What is the main function of the integumentary system?

The integumentary system primarily consists of the skin, mucous membranes, hair, and nails, making it the correct answer. This system serves several essential functions, the most fundamental being protective, covering the body and serving as a barrier against environmental hazards such as pathogens, chemical exposure, and physical trauma.

Skin, as the largest organ of the body, plays a pivotal role in thermoregulation and sensation, allowing organisms to detect changes in their environment. The hair and nails also contribute to protection and have roles in sensory perception. While other choices touch on aspects related to the integumentary system, such as defense against infection, they do not encompass the complete definition and structure it provides. Understanding that the integumentary system is defined by its components helps clarify its comprehensive role in both protecting and supporting various functions within the body.