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The foot is a biological structure found in many animals that is used for locomotion. In many animals, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws or nails.
In land animals, some arthropods and all vertebrates have complex foot organs. The arthropod foot is known as a tarsus, and is distal to the tibia. In primitive insects, the tarsus was a single segment, but in more highly evolved insects the tarsus is composed of up to five segments, generally bearing claws as well.
The feet of terrestrial vertebrates, called tetrapods, first evolved in amphibians from the fins of their aquatic ancestors, fish that ventured out of the water as early as 370 million years ago, in the Upper Devonian Period, perhaps to avoid predation and exploit the greater resource availability on land. The fore- and hindlimbs of these earliest tetrapods evolved from the pectoral and pelvic fins of their fish ancestors, but early forms of feet such as those of Ichthyostega already contained the basic shape of the foot still possessed by tetrapods (although early tetrapods often had more than five digits, the most common form of foot in extant tertrapods).
The feet of terrestrial vertebrates are characterized as either plantigrade, digitigrade, or unguligrade. In plantigrade animals, such as frogs or bears, the bottom of the entire foot supports the weight of the animal. In digitigrade animals, such as wolves or birds, the toes bear the animal's weight, while the upper regions of the foot, the ankle and wrist, remain elevated. Finally, in unguligrade animals, such as cows or horses, even the toes are elevated, the animal standing only atop its nails, which have evolved to bear weight and are called hooves.
The human foot is of the plantigrade form. The bottom of the foot is called the sole and the area just behind the toes is called the ball. The skin at the sole of the foot is denser than any other area of skin on the human body.
The major bones in the human foot are:
The articulations of the foot are:
The muscles of the foot include:
In different cultures across the world, feet are perceived and treated differently.
Customs about footwear while indoors vary significantly from place to place and usually depend on climate, weather, and other factors:
One way to measure short distances on the ground is by placing one foot directly in front of the other; this led to the adoption of the foot as a unit of length, even though not all human feet correspond to this measure.
It is a myth that the Imperial "foot" (304.8 mm) is about the length of the average European male foot. The average today is less than 270 mm and 90% of the population is within 20 mm of that. Very few men today have feet that are a "foot" long: most are more than 35 mm shorter. In the past, the average length would have been less. Even the overall length of most shoes remains well short of one "foot". Tradition has it that the Imperial foot was based upon the size of Hercules' foot.
Due to their position and function, feet are exposed to a variety of potential infections and injuries, including athlete's foot, bunions, ingrown toenails, Morton's neuroma, plantar fasciitis, plantar warts and stress fractures. In addition, there are several genetic conditions that can affect the shape and function of the feet, including a club foot or flat feet.
A doctor who specializes in the treatment of the feet practices podiatry and is called a podiatrist. A pedorthist specializes in the use and modification of footwear to treat problems related to the lower limbs.
Reflexology is an alternative therapy which involves the stimulation of the nerves and skin of the feet to improve a person's health.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Foot". A list of authors is available in Wikipedia.|