HESI A2 Science Test 2025 – 400 Free Practice Questions to Pass the Exam

The skin is recognized as the largest organ in the human body, covering an extensive surface area that can range from about 1.5 to 2 square meters in adults. It serves multiple crucial functions, including protecting internal organs, regulating body temperature, and providing sensory information. Composed of three primary layers—the epidermis, dermis, and subcutaneous tissue—skin is integral to the body's defense system and plays a role in the synthesis of vitamin D. Its size and multifaceted roles make it a vital organ that surpasses the size and functional scope of the liver, heart, or lungs.

The liver, while one of the largest internal organs, does not match the overall surface area of the skin. The heart is smaller and primarily functions in circulatory system tasks, while the lungs, though vital for respiration, also do not compare in size to the skin. Collectively, these functions and dimensions affirm the skin's status as the largest organ in the human body.