This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Osteology, Subject name: Pathology
[{'content': 'All of the following are true about osteoclasts except \nSelect and explain. \nA. Derived from monocytes, B. PTH acts directly on osteoclasts, C. Associated with bone demineralisation, D. Can phagocytose foreign bodies', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans b: (PTH acts directly onosleoclasts) Ref: Harrisson 17th edition p 2367OsteoblastsSynthesize & secrete matrixMesenchymal originSeen on surface of new boneOsteoblast derived matrix when mineralized is osteocyteMineralisation depends on osteoblast derived ALP (marker of blast)Controls1. CBFA1 (Runx 2)- Transcription factor regulating osteoblast function. Heterozygous inactivating mutation Icleidocranial dysplasia2 Indian hedgehog3 Wnt family members. Deficiency of Wnt family co receptor LRP 5- osteoporosis4 TGF beta, FGFs 2 & 18, PDGF, IGF 1 $ 25 PTH & l,25 dihydroxyD activate receptors expressed by osteoblastOsteoclastResorption of boneMultinucleated giant cell (2-5nuclei) from monocyte/macrophage lineage.Macrophage colony stimulating factors (M-CSF) plays a crucial role Osteoblasts control osteoclast activityRANK ligand expressed over osteoblast progenitor & stromal cells bind to RANK receptor on osteoclast progenitor to stimulate osteoclast differentiation.Osteoprotegerin binds to RANK ligand and inhibit osteoclast differentiation1L 18 is also an inhibitor of osteoclast differentiationPTH & 1,25 dihydroxyD increases osteoclast number & activityEstrogen decreases osteoblast number and activity}Both indirectly through RANK L and M CSF.Calcitonin has direct inhibitory effect on osteoclast formation', 'role': 'assistant'}]