8. HOW SMALL IS IT?

Relative sizes of some cellular ultrastructural elements

1000 nanometers (nm) = 1 micrometer (µm)
1000 micrometers (µm) = 1 millimeter (mm)

Structure Thickness, distance,
or diameter (nm)
cleft in gap junction 2
microfilaments (actin) 5 - 7
plasma membrane 7 - 8
intermediar filaments (neurofilaments, gliofilaments) 8 - 12
myosin 12 - 15
ribosomes 15 - 25
intercellular clefts in neuropil about 20
microtubules 20 - 25
glycogen granules 30
synaptic vesicles 40 - 60
periodicity in collagen 50 - 60
dense-core vesicles 60 - 120
nuclear pores 90
primary lysosomes 100 - 200
centriole 100 - 250
neurosecretory granules 100 - 400
mitochondria 100 - 500
cilia 200 - 400
human hair 70,000