Which of the following is included in the integumentary system?

The integumentary system is primarily concerned with protecting the body and maintaining homeostasis. It is composed of several key components, which include skin, nails, hair, and exocrine glands.

Skin serves as the body's first line of defense against pathogens, regulates temperature, and facilitates the sensation of touch. Nails provide protection to the distal phalanx and enhance the ability to grasp objects. Hair offers insulation and protection from environmental elements. Exocrine glands, such as sweat glands and sebaceous glands, play critical roles in thermoregulation and maintaining skin health through the secretion of sweat and oils.

This comprehensive understanding of the integumentary system encompasses all the listed components in the correct answer, highlighting its role in protecting and supporting the body's overall function. Other options include components that do not belong to this system; for instance, muscles are part of the muscular system, while nerves and blood vessels are primarily associated with the nervous and circulatory systems, respectively. Additionally, the option that limits the integumentary system to only nails and hair overlooks crucial aspects like skin and exocrine glands that are vital for its overall function.