Foot

Foot (plural: feet) is the end of limbs in vertebrates that helps in locomotion. It is one of the most complex structures in vertebrate anatomy. The foot is made up of several components or segments, including bones, muscles, tendons and ligaments. 

Functions of Foot

• The main function of the feet is to enable locomotion. It allows movement and several physical functions. 

• It also bears the weight of the body. It balances the entire body weight at different angles and positions.

• The structure of foot is designed to be able to absorb the shock while walking. 

• Feet also help an animal stand upright and perform various physical activities. 

• Along with helping in walking, climbing or jumping, it can also help in grasping or manipulation.

Postures of Foot

Three types of foot postures are generally observed. These include:

• Plantigrade

Most commonly seen in humans and animals like bears, this type of posture involves contact between the entire foot and the ground during locomotion. 

• Digitigrade

The type of feet where only the toes (phalanges) make contact with the ground during locomotion is called digitigrade. The ankle remains elevated, and this type of posture is seen in dogs and cats. 

• Unguligrade

This type of feet can be seen in running animals like horses with only tips of a few digits touching the ground during locomotion. 

Structure of a Human Foot

The human foot comprises 26 bones and 33 joints. It has structures such as the ankle, heel, arch, and digits. The arched part of the foot that is present between the toes and the ankle is called instep. Let us understand the structure and all the parts of foot in detail.

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The foot can be broadly divided into the following parts:

Hindfoot

It consists of the Talus (ankle bone) and Calcaneus (heel bone). The place where the tibia and fibula connect with the talus makes up the ankle. Calcaneus is the largest bone found in the foot and has a layer of fat cushioning it. It joins with the talus at the Subtalar joint.

Midfoot

It is made up of five bones called the cuboid(1), navicular(1) and cuneiform(3). These bones form the foot arches. The main function of these arches is to absorb shock while walking. The muscles and plantar fascia located in the foot join the midfoot with other parts. 

Forefoot

The forefoot of a human has five toes and five proximal bones forming the metatarsus. The bones of the toes are referred to as phalanges. One toe has two phalanges, while the other four have three phalanges. The phalanges are joined together with the interphalangeal joint while connecting with the metatarsus at the metatarsophalangeal joint.

Bones

The bones that are found in the foot are:

• Tarsus: 

talus, calcaneus, cuneiformes (3), cuboid, and navicular

• Metatarsus: 

Five metatarsal bones are present, known as the first, second, third, fourth, and fifth metatarsal bone

• Phalanges: 

14 phalanges can be seen in humans

Muscles

The muscles of the feet can be divided into the following categories:

• Central muscles (Located in the sole)

• Lateral muscles 

• Medial muscles 

• Dorsum muscles

The central, lateral and medial muscles are located in the sole of the feet, while the dorsum muscles are located in the part of the feet that face upwards.

Tendon

The movement of feet is only possible when the strong muscles apply a pull on the rigid bones and relocate them. For this, there has to be a connection between the muscles and the bones. This is provided by tendons which are thick and elastic bands of tissue present as a connection between the bones and associated muscles. They are responsible for aiding the movement. The Achilles tendon in the human foot connects the heel to the calf and helps in standing on toes, running, jumping and other activities. 

Ligaments

Since there are so many bones present in the foot, they have to be joined together. This is done with the help of strong and flexible tissues known as ligaments. These are extremely strong and connect various bones together. 

Conclusion

A structure that aids in locomotion and is located at the terminal end of a limb is termed the foot. In invertebrates, foot refers to the locomotory organs such as arthropods limbs and mollusc burrowing organs. 

Muscles, tendons and ligaments run along with the structure of foot and allow movement to occur. The human foot has a dorsum (the area that faces up when a person is standing) and a planum- (The part of the foot that faces downward). Both the mid and forefoot are included in the dorsum and planum. The foot can be further divided into forefoot, midfoot and hindfoot.