Lesson 14B: Skeletal Muscle Anatomy

Skeletal Muscle Anatomy

The ideas below are not module objectives, but rather these are concepts that you will hopefully feel more comfortable with after reviewing this lesson:

• Describe the criteria used to name skeletal muscles, and explain how understanding the muscle names helps describe shapes, location, and actions of various muscles.

• Label and practice gross muscle anatomy.

Use the images and video below as an overview to muscles, but note not all muscles shared in the drawings and video are required for our class. For required details, refer to additional images below and list of items in your lab applications.

Naming Skeletal Muscles

The Greeks and Romans conducted the first studies done on the human body in Western culture. The educated class of subsequent societies studied Latin and Greek, and therefore the early pioneers of anatomy continued to apply Latin and Greek terminology or roots when they named the skeletal muscles. The large number of muscles in the body and unfamiliar words can make learning the names of the muscles in the body seem daunting, but understanding the etymology can help. Etymology is the study of how the root of a particular word entered a language and how the use of the word evolved over time. Taking the time to learn the root 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 (Figure 14B) and what they do. Pronunciation of words and terms will take a bit of time to master, but after you have some basic information; the correct names and pronunciations will become easier.

Figure 14B: 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. (Image courtesy of OpenStax.)

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, its size compared to other muscles in the area, its location in the body or the location of its attachments to the skeleton, how many origins it has, or its action.

The skeletal muscle’s anatomical location or its relationship to a particular bone often determines its name. For example, the frontal belly of the occipitofrontalis muscle, also referred to as the frontalis, is located on top of the frontal bone of the skull. Similarly, the shapes of some muscles are very distinctive and the names, such as orbicularis, reflect the shape. For the buttocks, the size of the muscles influences the names: gluteus maximus (largest), gluteus medius (medium), and the gluteus minimus (smallest). Names were given to indicate length—brevis (short), longus (long)—and to identify position 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 relative to the midline, such as the rectus (straight) abdominis, or the oblique (at an angle) 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 flexor (decreases the angle at the joint), extensor (increases the angle at the joint), abductor (moves the bone away from the midline), or adductor (moves the bone toward the midline).

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 sternocleidomastoid, biceps brachii, and triceps brachii.

Videos

The following YouTube videos provide an overview of the muscles of the body. I highly recommend that you view them. Notice the first one only shares a basic look at muscles and groups them into general or broad categories (for instance, simply bicep for biceps brachii or quadriceps for rectus femoris, vastus lateralis, vastus medialis, vastus intermedius). The second one presents muscles that are named based on certain categories; even though not every muscle is shared, this information can be applied to all muscles covered in our class allowing for solid connections and recall. Pay particular attention to the muscles that you have been asked to learn (refer to your assignment list). Be sure that you have your audio turned on. Closed captioning is available.

Major Muscles of the Human Body (4:02)

How are muscles named? - Terminology - Human Anatomy | Kenhub (11:30)