List of abbreviations
of micros-
specialist terms
explained in
English +

Every attempt was made to provide correct information and labelling, however any liability for eventual errors or incompleteness is rejected!

dieser Seite

Dr. med.
H. Jastrow

of use
Overview skeletal muscle (Textus muscularis striatus skeletalis):
Pages with explanations are linked to the text below the images if available! (Labelling is in German)
 contracted human
eye muscle 1
contracted human
eye muscle 2
contracted human
eye muscle 3
human eye muscle
uncontracted human
eye muscle
T- and L- Tubuli, beta-Glykogen
granules 1 (rat)
T- + L- Tubuli, beta-Gly-
kogen granules 2 (rat)
T- and L- Tubuli 3
very large mitochondrium
nucleus and nucleolus
detail thereof nuclear pores myocyte
T-tubule, endothelium,
capillary (rat)
peripherical cell nucleus
rump muscle fibres +
capillaries (rat)
capillary with pores in
endothelium (rat)
large aggregation of
mitochondria (rat)
overview longitudinal
section 1 (monkey)
section 2 (monkey)
nucleus, fibrils
fibril bundles 1 (monkey) fibrils 2 (monkey) fibrils 3 (monkey) fibrils 4 (monkey)
fibrils +
mitochondria (monkey)
fibrils and mito-
chondria 2 (monkey)
thin fibrils in eye
muscle (monkey)
eye muscle detail (monkey) other detail with mito-
chondria (monkey)
fibrils + beta-glycogen
myofibrils (rat)
filaments, A- + i-
band, Z-stripe 1 (monkey)
filaments, A- + i-
band, Z-stripe 2 (monkey)
M- + H- stripe
A-band (monkey)
Z-stripe, i-band
mitochondrium (monkey)
i-band, Z-stripe,
beta-glycogen (monkey)
A-band, M- + H-
stripe 2 (monkey)
A-band, M- and H-
stripe 3 (rat)
x-section of filaments
cross-section: A-band,
M- and H-line (monkey)
satellite cell, cross-section
cross-section of Z-stripe
1 (monkey)
cross-section of Z-stripe
2 (monkey)
cross-section of Z-stripe
3 (monkey)
cross-section of the
i-band (monkey)
cross-section of A & i
band 1 (monkey)
cross-section of the
M-stripe (monkey)
cross-section of A & i
band 2 (monkey)
cross-section of A & i
band 3 (monkey)
T-tubule (monkey)
sarcomer (distance between
2 Z-stripes; rat)
synapse (rat)

Skeletal striated muscle cells  (Terminologia histologica: Myocyti striatae non cardiaci) are extremely long (several centimetres) and columnar in shape. Their diameters are between 10 and 100 µm, in most cases 40 - 80 µm. This diameter increases under contraction. Innumerable disc-like nuclei are always located to the margins of the cells and lie close to the cell membrane which is called here sarcolemma (Terminologia histologica: Sarcolemma). The cytoplasm of these muscle cells is called sarcoplasm (Terminologia histologica: Sarcoplasma) contains some hundreds to thousands of myofibrils (Terminologia histologica: Myofibrillae). The latter are round, several centimetres long and have diameters of (0.1 to1.5 µm). They consist of a periodic sequence of actin- and myosin filaments in parallel order and associated proteins (see below). Usually very large aggregations of mitochondria of crista-type lie in close vicinity. Further such mitochondria are seen in a regular order along the myofibrils adjacent to the Z-disc region with a central interruption caused by the very long T-tubules (= transverse tubules; Terminologia histologica: Tubulus T; Tubulus transversus) which extend as long tubular invaginations of the cell membrane very deep into the cytoplasm. These T-tubules are flanked on two opposing sides by long cisterns of the smooth endoplasmic reticulum (SER), which is called sarcoplasmic reticulum (Terminologia histologica: Reticulum sarcoplasmicum) in skeletal muscle cells. These cisterns of the SER are also termed longitudinal- or shorterL-Tubules (Terminologia histologica: Tubulus longitudinalis, Tubulus L). These 3 adjacent tubules (L-T-L) which are termed Triads (Terminologia histologica: Trias) are characteristic for skeletal musculature. The SER extends like a net from the cisterns next to the T-tubules around the fibrils. It is the essential storage site for calcium ions which are needed for muscular contraction. Larger or smaller amounts (depending on the type of muscle fibre) of beta-glycogen granules are present next to the myofibrils as well. A considerable quantity of invaginations and infoldings of the cell membrane is seen on the long ends of muscle cells. They serve for surface enlargement. The last actin filaments of the myofibrils are directly connected to integrin molecules which reach through the cell membrane and bind tightly to the basal lamina which is further connected to collagen fibrils of an adjacent tendon or a periosteum or a perichondrium.
Directly adjacent to the skeletal muscle cells small mononuclear myosatellite cells (Terminologia histologica: Myosatellitocyti) are present which are able to undergo mitosis whereby one new cell later will be incorporated into the muscle cell contributing its nucleus and cytoplasm since mitotic processes do not take place inside the large muscle cells themselves. However for growing and under training conditions a higher protein synthesis is required in muscle cells for increase in thickness thus more genetic information, i.e. new nuclei are necessary. The satellite cells are resting myoblasts located under the basement membrane coat of the muscle cell.

An English page with much more detailed information is available in the professional version of this atlas.

--> differential diagnosis of muscle tissues, heart muscle, smooth muscles, neuromuscular junction, L-tubules, beta-glycogen, actin filaments
--> Electron microscopic atlas Overview
--> Homepage of the workshop

Many images were kindly provided by Prof. H. Wartenberg; other images, page & copyright H. Jastrow. I am grateful to Dr. G. Spatkowski for the specimen of her eye muscle.