Anatomy: Animals Inside

Circulatory System

How do skin cells keep your blood from leaking out?

The skin is comprised of multiple layers of cells. The outermost layers are made of dead cells full of keratin. Sebaceous glands coat these dead cells with an oily secretion that makes them water resistant. However, they are not waterproof; about one pint of fluid from deeper tissues leaks through the skin’s surface every day and evaporates. This excretion is in addition to perspiration produced by excessive heat or strenuous activity. The very strong junctions holding the cells together, known as desmosomes, prevent large of amounts of fluid leakage across the skin barrier. The linkages are so efficient that the epidermal skin cells tend to slough off in sheets rather than individually.


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