The foot is situated at the distal part of the lower limb. It is one structure that has undergone several evolutionary changes. The foot of humans has changed from grasping to a supporting structure. It supports the whole body weight while standing and also plays a vital role in locomotion. Let’s learn more about the structure of the foot with a well-labelled diagram.
Well-labelled Diagram of Foot
- The foot contains 14 toe bones or phalanges, 7 tarsals and 5 metatarsals.
- The upper surface of the foot is called the dorsum of the foot, and the lower surface is called the plantar surface or sole. The sole of the foot is homologous to the palm of the hand.
- The seven tarsal bones are arranged in two rows. The proximal row has the calcaneus bone below and the talus above.
- The calcaneus or calcaneum is the largest tarsal bone that forms the prominence of the heel.
- The talus is the second largest tarsal bone that lies between the calcaneum and tibia.
- The distal row has four tarsal bones lying side by side. They are the medial cuneiform, lateral cuneiform, the intermediate cuneiform and the cuboid.
- Out of the three cuneiforms, the medial is the largest, and the intermediate is the smallest. The cuboid is present in front of the calcaneus and behind the 4th and 5th metatarsal bones.
- The navicular bone is interposed between the talus and the three cuneiforms, i.e., it is interposed between the proximal and distal rows.
- The 5 metatarsals are miniature bone structures numbered from the medial to the lateral side.
- The first metatarsal is the shortest bone and is just behind the big toe. The second one is the longest metatarsal bone, and the third metatarsal is the second-longest one. The third, fourth and fifth metatarsals are homologous to the third, fourth and fifth metacarpals of the hand, respectively.
- There are 14 phalanges or toe bones present in each foot. The big toe has 2 bones or phalanges while the remaining four toes have 3 phalanges each.
- The metatarsals and phalanges form the forefoot portion. The midfoot is formed by three cuneiforms, cuboid and navicular bone. The rearfoot is formed by the talus and calcaneus.
- The tibia is the larger medial bone of the leg and it is homologous to the radius of the upper limb. The medial side of the tibia projects downwards to form the medial malleolus.
- The fibula is the smaller lateral bone of the leg and is homologous to the ulna of the upper limb. The lower end of the fibula is called the lateral malleolus.
- The medial malleolus is a bony projection on the inner side of the ankle, and the lateral malleolus is a projection on the outer side of the ankle.
- The anterior margin of the lateral malleolus gives attachment to the anterior talofibular ligament. It proceeds from the anterior margins to the talus bone.
- Likewise, the posterior talofibular ligament is present horizontally from the lateral malleolus and connects the fibula to the talus.
- The triangular area above the medial surface of the lateral malleolus gives attachment to the anterior tibiofibular ligament anteriorly and the posterior tibiofibular posteriorly.
The foot structure has 26 bones and many muscles, tendons, nerves and blood vessels. The arches of the foot are formed by the metatarsal and tarsal bones and are strengthened by the tendons and ligaments. It helps to support the whole weight and balance the entire body. Also, the foot is the major locomotor part that also acts as a shock absorber.
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