Quiz Shoulder & Arm - Quiz Test
The glenohumeral joint is the articulation between the head of the humerus and the glenoid cavity of the scapula. It is a ball and socket type of synovial joint with. Which joint is formed where the humerus and scapula meet? Acromioclavicular. Scapulothoracic. Glenohumeral. Sternoclavicular. 5. Which part of the scapula serves as an attachment site for both rhomboids and serrates anterior? . Which joint is formed where the humerus and scapula meet ?.
It articulates with the humerus arm bone to form the shoulder joint the glenohumeral joint.
Shoulder & Arm
The scapula is a flat, triangular-shaped bone with a prominent ridge running across its posterior surface. This ridge extends out laterally, where it forms the bony tip of the shoulder and joins with the lateral end of the clavicle. By following along the clavicle, you can palpate out to the bony tip of the shoulder, and from there, you can move back across your posterior shoulder to follow the ridge of the scapula.
Move your shoulder around and feel how the clavicle and scapula move together as a unit. Both of these bones serve as important attachment sites for muscles that aid with movements of the shoulder and arm.
The right and left pectoral girdles are not joined to each other, allowing each to operate independently. In addition, the clavicle of each pectoral girdle is anchored to the axial skeleton by a single, highly mobile joint the sternoclavicular joint. This allows for the extensive mobility of the entire pectoral girdle, which in turn enhances movements of the shoulder and upper limb. Clavicle The clavicle is the only long bone that lies in a horizontal position in the body see Figure 8.
The clavicle has several important functions. First, anchored by muscles from above, it serves as a strut that extends laterally to support the scapula. This in turn holds the shoulder joint superiorly and laterally from the body trunk, allowing for maximal freedom of motion for the upper limb. The clavicle also transmits forces acting on the upper limb to the sternum and axial skeleton.
Finally, it serves to protect the underlying nerves and blood vessels as they pass between the trunk of the body and the upper limb. The clavicle has three regions: The medial end, known as the sternal end of the clavicle, has a triangular shape and articulates with the manubrium portion of the sternum. This forms the sternoclavicular joint, which is the only bony articulation between the pectoral girdle of the upper limb and the axial skeleton. The lateral or acromial end of the clavicle articulates with the acromion of the scapula, the portion of the scapula that forms the bony tip of the shoulder.
There are some sex differences in the morphology of the clavicle.
In women, the clavicle tends to be shorter, thinner, and less curved. In men, the clavicle is heavier and longer, and has a greater curvature and rougher surfaces where muscles attach.
The clavicle is the most commonly fractured bone in the body. Such breaks often occur because of the force exerted on the clavicle when a person falls onto his or her outstretched arm, or when the lateral shoulder receives a strong blow. Because the sternoclavicular joint is strong and rarely dislocated, excessive force results in the breaking of the clavicle, usually between the middle and lateral portions of the bone.
- What Is the Pectoral Girdle?
- Shoulder girdle
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If the fracture is complete, the shoulder and lateral clavicle fragment will drop due to the weight of the upper limb, causing the person to support the sagging limb with their other hand. Muscles acting across the shoulder will also pull the shoulder and lateral clavicle anteriorly and medially, causing the clavicle fragments to overlap. The clavicle overlies many important blood vessels and nerves for the upper limb, but fortunately, due to the anterior displacement of a broken clavicle, these structures are rarely affected when the clavicle is fractured.
Shoulder Structure, Function and Common Problems
Scapula The scapula is also part of the pectoral girdle and thus plays an important role in anchoring the upper limb to the body. The scapula is located on the posterior side of the shoulder.
It is surrounded by muscles on both its anterior deep and posterior superficial sides, and it does not directly articulate with the ribs of the thoracic cage. The scapula has several important landmarks Figure 8. The three margins or borders of the scapula, named for their positions within the body, are the superior border of the scapula, the medial border of the scapula, and the lateral border of the scapula.
The suprascapular notch is located lateral to the midpoint of the superior border. The corners of the triangular scapula, at either end of the medial border, are the superior angle of the scapula, located between the medial and superior borders, and the inferior angle of the scapula, located between the medial and lateral borders.
The inferior angle is the most inferior portion of the scapula, and is particularly important because it serves as the attachment point for several powerful muscles involved in shoulder and upper limb movements. The remaining corner of the scapula, between the superior and lateral borders, is the location of the glenoid cavity glenoid fossa. This shallow depression articulates with the humerus bone of the arm to form the glenohumeral joint shoulder joint, see Chapter 9. The small bony bumps located immediately above and below the glenoid cavity are the supraglenoid tubercle and the infraglenoid tubercle, respectively.
These provide attachments for muscles of the arm. The isolated scapula is shown here from its anterior deep side, lateral side and its posterior superficial side. The scapula also has two prominent projections. This process projects anteriorly and curves laterally. Cartilage is a stiff but flexible tissue that is good with weight-bearing which is why it is found in our joints. Cartilage has almost no blood vessels and is very bad at repairing itself. Bone is full of blood vessels and is very good at self repair.
The Pectoral Girdle | Anatomy & Physiology
It is the high water content that makes cartilage flexible. The muscles on the lateral side of the shoulder allow movement and stabilize the joint. These muscles are strong on the upper and back sides of the arm, but not on the underside. A strong outside force in this area can cause the head of the humerus to slip out of the glenoid socket, called dislocation. Since there is little bony stability in this joint, a number of ligaments and other soft tissues stabilize this joint.
The superior AC ligament is the most important horizontal stabilizer. The coracoclavicular ligaments help stabilize the clavicle vertically. The Sternoclavicular Joint SC Most of the rotation occurs at the sternoclavicular joint and joint stability comes from the soft tissues.
The posterior sternoclavicular joint capsule is the most important structure for preventing forward and backward displacement of the medial clavicle. The Rotator Cuff The rotator cuff consists of four muscle-tendon units that originate on the scapula and attach to the tuberosities of the humerus. The rotator cuff is the primary stabilizer during movement of the GH joint. Both overuse and traumatic injuries to the rotator cuff are the most common problems in the shoulder girdle.
The Subacromial Space The subacromial space is beneath the acromion and above the rotator cuff. The subacromial bursa outlines this space and provides frictionless gliding of the rotator cuff beneath the arch formed by the acromion and coracoacromion.
Bone spurs on the underside of the acromion narrow this space, irritate the bursa and contribute to tears in the rotator cuff. Bones of the Shoulder Girdle Click on image for larger labeled, picture. The bones of the shoulder girdle include the humerus, the scapula, and the clavicle. There are four articulations movements in the shoulder named for their anatomic locations: The scapula is the most complex of the bones in the shoulder and is part of the shoulder girdle.
The scapula floats on the rib cage, and is attached to it only with muscles. There are three landmarks on the scapula; the spine, acromion and coracoid processes. The roof of the glenohumeral joint is formed by the acromion.
The acromion articulates with the clavicle forming the acromioclavicular AC joint. A spine divides the back of the scapula into two sections. The muscles that attach below this spine are called infraspinatus muscles; the ones that attach above this spine are called supraspinatus muscles. The humerus is the ball part of the ball-and-socket joint. The head ball of the humerus articulates within the glenoid fossa.
Below the humeral head is the anatomic neck which separates the head ball from the tuberosities. Each tuberosity provides a place for the attachment for the anterior muscles of the rotator cuff—the 4 rotator cuff muscles originate from the scapula and their tendons attach at the humerus.
The bicipital groove separates the tuberosities. Just below the tuberosities is the surgical neck of the humerus and is the most common area for fractures of the proximal humerus.
Clavicle Shoulder Blade — lateral view Clavicle collar bone. The clavicle originates at the sternum breastbone just above the first rib, and is held in place by the acromioclavicular ligament, several muscles and the coracoclavicular ligament. The clavicle helps hold the shoulder out to the side while allowing the scapula to move around.
Shoulder Ligaments Click on image to see larger picture. There are several important ligaments about the shoulder girdle. Ligaments are soft tissue structures that connect bones to bones. Ligaments are strong, tough bands that are not particularly flexible. Once stretched, they tend to stay stretched and if stretched too far, they snap.
Ligaments, along with muscles and tendons, are the main source of stability for the shoulder. Shoulder ligaments also form the joint capsule that surround the glenohumeral joint. These passive stabilizers serve to keep the joints of the shoulder from dislocating.
Some of the main ligaments are the acromioclavicular, coracoclavicular and the coracoacromial.