Final answer:
The medial side of the tibia, which is easily palpable, is the portion primarily covered only by skin. The anterior border of the tibia and the medial side of its triangular shape run under the skin, facilitating palpation.
Step-by-step explanation:
The portion of the tibia that is primarily covered only by skin is the medial side. This side of the tibia, which is the larger bone of the leg positioned on the medial side, is directly under the skin along its entire length. The prominence of this section makes it easily palpable. The tibia, also known as the shinbone, is notable for being the main weight-bearing bone of the lower leg and is second in length only to the femur among the body's bones. Unlike the fibula, the tibia supports the weight of the body.
The anterior border of the tibia is identifiable by beginning at the tibial tuberosity and running inferiorly along the tibia's length. Both the anterior border and the medial side of the tibia's triangular shaft are immediately under the skin, allowing for easy palpation. The interosseous membrane of the leg connects the tibia to the fibula, with the interosseous border on the lateral side of the tibia, and the soleal line defining muscle attachment points on the posterior aspect.