Arm muscles

Generality

The muscles of the arm are the muscles located in the anatomical region between the shoulder and the elbow and consisting of the bone called the humerus.

There are a total of 4 arm muscles: the biceps brachialis muscle, the brachialis muscle, the coracobrachialis muscle and the triceps brachialis muscle. The first three reside in the anterior portion of the arm, while the triceps brachialis muscle occupies the posterior portion of the arm.

The arm muscles allow human beings to perform supination movements of the forearm, elbow flexion, elbow extension and adduction of the humerus.

Like most muscles in the human body, arm muscles can also experience contractures, strains, tears and tendon inflammation / injury.

Brief anatomical reference to the muscles

The muscles of the human body have two ends: an initial or proximal call and one called terminal or distal .

At each end, there is a tendon . A tendon is a formation of fibrous connective tissue, which connects a muscle to a bone element.

Therefore, the muscles find insertion on the skeleton by means of the tendons.

The anatomical texts and experts have a tendency to identify the initial extremity and the terminal extremity of a muscle with the tendon present on each of these extremities.

In anatomy, proximal and distal are two terms with the opposite meaning.

Proximal means "closer to the center of the body" or "closer to the point of origin". Referring to the femur, for example, it indicates the portion of this bone closest to the trunk.

Distal, on the other hand, means "farther from the center of the body" or "farther from the point of origin". Referred (always to the femur), for example, it indicates the portion of this bone furthest from the trunk (and closer to the knee joint).

Definition of arm muscles

The muscles of the arm are the muscles whose fibers take place, totally or only partially, in the anatomo-skeletal section constituted by the humerus ; the humerus is the arm bone.

The fact that the aforementioned muscles reside in the anatomo-skeletal section constituted by the humerus does not necessarily imply their connection with the bone in question; in other words, there are muscles in the arm that do not interact in any way with the humerus.

BRIEF DEFINITION OF ARM

The arm is the anatomical region of the human body between the shoulder, in a proximal position, and the forearm, in a distal position.

On the border between shoulder and arm, there is a group of 5 joints, the most important of which is certainly the glenohumeral joint .

On the border between arm and forearm, however, there is only one articulation: the so-called elbow joint, resulting from the interaction between the humerus and the bones of the ulna forearm and radium .

BRIEF ANATOMICAL CALL OF THE HOMER

To understand the arrangement of the arm muscles, it is essential to bring to the attention of readers some anatomical features of the humerus.

The humerus is, in the human being, the even bone that makes up the skeleton of the arm . It belongs to the category of long bones and takes part in the formation of two important joints: the glenohumeral joint of the shoulder (humerus-scapula) and the elbow joint (humerus-radius-ulna).

Like all long bones, the humerus can be divided into three main portions: the proximal end (or proximal epiphysis), the body (or diaphysis) and the distal end (or distal epiphysis).

  • The proximal end of the humerus is the bone portion closest to the shoulder and which forms the glenohumeral joint. At the proximal end, there are at least 6 regions of a certain anatomical relevance: the head, the anatomical neck, the greater tubercle, the lesser tubercle, the intertubercular groove and the surgical neck.
  • The body is the central portion of the humerus, between the proximal end and the distal end. Initially cylindrical and then prismatic in shape, the body of the humerus has at least three anatomically interesting regions: the deltoid tuberosity, the nutritive hole and the radial groove.
  • The distal end of the humerus is the bone portion closest to the forearm and which forms the elbow joint. Proceeding from top to bottom, the anatomically relevant regions of the distal end of the humerus are: the medial supracondylar ridge, the lateral supracondylar ridge, the medial epicondyle, the lateral epicondyle, the coronoid fossa, the radial fossa, the olecranon fossa, troclea and capitulum .

Functionally, the humerus is important because:

  • It is a series of joints, such as the glenohumeral joint and the elbow, which are fundamental for all arm movements. Thanks to the joints formed by the humerus, the human being is able to perform complex gestures, such as throwing a javelin, or simple gestures, such as writing or lifting an object.
  • It receives the muscles that support the movements of the aforementioned joints: in its upper part, it houses the terminal heads of the muscles that originate in the bones of the shoulder; in its lower part, it gives rise to the muscular elements that end in the bones of the forearm.
  • In young children, it is a support for four-legged locomotion.

In anatomy, medial and lateral are two terms of opposite meaning, which serve to indicate the distance of an anatomical element from the sagittal plane . The sagittal plane is the anteroposterior division of the human body, from which two equal and symmetrical halves are derived.

Mediale means "near" or "closer" to the sagittal plane, while lateral means "far or" farther "from the sagittal plane.

Anatomy

There are a total of 4 arm muscles.

Based on their localization in the arm, the anatomists divide them into two categories: the muscles of the so-called anterior compartment of the arm, which reside in the anterior region of the arm, and the muscles of the so-called posterior compartment of the arm, which occupy the posterior region of the arm.

The muscles of the anterior arm compartment are 3: the biceps brachialis muscle, the brachialis muscle and the coracobrachialis muscle .

The muscles of the posterior compartment of the arm, on the other hand, is only one, namely the triceps brachialis muscle .

FRONT COMPARTMENT: BRACHIAL BOOTS

The biceps brachialis muscle is an example of a muscle that belongs to the arm but has no relation to the humerus.

Its proximal end has two heads (or heads ), better known as a long head and a short head ; its distal end, on the other hand, is unique.

The biceps brachii muscle covers at least two fundamental functions: it allows the supination of the forearm and allows the flexion of the elbow.

  • Proximal extremity: the short head originates at the level of the coracoid process of the scapula, while the long head originates at the level of the so-called supraglenoid tubercle of the scapula.
  • Distal end: attaches to the radial tuberosity, which is a bony prominence of radium, and to the so-called bicipital aponeurosis.
  • Innervation: up to the musculocutaneous nerve . The musculocutaneous nerve is one of the 5 nerves that derive from the so-called brachial plexus . The brachial plexus is an important reticular formation of several spinal nerves (which are nerves of the peripheral nervous system), which have the task of innervating not only the shoulder, but also the entire upper limb (therefore arm, forearm and hand) .

    The other 4 nerves arising from the brachial plexus are: the radial nerve, the axillary nerve, the median nerve and the ulnar nerve.

  • Spraying: it is up to the brachial artery . The brachial artery is the most important arterial blood vessel in the arm. It runs parallel to the nerve branches of the brachial plexus and, at the elbow, separates into a radial artery and an ulnar artery.

FRONT COMPARTMENT: BRACHIALE

Located deeper than the biceps brachialis, the brachialis muscle occupies a position in the arm, quite close to the elbow.

It covers two important functions: it supports the biceps brachialis muscle in the flexing action of the elbow and constitutes the floor of the anatomical region known as the cubital fossa.

The brachial muscle presents a head only at the proximal end and a head only at the distal end.

  • Proximal end: originates at the level of the antero-lateral surface of the body of the humerus, near the deltoid tuberosity of the latter.
  • Distal end: it engages on the ulna, precisely in the ulnar coronoid process and in the ulnar tuberosity.
  • Innervation: up to the musculocutaneous nerve.
  • Spraying: up to the recurrent radial artery . The recurrent radial artery is a branch of the radial artery, which originates from the latter just after the elbow. It also provides spraying of the brachioradial muscle.

FRONT COMPARTMENT: CORACOBRACHIAL

The coracobrachial muscle is a very small muscle, with one end only at the proximal end and one end only at the distal end.

In the arm, it is in a proximal position - so it is close to the shoulder - and passes through the armpit.

The coracobrachial muscle provides two functions: adduction of the humerus and flexion of the arm in the direction of the glenohumeral joint.

  • Proximal end: originates at the level of the coracoid process of the scapula.

    The coracobrachial muscle represents the smallest muscle, between the three muscular elements that start at the level of the coracoid process of the scapula (the other two are the aforementioned biceps brachial muscle and the minor pectoral muscle).

  • Distal end: it engages on the antero-medial region of the humerus body.
  • Innervation: up to the musculocutaneous nerve.
  • Spraying: it is up to the brachial artery.

BACK COMPARTMENT: BRACHIAL TRICEPS

The triceps brachialis muscle is a large muscular element, constituted, in its proximal end, by three heads (or heads). These heads are named: medial head ( medial head), lateral head (lateral head) and long head (or long head).

Antagonist of the biceps brachialis and brachialis muscles, the triceps brachialis muscle extends the elbow and contributes to the stability of the shoulder joints.

  • Proximal extremity: the long head originates at the level of the infraglenoid tubercle of the scapula; the lateral head originates just above the radial groove of the humerus; finally, the medial head finds its origin just below the radial groove of the humerus.
  • Distal end: hooks onto the olecranon of the ulna.
  • Innervation: it is up to some branches of the radial nerve . Arising from the brachial plexus, the radial nerve is that important peripheral nerve that arises in the armpit and runs, first, the arm and, then, the forearm.
  • Spraying: is for the deep brachial artery . The deep brachial artery is a branch of the brachial artery.

Functions

The arm muscles allow movements such as supination of the forearm, elbow flexion, extension of the elbow and adduction of the humerus .

SUPINATION OF THE HANGER

The supination of the forearm is the movement of rotation towards the outside of the forearm.

In the figure below, the supination movement of the forearm is shown, in comparison with the pronation movement (inward rotation).

ELBOW FLEX

Through the bending of the elbow, the human being approaches the forearm to the arm.

The figure below shows the elbow flexion.

ELBOW EXTENSION

Through the extension of the elbow, the human being removes the forearm from the arm. In other words, it extends the upper limb in the tract that goes from the humerus to the end of the forearm.

The figure below shows the extension of the elbow.

ADDUCTION OF THE HUMERUS

The adduction of the humerus is the movement that serves to bring the arm closer to the trunk. It is opposed to the abduction movement, which consists in moving the arm away from the trunk and positioning it perpendicularly to the latter.

The figure below shows the adduction movement of the humerus.

diseases

Like most muscles in the human body, arm muscles can also experience contractures, strains, tears and tendon inflammation / injury.

These injuries usually affect active people, such as those who practice sports.

SIGN OF ARM OF IRON OR SIGN OF POPEYE

Among the possible injuries to the muscles of the arm, there is the rupture of the long head of the biceps brachial muscle.

This problem is characterized by the appearance, approximately in the vicinity of the elbow, of a very particular swelling, which doctors call with the words of " sign of arm wrestling " or " Popeye sign ".

The rupture of the long head of the biceps brachialis muscle, as well as the rupture of all other tendons of the arm muscles, is a very rare injury.

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