Final answer:
The big toe lacks a dorsal and plantar interosseous muscle because its anatomical structure differs from other toes, it only has two phalanges, and it's supported by muscles that act across multiple toes, providing stability and support for balance and weight bearing.
Step-by-step explanation:
The big toe does not have a dorsal and plantar interosseous muscle because the anatomy and muscular composition of the big toe, also known as the hallux, are different from the other toes. The hallux has only two phalanges - the proximal and distal phalanges - while other toes have three. Moreover, the intrinsic muscles of the foot that contribute to toe movements are organized into groups that provide support and movement across several toes rather than focusing on individual digits.
The muscles that facilitate flexion of the foot, such as plantar flexion and toe movements, are divided into compartments and layers rather than being associated with single toes. The extensor hallucis longus and flexor hallucis longus specifically act on the big toe by extending and flexing it, respectively. The absence of interosseous muscles in the big toe is thus related to its specific anatomical needs and role in providing stability and support for walking and bearing body weight.