Final answer:
The middle portion of the foot is composed of the five metatarsal bones. These articulate with tarsal bones proximally and phalanges distally, forming the mid-foot and ball of the foot.
Step-by-step explanation:
The bones that make up the middle portion of the foot are the metatarsal bones. The human foot comprises three groups of bones: the tarsals (composing the posterior part of the foot), the metatarsals (forming the mid-foot), and the phalanges (bones of the toes).
There are five metatarsal bones, numbered 1 to 5, with the first metatarsal being shorter and thicker and located at the medial side of the foot, whereas the second is the longest. These bones articulate proximally with the cuboid or cuneiform bones (which are part of the tarsal bones) and distally with the proximal phalanges of the toes, forming the metatarsophalangeal joints. The expanded distal ends of the metatarsals are the heads that rest on the ground and form the ball of the foot.
Each toe is primarily composed of phalanges, with the big toe having only two (proximal and distal phalanges), and the other four toes each having three phalanges (proximal, middle, and distal).