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How does the stratum corneum protect the body?

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A pangolin walks through grass with a blue circle around it and the word endangered written in white across the image. — Integument The pangolin is the only mammal in the world covered in scales.

The stratum corneum, the outermost layer of the epidermis, serves as a vital protective barrier for the body. It protects underlying tissues from environmental injury, including exposure to pathogens, toxins, and UV radiation.1

This layer functions through a combination of structural and chemical properties:

Barrier to Permeability: The stratum corneum regulates skin permeability and prevents the outward loss of water. This is primarily achieved in the lower part of the layer, where the spaces between flattened, keratin-filled cells are tightly packed with lamellae of waxy lipids. These lipid bilayers act as a seal against the environment.123
Structural Integrity: The layer consists of keratin-rich cells called corneocytes, which are connected by desmosomes and embedded in a lipid matrix. This arrangement provides the skin with necessary structural integrity.1
Maintenance: The stratum corneum is dynamic; its outer layers are continually shed through a process called desquamation, where corneocyte layers are sloughed off as desmosomes are enzymatically broken down.13