WHAT IS MYOLOGY? MAIN FEATURES - ANATOMY AND PHYSIOLOGY - 2025

The myology is the branch of anatomy that is responsible for the study of muscle tissues. Two main subdivisions of myology are distinguished: animal and human.

Muscles are varied in form and function. In the case of humans, the muscles are elongated in the extremities, which makes them provide protection to the joints. On the other hand, in the trunk they are wide and flat, and they line the thoracic cavity.

Depending on their function, one can speak of flexor muscles, which allow flexing (such as the biceps), or extensors, which allow extending (such as the triceps), among other purposes. All this is a reflection that the object of study of myology is quite broad.

It can be said that the object of this science includes the study of the functions of the muscles, their classification, the location of the point of origin and insertion, the conditions that they may suffer, among other aspects.

Animal myology

In animals, two primary levels of organization can be distinguished: vertebrates and invertebrates.

In vertebrates, the musculature covers the bones of the skeleton and gives them strength and protection. Most of the muscles are attached to the bones through tendons.

With regard to invertebrates, two classifications can be established: soft invertebrates and invertebrates with a chitin-covered body.

Soft ones, like caterpillars, are made up of muscular tissues that are organized in cylindrical layers. The contractions of this tissue is what allows these animals to move.

In chitin-bodied invertebrates, such as insects, the muscles attach directly to the "skeletal" structure of the animal. This gives them strength.

For example, a grasshopper can travel a great distance with a single jump thanks to the muscles present in its limbs.

Types of muscles in vertebrates

Muscles in vertebrates can have various forms and functions from one animal species to another.

However, three main classes of muscles can be distinguished in animals: spindle, flat, and orbicular.

- Spindle muscles

The fusiform muscles are those that have an elongated shape. In the center they are wide, while at the ends they are thin. These muscles are typical of the extremities.

- Flat muscles

The flat muscles reach a greater extension than the fusiform ones. These are the ones that cover areas like the head and trunk.

- Orbicular muscles

Orbicularis muscles are circular and hollow in shape. They are found around the mouth, in the eyes and in the anus, among other areas.

Human myology

In humans, various types of muscles can be distinguished according to their histological characteristics, their dimensions, and their function.

According to its histological characteristics

In humans, three types of muscles are distinguished according to their histological characteristics: smooth, striated, and cardiac. The latter is a combination of the first two.

- Smooth muscle

Smooth muscle is made up of elongated cells. One characteristic of these muscles is that they shorten when contractions occur. When they relax they return to their natural size.

Smooth muscles are connected to the autonomic nervous system. This means that the movements of these muscles are involuntary.

They are typical of hollow organs, such as blood vessels and the digestive tract. They are also found in some areas of the skin.

- Striated muscle

Striated muscles are made up of elongated cells, joined together in a way that creates a structure called the muscle fiber. This type of tissue is what covers the bones.

Unlike what happens with smooth muscle tissue, striated muscle movements are part of the peripheral system. This means that they are made at the individual's will.

- Cardiac muscle

The heart muscle takes elements from the tissues already mentioned. Like the striatum, it is made up of cells that are organized into a kind of fiber.

However, the movements of the heart muscle are automatic and involuntary, as is the case with smooth tissue. This type of muscle is found in the layer of the heart called the myocardium.

According to its dimensions

According to their shape, the muscles can be long, flat and short.

- Long muscle

As the name implies, this type of muscle is characterized by its length. They are those that are found in both the upper and lower extremities.

- Flat muscle

The flat muscle is characterized by its extension, since they cover large areas. These are mainly found on the trunk and abdomen.

Some examples of flat muscles are the trapezius, the dorsal muscle that runs from the neck to the middle of the back; and the abdominal muscle, which is found in the lower part of the trunk.

According to its function

According to their function, six types of muscles can be differentiated: rotators, fixators, abductors, adductors, flexors and extensors.

- Rotators

An example of these is the quadratus muscle, which is located on top of the femur. It intervenes in the rotation of the thigh outwards.

The peroneus anterior is also a rotator muscle, which allows the foot to be rotated.

- Fixers

Among the fixing muscles, the crural quadriceps stands out, which is attached to the tibia; and the serratus major muscle, which allows the shoulder blade to be fixed and rotated.

- Abductors

Between the abductor muscles, the peroneus brevis protrudes, which acts as an abductor of the foot; and the supraspinatus muscle, which is the abductor of the arm.

- Adductors

One of the most important adductor muscles is the mediated adductor muscle, which is not only involved in adduction of the thigh, but also allows it to be flexed and rotated.

The coracobrachialis muscle also stands out, which is involved in the adduction of the arm, as well as its rotation and flexion.

- Flexors

The flexor muscles include the palmar major muscle and the anterior ulnar muscle, which are involved in flexing the wrist. The gluteus minimus muscle also stands out, which allows the pelvis to flex.

- Extenders

There are two very important extensor muscles: the posterior ulnar muscle, which is involved in the extension of the wrist; and the extensor muscle of the toes, which allows to extend the toes when the foot is not resting on a surface.

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