Which nerve is a sensory branch of the femoral nerve (nervus femoralis) and provides sensory innervation to the medial lower leg and foot?

The nerve that is a sensory branch of the femoral nerve (nervus femoralis) and provides sensory innervation to the medial lower leg and foot is the Saphenous nerve (nervus saphenus).

Here are the steps to understand this:

1. The femoral nerve is one of the largest nerves in the leg. It's responsible for the movements and sensations in the thigh, knee, and foot.

2. The femoral nerve has several branches, one of which is the saphenous nerve.

3. The saphenous nerve is purely sensory and is the longest branch of the femoral nerve.

4. It descends along the medial side of the leg, providing sensory innervation to the skin of the medial side of the leg and foot.

So, the saphenous nerve is the nerve that provides sensory innervation to the medial lower leg and foot.