Back and Shoulder Muscles (Alizz Art)

Synonyms: deltoid muscle; trapezius muscle; latissimus dorsi muscle; infraspinatus muscle; teres major muscle

Summary

Deltoid muscle : What are deltoid muscles? Your deltoid muscles are in your shoulder, which is the ball-and-socket joint that connects your arm to the trunk of your body. Deltoid muscles help you move your arms in different directions. They also protect and stabilize your shoulder joint.

Trapezius muscle :Your trapezius muscles are two big muscles on either side of your upper back. They help you move your head, neck and upper back, and maintain and adjust your posture.

Latissimus dorsi muscle : The latissimus dorsi (or "lats") is a large back muscle crucial for arm movement like extending, adducting (bringing towards the body), and internally rotating the shoulder, essential for activities like climbing or pull-ups, and also helps with spine stability. and forced breathing (inspiration/expiration).

Infraspinatus muscle : The infraspinatus muscle's action on the shoulder is primarily through its function as a rotator cuff muscle providing glenohumeral stability. The rotator cuff applies compression upon the head of the humerus that allows for the stabilization of the humeral head during shoulder abduction.

Your shoulder joint (glenohumeral joint) is a ball-and-socket joint that connects your upper arm bone (humerus) and shoulder blade (scapula).

Teres major muscle : It's crucial for stabilizing the shoulder joint, helping to keep the humeral head in place, and assists in pulling the trunk upward during activities like climbing. 

How to draw the muscles

the first drawing shows the skeleton structure where the muscles are positioned.

The second drawing shows all the muscles stretched so they can be more easily identified.

The third drawing shows a closer look and the shoulder joint and its muscle group that help with the movement.

Origin and Insertion

Back muscles originate from various points, primarily the vertebrae (spinous & transverse processes), ribs, skull, scapula (shoulder blade), and the iliac crest (hip bone)

All of these muscles are present in the back or dorsal part if the upper body.

Function

Strengthening of the dorsal upper body and helping with complex movements

Advanced

Reference Pictures (for study only)