11.3 Explain the criteria used to name skeletal muscles

Taking the time to learn the Latin and Greek roots of the words is crucial to understanding the vocabulary of anatomy and physiology. When you understand the names of muscles it will help you remember where the muscles are located and what they do (Figure 11.3.1, Figure 11.3.2, and Table 11.2).

Understanding a Muscle Name from the Latin

Example	Word	Latin Root 1	Latin Root 2	Meaning	Translation
abductor digiti minimi	abductor	ab = away from	duct = to move	a muscle that moves away from	A muscle that moves the little finger or toe away
	digiti	digitus = digit		refers to a finger or toe
	minimus = mini, tiny			little
adductor digiti minimi	adductor	ad = to, toward	duct = to move	a muscle that moves towards	A muscle that moves the little finger or toe forward
	digiti	digitus = digit		refers to a finger or toe
	minimi	minimus = mini, tiny		little

Here are two examples of how root words describe the location and function of muscles.

Mnemonic Device for Latin Roots

Anatomists name the skeletal muscles according to a number of criteria, each of which describes the muscle in some way. These include naming the muscle after its shape, size, fiber direction, location, number of origins or its action.

• Muscle Shape: The names of some muscles reflect their shape. For example, the deltoid is a large, triangular-shaped muscle that covers the shoulder. It is so-named because the Greek letter delta is a triangle.
• Muscle Location: The skeletal muscle’s anatomical location or its relationship to a particular bone often determines its name. For example, the frontalis muscle is located on top of the frontal bone of the skull. Other examples are muscles of the arm that include the term brachii (of the arm).
  • Some muscles indicate their positions relative to the midline, which is related to muscle location: lateralis (to the outside away from the midline), and medialis (toward the midline).
  • The location of a muscle’s attachment can also appear in its name. When the name of a muscle is based on the attachments, the origin is always named first. For instance, the sternocleidomastoid muscle of the neck has a dual origin on the sternum (sterno) and clavicle (cleido), and it inserts on the mastoid process of the temporal bone.
• Muscle Size: For the buttocks, the size of the muscles influences the names: gluteus maximus (largest), gluteus medius (medium), and the gluteus minimus (smallest). Another example are the pectoral muscles including major or minor.
  • Names are often used to indicate length, which is related to muscle size. For example, brevis (short), longus (long).
• Muscle Fiber Direction: The direction of the muscle fibers and fascicles are used to describe muscles. For example, the abdominal muscles all indicate (remove indicated) the direction of the fibers such as the rectus (straight), the obliques (at an angle) and the transverse (horizontal) muscles of the abdomen.
• Number of Muscle Origins (or muscles in a group): Some muscle names indicate the number of muscles origins, or number of muscles in a group, depending upon one’s perspective. For example, when considering the anterior thigh muscle(s), known as the quadriceps, some consider it to be a single muscle with four heads (origins) and others consider the quadriceps to be a group of four muscles. In either case, the prefix quad- refers to four. One example of this is the quadriceps, a group of four muscles located on the anterior (front) thigh. Other examples include the biceps brachii and the triceps brachii. The prefix bi indicates that the muscle has two origins and tri indicates three origins.
• The last feature by which to name a muscle is its action. When muscles are named for the movement they produce, one can find action words in their name. Some examples are flexors (decrease the angle at the joint), extensors (increase the angle at the joint), abductors (move the bone away from the midline), or adductors (move the bone toward the midline).