9/3/2023 0 Comments Xsection of muscle![]() ![]() Note also the the cytoplasm of the muscle cells has a stippled, punctate appearance which is due to the bundling of thick and thin filaments into myofibrils as mentioned above. This is because different myofibrils may not be aligned.In transverse sections of skeletal muscle cells ( slide 58, even slide boxes), observe the cylindrical shape of the cells (fibers) and the peripherally-located nuclei. Note that sometimes the cross striations are not aligned all the way across the cell. A less regular longitudinal striping can sometimes be seen within the muscle fibers and is due to the bundling together of the thick and thin filaments into myofibrils, which are arranged parallel to the long axis of the cell.Here are some good examples showing cross striations: #058L Webscope #058L Webscope However, they can be seen clearly on some areas of almost all slides, and it is just necessary to do some looking around for a favorable area on your slide. It is admittedly difficult to see the Z line and especially the H zone with the light microscope. The dark Z line which bisects the I band. The lighter H zone which bisects the A band.You should recognize: (Using your microscope and glass slides may help to see these fine structures) A sarcomere consists of the structures between two Z lines. Cross striations can be seen, and are due to the structure of the sarcomere.Note that each cell contains large numbers of nuclei. Peripheral position of the elongate nuclei just inside of the sarcolemma (plasma membrane).This is why it is important to look at other features of the cell to determine what exactly it is. Cells with peripheral nuclei that are cut at an angle can appear to have centrally located nuclei. Why? Again the answer to the question is in the plane of section. You might see occasional nuclei which appear to be centrally located, but aren’t. Be sure you can identify the borders of the muscle cell.These cells are very long you cannot see their ends. Nonbranching, cylindrical shape of the cell (also referred as muscle fiber).In longitudinal sections of skeletal muscle ( Slide 58, odd-numbered slide boxes), observe the following : 058T Skeletal muscle H&E cross Webscope Imagescope.058Thin skeletal muscle H&E longitudinal Webscope Imagescope.058Lex Skeletal muscle H&E longitudinal Webscope Imagescope.058L skeletal muscle H&E longitudinal Webscope Imagescope.You should be able to recognize each type of muscle in both planes of section. In contrast, cardiac and smooth muscles are called involuntary muscles because their contractions are either spontaneously generated or are under the control of the autonomic nervous system.Įach of these three types of muscle has a characteristic appearance in both cross and longitudinal sections. Skeletal muscle is also called voluntary muscle, because its contraction is under conscious neural control. Such an arrangement is not seen in smooth muscle cells. This regular arrangement imparts a cross-striated (or striped) appearance. Skeletal and cardiac muscle cells are called striated muscle because of the very regular arrangement of their intracellular contractile units, sarcomeres, at the light microscope (LM) and electron microscope (EM) levels. There are three major types of muscle, and their structure reflects their function. Be familiar with the regenerative potential of each muscle type. ![]() Understand where stem cells are located in skeletal muscle and be able to identify their location at both the light and EM levels.Know the structural elements that harness muscle contraction (i.e., the shortening of myofibrils) to the movement of a body part (i.e., via connection to bone) as well as the mechanism by which muscle cells (skeletal, cardiac and smooth muscle) contract.Be able to describe and understand the structural basis of muscle striation at the light microscope and EM levels and the molecular level.Be able to name and to identify the three types of muscle at the light and electron microscope levels, including distinctive features of each, such as the intercalated discs of cardiac muscle. ![]()
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