| Comments |
Abstract:"Finally, based on the average speed of remodelling in the adult, [investigators] calculate that 9.1 million osteocytes are replenished throughout the skeleton on a daily basis, indicating the dynamic nature of the osteocyte network." p.147 right column 2nd paragraph:"Although some osteocytes, such as those in the inner ear, may exist
for as long as human life [ref 38], the majority are regularly removed and
replaced due to the renewal of the bone matrix during remodelling.
Parfitt [ref 25, Table 7] estimated the average skeletal remodelling rate
(Rem.R) to be 7.6%/year (combining both cortical and trabecular turnover
rates). Over the entire human skeleton bone volume (BV), this
corresponds to a volume of renewed bone matrix of 133 cm^3/year
(0.36 cm^3/day). Assuming this renewed bone to contain the same
density of osteocytes, this corresponds to the replacement of
2.66 × 10^9–3.99 × 10^9 (average 3.33 billion) new osteocytes per year
(9.1 million per day)." p.148 left column bottom paragraph:"A large number of osteocytes are replaced rapidly by remodelling —
an estimated 9.1 million per day. This level of replacement falls below
that of red blood cells (at 34.6 billion per day) [ref 50], but is far greater
than the level of renewal estimated for hippocampal neurons (ref 700 per
day) [ref 51]." |