Cardiac muscle is found only in the heart, the immediate proximal ends of aorta, pulmonary artery and pulmonary veins. It is also known as involuntary and striated muscle. Since the contraction is not under the control of the animal and the muscle fibers also shows the cross striations under microscope as the skeletal muscle fibers, they can be called as involuntary and striated
Unlike the skeletal muscle fibers they are single nucleated, smaller in size and often have multiple branches. They are attached to the adjacent cells to form a branching network
The firm end-to-end attachments between cardiac muscle cells are visible under the microscope as dark, transverse lines between the cells. These attachment sites are called intercalated discs
