Delta-shaped muscle


Latin: Deltoid muscle
English: deltoid muscle

Synergists: M. pectoralis major, M. biceps brachii, M. latissiums dorsi, M. triceps brachii
Antagonists: M. latissimus dorsi, M. triceps brachii, M. pectoralis major, M. biceps brachii


The delta-shaped muscle is an upper arm muscle, the shape of which is reminiscent of an upside-down Greek delta, which is why it gets its name. According to its origin, it is made up of three parts, one part from the outer clavicle, another part from the shoulder blade and a third part from the shoulder blade bone. As a triangular muscle, it surrounds the shoulder joint from the front, back, top and side. It is also known as the deltoid muscle and its different parts are involved in different arm movements.

Due to its location directly under the skin, the trisection can be easily recognized in slim and defined people. It is the largest muscle in the shoulder muscles.

The deltoid muscle is specifically trained in weight training.
Due to its tension, the deltoid muscle can move the arm in all directions of movement; its most important function is to raise the arm laterally, especially when it is spread over 90 °.


Approach: Humerus (Deltoid tuberosity - roughening of the humerus)


Pars claviculares: lateral third of the collarbone
Pars acromiales: Acromion - the bony process of the scapula
Pars spinales: originates on the spina scapulae - bony elevation of the shoulder blade

Innervation: Axillary nerve of the brachial plexus (segments C5-6)


The function of the Delta-shaped muscle varies depending on the activity of the different muscle parts. It enables the arm to move in all directions. The deltoid muscle (Musculus deltoideus) is formed by the vom Shoulder roof outgoing middle section to the main lifter of the arm.

Pars clavicularis - Clavicle portion:

  • Highlight (Anteversion) of the arm
  • Incentive (Adduction) from the arm
  • Internal rotation from the arm

Pars acromialis - Shoulder roof proportion:

  • Abspreitzung (Abduction) from the arm

Pars spinalis - Shoulder blade portion

  • Splay (Abduction) from the arm
  • External rotation from the arm
  • Lifting back (Retroversion) from the arm

Figure deltoid

Illustration of the deltoid muscle (Musculus deltoideus): right shoulder seen from behind (A) and from the side (B).

(Deltoid muscle)

  1. Deltoid -
    (1a. + 1b. + 1c.)
    Deltoid muscle
    1a. Posterior deltoid
    (Part of the bone) -
    Pars spinalis
    1b. Middle deltoid
    (Shoulder height part) -
    Pars acromialis
    1c. Anterior deltoid
    (Clavicle part) -
    Pars clavicularis
  2. Scapula bone -
    Spina scapulae
  3. Shoulder blade - Scapula
  4. Collarbone - Clavicle
  5. Upper arm shaft -
    Corpus humeri

You can find an overview of all Dr-Gumpert images at: medical illustrations

Common illnesses

The delta-shaped muscle is essentially involved in shoulder mobility. The shoulder joint is a predominantly muscular joint.
The so-called rotator cuff, a muscle group consisting of four muscles, plays a decisive role in the stability of the shoulder joint.
But even with degenerative changes in the tendons of the delta-shaped muscle, shoulder mobility and stability are restricted.
With paralysis of the axillary nerve, atrophy of the deltoid muscle often occurs.
In addition, the delta-shaped muscle plays a major role in various neurological diseases, such as neuralgic shoulder amyotrophy.