The 9 muscles of the arm (classified and explained)

Summary of the most important types of arm muscles, with their characteristics and functions.

What we commonly refer to as the arm is actually the entire upper extremity, consisting of the arm and forearm being anatomically precise.

The muscles of the arms and forearms allow us to perform everyday actions such as writing, picking up an object, pointing, holding a weight and many more. Our upper extremities are capable of many movements without which human life would be very different.

Here we will see what the muscles of the arm and forearm the muscles of the arm and forearmWe will discover them below, all of them involved in the manual tasks of our daily life.

The muscles of the arm and forearm

The muscles of the arm and forearm can be classified according to different criteria. In this article we are going to explain the muscles of the upper extremity according to their position but, also, it is usual to find them differentiated according to whether they are short or long, which allows the muscles to have one or the other movement.

But before going into detail on what the muscles of the arm are, we must first understand that what we commonly call the arm is not anatomically correct. The arm in its popular sense corresponds to the human upper extremity in the anatomical sense, since terminologically speaking correctly the arm is the upper limb.Terminologically speaking correctly the arm is only part of our upper extremities. Thus we can say that the human upper extremities can be divided into two:

• Arm: region extending from the clavicle to the elbow.
• Forearm: region extending from the elbow to the wrist.

Within these two anatomical regions we can differentiate in turn two other parts:

Anterior face of the arm and forearm.

The anterior aspect of the arm and forearm is the one located on the palm side of the hand.. To see the anterior part of your upper extremities you only need to place your arms close to your trunk, with the palms of your hands facing upwards. By doing this simple exercise you will be seeing the front side of your arms and forearms.

Back of the arm and forearm

The back of the arm and forearm is the part that is on the side of the back of the hand.. To see the back of your limbs just place your arms as before but with the palms facing down.

Types of arm muscles

In the arm itself we can find two groups of muscles: the muscles of the anterior aspect and the muscles of the posterior aspect.. The muscles of the anterior aspect are responsible for flexion movements, while those of the posterior aspect are responsible for contraction (contractor muscles). These Muscle groups are called antagonistic or antagonistic to each other because when an anterior muscle flexes, the posterior muscle contracts.

1. Anterior arm muscles

The main anterior arm muscles are the following.

1. 1. Biceps brachii

The biceps brachii is a muscle that extends from the clavicle to the elbow, at the intertubercular groove of the humerus.. Its main functions are rotation of the forearm and flexion of the forearm at the elbow. The biceps brachii is a very bulky muscle that, when contracted, can be easily observed. It consists of two parts or "heads" (hence the name biceps): the short portion of the biceps and the long portion of the biceps.

1.2. Brachialis

This muscle is located at a deeper level than the biceps brachii and has a smaller size than the biceps brachii.. Its shape is broad and flattened. The brachialis is the main flexor muscle of the forearm over the upper arm.

1.3. Coracobrachialis

The coracobrachialis is a thick, prismatic muscle that occupies the space from the scapula to the biceps through the short portion of the biceps brachii. This muscle specializes more in fast movements than in generating force, something that is done by theThis muscle specializes more in fast movements than in generating force, something that the much more voluminous biceps takes care of. The main function of the coracobrachialis is to elevate the arm keeping the shoulder low, balancing the movement of the arm and restoring the anatomical position.

2. Posterior arm muscles

As for the posterior muscles of the upper arm, the two main ones are as follows:

2.1. Triceps brachii.

This muscle occupies most of the posterior region of the upper arm.. As its name suggests, the triceps is made up of three portions or "heads": the long portion and the vastus internus and externus. The main function of this movement is antagonistic to that of the biceps, being in charge in this case of the extension of the forearm over the elbow.

2.2. Anconius muscle

The anconeus muscle is small and triangular in shape, and contacts the triceps and the elbow at its proximal extremity.. It cooperates with the triceps brachii during the extension of the forearm over the elbow.

3. Muscles of the forearm

The muscles found in the forearm can be classified into the following three groups.

• Flexors of the fingers: on the anterior aspect of the forearm.
• Finger extensors: on the posterior aspect of the forearm.
• Supinators or external rotators of the forearm: on the radial border, towards the thumb.

3.1. Muscles of the front of the forearm

The list of the muscles of the anterior forearm is as follows. is as follows.

• Pronator teres muscle
• Pronator quadratus muscle
• Radial flexor carpi radialis muscle
• Palmaris longus muscle
• Ulnar flexor carpi ulnaris muscle
• Superficial flexor digitorum muscle
• Deep flexor digitorum muscle
• Long flexor muscle of the thumb

Among them we can highlight the following.

3.1.1. Deep flexor muscle of the fingers

The deep flexor muscle of the fingers, together with the superficial common flexor of the fingers of the hand, allows to flex the fingers, except for the thumb.except for the thumb. This muscle has an associated long tendon that runs along the forearm and crosses the carpal tunnel until it inserts on the palmar side of the phalanges of the fingers.

3.1.2. Superficial flexor muscle of the fingers

The flexor digitorum superficialis muscle, together with the previous one, allows flexion of the fingers, specifically flexion of the middle phalanx over the proximal phalanx and the hand over the forearm..

3.2. Muscles of the posterior part of the forearm

The list of the muscles of the back of the forearm is as follows:

• Extensor digitorum muscle
• Ulnar extensor carpi ulnaris muscle or posterior ulnar muscle.
• Abductor pollicis longus muscle
• Extensor pollicis brevis muscle
• Extensor pollicis longus muscle
• Index extensor muscle
• Short palmar muscle or palmar cutaneous muscle

Of all these muscles, most notable is the extensor digitorum extensor muscle..

The extensor digitorum muscle runs along the entire forearm, going from the elbow to the dorsal part of the wrist where it is associated with four tendons, passing through them to the second (index), third (middle or middle), fourth (ring) and fifth (little) fingers of the hand, all except the thumb. This muscle is responsible for the extension of the wrist and the proximal phalanx of the fingers, although it is also slightly involved in the extension of the arm.

3.3. Lateral forearm muscles

Finally it is time to talk about the lateral muscles of the forearm. Among them we find:

• Supinator brevis muscle
• First radial or long radial
• Second radial or short radial
• Supinator longus muscle

The most notable muscle in this region is the supinator longus muscle..

This is located on the upper outer part of the forearm, near the elbow. This muscle helps rotate the forearm both externally and internally. Depending on the arrangement of the elbow, different movements can be made, giving the forearm a great variety of movements.