What defines the anatomical guide for the femoral artery?

The anatomical guide for the femoral artery is defined by its relationship to the sartorius muscle, which serves as a key landmark in identifying the artery's location. The femoral artery runs in the thigh, and when assessing it anatomically, the sartorius muscle provides a lateral border. This understanding is critical in both anatomical studies and practical applications such as catheterization or surgical procedures.

The other options do not accurately describe the specific anatomical guide for the femoral artery. The axillary space relates to the brachial plexus and the upper limb, while the popliteal space pertains to the posterior aspect of the knee, and the medial and lateral epicondyles reference the elbow region. Therefore, option A, indicating the sartorius muscle as the lateral border, correctly identifies the anatomical context for locating the femoral artery.