Final answer:
The shoulder joint is susceptible to injuries like clavicle fractures and acromioclavicular joint dislocations due to its structure and range of motion, particularly when subjected to strong impacts or falls.
Step-by-step explanation:
The shoulder joint is prone to injuries due to its wide range of motion and the fact that the humeral head is particularly vulnerable when the upper limb is fully abducted, such as during sports activities. Two possible injuries of the pectoral girdle resulting from a strong blow to the shoulder or a hard fall onto an outstretched hand are: clavicle fractures and acromioclavicular joint dislocations.
Clavicle fractures are commonplace and typically happen when the lateral shoulder receives a severe blow or when an individual falls onto outstretched arms. The fracture often causes the shoulder and lateral clavicle fragment to drop due to the weight of the upper limb. On the other hand, a dislocation of the acromioclavicular joint, also known as a 'shoulder separation', can occur from a significant impact to the lateral shoulder, rupturing the acromioclavicular and coracoclavicular ligaments and resulting in the scapula separating from the clavicle.