Fig. 1 shows the bones of the lower limb of a performer who takes part in sport regularly. (a) Name the longest bone in the body shown in the diagram. [1] (...

(a) Longest bone in the body

The longest bone shown in the diagram is the femur (thigh bone). It extends from the hip joint to the knee joint and acts as a powerful lever for movements such as running, jumping, and kicking. [1]

(b) Small bone at the front of the knee

The small bone at the front of the knee joint is the patella (kneecap). It is a sesamoid bone embedded within the quadriceps tendon. [1]

(c) Axial or appendicular?

The bones of the lower limb belong to the appendicular skeleton. The appendicular skeleton comprises the limbs and limb girdles, as opposed to the axial skeleton which forms the central axis of the body (skull, spine, ribs, sternum). [1]

(d) How lower limb bones help a sprinter

• The femur acts as a lever, allowing the powerful muscles attached to it (quadriceps, hamstrings, gluteals) to generate the force needed to push off the ground during each stride. The longer the lever, the greater the potential range of motion and stride length. [1]
• The tibia and fibula support body weight during the landing phase of each stride. They absorb and transfer the ground reaction force back through the leg, enabling the sprinter to maintain speed without the lower leg collapsing. [1]
• The patella protects the knee joint from the repeated high-impact forces experienced during sprinting. It also improves the mechanical efficiency of the quadriceps by acting as a pulley, allowing the tendon to glide smoothly over the knee during rapid extension. [1]

[max 3]