main cartilages are:  The thyroid cartilage (which the thyroid gland sits on the bottom of), the cricoid cartilage, the two paired arytenoid cartilages, and the epiglottis.  (There are other cartilages, the corniculate and cuneiform cartilages, but they don't have quite as much to do with voice production.)  I'm including two pictures below of these structures.  In one, they're all separated, and in the other, they're all together as they are in the body, as viewed from behind.

The thyroid and cricoid cartilages are attached by the cricothyroid joint (or articulation as in the above picture), which allows for the "rocking" motion of the thyroid during phonation.  The epiglottis is considered the entrance to the larynx.  It mainly serves to close off the glottis when swallowing (by folding down when the larynx elevates), but it also forms part of the pharyngeal wall during phonation.


The hyoid bone does not directly articulate to any other bone in the body.  However, it is attached to the thyroid via the hyothyoid membrane.  Why is it a bone and not cartilage like everything these?  I'm not sure, but I assume by being a more sturdy material, bone, it provides stronger support for the laryngeal cartilages.  The hyoid bone is a major point of attachment for many muscles above the larynx.  I believe it has something like 30 or 40 muscles that attach to it (the actual number escapes me at the moment).  We're only going to talk about a few, cause we're much more interested in the laryngeal elevators and articulatory muscles.


I do want to discuss the arytenoids in some detail here before getting into laryngeal musculature.  The arytenoids are pyramidal-shaped cartilaginous structures (and from a certain angle, they sort of look like a shark's tooth.)  The joint that attaches them to the cricoid allows for rotation of the arytenoids, which allows the vocal folds to close.  There are two main processes (or protrusions) that should be discusses here.  The first one, the vocal process, cannot be viewed from above (unfortunately), but it is the point near the base of the arytenoid on the opposite side from the view you currently see up there.  The other, the muscular process, can be seen.  It's the point at the base on the outside of each arytenoid in the above view.  These two points serve as important attachment points for intrinsic laryngeal musculature, so it's good to remember them.


Okay, so I was going to launch right into intrinsic laryngeal musculature, but I think if I did that, this would turn in to some monster-post.  So I'll just finish this one here and start up with intrinsic musculature next.