Osteoclast cross-section, illustration. Osteoclasts are large, multinucleated bone cells with a ruffled border and a high number of vesicles and vacuoles. They are essential for the maintenance and repair of bones. Osteoclasts are found in small depressions, called Howslips lacunae, on the surface of bones. Osteoclasts continuously remodel bone surface by degrading and resorbing older bone material in response to growth or changing mechanical stress. As they do this, osteoblasts form and remodel new bone. As we age, osteoblasts and the formation of new bone material diminishes. However osteoclasts continue to function, leading to conditions such as osteoporosis, in which bones become weaker and more susceptible to fractures.