The integumentary system is composed of the skin, hair, nails, and associated glands. The integumentary system is the largest organ in the body and serves as a barrier between the internal organs of the body and the outside world. Functions of the integumentary system include physical protection and immunity, wound healing, regulation of body temperature, sensation, and vitamin D synthesis. Skin, hair, and nails serve as a physical barrier to keep pathogens out and to keep internal organs inside the body. The skin is composed of 3 layers, including the epidermis, the dermis, and the hypodermis, while the nails are made up of a protein called keratin. In addition, there are many nerve cells within the skin, causing humans to experience pain, touch, temperature, etc. There are also many blood vessels running through the skin that help maintain body temperature. These vessels constrict to retain heat and dilate to release heat in processes called vasoconstriction and vasodilation. Additionally, four types of glands are found in human skin, including sudoriferous (sweat) glands, sebaceous glands, ceruminous glands, and mammary glands.
Diagram of the Integumentary System
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U.S. National Library of Medicine. (2020, November 10). Skin layers. MedlinePlus. https://medlineplus.gov/ency/imagepages/8912.htm. b
Kim, J. Y., & Dao, H. (2021, May 9). Physiology, integument. National Center for Biotechnology Information. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK554386/.