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Shoulder Muscles

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Shoulder Muscles and their Anatomy

MVSAT 2024

Our shoulders are made of 8 muscles and bones. These muscles are connected with the bones by ligaments and tendons. All these muscles work with proper coordination and enable us to move our hands and perform various kinds of functions. In this article, we will study the different kinds of shoulder muscles and their anatomical significance in the formation of a shoulder.

What are Shoulder Muscles?

As mentioned earlier, shoulder muscles are the muscular connective tissues present in the shoulder region of the human skeleton. There are 8 such muscles present in both arms. There are three bones that form our shoulders. They are the humerus, clavicle, and scapula.

All these muscles are associated with these bones and nervous tissues for proper coordination and hand movements. In fact, these muscles contribute to the shape of our shoulders and the underarm. Their prime functions apart from the movement of the bones are to maintain the joint structure and protect it from shocks, jerks, forces, and injuries.

The joint in each shoulder is called the glenohumeral joint. It is a type of ball and socket joint formed by the glenoid fossa present in the scapula and the ball head of the humerus.

Types of Shoulder Muscles

As per the shoulder muscle anatomy, there are 8 different types of muscles present in this location.

  1. Deltoid

A deltoid is the largest muscle present in a human shoulder. It is triangular in shape covering the ball and socket joint at the side and top portion of the arm. As mentioned earlier, this triangular muscle gives a round shape to the joint. It also forms the upper end of the arm.

Its front top end starts from the scapula and clavicle. It then continues to the center of the humerus stretching to form a snout shape. There are different clusters of fibers that have different functions to perform. One of the prime functions is to raise the arm. It also assists the chest muscles of the pectoralis to move. Deltoids are responsible for maintaining the shape of the joints when weights are lifted by an individual.

  1. Infraspinatus

As per the shoulder muscle anatomy, this is a rotator cuff muscle that enables an arm to rise and set. This muscle thus helps in lowering and raising the arms.

  1. Triceps Brachii

These are back arm muscles present at the back of the upper arm right beside the deltoid. This set of muscles enables a person to raise his arm.

  1. Pectoralis Major

This is a set of front shoulder muscles shaped like a fan that stretches straight from the collarbone to the armpit. It widens at the collarbone end and constricts to form a strong band of muscles at the armpit. In fact, this muscle flows down to the lower portion of the chest down from the shoulder region.

  1. Pectoralis Minor

This is also another set of front shoulder muscles that connects the upper ribs with the shoulder area. It enables a person to stretch their arms wider and also to bring them closer in coordination with the pectoralis major.

These two sets of pectoralis muscles work with the back shoulder muscles to make different arm movements such as stretching and closing.

  1. Teres Major

This is a typical set of muscles that helps the upper arm to rotate.

  1. Biceps Brachii

It is popularly known as biceps. This set of muscles is present right on the top portion of the humerus bone of the upper arm. It is used to flex and relax the elbow joint connecting the upper and the lower arm. It is connected with the shoulder joint and the elbow joint.

  1. Latissimus Dorsi

This is a set of back shoulder muscles present right beside the arm stretching from the shoulder joint to the ribs. This muscle is also bigger in size and helps in moving the arms closer and away from the body. It also helps the arms to rotate.

  1. Subscapularis

It is also a front shoulder muscle present in the chest that connects the collar bone with the humerus. It also helps to rotate the upper arm.

  1. Supraspinatus

It is a small set of muscles present at the top of the collar bone connected to the shoulder joint. This muscle helps us to raise our shoulder joints closer to the ears and our upper arms.

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Brief Description of the Shoulder Muscle Anatomy

The infraspinatus, supraspinatus, subscapularis, and teres minor are the ones that cumulatively form the rotator cuff. These are the core muscles around shoulder joint that enable a person to lift things and to maintain the shape of the joint. Due to overwork and exertion, these muscles cramp and cause shoulder pain or joint pain.

The muscle from collarbone to upper arm is deltoid, the largest one in the family. The rest of the muscles are there to link the shoulder joint with ribs, sternum, clavicle, or collar bone. Together, they form a unit that helps move the upper arm and keep the shoulder joint stable. Refer to the shoulder diagram and understand how these muscles are distributed.

This is all you need to know about the shoulder muscles and their anatomical positions. Find out the locations and connections of the muscles mentioned above and understand their specific functions. Together these deep shoulder muscles form this part of the human anatomy that helps in moving arms, lifting loads, and performing various other functions.  

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FAQs on Shoulder Muscles

1.  What is a Muscle?

It is a connective tissue formed of certain cellular fibers that relax and contract for moving bones in our body. There are more than 600 muscles present in our body. These muscles are controlled and coordinated by the central and peripheral nervous systems of the human body.

2. What do Connect the Bones Together?

The bones are connected by the ligaments. They are long and strong fibrous straps that connect two bones to form joints. These joints are protected by the ligaments from shocks, jerks, and body movements.

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