True statements about osteoblasts are all except:
(A) Derived from osteoprogenitor cells (B) Regulated by BM P (C) Have a plasma membrane showing multiple folds (D) Have neuropeptide receptors
(C) Ans: C. Have a plasma membrane showing multiple folds(Ref Gray's 40/e p87, 88, 91)Characteristic of osteoclasts:Plasma membrane showing multiple folds.I.e. ruffled borders are involved in osteocytic resorption.Osteoclasts:Large (40 or more) polymorphic cells.Have upto 20 oval, closely packed nuclei.Howship's lacunae - Lie in close contact with bone surface in resorption bays.Cytoplasm:Contains numerous coated transpo vesicles & microtubule arrays.Involved in vesicles transpo between Golgi stacks & ruffled membrane.Ruffled membrane - Highly infolded cell surface of active osteoclasts at local bone resorption sites.Osteoblasts:Derived from osteoprogenitor (stem) cells of mesenchymal origin.Present in bone marrow & other connective tissues.Proliferate & differentiate after stimulated by bone morphogenetic proteins (BMPs a into osteoblasts prior to bone formation.