b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”210 Tissue Engineering and Nanotheranostics
they have no membrane cover. Also the centrioles duplicate each
other in a unique way, and upon duplication the newer of the dupli
cated pairs moves away and onto the other side of the nucleus to drive
the separation and duplication of the cell itself.
From a microscopic perspective, each centriole appears as a hol
low cylinder approximately 400–500 nm long, 200 nm in outside
diameter and 50 nm in inside diameter. Upon closer examination, the
centriole is seen to be composed of parallel hollow tubes known as
“microtubules”. The microtubules have the length of a centriole
(approximately 400–500 nm), but with an outside diameter of only
25 nm. The wall thickness of a microtubule is 5 nm and thus the
inside diameter is approximately 10 nm.
Each centriole has at least 27 microtubules, arranged in 9 “blades”
of 3 each. Some centrioles also have two microtubules along the cen
triole axis of the centriole center.
Figure 2 shows a sketch of a centriole pair.
The blades (or triplets) of the microtubules are parallel to each
other and in a plane; but the plane is slightly inclined to the radial
Fig. 2. A centriole pair.