Skeletal

Cells

The cylinder shaped muscle fibers make very different histological impressions. These impressions depend on whether they are cut in a cross section A cut or slice of the body or an organ for study. or in a longitudinal section.  When cut in a cross section, it is much like breaking a piece of chalk in two pieces. The skeletal muscle fibers have the 2-D circular shape you would expect from a 3-D cylinder shape.  Cut in a longitudinal section, these cellsThe basic structural and functional units of life. create a 2-D square shape.  This would be similar to trying to cut the piece of chalk length-wise.  Try this for yourself.  Take a waterThe universal solvent essential for life. bottle and cut it in half, separating the top from the bottom.  Put the cut face on a piece of paper and trace the outline (you get a circle).  Now take a water bottle and cut it in half separating the front of it from the back.  Put the cut face on a piece of paper and trace the outline.  You don’t get a circle shape. 

The darkly-stained nucleiClusters of neurons in the CNS responsible for processing information. of skeletal muscle are pushed to the side regardless of the shape revealed in a 2D impression. This makes more room for the myofibrils, or contractile proteinsProteins (actin and myosin) responsible for muscle contraction.. These proteinsLarge molecules made of amino acids with various functions in the body. make up more than 80% of the cell volume.  These myofibrils contain the dark and light banding that creates the striations common to skeletal and cardiac muscles.

Wrappings

Microscopic pictures of skeletal muscle can help illustrate the wrappings around skeletal muscle. These wrappings fuse into the tendon or aponeurosis. They connect the muscle to a bone. These wrappings, from superficialNear the surface of the body. to deepAway from the surface of the body., are the epimysium, the perimysium, and the endomysium. Between these wrappings are the arteriesBlood vessels that carry oxygenated blood away from the heart (except pulmonary arteries, which carr and veinsBlood vessels that return deoxygenated blood to the heart (except pulmonary veins, which carry oxyge. They supply your skeletal muscles with blood. Nerves control them.

The epimysium is an extension of the tendon or aponeurosis and surrounds the entire muscle. The perimysium surrounds bundles of muscle fibers called facilities. Individual muscle fibers are surrounded by the endomysium. Important to note that the endomysium is not the cell membrane of the cardiac muscle fiber. Cell membranes of muscle fibers are called sarcolemma and are discreet from the endometriumThe inner lining of the uterus that thickens during the menstrual cycle to support a potential pregn. When individual muscle fibers contract they pull on the endomysium which exerts for force on the perimysium of the fasciclesBundles of nerve fibers within a nerve.
or
Bundles of nerve fibers within a muscle.. which then exerts force on the epimysium attached to the tendon which is attached to a bone. This is what creates the leveraging force of movementA fundamental property of life involving motion of the body or its parts. of skeletal muscle.

Figure 1: Skeletal muscle, longitudinal section, H&E, Slide 058L
Figure 2: Skeletal muscle, longitudinal section, H&E Slide 058-Thin
Figure 3: Skeletal muscle, cross section, H&E, 40X. Slide 058 T
All by University of Michigan Histology, licensed under CC BY-NC-SA 3.0.