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How does the skin normally prevent loss of body fluids?

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Cross-section diagram of human skin showing burn depth by degree, with arrows indicating that first-degree burns affect only the epidermis, second-degree burns reach the dermis, third-degree burns extend into subcutaneous tissue, and fourth-degree burns penetrate to muscle. — burn This diagram shows how burn injuries are classified by severity. First-degree burns damage the outer skin, known as the epidermis. First-degree burns are the least severe form of burn injury. Second-degree burns damage the outer skin and some of the underlying skin, known as the dermis, which also includes some connective tissue. Third-degree burns damage all the layers of skin, including subcutaneous tissue. Fourth-degree burns, which are the most severe, destroy every layer of skin and also damage muscle, tendons, and bones.

The skin prevents the loss of body fluids primarily through a specialized barrier located in the lower portion of the stratum corneum. In this region, the spaces between the compacted, keratin-filled cells are tightly packed with lipid (waxy) platelets. These lipids are produced within membrane-coating granules in the underlying epidermal cells and act as a seal to prevent water evaporation.12

Additionally, the dermis plays a supportive role in fluid management. It contains a ground substance of mucopolysaccharide materials (glycosaminoglycans) that can hold significant quantities of water, helping to maintain the skin's turgidity.23

When the skin is damaged by severe burns, this protective barrier is compromised. The resulting leakage of fluids and salts from the body is a grave complication, as it can lead to a dangerous drop in blood volume and disrupt the body's osmotic balance.4