Final Answer:
Skeletal muscles and cardiac muscles are striated muscles. They are classified as striated muscles due to the presence of repeating sarcomeres, which contain alternating dark and light bands, giving the muscle fibers a striped or striated appearance under a microscope.
Step-by-step explanation:
Striated muscles, such as skeletal and cardiac muscles, exhibit a striped or striated appearance when observed under a microscope. This distinctive striation is attributed to the structural organization of these muscles at the microscopic level. The basic structural unit of striated muscles is the sarcomere.
Sarcomeres are repeating units along the length of the muscle fibers, and they consist of myofilaments, primarily actin and myosin. The arrangement of these myofilaments within the sarcomere creates alternating dark (A bands) and light (I bands) bands.
In skeletal muscles, sarcomeres are organized in a highly ordered manner, resulting in the characteristic striated pattern. The voluntary contraction and relaxation of skeletal muscles are essential for body movement.
In cardiac muscles, while the striated appearance is also due to sarcomeric organization, the arrangement is less regular compared to skeletal muscles. Cardiac muscles are involuntary and exhibit rhythmic contractions to pump blood through the heart.
The striated appearance in both types of muscles is not only a visual characteristic but also reflects the functional organization of contractile proteins within the sarcomeres. This organization is vital for the coordinated and efficient contraction of muscle fibers, allowing for the precise control of movement and the pumping action of the heart. In summary, the classification of skeletal and cardiac muscles as striated muscles is based on their shared microscopic appearance resulting from the organized arrangement of sarcomeres and contractile proteins.