
The frog is a part of a
horse hoof
A horse hoof is the lower extremity of each leg of a horse, the part that makes contact with the ground and carries the weight of the animal. It is both hard and flexible. It is a complex structure surrounding the distal Phalanx bones, phalanx o ...
, located on the underside, which should touch the ground if the horse is standing on soft footing. The frog is triangular in shape, and extends midway from the heels toward the toe, covering around 25% of the bottom of the hoof.
The frog is a V-shaped structure that extends forward across about two-thirds of the sole. Its thickness grows from the front to the back and, at the back, it merges with the heel
periople. In its midline, it has a central groove (
sulcus) that extends up between the bulbs.
The color of the frog varies between horses and can have no pigment making it cream colored, or with pigment fully or partially giving darker color. Its rubbery consistency suggests a role as a shock absorber and grip tool on hard, smooth ground. The frog also acts like a pump to move the blood back to the heart, a great distance from the relatively thin leg to the main organ of the circulatory system.
In the stabled horse, the frog does not wear but degrades, due to bacterial and fungal activity, to an irregular, soft, slashed surface. In the free-roaming horse, it hardens into a callus consistency with a near-smooth surface. For good health, the horse requires dry areas to stand. If chronically exposed to bacteria, for example standing in manure, the frog will develop an infection called thrush.
The frog is anatomically analogous to the human fingertip.
Digit remnants
A 2018 study on horse foot morphology has suggested that the frog is actually composed of remnants of digits II and IV. This indicates that horses are not truly monodactyl and posits a more complex formation of the horse foot than simple side toe reduction.
See also
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Circulatory system of the horse
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Equine anatomy
Equine anatomy encompasses the gross and microscopic anatomy of horses, ponies and other equids, including donkeys, mules and zebras. While all anatomical features of equids are described in the same terms as for other animals by the Internati ...
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Farrier
A farrier is a specialist in equine hoof care, including the trimming and balancing of horses' hooves and the placing of shoes on their hooves, if necessary. A farrier combines some blacksmith's skills (fabricating, adapting, and adju ...
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Horse hoof ยง sole
References
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Equine hoof
Horse anatomy