Smooth Muscle Cross Section

Here is a cross section of the ileum.

Smooth muscle cross section. Move further out to see the outer sheet of smooth muscle which runs longitudinally along the intestine and will therefore be seen in cross section. Note again the spindle shaped cells and centrally located nucleus in each cell. You can readily observe the appearance of smooth muscle cells in cross and longitudinal profiles.

Basic histology smooth muscle cross section. Of course a smooth muscle cell nucleus will appear round in cross section rather than elongated. Skeletal muscles also called the striated muscles are a set of muscles that are attached to the bones and their main function is to facilitate skeletal and tissue movement they are called striated muscles because of their appearance which is due to the presence of nuclei actin and myosin in the cells at the edges of the muscles.

A majority of fibers will have no visible nucleus i e it is out of the plane of section. Smooth muscle located in the wall of the digestive tract is arranged in distinct circular and longitudinal layers. It is not the same as the anatomical cross sectional area which is the area of the crossection of a muscle perpendicular to its longitudinal axis.

Those between the masses of smooth muscle cytoplasm belong to fibroblasts or blood vessels. It is represented here as two layers an outer longitudinally oriented layer and an inner circularly arranged layer. In muscle physiology physiological cross sectional area is the area of the cross section of a muscle perpendicular to its fibers generally at its largest point.

Look at slide 155 which is a longitudinal section of the gi tract at the gastro esophageal junction to see more smooth muscle in various planes of section. There are other nuclei too. Recall that each smooth muscle fiber is a single cell each with its own nucleus.

When smooth muscle fibers are cut perpendicular to the long axis you will see a ring of cytoplasm and it is easy to see the cell borders. In a non pennate muscle the fibers are parallel to the longitudinal axis and therefore pcsa and acsa coincid. Find the smooth muscle in the outer perimeter of this section.