Sole (foot)

The sole is the bottom of the foot.

In humans the sole of the foot is anatomically referred to as the plantar aspect. The equivalent surface in ungulates is the hoof.

Human sole
The skin on the sole of the foot lacks the vellus hair and pigmentation found on the rest of the body, and has a high concentration of sweat pores. The soles are crossed by a set of creases that form during embryogenesis and contain the thickest layers of skin on the human body due to the weight that is continually placed on them. Like the palm, the sweat pores of the sole lack sebaceous glands.

Innervation
The soles of the feet are extremely sensitive to touch due to a high concentration of nerve endings. This makes them sensitive to surfaces that are walked on, ticklish and some people find them to be erogenous zones. Medically, the soles are the site of the plantar reflex, the testing of which can be painful due to the sole's sensitivity.

Arches
The sole of the adult foot is normally arched. Arches may fail to develop during childhood or may flatten during pregnancy and old age resulting in flat feet.

In culture
In Western culture the sensitivity of the sole makes it a target for tickling or sexual stimulation. .

In certain parts of Asia and the Middle East it is considered a great offense to show the sole of one's foot.

Because the skin of the sole is often thick and tough, some individuals attempt to beautify their feet by exfoliating the skin and moisturizing to soften the skin.

Sole of animals
Sole is a ventral side of the foot of various animals.

Gastropods have only one sole, because they have one foot. They have suprapedal gland in the front end of the sole.