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Deltoid muscle
 
 
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In human anatomy
Human anatomy

Human anatomy, which, with physiology and biochemistry, is a complementary basic medical science is primarily the scientific study of the morphology of the adult human body....
, the deltoid muscle is the muscle
MUSCLE

MUSCLE is public domain, multiple sequence alignment software for protein and nucleotide sequences.MUSCLE is integrated into UGENE bioinformatics tool as a plugin....
 forming the rounded contour of the shoulder
Shoulder

In human anatomy, the shoulder joint comprises the part of the body where the humerus attaches to the scapula. The shoulder refers to the group of structures in the region of the joint....
.

It was previously called the Deltoideus and the name is still used by some anatomists. It is called so because it is in the shape of the Greek
Greek alphabet

The Greek alphabet is a set of twenty-four letters that has been used to write the Greek language since the late 9th century BC or early 8th century BCE....
 letter Delta
Delta (letter)

Delta is the fourth letter of the Greek alphabet. In the system of Greek numerals it has a value of 4. It was derived from the Phoenician alphabet Dalet , but in the Ancient Greek language, it represented a voiced dental plosive ....
 (triangle).

The deltoid is a frequent site to administer intra-muscular injections.

rises in three distinct sets of fibers:



this extensive origin the fibers converge toward their insertion, the middle passing vertically, the anterior obliquely backward and laterally, the posterior obliquely forward and laterally; they unite in a thick tendon
Tendon

A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension . Tendons are similar to ligaments except that ligaments join one bone to another....
, which is inserted into the V-shaped deltoid tuberosity
Deltoid tuberosity

The deltoid tuberosity is the region on the shaft of the humerus to which the deltoid muscle attaches....
 on the middle of the lateral
Human anatomical terms

Human anatomical terms make up a distinct Scientific classification to describe areas of the body, to provide orientation when describing parts of human anatomy, and to distinguish different movements of the body....
 aspect of the shaft of the humerus
Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow.Anatomically, it connects the scapula and the ulna, and consists of the following three sections:...
.






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In human anatomy
Human anatomy

Human anatomy, which, with physiology and biochemistry, is a complementary basic medical science is primarily the scientific study of the morphology of the adult human body....
, the deltoid muscle is the muscle
MUSCLE

MUSCLE is public domain, multiple sequence alignment software for protein and nucleotide sequences.MUSCLE is integrated into UGENE bioinformatics tool as a plugin....
 forming the rounded contour of the shoulder
Shoulder

In human anatomy, the shoulder joint comprises the part of the body where the humerus attaches to the scapula. The shoulder refers to the group of structures in the region of the joint....
.

It was previously called the Deltoideus and the name is still used by some anatomists. It is called so because it is in the shape of the Greek
Greek alphabet

The Greek alphabet is a set of twenty-four letters that has been used to write the Greek language since the late 9th century BC or early 8th century BCE....
 letter Delta
Delta (letter)

Delta is the fourth letter of the Greek alphabet. In the system of Greek numerals it has a value of 4. It was derived from the Phoenician alphabet Dalet , but in the Ancient Greek language, it represented a voiced dental plosive ....
 (triangle).

The deltoid is a frequent site to administer intra-muscular injections.

Origin

It arises in three distinct sets of fibers:

  • Anterior fiber: from the anterior border and upper surface of the lateral clavicle.
  • Middle fibers: from the lateral margin and upper surface of the acromion
  • Posterior fibers: from the lower lip of the posterior border of the spine of the scapula, as far back as the triangular surface at its medial end


Insertion

From this extensive origin the fibers converge toward their insertion, the middle passing vertically, the anterior obliquely backward and laterally, the posterior obliquely forward and laterally; they unite in a thick tendon
Tendon

A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension . Tendons are similar to ligaments except that ligaments join one bone to another....
, which is inserted into the V-shaped deltoid tuberosity
Deltoid tuberosity

The deltoid tuberosity is the region on the shaft of the humerus to which the deltoid muscle attaches....
 on the middle of the lateral
Human anatomical terms

Human anatomical terms make up a distinct Scientific classification to describe areas of the body, to provide orientation when describing parts of human anatomy, and to distinguish different movements of the body....
 aspect of the shaft of the humerus
Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow.Anatomically, it connects the scapula and the ulna, and consists of the following three sections:...
. At its insertion the muscle gives off an expansion to the deep fascia
Deep fascia

Deep fascia is a layer of fascia which can surround individual muscles, and divide groups of muscles into compartments.Examples include:* Fascia lata...
 of the arm.

Action

When all its fibers contract simultaneously, the deltoid is the prime mover of arm abduction along the frontal plane. The arm must be internally rotated. This makes the deltoid an antagonist muscle of the pectoralis major and latissimus dorsi during arm adduction.

The anterior fibers are involved in shoulder abduction when the shoulder is externally rotated. The anterior deltoid is weak in strict transverse flexion but assists the pectoralis major during shoulder transverse flexion / shoulder flexion (elbow slightly inferior to shoulders).

The posterior fibers are strongly involved in transverse extension particularly since the latissimus dorsi is very weak in strict transverse extension. The posterior deltoid is also the primary shoulder hyperextensor.

The lateral fibers are involved in shoulder abduction when the shoulder is internally rotated, are involved in shoulder flexion when the shoulder is internally rotated, and are involved in shoulder transverse abduction (shoulder externally rotated) -- but are not utilized significantly during strict transverse extension (shoulder internally rotated).

Training

Bench Press
The deltoid muscle has three sections, the front head, the side head and the rear head. These heads have different actions and so need different strength training
Strength training

Strength training is the use of resistance to muscular contraction to build the physical strength, Anaerobic exercise and Muscle hypertrophy of skeletal muscles....
 exercises to completely train the whole of the muscle.

  • The Front deltoid is used in all pressing movements, such as the bench press
    Bench press

    The bench press is a strength training exercise in which, while lying on his back, the person performing the bench press lowers a weight to the level of the chest, then pushes it back up until the arm is straight and the elbows locked ....
    , and can be trained adequately without any isolation movements. However for isolation front dumbbell raises are the most commonly used.


  • The middle head of the deltoid is the main abductor at the gleno-humeral joint (shoulder) and is commonly trained using side lateral raises (also known as the shoulder fly
    Fly (exercise)

    A fly is a strength training exercise in which the hand and arm move through an range of motion while the elbow is kept at a constant angle. Flies are used to work the muscles of the Torso....
    ). The middle head also benefits from overhead pressing movements.


  • The rear head of the deltoid is best trained with bent-over dumbbell laterals (an inverted fly
    Fly (exercise)

    A fly is a strength training exercise in which the hand and arm move through an range of motion while the elbow is kept at a constant angle. Flies are used to work the muscles of the Torso....
    )


The Deltoid is a classical example of a multipennate
Pennate muscle

A pennate muscle is a muscle with fascicles that attach obliquely to its tendon. These types of muscles generally allow better stabilization and force production but less flexibility....
 muscle.

The middle fibres of the muscle arise in a bipenniform manner (like a bird's feather) from the in number, which pass upward from the insertion of the muscle and alternate with the descending septa. The portions of the muscle arising from the clavicle and spine of the scapula are not arranged in this manner, but are inserted into the margins of the inferior tendon.

Additional images


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