Which part of the muscular system is responsible for protecting internal organs?

The skeletal muscles play a significant role in protecting internal organs primarily due to their structure and function. These muscles, attached to the skeleton, help create a protective framework for the body, supporting the organs located within the thoracic and abdominal cavities.

While the skeletal muscles themselves do not directly shield organs in the same way that bones or cartilage might, they contribute to the overall stability and integrity of the body’s structure. They allow for movement and posture, which are essential for maintaining an effective defense against external threats or impacts that could otherwise harm the internal organs.

In contrast, cardiac muscles are specialized for pumping blood and are found only in the heart. While they are vital for circulation, they don't provide protective functions for the organs outside of the heart. Involuntary muscles, such as smooth muscles found in walls of hollow organs like the intestines and blood vessels, assist in various internal functions but are not designed for organ protection. Veins are blood vessels that transport blood but do not have a protective role in terms of safeguarding organs.

Thus, the role of skeletal muscles in maintaining body structure and facilitating movement affords a level of protection to its organs, making it the correct answer.