Evolutionary uprightness has made unique some parts of the human skeleton, which have no analogues among similar parts of the bone skeleton in other representatives of the animal world. Firstly, the shape of the spine has changed, which allowed the person to be constantly in an upright position relative to the surface of his movement. And secondly, nature, given the constant load on the legs, changed the skeleton of the foot so that it, in turn, does not experience fatigue while walking or standing. Every day, making a motor act involving the lower extremities, a person, one way or another, exerts pressure of his own mass on this seemingly fragile and small anatomical region. The structure of the foot is very complex in nature, because this structural unit contains a large number of bones, ligaments, joints, and very thin muscles that are also different in their functional characteristics. The backbone here, as well as in any other part of the body, are the bones that form the characteristic appearance of the foot. As in the hands of the upper limbs, and in the foot, there are three important departments.
- Tarsus. This is the part that connects the large tubular bones of the lower limb with small ones. According to their histological structure, the bones of the tarsus can be classified as spongy, having very short sizes. In total, there are seven small bones in the tarsus, of which the talus and calcaneus are the largest. The rest, namely three sphenoid, cuboid and scaphoid bones are significantly inferior in size to the first two. The structure of the foot is especially because it has a large number of articular joints on a relatively small surface. The talus together with the bones of the lower leg forms the ankle joint. The remaining bones of the human foot are also connected to each other using other joints.
- Metatarsus. It is the middle part between the tarsal bones and phalanges of the toes. Metatarsal bones are located somewhat distal from the three sphenoid and cuboid bones. Three landmarks are distinguished in the metatarsal bones: the head that connects them to the phalanges, the body and the base that connects these anatomical structures to the bones of the tarsus with small joints.
- Phalanges of the fingers. There are usually three of them, not counting the first finger, in which there are only two phalanges. This is the only part in the foot that can bend and unbend, not taking into account the ankle joint, which is half half the bones of the leg.
The structure of the foot has another specific feature, and all thanks to the vertical position of the whole body. The fact is that the longitudinal axis of the foot is located almost at right angles to the vertical axis of the proximal part of the lower limb, however, the bones of this area are not in the same plane, because some of them form a longitudinal, and the other part a transverse arch. The concave half of the foot is facing the sole, and the convex half is facing the back surface, respectively. This structure of the foot provides springiness, smoothness and elasticity of the gait. At rest, in a healthy person, only the calcaneus (its tubercle) and metatarsal bone heads are tightly touched to the floor. Everything else that lies on the ground is the soft tissues of the foot. At this moment, i.e. at rest, the supporting arch, which is represented by the outer surface of the foot, also touches the ground, and its opposite inner edge is slightly raised from the floor and plays the role of a spring (spring arch). During walking, the spring arch flattens, then returns to its original position, thereby softening the step and minimizing the load of the body weight on the foot itself.