Model Guide

BS36
SEIT 1876
Quergestreifte Muskelfaser
mit motorischer Nervenendplatte
Striadet Muscle Fiber
with Motor End-Plate
Fibre musculaire striee avec plaqu LIBRARY
motrice des terminaisons nerveuse USEONLY
Fibra muscular estriada,
CIRCDESK
MODEL
con placa terminal motriz
DO NOT CHECK IN.
BARCODE ON OUTER CONTAINER
QM
151
.5875
2012
GUIDE
Striated Muscle
Fiber with
Motor End-Plate
Enlarged approximately 4000 times
I. Striated muscle fiber
The striated muscle fiber is not a simple
cell, but a multinuclear cylindrical plasmodium (in its normal state).
The
(1)
(2)
(3)
principal constituents are:
Sarcoplasm cytoplasmic matrix
Nuclei
Myofibrils; they are grouped together in columns such that in cross section there appears an alternating light
and dark pattern.
Cohnheim's areas
Sarcolemma: it is a finely layered
matrix, consisting of the plasmalemma, the basal membrane and the
reticular fibrous lattice, which is connected to the endomysium (6).
Microscopically the myofibrils appear
striated and the exceptionally large number of fibrils impart the striation to the entire muscle fiber. Each fibril consists of various refactive substances which alternate
periodically in the following pattern:
A (Q) - stripes = a dark anisotropic substance giving a double refractions of light in
the polarising microscope.
I - stripes = light substances giving a
single refraction of light.
In addition to the anisotropic and isotropic stripes there are fine lines.
M - line across the middle of the
Q^tripe
Z - line continuous across the middle of
the I-stripe and intervening sarcoplasm to
the sarcolemmae.
SEIT 1876
SEIT 1876
In the myofibrils two types of protein filaments can be identical with the electron
microscope. The short and thick myosin filaments found only in the A-substance and
which are slightly thicker at the M-line. The
longer and thinner actin filaments are located in the I-stripes and insert between the
myosin filaments of the A-stripes.
II. Terminal section of a
medullated nerve fibre
with motor end-plate on
the medullated nerve
fiber (neurit)
On a medullated nerve fibre (neurit) (7)
we distinguish:
(8)Axis cylinder (axon and neuraxon)
consisting of a cylindrical protoplasmic
mass (neuroplasm), where parallel neurofibrils are situated.
The myelin sheath (9) ends just before the
motor axon branches out to contact the
sarcoplasm. The colouring of the mitochondria in the terminal axoplasm shows
the existance of very small granules (10)
principally in the longitudinal axis of the
branches. These granules stain the same as
mitochondria.
W ith the use of silver staining procedures it
was demonstrated that the motor axon extends beyond the myelin sheath into the
terminal branches (11), and that despite a
dichotomous division the diameter
remained constant.
The terminal neurofibrils appear in all
sections of the branches as bundles (12).
The nerve branches are connected with the
Schwann cells (13). The synaptic vesicles
are held in a sarcoplasmic cavity (14), which
in this area is rich in nuclei (15) and mitochondria (16). The contact between axoplasma and sarcoplasma appears as a thin
line (subneural lamella) (17) and on the
border line between axo-and sarcoplasma
looks like a palisade fence. In a frontal
plane the lamella resemble a finger print
(18).
At the margin they are more compact.
The terminal nerve branches are enclosed
within the synaptic vesicle (19).
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