Muscle Nomenclature

Muscle names are often based on anatomic characteristics which give the student trying to learn all the muscles, origins, insertions and actions a small help. Thankfully, few seem to be named at random. Let’s look at some names of muscles we will see in this lesson to illustrate the various conventions used.

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Origin/Insertion or Both	Example: Sternocleidomastoid muscle This muscle has two origins: on the sternum (sterno); the clavicle (cleido); and inserts on the mastoid process of the temporal bone (mastoid). Knowing this along with fact that the insertion generally moves towards the origin you can also figure out that this muscle pulls the mastoid process towards the clavicle and sternum rotating and tilting the head.
Size	Example: Depressor anguli oris This muscle depresses (depressor) the angle (anguli) of the mouth (oris).
Size	Example: Zygomaticus major/minor These muscles apply two rules for naming. Both are named for their origin (zygomatic arch) but rather that putting in the insertion they are ranked by size with the zygomaticus major being the larger of the two.
Shape	Example: Trapezius While this name tells nothing about the origin, insertion, size or action it does tell its shape which is roughly trapezoidal.
Location	Example: Orbicularis oris Orbicularis refers to its circular shape, so this applies to two conventions also. The oris locates it around the mouth. There is also a circular muscle around the eye called the orbicularis oculi.
Relative Position	Example: Lateral/medial pterygoids This one gives the origin on a pterygoid plate but confusingly there are two pterygoid plates named the medial and lateral. This causes some confusion as the lateral and medial refer to the position of the two muscles relative to one another rather than referring to their origins which in both cases is mainly on the lateral pterygoid plate of the sphenoid bone.

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