Normal heart muscle histology (400X)

Cardiac muscle cells are smaller than skeletal muscle cells, but larger than smooth muscle cells. They have a single central nucleus, which is in contrast to the multiple nuclei seen in skeletal muscle cells. In addition, cardiac muscle cells have a high density of mitochondria, which produce the energy needed for sustained muscle contractions. 

Smooth muscle cells, in contrast, are spindle-shaped with a single central nucleus and lack striations. They do not have intercalated discs and have a lower density of mitochondria compared to cardiac muscle cells. Skeletal muscle cells are long, cylindrical cells with multiple nuclei and are striated like cardiac muscle cells, but are not branched and lack intercalated discs. 

Overall, the histologic appearance of cardiac muscle cells is unique and allows for their specialized function in generating the mechanical force needed to pump blood throughout the body.