The musculus deltoideus belongs to the shoulder muscles. It is involved in all motions of the shoulder joint and encloses it entirely.
Musculus deltoideus – location
The musculus deltoideus consists of three muscle parts:
- The pars clavicularis (front part),
- the pars acromialis (middle part), and
- the pars spinalis (back part).
All parts of the deltoid muscle have different origins. The pars clavicularis originates from the collarbone (clavicula), the pars acromialis begins at the acromion, and the pars spinalis comes from the spina scapulae. All parts of the musculus deltoideus insert into the upper-outer part of the humerus (tuberositas deltoidea)
Musculus deltoideus – function
- The front part of the musculus deltoideus moves the arm to the front (anteversion), pulls the arm toward the body (adduction), and rotates it to the inside.
- The middle part abducts the arm from the body. With increasing abduction the other parts of the deltoid muscle are involved as well.
- The back part moves the arm to the back (retroversion), moves the arm toward the body (adduction), and rotates it to the outside.
Musculus deltoideus – importance and training
The musculus deltoideus gives the shoulder its round shape and encloses it entirely. The shoulder has a high mobility what is reached by a lack of bony stabilization. For that reason it requires an increased amount of muscular stabilization what is given by the deltoid muscle.
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