So...intrinsic vs. extrinsic, what's the deal? Back in the day when I was in vocal ped., we were taught that intrinsic muscles are all contained within the larynx itself. That is, these muscles all have their origin and insertion points within the laryngeal structure (so somewhere on those cartilages we just went through.) The extrinsic muscles have either their origin or insertion point in the larynx, but the other point is outside of it.
That is all absolutely true. However, another important component of the difference between intrinsic and extrinsic is in their function. Intrinsic muscles are concerned with fine motor movements and extrinsic are concerned with gross motor movements. (This is good to remember, because the tongue also has intrinsic and extrinsic muscles with the same distinction.) So for our purposes, intrinsic muscles will be involved in the minute vocal adjustments required for communication (pitch, volume, etc.), and the extrinsic muscles have more to do with where the larynx is located in the throat, i.e. elevated for swallowing, neutral for speech (ideally), lower for operatic singing (ideally) etc. Also important for our purposes: The intrinsic muscles are divided into adductors (or muscles that close the vocal folds) and abductors (muscles that open the vocal folds...there's only really one...I always thought it's sort of weird to have a whole category for one muscle), glottal tensors, and glottal relaxers.*
The first adductor is the lateral cricoarytenoid. It originates from the superior-lateral surface of the cricoid cartilage, which is the top-front/side of the cricoid, and inserts into the muscular process of the arytenoid. This muscle is a little hard to see in a model, because it is usually blocked from view by the thyroid. (You can see it on the picture below because this view is from the side, as if the side of the thyroid had been cut away.)
The transverse arytenoid muscle originates from the outer side of the arytenoid and inserts into the outer side of the other arytenoid. Contraction results in pulling the two arytenoids closer together than just the lateral cricoarytenoid by itself. This muscles as a lot to do with medial compression, which is the degree of force that brings the vocal folds together at the midline. It's the muscle underneath the criss-cross muscles pictured below.
The abductor of the vocal folds is the posterior cricoarytenoid muscle, and you can see it in the above picture as the lowest muscle pictured. This guy originates from bottom-back of the cricoid and inserts into the bottom-back of the arytenoid (so it courses upwards). Contraction results in pulling the muscular process of the arytenoids back, which rocks the arytenoid cartilage outwards and abducts the vocal folds. I believe scientists used to think this muscle didn't have a whole lot to do...which makes sense given muscular elasticity would naturally abduct the folds upon the end of phonation, but we now know that this guy has a big part to play during speech and inhalation. This is what allows for more opening of the glottis when we're breathing, either during exercise or at rest, and it also opens the glottis when we make plosive consonants that require very fast, short bursts of air through the larynx. So it's actually a pretty active little muscle...and loss of function in this guy causes a lot of issues for folks being able to breath easily.
The two glottal tensors are the cricothyroid muscle and the thyrovocalis muscle (which is a part of the thyroarytenoid muscle). The cricothyroid actually has two parts to it: the pars recta ("straight part") and the pars oblique ("angled part"). The pars recta originates from the front surface of the cricoid and inserts into the lower part of the back-front of the thyroid. The pars oblique originates just to the side of the pars recta origination, and inserts higher up on the thyroid cartilage than the pars recta. The pars recta portion is what rocks the thyroid cartilage downward. (This movement does result in the cricoid rising, but that is due to the flexibility of the tracheal cartilage rather than direct muscular movement.) This movement stretches the vocal folds, changing the pitch of the voice. The pars oblique portion slides the thyroid slightly forward (via the thyrocricoid joint), which also tenses the vocal folds, elevating the vocal pitch. (Unfortunately, I couldn't find a good, public-domain image of this muscle for ya.)
The thyrovocalis is the middle muscle of the vocal folds. In fact, this is the muscle that makes up the inner layer of the vocal folds. It originates from the inner surface of the thyroid cartilage and inserts into the vocal process of the arytenoids. Contraction of this muscle tenses the vocal folds by drawing the thyroid and cricoid cartilages farther apart. Notice that that motion is the opposite of the cricothyroid muscle, which pulls the thyroid and cricoid together by rocking and sliding. Although it moves the thyroid and cricoid in the opposite way of the cricothyroid muscle, it works in conjunction with it to tense the vocal folds even further through the antagonistic movement. (For yogis out there: This is a bit like how drawing the arms up into the shoulder blades while simultaneously lowering into "push up" position results in more muscle tone to support your body weight...sort of. Can't think of a better example right now...)
The glottal relaxer, the thyromuscularis, is paired with the thyrovocalis in a special way I'll talk about below.
This muscle originates from the same place as the thyrovocalis and inserts into the muscular process of the arytenoids. Contraction of the more-medial (or middle) portion of this muscle also has the same results as the thyrovocalis. However, contraction of the the same section might also relax the vocal folds by pulling the arytenoids toward the thyroid cartilage without changing the rocking motion of the thyroid. So, anatomically, there is not really a difference between the thyrovocalis and the thyromuscularis, but functionally, they are distinctly different. Hence, some sources lump them together into the thyroarytenoid muscle rather than maintaining a distinction in function by separating them. However, since operatic singing requires more finely-tuned laryngeal function than daily voice use, I feel this distinction is an important one to highlight.
And there you have it. Your intrinstic laryngeal muscles (or the main ones we'll talk about anyway. There are some supporting muscles to these, but their impact on vocal function is questionable, while their necessity in the swallowing process is well known. I'm just not going to get into swallowing here.)
*Citation: Seikel, J. A., King, D. W., & Drumright, D. G. (2010). Anatomy and physiology for speech, language, and hearing. Clifton Park, NY: Delmar.
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