In which type of muscle are dense bodies found instead of Z discs?

Dense bodies are unique structural components found in smooth muscle cells. They serve a similar role to Z discs in striated muscles, acting as anchoring points for the actin filaments within the cells. However, unlike striated muscle types (skeletal and cardiac), which have Z discs that define the boundaries of sarcomeres, smooth muscle cells do not form discrete sarcomeres. Instead, the dense bodies connect to the actin filaments and help facilitate the contraction process through a different mechanism, allowing smooth muscle to contract in multiple directions rather than just the linear fashion seen in skeletal and cardiac muscle.

This structural difference reflects the unique function of smooth muscle as it adapts to various physiological requirements, such as providing involuntary movements in organs and blood vessels. In skeletal and cardiac muscle, the presence of Z discs is essential for organizing the contractile units (sarcomeres) that enable their striated appearance and highly regulated contraction. Thus, dense bodies are a distinguishing feature of smooth muscle, confirming that this is the correct choice.