Final answer:
The plantar surface of the foot is supported by the plantar aponeurosis, a key structure in maintaining the foot's arch and supporting body weight.
Step-by-step explanation:
The plantar surface (sole) of the foot is supported by the plantar aponeurosis. This deep fascia runs from the calcaneus bone to the toes and is the principal support for the longitudinal arch of the foot. The intrinsic muscles of the foot work together in two groups: the dorsal group, which includes the extensor digitorum brevis and assists in extending the toes; and the more complex plantar group, consisting of four layers that provide support and flexibility for various movements including flexing the toes. These structures are essential for maintaining the foot's arch and for supporting the weight of the body during activities such as walking and running.