Summary IV

Hypothesis: "elastic properties of the fibril "depend on/correlate with" the shape and volume fraction of HA platelets.

The above articulates a central concept in injury prevention--bone "strength" correlates with the shape and % of the mineral platelets.

That was the Planck Instiut piece which, with unusual thoroughness, aims to discover the "elastic properties" of each microscopic component of bone, smallest to largest.

at nano level bone is:

collagen molecules--insides of the fibril (cell)
collagen fibrils
collagen fibril arrays

The "fibril" is the Type I Collagen Bone Cell that, in addition to nucleus, mitochondria etc. contains water and after birth secretes HA (hydroxyapetite) crystals (mineral salts) in the interior of each cell and also in rings around the outside surface that coat the fibril.

Between separate fibrils there is nano spacing filled in with bone glue proteins. We learn, through Planck, that fibrils vis a vis each other randomly self arrange into "fibril arrays", and that possibly we might influence the manner of arrangement by our exercise program.

Planck further breaks these "elastic properties" of bone:

constituents
orientation
distribution
shape.

Lest we blithely think this gets too complex, Planck notes the above as having "crucial importance", which we may recognize when we consider that the fibril arrays build themselves in concentric rings called osteons--which are the basic structures of cortical bone.

And, with this intro Planck gets down to business. Extra fibrillar mineralization are the mineral blobs on each fibril's surface. These blobs form the fibril outer coating. The blobs come in various shapes and sizes varying (possibly) according to what we've done with the bone. Through "molecular dynamic computer simulations" we test how the presence (shape and volume) of HA crystals influences mechanical behavior of the cells and molecules!

The outcome? Indeed strength and toughness depends on size and arrangement pattern (shape), which we may possibly influence!

Training:

3/20 and 21 Sat. and Sun. Off. 6 inches of snow.