The tibia also known as the shinbone or the shank bone connects the knee to the ankle. The shin is the front part of the leg [the back of the leg is generally referred to as the calf muscle]. The tibia is the second biggest bone in the body; femur being the first. The fibula is another bone which together with the tibia makes up the bones of the leg connecting the foot to the thigh.
Shin splints is the name given to pain experienced in the front part of the leg due to any reason. It must be noted here that this is not a final diagnosis but is only a symptom pointing to a host of differential diagnoses.
The muscles of the anterior compartment of the leg are:
1) mainly the tibialis anterior which arises from the upper two thirds of the lateral surface of the shaft of the tibia; and is inserted into the infero-medial [down and inward] side of the base of the first metatarsal bone [one of the long bones of the foot] and the adjacent medial cuneiform bone. The actions of this muscle are important here as this plays a role in the mechanism behind shin splints. It causes dorsi-flexion [upward movement of the foot with a fixed ankle joint thereby decreasing the angle between the two] of the foot. It also maintains the arch of the foot on the inner side. Lastly it also inverts the foot.
2) Other muscles worth just a mention here are the extensor digitorum longus, extensor hallucis longus, and peroneus tertius.
The blood supply to the shin is by the anterior tibial artery and the nerve supply is by the deep peroneal nerve.