Histology - Muscle

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A few preliminary remarks.

We do not have a section of an entire skeletal muscle. Therefore we cannot see all the connective tissue layers together, especially the epimysium. The concepts are illustrated in the picture here.

This diagrammatic representation shows an imaginary muscle with four fascicles (bundles). Remember that in muscle, a 'fibre' is a cell! The thick outer covering is the epimysium. Perimysium covers individual fascicles and is also seen as masses of loose connective tissue in between the fascicles. The three pointers in the picture show both these concepts. Endomysium, which surrounds individual muscle cells, is shown as fine green lines shown by the blue arrow.

The yellow arrows show bundles of blood vessels and nerves in the connective tissue. These can be seen in and just under the epimysium as well in a section, and capillaries and fine nerve fibres run in the endomysium (both not shown here).

The appearance shown here is fairly similar to what we would see in a section stained by the Masson Trichrome method (not in your box). This method shows connective tissue as green or blue, muscle cell cytoplasm as deep magenta/red and nuclei as blue-black.

Observe the nuclei as dots on the periphery of the muscle cells. The peripheral nuclei of skeletal muscle are recognisable as peripheral only in a transverse section! The next picture illustrates why.

This represents a longitudinal section through a part of a muscle cell. All nuclei are close to the cell membrane. However, only the nucleus labelled '1' can be identified as peripheral, others appear to be in the middle of the cell.

This is what slide no. 6 looks like when viewed with the unaided eye. The pink masses between the artery and the vein are muscle tissue. One has predominantly transverse sections, the other, longitudinal.

See the diagrammatic appearance in the pictures above and try and recognise these under the microscope.

Remember that shrinkage often separates muscle cells from each other. This is to our advantage!