Video: How are muscles named?

Fidget! Pepper! Corky! Blob! Dot! Patch! Lucky! Think it's difficult to memorize the names of the 101 Dalmatians? Try wrapping your brain around 640 muscles of the human body. Thankfully, the anatomists who invented muscle names weren't the most creative. Most muscles are usually named by their appearance, location, and attachments. Oh, and if you know Latin and a little bit of Greek too – major bonus. But don't worry, understanding how these muscles get their names will actually help us remember them. Alrighty, then, let's find out how these muscles get their names.

In today's tutorial, we'll be taking a closer look at why and how muscles are named in order to make it easier to identify each muscle and remember them. We'll take a look at some basic methods used to name a muscle which usually consider one or more of the following characteristics – shape, size, orientation of fibers, action, number of attachments, points of attachment, and location. We'll talk a little about each of these as we go along.

So starting at the beginning, let's look at muscles that derive their name from their shape. You may have come across this muscle before. This is our deltoid muscle. As you can see, this muscle is triangular in shape. If you happen to know your Greek alphabet well, you'll know that the Greek letter delta when written is shaped like a triangle, and therefore, gives rise to the name deltoid.

Another muscle that is named after its shape is the orbicularis oculi muscle. This is the pepperoni-like muscle that encircles your eye. Orbicularis is the Latin word for circular, perfectly describing the shape of this muscle. The same applies for the orbicularis oris muscle, which circles around the circumference of our lips.

The rhomboid muscles of the back are also named for their shape. The Greek word, rhombus, describes a parallelogram shape characteristic of the two rhomboid muscles, thus giving them their names rhomboid major and minor.

The next muscle is slightly different. The morphology of a muscle with its regard to its dimensions can also be used to derive the name of a muscle, and in this case, we're looking at a muscle whose main attribute is its flatness. The Greek word platus means flat and wide, thus giving this delicate flat muscle the name platysma. See what I mean? Not the most creative, but it makes things a little easier for us when we're trying to remember these names.

Moving on to the serratus anterior muscle, we can see that the anterior attachments of the muscle are shaped like the beveled edge of a saw and that's exactly where this muscle gets its name as the Latin word serrare means saw.

We've met a few muscles that are named after their shapes. Now, we'll take a look at some that are named after their size.

On the anterior aspect of the thigh, we meet the three vastus muscles. If you know your Latin well, you already know that these muscles are going to be pretty significant as vastus in Latin translates to great. As predicted, the three vastus muscles travel down the length of the thigh resulting in three large or great muscles.

Another way to describe how large a muscle is in comparison to another is by using the term major. For example, pectoralis major, the large chest muscle, has a sister muscle known as pectoralis minor. I wonder which is the bigger of the two. That's right – it's pectoralis major.

The terms maximus and minimus can also be used to describe the size of a muscle. Maximus comes from the Latin, meaning, largest or greatest. As we can see here, the gluteus maximus muscle is the largest muscle in the gluteal region, hence, the use of the word maximus. The term minimus is the Latin word for least or smallest. We can see it being used here for the gluteus minimus muscle, which is the smallest of the three gluteal muscles, or in the case of the hand, the flexor digiti minimi muscle, which flexes the little finger.

Muscle names can also be derived by their relative length. The word longus is used for long muscles such as the longus capitis muscle, a long muscle attached to the head, while the term brevis which is the Latin word for short is used to describe shorter muscles such as the abductor pollicis brevis muscle, a short muscle of the thumb.

Muscles can also be named after their fiber orientation. This is the direction in which the muscle fibers lie. Muscle fibers can lie in a transverse, oblique, or rectus position. Let's explore what these mean. The term transverse which is used in the naming of the transverse muscle of the tongue is used to describe muscle fibers that run perpendicular to the midline. The term oblique is used to describe muscle fibers that run diagonally at an angle or a slant. Here we can see the external abdominal oblique muscle whose fibers run in an oblique direction. And finally, the term rectus describes muscle fibers that run parallel to the midline such as in the case of the rectus abdominis muscle, which is seen here.

The word rectus in Latin means straight and can be used to describe a muscle that runs in a linear direction. For example, in this bird's eye view of the eye, we can see the straight muscle fibers of the superior rectus muscle, which is one of the four rectus muscles that controls the movement of the eye.

Moving on, let's take a look at some muscles that are named by their actions. These muscle names are very helpful as they give us an idea of the movements that they carry out. I'm not going to bore you with every movement, but let's just take a look at a few. Muscles can be described as flexors or extensors like the flexor hallucis brevis muscle, which flexes the great toe, or the extensor digiti minimi muscle that extends the little finger. Supinators or pronators include the supinator muscle, which supinates the forearm on contraction, and the pronator teres muscle, which pronates the forearm. Some muscles named after their action are not so obvious, however. Take the risorius muscle, for example. It is also known as the smiling muscle as risus in Latin means laugh or smile. When this muscle contracts, it pulls the corner of the mouth upwards creating a smile and is used in laughing.

There are many more examples of muscles that are named by their actions such as the adductor pollicis muscle that adducts the thumb or the pyloric sphincter muscle, which constricts the pyloric orifice of the stomach on contraction, but I think you probably get the picture.

We've had a look at some of the many muscles that are named after their actions, so now we're going to take a look at muscles that derive their name from the number of heads or bellies. A well-known muscle, the biceps brachii muscle, is a great example of this. The term bicep comes from the Latin meaning two-headed. Bi- translates to two while cep- is borrowed from the Greek word cephalus or kephalos which means head. Similarly, on the posterior surface of the arm, we meet the triceps brachii muscle, which has three heads. Following on from this logic, we finally meet the quadriceps femoris muscle, which – can you guess? – has four heads.

Muscle names can also give us a clue to the attachments from which the muscle arises. For example, the sternohyoid muscle of the neck extends from the posterior surface of the manubrium of the sternum to the body of the hyoid bone. Sometimes, a muscle name can give us a lot more information than we realize.

Finally, we're going to take a look at one final way in which a muscle can be named and that is according to its location in the body. The tibialis anterior muscle is named after its location over the tibia bone of the leg.

Muscles can also be named by their position or location in relation to other muscles and structures. For example, muscles can be described as being inferior to a muscle or structure such as the infrahyoid muscle group. All of these muscles are located inferior to or beneath the hyoid bone. Supra- indicates that a muscle is superior or more cranial to another muscle or structure; for example, the supraspinatus muscle. This muscle sits superior to the spine of the scapula compared to its counterpart, the infraspinatus muscle.

Muscles can also be described as medialis, intermedius, and lateralis. A great example of these is the vastus muscles – vastus medialis, vastus intermedius, and vastus lateralis. This describes their positioning in relation to the midline. Medialis meaning closer to the midline, intermedius meaning intermediate, and lateralis or lateral meaning to the side or away from the midline.

That brings us to the end of the tutorial. Let's wrap up with a quick summary to go over the seven different ways muscles are named.

We began this tutorial with looking at muscles that are named according to their shape. We met the triangular deltoid muscle, the circular orbicularis oculi muscle, the flat platysma muscle, and the saw-like serratus anterior muscle. Muscles that were named after their size came next. We met the great vastus muscles, pectoralis major and minor, gluteus maximus and minimus, as well as the long longus muscle and the short brevis muscles.

Muscles can also be named by their fiber orientation. We explored the transverse, oblique, and rectus fiber types and their associated muscles. Next, we met many muscles that are named after their actions. The flexors and extensors of the foot and forearm, abductors and adductors of the thumb, the supinators and pronators of the forearm, and sphincter muscles were explored here. Muscles named after their number of origins came next. Biceps brachii was seen to have two origins, triceps brachii three heads, and the quadriceps femoris muscle which has four heads.

As we have seen, muscles can also be named after their origins and insertions such as the sternohyoid muscle which originates from the sternum and inserts onto the hyoid bone. Finally, we met muscles that are named after their locations such as the anterior tibial muscle.

That brings us to the end of today's tutorial. I hope this tutorial has helped you remember your muscle names.