Bone cells: osteoclasts

These spicules of bone are being resorbed by osteoclasts; large, motile cells with multiple nuclei. Throughout life, bone is resorbed and deposited to both renew and repair the matrix and to respond to mechanical stresses. Resorption results in the formation of depressions in the bone called Howship’s lacunae. Osteoclasts belong to the monocyte lineage and are not related to osteoblasts or osteocytes. Spongy bone, 400x, 1000x

The ruffled border consists of the highly folded plasma membrane on the bone-facing surface of an active osteoclast. The ruffled border creates a microenvironment into which the osteoclast secretes acid and proteases to dissolve and degrade the bone matrix, resulting in a Howship’s lacuna.

The ruffled border consists of the highly folded plasma membrane on the bone-facing surface of an active osteoclast. The ruffled border creates a microenvironment into which the osteoclast secretes acid and proteases to dissolve and degrade the bone matrix, resulting in a Howship’s lacuna.

Osteoblasts are depositing bone onto the surface of the spicule opposite from the osteoclast.

Osteoblasts are depositing bone onto the surface of the spicule opposite from the osteoclast.

Bone lining cells are quiescent, flattened osteoblasts that cover bone surfaces where neither bone resorption nor bone formation is occurring. They can be induced to proliferate and differentiate into osteoblasts and may also represent a source of “determined” osteogenic precursors. Bone lining cells maintain bone remodeling and mineral homeostasis.

Osteocytes are located within lacunae, small spaces within the mineralized bone matrix.

Osteocytes are located within lacunae, small spaces within the mineralized bone matrix.

These images were taken of a slide in the University of Cincinnati collection.