Muscles of the head

Muscles of the shoulder

The shoulder is composed of several bony structures, ligaments, bursae and muscles. The shoulder joint muscles, also known as the rotator cuff, are primarily responsible for the mobility of the shoulder. As the name suggests, this rotator cuff ensures that the shoulder can rotate and is mobile in almost any spatial plane.

The shoulder muscles include the supraspinatus muscle. This originates from the upper part of the shoulder blade and extends from here to the head of the upper arm bone (humerus). If the supraspinatus muscle is tensed, it ensures that we can stretch the upper arm out to the side, for example if we have to lift the arm around another person and have to lift it first.

The next muscle that is important for guiding the shoulder is the muscle infraspinatus. This originates at the lower part of the shoulder blade (scapula) and from here also pulls to the head of the humerus. When tensed (contracted), this muscle ensures that we can rotate the upper arm outwards.

The third muscle of the shoulder muscles is the muscle teres minor. This muscle originates at the outer edge of the shoulder blade and also moves from here to the head of the upper arm bone. When the muscle teres minor is tensed, the shoulder and thus the upper arm rotates outwards and in addition the upper arm is pulled back to the body.

The last muscle of the shoulder muscles is the subscapularis muscle. This muscle originates on the inside of the shoulder blade, i.e. it does not lie on the outside of the shoulder blade, but is hidden between the shoulder blade and the ribs. This muscle also moves from the shoulder blade to the head of the humerus. The subscapularis muscle serves as a sliding rail so that the shoulder blade and the ribs are not too close together, and the upper arm can be rotated inwards by tensing the muscle, for example if you want to close the zipper of your jacket and have to turn your arm inwards first.