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'''Osteoclasts'''

'''Osteoclasts'''

Osteoclasts are giant (multinucleate [[Monocytes|monocytes]]) cells. Histologically, they are large, often multinucleated cells. They have an acidophilic cytoplasm. They sit in the bone surface depression known as, '''howship's lacuna'''. Osteoclasts respond to vitamin D by increasing their numbers and activity (parathyroid independent). Osteoclasts act to resorb the bone ECM. They firstly dissolve mineral followed by collagen, using the brush border. They do <u>not</u> have receptors for PTH, but do have receptors for [[Bones - normal#Bone resorption|calcitonin]].  

Osteoclasts are giant (multinucleate [[Monocytes|monocytes]]) cells. Histologically, they are large, often multinucleated cells. They have an acidophilic cytoplasm. They sit in the bone surface depression known as, '''howship's lacuna'''. Osteoclasts respond to vitamin D by increasing their numbers and activity (parathyroid independent). Osteoclasts act to resorb the bone ECM. They firstly dissolve mineral followed by collagen, using the brush border. They do <u>not</u> have receptors for PTH, but do have receptors for [[Calcium#Calcitonin|calcitonin]].  

Osteoblasts, osteocytes, chondroblasts and chondrocytes are derived from the stromal fibroblastic system ('''osteoprogenitor cells'''). Osteoclasts are derived from the haematopoietic system.

Osteoblasts, osteocytes, chondroblasts and chondrocytes are derived from the stromal fibroblastic system ('''osteoprogenitor cells'''). Osteoclasts are derived from the haematopoietic system.