Table 8. Electron Microscopic
Classification of Human Extraocular Muscle Neuromuscular Junctions and
Corresponding Fiber Morphology
|
Neuromuscular Junction Type |
Classification |
1 |
2 |
3 |
3a |
4 |
5 |
Number observed |
2 |
10 |
3 |
2 |
3 |
1 |
Schwann cell investment |
+ |
+ |
+ or - |
- |
+ |
+ |
Terminal axon |
Thick |
Thin |
Thin |
7 |
7 |
7 |
Diameter |
3 μm |
1 μm |
|
|
|
|
Terminal varicosity |
? |
± |
+ |
+ |
9 |
9 |
Neurofilaments |
+ |
- |
- |
- |
- |
|
Synaptic vescicles |
|
|
|
|
|
|
Clear |
+ |
+ |
+ |
+ |
+ |
+ |
Granulated |
+ |
+ |
|
+ |
+ |
|
Ellipsoidal |
|
+ |
|
+ |
|
|
Muscle cell at neuromuscular junction |
|
|
|
|
|
|
Junctional folds |
+ |
+ |
- |
- |
± |
± |
Soleplate specializations* |
- |
- |
+ |
- |
+ |
± |
Depression of cell surface |
+ |
- |
- |
- |
- |
± |
Incidence of laminated structures |
2/2 |
2/10 |
0/3 |
0/2 |
2/3 |
1/2 |
Muscle cell morphology |
|
|
|
|
|
|
T systems and triads |
+ to + + |
+ |
± |
+ |
+ + to + + + |
+ + |
Sarcoplasmic reticulum |
+ to + + |
+ |
± |
± to + |
+ + to + + + |
+ |
Glycogen granules |
+ to + + |
+ |
± |
+ to + + |
+ to + + |
± to + |
Mitochondria |
+ to + + |
+ to + + |
± |
+ to + + |
+ to + + |
+ |
Z line |
Straight, slender |
Irregular |
Inconspicuous |
Irregular, thicker |
Straight, slender |
Straight, thick |
Myofibrils |
Moderately defined at T band level |
Irregular |
Irregular |
Slightly regular |
Well-defined at I band level |
Irregular |
*Hill-like elevations or bridgelike process.
Mukuno K: Fine structure of the human extraocular muscles: III. Neuromuscular
junctions in the normal human extraocular muscles. Acta Soc Ophthalmol
Jpn 72:104, 1968.
|