Shoulder Muscles Anatomy- Function Diagram, Issues

shoulder muscles

Shoulder muscle anatomy

Shoulder in humans is a large joint which covered and work with several muscles. These muscles of the shoulder give the round shape to the shoulder.

Shoulder muscles are majorly divided into two groups

  1. Deltoid
  2. Rotatory muscles

1.Deltoid muscles

shoulder muscles


Deltoid muscles are those muscles which give the shoulder rounded shape. It is commonly known as “common shoulder muscles”. In the fitness community, there are known as Delts.
The deltoid name come from Greek name delta which is a name of sign /\. Deltoid muscle group look like delta sign.

Deltoid muscles are divided in three parts

  • Anterior delt or front delt.
  • Lateral delt (middle delt,outer delt or side delt).
  • Posterior delt or rear delt.

Anterior deltoid

This part of the deltoid muscle is the front part of the shoulder. It is located at the front of the shoulder. This part of the deltoid muscle border touches the chest muscles.

Function of This muscle

  • Shoulder flexion.
  • It works when you raise your hand at front position.

Lateral Deltoid

shoulder muscles

Lateral deltoid is located in the middle of your deltoid muscle group. At the side of your shoulder. This muscle gives a wider look to the shoulder.

Function of this muscle

  • Abduction of shoulder.
  • Waving arms like bird swing. This muscle works.

Posterior Deltoid

shoulder muscles

This is the third muscle of shoulder deltoids. Which is located behind or back the shoulder. let’s do this movement to understand the function of rear delt. Raise your hands from the side and make a “T” sign or “L” sign from one arm. Try to pull your arm back and feel or touch your rear delts.

Rear delt workout

Function of posterior Deltoid

  • Highly active in Hyperextension of shoulder.
  • External rotation.
  • Horizontal abduction.

2.Rotatory Muscles ( Rotatory cuff)

shoulder muscles

Rotatory muscles or rotary calf is a name of 4 muscle group and their tendons. These muscles provide strength and stability. when we make movements with the shoulder .

These muscles originate from scapula and connect to the head of the humerous bone. Making a cuff at the shoulder joint.

These 4 muscles are

  • Supraspinatus.
  • Infrapinatus.
  • Teres minor.
  • Sub scapulars.

Function of rotatory muscles( Rotatory cuff)

  • Abduction of arm or shoulder.
  • Exo rotation(The rotation of a limb away from the midline of the body).
  • Endorotation (The rotation of a limb toward the midline of the body)

Rotator cuff issues

These muscles provide rotating capability to the Arm.

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