Chapter 11. The Muscular System

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 11.31, Figure 11.32, and Table 11.31).

 

The top panel shows the anterior view of the human body with the major muscles labeled. The bottom panel shows the posterior view of the human body with the major muscles labeled.

Figure 11.31 – Overview of the Muscular System: On the anterior and posterior views of the muscular system above, superficial muscles (those at the surface) are shown on the right side of the body while deep muscles (those underneath the superficial muscles) are shown on the left half of the body. For the legs, superficial muscles are shown in the anterior view while the posterior view shows both superficial and deep muscles.

 

This table shows two examples of muscle names and how to translate them based on their Latin roots. The first row uses abductor digiti minimi as an example. The word abductor comes from the Latin roots ab, which means away from, and duct, which means to move. Therefore an abductor is a muscle that moves away from something. The word digiti comes from the Latin root digititus, which means digit and refers to a finger or toe. The word minimi comes from the Latin root minimus, which means minimum, tiny, or little. Therefore, the abductor digiti minimi is a muscle that moves the little finger or toe away. The second row uses the adductor digiti minimi as an example. The word adductor comes from the Latin root ad, which means to or toward, and duct, which means to move. Therefore an adductor is a muscle that moves toward something. As with the abductor digiti minimi, digiti refers to a finger or toe and minimi refers to something that is little. Therefore the adductor digiti minimi is a muscle that moves the little finger or toe forward.

Figure 11.32: Here are two examples of how root words describe the location and function of muscles

Mnemonic Device for Latin Roots (Table 2)
Example Latin or Greek Translation Mnemonic Device
ad to; toward ADvance toward your goal
ab away from n/a
sub under SUBmarines move under water.
ductor something that moves A conDUCTOR makes a train move.
anti against If you are antisocial, you are against engaging in social activities.
epi on top of n/a
apo to the side of n/a
longissimus longest “Longissimus” is longer than the word “long.”
longus long long
brevis short brief
maximus large max
medius medium “Medius” and “medium” both begin with “med.”
minimus tiny; little mini
rectus straight To RECTify a situation is to straighten it out.
multi many If something is MULTIcolored, it has many colors.
uni one A UNIcorn has one horn.
bi/di two If a ring is DIcast, it is made of two metals.
tri three TRIple the amount of money is three times as much.
quad four QUADruplets are four children born at one birth.
externus outside EXternal
internus inside INternal

Table 11.31

 

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.

  • 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.
  • 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).
  • 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—brevis (short), longus (long)
  • Some muscles indicate their positions relative to the midline: lateralis (to the outside away from the midline), and medialis (toward the midline).
  • The direction of the muscle fibers and fascicles are used to describe muscles. For example, the abdominal muscles all indicated the direction of the fibers such as the rectus (straight), the obliques (at an angle) and the transverse (horizontal) muscles of the abdomen.
  • Some muscle names indicate the number of muscles in a group. One example of this is the quadriceps, a group of four muscles located on the anterior (front) thigh.
  • Other muscle names can provide information as to how many origins a particular muscle has, such as the biceps brachii. The prefix bi indicates that the muscle has two origins and tri indicates three origins.
  • 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.
  • 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).

Chapter Review

Muscle names are based on many characteristics. The location of a muscle in the body is important. Some muscles are named based on their size and location, such as the gluteal muscles of the buttocks. Other muscle names can indicate the location in the body or bones with which the muscle is associated, such as the tibialis anterior. The shapes of some muscles are distinctive; for example, the direction of the muscle fibers is used to describe muscles of the body midline. The origin and/or insertion can also be features used to name a muscle; examples are the biceps brachii, triceps brachii, and the pectoralis major.

 

Review Questions

Critical Thinking Questions

1. Describe the different criteria that contribute to how skeletal muscles are named.

Glossary

abductor
moves the bone away from the midline
adductor
moves the bone toward the midline
bi
two
brevis
short
extensor
muscle that increases the angle at the joint
flexor
muscle that decreases the angle at the joint
lateralis
to the outside
longus
long
maximus
largest
medialis
to the inside
medius
medium
minimus
smallest
oblique
at an angle
rectus
straight
tri
three

Solutions

Answers for Critical Thinking Questions

  1. In anatomy and physiology, many word roots are Latin or Greek. Portions, or roots, of the word give us clues about the function, shape, action, or location of a muscle.