Where is the longest bone in the human body?

Femoral femur is the largest long tubular bone in human body, which is divided into two ends. The upper end is inward and upward, and its end is spherical, which is called femoral head and is related to acetabulum. A little below the center of the head, there is a small concave, called femoral head concave, which is the attachment of femoral head ligament. The thinner part below the head is called the femoral neck. The included angle between the neck and the body is called the neck trunk angle, which is about 120 ~ 130. On the outside of the neck joint, there is an upward protrusion called the big rotor, and the smaller protrusions on the inside and below are called the small rotor. There is a depression on the inner side of the big rotor, which is called rotor nest. Between the big rotor and the small rotor, there is an intertrochanteric line in front and an intertrochanteric ridge in the back. The body is thick and cylindrical, all slightly protruding forward. The front is smooth and the back has longitudinal ridges, which are called thick lines. Thick lines can be divided into inner lips and outer lips. The two lips are close in the middle of the body, while the upper and lower ends are gradually separated. The lateral lip moves upward and outward as gluteal muscle tuberosity, and the medial lip terminates in the lesser trochanter. The two lips form two bone ridges downward, which are connected with the medial and lateral epicondylar of the lower femur respectively. The triangular bone surface behind the lower femur surrounded by two lips is called the popliteal plane. There are two backward-curled ridges at the lower end, which are called medial condyle and lateral condyle respectively. There are articular surfaces below and behind the two condyles related to the upper end of tibia, and the smooth articular surface in front is connected with patella, which is called patella surface. At the back, there is a deep depression between the two condyles, which is called intercondylar fossa. The medial surface of the medial condyle and the lateral surface of the lateral condyle each have a rough protrusion, which is called the medial epicondyle and the lateral epicondyle respectively. There is a triangular protrusion above the medial epicondyle, called adductor tubercle, which is the attachment point of adductor tendon.