Type I collagen secretion in the bone matrix formation is mediated by
A. chondroblasts
B. chondrocytes
C. endothelial cells
D. macrophages
E. osteoblasts
F. osteoclasts
G. osteocytes
agree...
calendar you are always the first one to answer! you're doing great...when r u taking the exam? GL
Hey guys,
Not too fast. G is the answer. Blasts mean immature or stem cells.
High yield Histology (lippincott williams & wilkins) 2nd edition, p.33:
Osteoblasts: secrete osteoid, which is unmineralized bone atrix consisting of proteoglycans, glycoproteins, and type I collagen.
p. 34 also states:
Osteoblasts secrete IL-1, which is a potent stimulator of osteoclast activity.
C. Osteocytes:
1. osteocytes and their cytoplasmic processes are surrounded by bone matrix because they reside in spaces called lacunae and canaliculi, respectively. Cytoplasmic processes of neighboring osteocytes communicate via gap junctions.
2.osteocytes do not undergo mitosis. (That's all about osteocytes they mentioned)
Calendar,
well, I do not want to dispute what High yield Histology (lippincott williams & wilkins) described. When you know something you do not have to rely on books. There are often a small % in books are incorrect because they just copied it from one source or the other.
For my PhD dissertation, I studied bone biology. I know what I am talking about on this topic. I am sure osteoblasts make type I collagen. Once they stop proliferation, start to differentiate, and make much more type I collagen, we no longer call them osteoblasts. We call them osteocytes. So if osteocyte is on the list, pick it over osteoblast; if not, pick osteoblast. With that said, osteocyte could be a wrong answer on the real test because not every test question is written by real expert in the field.
...............
Wait, before I click submit, I did check a few sources for the definition of osteoblasts and osteocytes. They are all truly traditional HISTOLOGY/endpoint definition, not embryological or developmental definition. Maybe the USMLE just wants the examinees to know this traditional one, not the correct modern one. Now I have a better understanding why some people said knowing too much might hurt you on the real exam.
Sorry, guys, tried to help. Now I think you should stick to your original answer, not the way I thought you should answer it.
Thank you Ericz. I am not very familiar to this area, I am glad this didn't show up in my exam. I am sure if you know the updated one, just pick it. Have faith in yourself.
Osteoblast is definitely not stem cells. Not all "blast" means undifferentiated cell. It is differentiated from bone marrow stem cells, but not at terminal stage. The relationship between osteoblast and osteocyte may be just like one between monocyte and macrophage.