New Members Pencak Silat Posted April 6, 2012 New Members Share Posted April 6, 2012 (edited) Avian medullary bone is described as a secondary bone tissue that provided calcium for producing eggshell, and have no biomechanical function. Medullary bone are thought only found in avian at first, until in 2005 medullary bone like-tissue also found in dinosaur fossil, but it is still dubious by many experts. Medullary tissue is a very brittle and fragile type of bone that the spicules of medullary bone easily separated from the originating layer, but why the thin basal layer remains attached to the cortex? This is the link where it showed two pictures of medullary spicules easily separated from the cortical bone but leave some portions on the cortex. (http://www.sciencemag.org/content/suppl/2005/05/27/308.5727.1456.DC1/Schweitzer.SOM.pdf) Did the thin basal layer have any mechanical strength or will it eventually completely separated from cortical bone after sometime? I think the medullary bone will be totally removed from the cortex. Edited April 6, 2012 by Pencak Silat Link to comment Share on other sites More sharing options...
Auspex Posted April 6, 2012 Share Posted April 6, 2012 In birds, the primary function of medullary bone is to cache a reservoir of calcium for the creation of eggshell; if it also happens to provide structural support, this would be a secondary advantage. Typically, this temporary cache of available calcium is completely depleted in the process of egg formation, and some skeletal calcium must still be used, so I doubt that a secondary function of structural support is relied on (or strongly selected for in an evolutionary sense). "There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant “Try to learn something about everything and everything about something.” - Thomas Henry Huxley >Paleontology is an evolving science. >May your wonders never cease! Link to comment Share on other sites More sharing options...
New Members Pencak Silat Posted April 6, 2012 Author New Members Share Posted April 6, 2012 (edited) In birds, the primary function of medullary bone is to cache a reservoir of calcium for the creation of eggshell; if it also happens to provide structural support, this would be a secondary advantage. Typically, this temporary cache of available calcium is completely depleted in the process of egg formation, and some skeletal calcium must still be used, so I doubt that a secondary function of structural support is relied on (or strongly selected for in an evolutionary sense). Assuming we are going to sectioning an avian or a ratite femur, then we see the medullary bone lines along the cortex wall. I recalled that the bone tissue is fragile, but if you go to the link given, the thin basal layer remain attached to the bone wall whereas the spicules separating easily from the layer. Why the layer remain attached, did it remain attached to the cortex or eventually all the medullary bone will completely separated from the cortical bone? And can we easily remove the entire medullary bone from the cortex using utensils such as spatula and even our fingers? Edited April 6, 2012 by Pencak Silat Link to comment Share on other sites More sharing options...
Auspex Posted April 6, 2012 Share Posted April 6, 2012 Medullary "bone" is calcium that is sequestered for use in the formation of eggshell, so that structural bone need not be greatly impaired in its primary function during the breeding period. Outside the breeding period, formation of medullary bone is dispensed with completely, and if any were to be left over, it would be absorbed for other metabolic uses. "There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant “Try to learn something about everything and everything about something.” - Thomas Henry Huxley >Paleontology is an evolving science. >May your wonders never cease! Link to comment Share on other sites More sharing options...
New Members Pencak Silat Posted April 7, 2012 Author New Members Share Posted April 7, 2012 I see, the degree of calcification of medullary bone is higher than that of cortical bone. But does it mean that the medullary bone are harder than the cortical bone/cortex? Link to comment Share on other sites More sharing options...
Auspex Posted April 7, 2012 Share Posted April 7, 2012 I do not know that it is "harder"; it is, after all, meant to be resorbed when needed. Here is a link to a paper that might be useful: LINK "There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant “Try to learn something about everything and everything about something.” - Thomas Henry Huxley >Paleontology is an evolving science. >May your wonders never cease! Link to comment Share on other sites More sharing options...
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