Which structure is NOT part of the boundaries of the femoral triangle?

The femoral triangle is an anatomical region located in the upper thigh, defined by three key structures that serve as its boundaries. The base of the triangle is formed by the inguinal ligament, while the lateral boundary is demarcated by the sartorius muscle, and the medial boundary is defined by the adductor longus muscle. The floor of the triangle consists of the iliopsoas muscle laterally and the pectineus muscle medially.

Among the options given, biceps femoris is not associated with the boundaries of the femoral triangle. Instead, it is a muscle of the posterior thigh that is involved in flexing the knee and extending the hip. Its position is outside the confines of the femoral triangle, which is predominantly formed by muscles that are anterior and medial to the thigh region.

In summary, the correct answer highlights that biceps femoris does not belong to the anatomical structure defining the femoral triangle, while the adductor longus, sartorius, and pectineus all play critical roles in forming its boundaries.