Final answer:
The quadrangular space is bordered by the infraspinatus and teres major muscles, the long head of the triceps brachii, and the surgical neck of the humerus, which allow passage of the axillary nerve and posterior circumflex humeral vessels.
Step-by-step explanation:
The quadrangular space is an anatomic region located in the posterior aspect of the shoulder, through which the axillary nerve and the posterior circumflex humeral vessels pass. The four borders of the quadrangular space are:
- Infraspinatus muscle forming the upper border.
- Teres major muscle as the lower border.
- The long head of the triceps brachii muscle as the medial border.
- The surgical neck of the humerus forms the lateral border.
The significance of the quadrangular space is highlighted in clinical scenarios such as humeral fractures, where damage to the axillary nerve can occur due to its close association with the humerus. Knowledge of this space is essential for medical professionals dealing with conditions that affect the musculature and neurovascular structures of the upper limb.