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==Human foot== ==Human foot==
Feet can be harmful when put in someone's asshole.
===Anatomy===
The human foot and ankle is a strong and complex mechanical structure containing more than 26 bones, 33 joints (20 of which are actively articulated), and more than a hundred muscles, tendons, and ligaments.<ref name="Podiatry-Channel">Podiatry Channel, ''Anatomy of the foot and ankle''</ref>

An anthropometric study of 1197 North American adult Caucasian males (mean age 35.5 years) found that a man's foot length was 26.3&nbsp;cm with a standard deviation of 1.2&nbsp;cm.<ref>{{cite journal |author=Hawes MR, Sovak D |title=Quantitative morphology of the human foot in a North American population |journal=Ergonomics |volume=37 |issue=7 |pages=1213–26 |year=1994 |month=July |pmid=8050406 |doi= 10.1080/00140139408964899|url=}}</ref>

The foot can be subdivided into the hindfoot, the midfoot, and the forefoot:

The '''hindfoot''' is composed of the ] or ankle bone and the ] or heel bone. The two long bones of the lower leg, the ] and ], are connected to the top of the talus to form the ]. Connected to the talus at the ], the calcaneus, the largest bone of the foot, is cushioned inferiorly by a layer of fat.<ref name="Podiatry-Channel" />

The five irregular bones of the '''midfoot''', the ], ], and three ] bones, form the ] which serves as a shock absorber. The midfoot is connected to the hind- and fore-foot by muscles and the ].<ref name="Podiatry-Channel" />

The '''forefoot''' is composed of five toes and the corresponding five proximal long bones forming the ]. Similar to the fingers of the hand, the bones of the toes are called ] and the ] has two phalanges while the other four toes have three phalanges. The joints between the phalanges are called ] and those between the metatarsus and phalanges are called ] (MTP).<ref name="Podiatry-Channel" />

{{anchor|instep}}
The '''instep''' is the arched part of the top of the foot between the toes and the ankle.

====Skeleton====
]
* ], ]
* ]: ], ], ], ], and ]
* ]: ], ], ], ], and ]
* ]

There can be many ]s near the metatarsophalangeal joints, although they are only regularly present in the distal portion of the ].<ref name="Platzer-220">Platzer 2004, p 220</ref>

=====Arches=====
{{Main|Arches of the foot}}
The human foot has two ] arches and a transverse arch maintained by the interlocking shapes of the foot bones, strong ligaments, and pulling muscles during activity. The slight mobility of these arches when weight is applied to and removed from the foot makes walking and running more economical in terms of energy. As can be examined in a footprint, the medial longitudinal arch curves above the ground. This arch stretches from the heel bone over the "keystone" ankle bone to the three medial metatarsals. In contrast, the lateral longitudinal arch is very low. With the cuboid serving as its keystone, it redistributes part of the weight to the calcaneus and the distal end of the fifth metatarsal. The two longitudinal arches serve as pillars for the transverse arch which run obliquely across the tarsometatarsal joints. Excessive strain on the tendons and ligaments of the feet can result in fallen arches or ].<ref name="Marieb-Hoehn-244">Mareb-Hoehn 2007, pp 244-45</ref>

====Muscles====
The muscles acting on the foot can be classified into extrinsic muscles, those originating on the anterior or posterior aspect of the lower leg, and intrinsic muscles, originating on the dorsal or plantar aspects of the foot.

=====Extrinsic=====
]
All muscles originating on the lower leg except the ] are attached to the bones of the foot. The tibia and fibula and the interosseous membrane separate these muscles into anterior and posterior groups, in their turn subdivided into subgroups and layers.
<ref name="Platzer-256">Platzer 2004, p 256</ref>

'''Anterior group'''

'''Extensor group''': ] originates on the proximal half of the tibia and the interosseous membrane and is inserted near the ] of the first digit. In the non-weight-bearing leg tibialis anterior flexes the foot dorsally and lift its medial edge (]). In the weight-bearing leg it brings the leg towards the back of the foot, like in rapid walking. ] arises on the lateral tibial condyle and along the fibula to be inserted on the second to fifth digits and proximally on the fifth metatarsal. The extensor digitorum longus acts similar to the tibialis anterior except that it also dorsiflexes the digits. ] originates medially on the fibula and is inserted on the first digit. As the name implies it dorsiflexes the big toe and also acts on the ankle in the unstressed leg. In the weight-bearing leg it acts similar to the tibialis anterior.
<ref name="Platzer-258">Platzer 2004, p 258</ref>

'''Peroneal group''': ] arises on the proximal aspect of the fibula and ] below it on the same bone. Together, their tendons pass behind the lateral ]. Distally, peroneus longus crosses the plantar side of the foot to reach its insertion on the first tarsometatarsal joint, while peroneus brevis reaches the proximal part of the fifth metatarsal. These two muscles are the strongest pronators and aid in plantar flexion. Longus also acts like a bowstring that braces the transverse arch of the foot.
<ref name="Platzer-260">Platzer 2004, p 260</ref>

{{double image|right|Gray438.png|100|Gray439.png|80|Deep and superficial layers of posterior leg muscles}}
'''Posterior group'''

The '''superficial layer''' of posterior leg muscles is formed by the ] and the ]. The triceps surae consists of the ] and the two heads of the ]. The heads of gastrocnemius arise on the ], proximal to the condyles, and soleus arises on the proximal dorsal parts of the tibia and fibula. The tendons of these muscles merge to be inserted onto the calcaneus as the ]. Plantaris originates on the femur proximal to the lateral head of the gastrocnemius and its long tendon is embedded medially into the Achilles tendon. The triceps surae is the primary plantar flexor and its strength becomes most obvious during ballet dancing. It is fully activated only with the knee extended because the gastrocnemius is shortened during knee flexion. During walking it not only lifts the heel, but also flexes the knee, assisted by the plantaris.<ref name="Platzer-262">Platzer 2004, p 262</ref>

In the '''deep layer''' of posterior muscles ] arises proximally on the back of the interosseous membrane and adjoining bones and divides into two parts in the sole of the foot to attach to the tarsus. In the non-weight-bearing leg, it produces plantar flexion and supination, and, in the weight-bearing leg, it proximates the heel to the calf. ] arises on the back of the fibula (i.e. on the lateral side), and its relatively thick muscle belly extends distally down to the ] where it passes over to the medial side to stretch across the sole to the distal phalanx of the first digit. The ] is also part of this group, but, with its oblique course across the back of the knee, does not act on the foot.
<ref name="Platzer-264">Platzer 2004, p 264</ref>

=====Intrinsic=====
On the '''back''' (top) '''of the foot''', the tendons of ] and ] lie deep to the system of long extrinsic extensor tendons. They both arise on the calcaneus and extend into the dorsal ] of digits one to four, just beyond the penultimate joints. They act to dorsiflex the digits.
<ref name="Platzer-268">Platzer 2004, p 268</ref>

{{triple image|right|Gray443.png|83|Gray444.png|91|Gray445.png|100|Plantar aspects of foot, varying depths (superficial to deep)}}

Similar to the intrinsic muscles of the hand, there are three groups of muscles in the '''sole of foot''', those of the first and last digits, and a central group:

'''Muscles of the ]''': ] stretches medially along the border of the sole, from the calcaneus to the first digit. Below its tendon, the tendons of the long flexors pass through the ]. It is an abductor and a weak flexor, and also helps maintain the arch of the foot. ] arises on the medial cuneiform bone and related ligaments and tendons. An important plantar flexor, it is crucial for ballet dancing. Both these muscles are inserted with two heads proximally and distally to the first metatarsophalangeal joint. ] is part of this group, though it originally formed a separate system (see ].) It has two heads, the oblique head originating obliquely across the central part of the midfoot, and the transverse head originating near the metatarsophalangeal joints of digits five to three. Both heads are inserted into the lateral sesamoid bone of the first digit. Adductor hallucis acts as a tensor of the plantar arches and also adducts the big toe and then might plantar flex the proximal phalanx.
<ref name="Platzer-270">Platzer 2004, pp 270-72</ref>

'''Muscles of the ]''': Stretching laterally from the calcaneus to the proximal phalanx of the fifth digit, ] form the lateral margin of the foot and is the largest of the muscles of the fifth digit. Arising from the base of the fifth metatarsal, ] is inserted together with abductor on the first phalanx. Often absent, ] originates near the cuboid bone and is inserted on the fifth metatarsal bone. These three muscles act to support the arch of the foot and to plantar flex the fifth digit.
<ref name="Platzer-272">Platzer 2004, p 272</ref>

{{double image|right|Gray446.png|100|Gray447.png|100|Central muscles of foot}}
'''Central muscle group''': The four ] arise on the medial side of the tendons of flexor digitorum longus and are inserted on the medial margins of the proximal phalanges. ] originates with two slips from the lateral and medial margins of the calcaneus and inserts into the lateral margin of the flexor digitorum tendon. It is also known as flexor accessorius. ] arise inferiorly on the calcaneus and its three tendons are inserted into the middle phalanges of digits two to four (sometimes also the fifth digit). These tendons divide before their insertions and the tendons of flexor digitorum longus pass through these divisions. Flexor digitorum brevis flexes the middle phalanges. It is occasionally absent. Between the toes, the ] and ] stretch from the metatarsals to the proximal phalanges of digits two to five. The plantar interossei adducts and the dorsal interossei abducts these digits and are also plantar flexors at the metatarsophalangeal joints.
<ref name="Platzer-274">Platzer 2004, p 274</ref>


===Medical aspects=== ===Medical aspects===

Revision as of 03:20, 17 December 2010

For other uses, see Foot (disambiguation).
It has been suggested that Foot type be merged into this article. (Discuss) Proposed since August 2009.
Foot
Details
Arterydorsalis pedis, medial plantar, lateral plantar
Nervemedial plantar, lateral plantar, deep fibular, superficial fibular
Identifiers
Latinpes
MeSHD005528
TA98A01.1.00.040
TA2166
FMA9664
Anatomical terminology[edit on Wikidata]

The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, 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.

Human foot

Feet can be harmful when put in someone's asshole.

Medical aspects

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 disorders that can affect the shape and function of the feet, including a club foot or flat feet.

This leaves humans more vulnerable to medical problems that are caused by poor leg and foot alignments. Also, the wearing of shoes, sneakers and boots can impede proper alignment and movement within the ankle and foot. For example, high heels are known to throw off the natural weight balance (this can also affect the lower back). For the sake of posture, flat soles and heels are advised.

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.

Evolutionary variations

Main article: Comparative foot morphology

A paw is the soft foot of a mammal, generally a quadruped, that has claws or nails. A hard foot is called a hoof.

Depending on style of locomotion, animals can be classified as plantigrade (sole walking), digitigrade (toe walking), or unguligrade (nail walking).

The metatarsals are the bones that make up the main part of the foot in humans, and part of the leg in large animals or paw in smaller animals. The number of metatarsals are directly related to the mode of locomotion —five digits being the most primitive setup, with many larger animals having their digits reduced to two (elk, cow, sheep) or one (horse). The metatarsal bones of feet and paws are tightly grouped compared to, most notably, the human hand where the thumb metacarpal diverges from the rest of the metacarpus.

See also

Footnotes

  1. France 2008, p 537

References

External links

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