Comparative observations of the structural features of three muscle fibers, smooth muscle, skeletal muscle and cardiac muscle, in longitudinal and transverse sections.
Operation method
Observational experiments on muscle tissue
Materials and Instruments
Smooth muscle, skeletal muscle, cardiac muscle Move non-striated muscle For more product details, please visit Aladdin Scientific website.
Slide Coverslip Skimmed absorbent cotton Blood-prick needle Oil for oil microscope Microscope.
(A) Observation of smooth muscle isolation mounts (H-E staining)
1. Observation with low magnification First, use low magnification to search for and find the smooth muscle, then change to high magnification.
2. High magnification observation The overall morphology of smooth muscle fibers can be seen. Smooth muscle fibers are long shuttle-shaped, the nucleus is long oval, located in the middle of the cell. The myogenic fibers are not clearly distinguishable on conventional stained specimens.
(II) Observation of transverse section of cat small intestine (H-E staining)
1. Observation with the naked eye: find the reddish stained myenteric layer of the small intestine wall.
2. Low magnification observation Observation of the muscle layer can be seen in the longitudinal and transverse sections of smooth muscle at two levels: the longitudinal section is smooth and pike-shaped; the transverse section is irregularly rounded with different sizes.
3. High magnification observation Note the difference in structure between the longitudinal and transverse sections.
(l) Longitudinal section: smooth muscle fibers are spindle-shaped, the nucleus is long oval or rod-shaped, stained dark blue-purple, and its width is almost equal to the width of smooth muscle fibers. The cytoplasm is stained red.
(2) Transverse section Many round nuclei stained blue-purple can be seen, surrounded by cytoplasm stained red, which is the transverse section of the smooth muscle fiber with nuclei. This is the cross section of the smooth muscle fiber with the nucleus. In addition, there are many smooth muscle fibers of different sizes with only red cytoplasm, because the nucleus has not been cut.
Skeletal muscle
(A) Observations on longitudinal and transverse sections (hematoxylin-stained) of cat skeletal muscle
The general morphology of skeletal muscle fibers (position of the nucleus and the light and dark transverse stripes)
1. Observe with low magnification. Find the longitudinal section (myofibrils are long and striped) and transverse section (myofibrils are polygonal) of myofibrils [there is a connective tissue between the myofibrils.
2. High magnification observation Note the difference in structure between the longitudinal and transverse sections.
(1) longitudinal section of muscle fibers long strip, outside of the myofilm, close to the inner side of the myofilm, there are many stained blue-purple ovoid cytosolic myofibrils along the myofibrillar axis, there are obvious transverse stripes, stained dark for the A band, stained light for the I band. If the section is well stained, the Z line within the I band and the H band within the A band can also be seen (best observed with oil microscope).
(2) Transverse section: Myofibrils are polygonal or irregularly rounded, with myosin membranes, and ovoid nuclei are close to the inner side of the myosin membranes. The myofibrils are in the form of small blue dots and are unevenly arranged within the myoplasm, so that they appear as small cells of myofibrils in the transverse section.
(ii) Demonstration of observation of transmission electron microscope pictures of skeletal muscle fibers in the systolic and diastolic states
Note the distribution of thick and thin myofilaments. In which area do the myotubes change during contraction and where do their changes appear? Where is the transverse tubule located in mammals?
Myocardium
Take a section of monkey or dog myocardium (stained with iron hematoxylin) and observe it.
(i) Low magnification observation
For myocardial section, it is preferable to take ventricular muscle as the material. Since ventricular muscle is divided into multiple layers, longitudinal, transverse and oblique sections can be seen on the section. In longitudinal section, the myocardial fibers are in the form of bands with branches, and in transverse section, the myocardial fibers are irregularly rounded.
(ii) High magnification observation
In the longitudinal section, the myocardial fibers were anastomosed with each other's branches to form a mesh. The nucleus is ovoid and located in the center of the fibers. When the iridescent aperture of the microscope is narrowed and the light is dimmed, the transverse striations of the cardiac muscle fibers can be seen, but they are not as obvious as those of the skeletal muscle fibers. In the muscle fibers and their branches can be seen stained dark blue trapezoidal transverse lines, that is, intercalated discs. There is connective tissue and blood vessels between the muscle fibers.
In cross section, cardiac muscle fibers are irregularly rounded. Some had cytosolic nuclei and some had no nuclei, which was due to the fact that the section cut or did not cut the nuclei.