Bones & Joints of the Shoulder Girdle Flashcards
Bones of the Shoulder Girdle & Arm
Clavicle
Scapula
Manubrium of the sternum
Proximal humerus
Joints of the Shoulder Girdle
- Sternoclavicular joint (SC joint)
- Acromioclavicular joint (AC joint)
- Glenohumeral joint (GH joint)
Clavicle
- It is a long bone
- Connects the upper limb to the axial skeleton (only bone to do so)
- Acts as a strut to hold the upper limb away from the trunk for maximum range of motion
- Articulates at acromioclavicular (AC) and sternoclavicular (SC) joints
- Superior surface is smooth
- Inferior surface is rough for the attachment of ligaments and muscles
Scapula
- Flat bone
- Triangle shaped bone
- Overlies posterolateral aspect of 2nd to 7th ribs
- Important for connection of the upper limb to the thoracic cage as well as a significant portion of upper limb range of motion
Humerus
-Largest bone of the upper limb
-Long bone
-Articulates with:
.Scapula at the glenohumeral (GH) joint
.Radius and ulnar at the elbow joint
-Serves as location for many muscle attachments
Sternoclavicular Joint
- Articulation between the sternal/proximal end of clavicle and the manubrium of the sternum (only articulation b/w upper limb and axial skeleton)
- Saddle synovial joint - however it functions like a ball & socket joint
- Articular disc (fibrocartilage, shock absorber)
Acromioclavicular Joint
- Articulation between the acromial/distal end of clavicle and acromion of the scapula
- Plane type of synovial joint
- Articular disc - Fibrocartilage
- No muscles directly cross and move the AC joint. Rather, the axioappendicular muscles move the scapula, which then moves the acromion on the clavicle
Glenohumeral Joint
- Articulation between the humeral head and the glenoid fossa/cavity of the scapula
- Ball and socket type of synovial joint
- Wide range of movement, however as a result it is relatively unstable
- Glenoid labrum – fibrocartilaginous ring increases congruency
- Relies heavily upon the rotator cuff muscles for stability
Sternoclavicular Jointn Ligaments
- Sternoclavicular ligaments (anterior and posterior) (relatively weak) – b/w the sternum & clavicle
- Interclavicular ligament (relatively weak) – b/w the two clavicles
- Costoclavicular ligament (very strong!) – b/w rib 1 and inferior clavicle
Sternoclavicular Joint Nerve Supply/Movements
- Medial supraclavicular nerve
- Nerve to subclavius
- Protraction & retraction of the clavicle
- Elevation & depression of clavicle
- Rotation about the longitudinal axis – assists the above movements
Acromioclavicular Joint Ligaments
Acromioclavicular ligament (weak) - b/w the clavicle and acromion Coracoclavicular ligament (very, very strong) - Conoid and Trapezoid parts - b/w the coracoid process of scapula and clavicle, holds the scapula up onto the clavicle Coracoacrominal ligament - b/w the coracoid process and acromion of the scapula, provides indirect protection from superior displacement of the humerus
Acromioclavicular Joint Nerve Supply/Movements
lateral supraclavicular nerve
lateral pectoral nerve
axillary nerve
Acromion of the scapula glides on the acromial end of the clavicle as the scapula moves on the thoracic cage
Axioappendicular muscles move the scapula which in turn moves the acromion on the clavicle
Glenohumeral Joint Ligaments
- Glenohumeral ligaments (Superior/Middle/Inferior) that reinforce the joint anteriorly
- Transverse humeral ligament – b/w greater and lesser tubercle of humerus, holds long biceps tendon in place (see image next slide)
- Coracohumeral ligament – strong band b/w the coracoid and greater tubercle of humerus
- Coracoacromial ligament - indirect protection, prevents superior displacement of the humerus – b/w the coracoid process and acromion of the scapula
Glenohumeral Joint Nerve Supply/Movements
- Axillary nerve
- Suprascapular nerve
- Lateral pectoral nerve
Flexion/extension
Abduction/adduction
Internal (medial) and external (lateral) rotation
Circumduction
Glenoid Labrum
- A fibrocartilaginous ring-like structure that lines the outer rim of the glenoid fossa
- Increases depth of fossa to increase congruency of glenohumeral joint
- Maintains negative pressure within the joint (like the suction of a vacuum)
- Provides insertion for stabilising structures – eg articular capsule and glenohumeral ligaments