Shoulder Anatomy Animated Tutorial

the shoulder is an elegant piece of machinery it has the greatest range of motion of any joint in the body however this large range of motion can also lead to shoulder joint problems understanding that different parts of the shoulder can help you understand how the shoulder works how it can be injured and how challenging recovery can be when the shoulder is injured the important structures of the shoulder can be divided into several categories these include bones joints ligaments tendons muscles nerves blood vessels and Bursa the bones of the shoulder are the humerus or the upper

arm bone the scapula or the shoulder blade and the clavicle or the collarbone the roof of the shoulder is formed by a part of the scapula called the acromion there are actually four joints that make up the shoulder the main shoulder joint called the glenohumeral joint is formed where the ball of the humerus fits into a shallow socket on the scapula this shallow socket is called the glenoid the acromioclavicular or AC joint is where the clavicle meets the acromion the sternoclavicular or SC joint supports the connection of the arms and shoulders to the main skeleton

on the front of the chest a false joint is formed where the shoulder blade glides against the rib cage this joint called the scapulothoracic joint is important because it requires that the muscles surrounding the shoulder blade work together to keep the socket properly aligned during shoulder movement articular cartilage is the material that covers the ends of the bones of any synovial joint articular cartilage is about 1/4 of an inch thick and most large weight-bearing joints it is a bit thinner and joints such as the shoulder which don't normally support weight articular cartilage has a rubbery

consistency it is very slippery which allows the joint surfaces to slide against one another with very little friction articular cartilage functions to absorb shock and provide an extremely smooth surface to make motion easier there are several important ligaments in the shoulder ligaments are soft tissue structures that connect bones to bones the joint capsule is a watertight sac that surrounds a joint in the shoulder the joint capsule is formed by a group of ligaments that connect the humerus to the glenoid these ligaments are the main source of stability for the shoulder they help hold the shoulder

in place and keep it from dislocating ligaments attach the clavicle to the acromion in the AC joint two ligaments connect the clavicle to the scapula by attaching to the coracoid process a bony nob that sticks out of the scapula in the front of the shoulder a special type of ligament forms a unique structure inside the shoulder call the labrum the labrum is attached almost completely around the edge of the glenoid when viewed and cross-section the labrum is wedge-shaped the wedge shape and the way the labrum is attached create an elevated rim around the glenoid socket

this is important because the glenoid socket is so flat and shallow that the ball of the humerus does not fit tightly the labrum creates a deeper cut for the ball of the humerus to fit into the labrum is also where the biceps tendon attaches to the glenoid tendons are much like ligaments except that tendons attach muscles to bones muscles move the bones by pulling on the tendons the biceps tendon runs from the biceps muscle across the front of the shoulder to the glenoid at the very top of the glenoid the bicep tendon attaches to the

bone and actually becomes part of the labrum this connection can be a source of problems when the biceps tendon is damaged and pulls away from its attachment to the glenoid for tendons connect the deepest layer of muscles that rotator cuff muscles to the humerus just before these muscles attach to the upper end of the humerus they joined together to form a single tendon called the rotator cuff the rotator cuff muscles lie just outside the shoulder joint these muscles help raise the arm from the side and rotate the shoulder in many directions the rotator cuff muscles

and tendons also help keep the shoulder joint stable by contracting and holding the humeral head tightly in the glenoid socket as the humerus moves the large deltoid muscle forms the outer layer of shoulder muscle the deltoid is the largest strongest muscle of the shoulder the deltoid muscle provides the power to lift the arm once the arm is away from the side the main nerves that travel into the arm run through the axilla under the shoulder three main nerves begin together at the shoulder the radial nerve the ulnar nerve and the median nerve these nerves carry

the signals from the brain to the muscles that move the arm the nerves also carry signals back to the brain about sensations such as touch pain and temperature there's also an important nerve that travels around the back of the shoulder joint to supply sensation to a small area of skin on the outside of the shoulder and motor signals to the deltoid muscle this nerve is called the axillary nerve traveling along with the nerves are the large vessels that supply the arm with blood the large axillary artery travels through the axilla if you place your hand

in your armpit you may be able to feel the pulsing of this large artery the axillary artery has many smaller branches that supply blood to different parts of the shoulder the shoulder has a very rich blood supply sandwiched between the rotator cuff tendons and the deltoid muscle our structures known as Bursa births are everywhere in the body they are found wherever two body parts move against one another and there is no joint to reduce the friction a bursa is simply a watertight sac between two moving surfaces that contains a small amount of lubricating fluid as

you can see the shoulder is extremely complex with a design that provides maximum mobility and range of motion besides big lifting jobs the shoulder joint is also responsible for getting the hand in the right position for any function when you realize all the different ways and positions we use our hands every day it is easy to understand how hard daily life can be when the shoulder isn't working well