<P> A corn (or clavus, plural clavi) is a specially shaped callus of dead skin that usually occurs on thin or glabrous (hairless and smooth) skin surfaces, especially on the dorsal surface of toes or fingers . They can sometimes occur on the thicker palmar or plantar skin surfaces . Corns form when the pressure point against the skin traces an elliptical or semi-elliptical path during the rubbing motion, the center of which is at the point of pressure, gradually widening . If there is constant stimulation of the tissue producing the corns, even after the corn is surgically removed, the skin may continue to grow as a corn . </P> <P> The hard part at the center of the corn resembles a funnel with a broad raised top and a pointed bottom . Because of their shape, corns intensify the pressure at the tip and can cause deep tissue damage and ulceration . The scientific name for a corn is heloma (plural helomata). A hard corn is called a heloma durum, while a soft corn is called a heloma molle . </P> <P> The location of the soft corns tends to differ from that of hard corns . Hard corns occur on dry, flat surfaces of skin . Soft corns (frequently found between adjacent toes) stay moist, keeping the surrounding skin soft . The corn's center is not soft however, but indurated . </P> <P> The specific diagnostic workup and treatments for corns may differ substantially from other forms of calluses . </P>

What type of cell injury is the formation of a callus on the foot