Which body system maintains boundaries and protects deep tissues from injury?

The integumentary system is the correct answer because it comprises the skin and its associated structures, such as hair, nails, and glands. This system serves several crucial functions, including protecting the body from environmental hazards like pathogens and physical injury, maintaining water balance, and regulating temperature. The outer layer of the skin, known as the epidermis, acts as a barrier, shielding underlying tissues from harmful substances and microorganisms. Additionally, beneath the outer layer, deeper tissues are protected from extremes in temperature and physical trauma.

In contrast, the nervous system primarily focuses on communication and control within the body through nerve impulses, rather than providing physical protection. The muscular system facilitates movement and posture but does not directly contribute to maintaining boundaries. Lastly, the skeletal system provides structural support and protection for vital organs but does not play an active role in protecting the body's surfaces from external injuries. Thus, the integumentary system is specifically designed for the function of maintaining boundaries and protecting deeper tissues.