There are three types of muscles: cardiac, skeletal, and smooth muscle.
Each type has distinct functions as well as structural characteristics that can be identified histologically.
Cardiac muscle makes up the majority of tissue found in the wall of the heart.
Each mature cardiac muscle cell or cardiomyocyte is relatively short, with a length approximately 85-120 µm long and a diameter approximately 15-30 µm.
Histologically, cardiac muscles have quite a few unique characteristics that make it easier to differentiate them from skeletal muscles.
Unlike skeletal muscle, cardiac muscle fibers are branched cells with only 1-2 centrally located nuclei.
Also unique to cardiac muscles are the intercalated discs, which are the specialized junctions between neighboring cells that allow the cells to have synchronized contractions and pump blood out of the heart efficiently.
Let’s first take a look at a longitudinal section of cardiac muscle cells that was stained with Hematoxylin and Eosin (or H&E for short).
If we compare cardiac muscle cells to skeletal muscle cells, we can see there are some key differences between the two muscle types.