These provide mobility for the wide range of actions of the hands and arms making it a highly mobile joint in the body.
The shoulder has the ability to
- be raised in front and behind the torso,
- as well as move a full 360 degrees in the saggital area.
These muscles must be stable enough to enable actions such as pulling, lifting and pushing. The compromise between stability and mobility is usually what causes shoulder problems unlike those encountered by other joint such as the hip.
Anatomy of the Shoulder Muscles
• The serratus anterior arise from the surface of the eight ribs and inserts along the border of the medial. This muscle fixes the scapula into thoracic wall and helps in rotating and abducting of the shoulders.
• The subclavius originates from the 1st rib and inserts on the subclavian opening of the clavicle. It stabilizes the clavicle and depresses the lateral clavicle.
• The pectoralis minor arises from the 3rd, 4th and 5th ribs and inserts into the medial border close to the scapula surface on the upper side. It assists in respiration and rotating the scapula medially. This muscle also helps in protracting the scapula as well as drawing the scapula inferiorly.
• The traezius originates from the ligamentum nuchae and occipital bone as well as from the corresponding portion of supraspinal ligaments. The muscle inserts on the lateral clavicle and the acromion process. It performs different actions on the scapula ( shoulder blade) such as upward rotation, depression, adductions and elevation.
Anatomy of the Shoulder Bones
The clavicle or collarbone is the only bony part that attaches between the trunk and upper limb. It forms the front part of the shoulder girdle and runs along the entire length where it is palpable with a gentle S-shape. It articulates at one end with the sternum and acromion of the scapula (shoulder Blade) at the other end. The articulation between the acromial of the clavicle and acromion of the scapula forms the shoulder roof. Other bones that form the shoulder include the scapula which is a triangular bone forming the shoulder girdle and while the humerus forms the upper arm.
The axillary artery is usually the main blood vessel that supplies oxygenated blood to the armpit. It also supplies the upper limb and thorax and originates from the lateral margins of the 1st rib. The axillary vein runs parallel to the artery transporting deoxygenated blood back to the heart.
There are several nerves that travel down the arm passing through the axilla under the shoulder joint. The 3 main nerves arise from the shoulder; they include the radial, ulnar and median nerves. These nerves carry signals to and from the brain about sensations such as pain, temperature and touch.
Muscle Knots in the Shoulder
These cause pain, essentially they are sections within muscles that have constricted, this is called myofascial trigger points. It is quite common. It is caused by something that has triggered a reaction resulting in the muscle not relaxing. Every action we do with muscles results in the muscle turning itself on and off, in this case the muscle stays switched on.
Shoulder muscles enable you to perform highly complex tasks since they are designed for maximum mobility and a wide range of motions. Apart from pulling, lifting and pushing the muscles are also responsible for holding the hand in appropriate position for other functions. When you realize all the complex tasks that are accomplished by the shoulder joint then it is easy to understand how hard life can be if the shoulder is not functioning well because of the shoulder muscles.