Stratum granulosum

Stratum granulosum (or granular layer) is a thin layer of the epidermis that lies between the stratum spinosum and the stratum corneum. This layer contains granules of keratohyalin, a protein that contributes to the formation of the skin's barrier properties.

Structure

The stratum granulosum is typically composed of three to five layers of flattened cells. These cells contain keratohyalin granules and lamellar bodies, which are involved in the process of keratinization.

Keratohyalin granules

Keratohyalin granules are dense, irregularly shaped granules that are rich in histidine- and cysteine-rich proteins. These proteins bind to the keratin filaments in the cells of the stratum granulosum, causing the cells to become more compact and rigid.

Lamellar bodies

Lamellar bodies are secretory organelles that release a lipid-rich substance into the extracellular space. This substance contributes to the formation of the skin's water barrier.

Function

The primary function of the stratum granulosum is to aid in the skin's barrier properties. The keratohyalin granules and lamellar bodies released by the cells in this layer contribute to the formation of the skin's water barrier, preventing dehydration and protecting the body from environmental hazards.

Clinical significance

Abnormalities in the stratum granulosum can lead to a variety of skin disorders. For example, a decrease in the number of lamellar bodies can lead to dry skin and ichthyosis vulgaris, a common genetic skin disorder.

See also

• Epidermis (skin)
• Stratum corneum
• Stratum spinosum
• Keratinization
• Ichthyosis vulgaris

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Stratum granulosum

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  Diagram showing the layers of the epidermis, including the stratum granulosum.
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  Microscopic view of normal epidermis and dermis with intradermal nevus.
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  Illustration of skin layers, highlighting the stratum granulosum.