Stratum granulosum
Encyclopedia
The stratum granulosum is a thin layer of cells in the epidermis. Keratinocytes migrating from the underlying stratum spinosum
become known as granular cells in this layer. These cells contain keratohyalin
granules, protein structures that promote hydration and crosslinking of keratin.
At the transition between this layer and the stratum corneum
, cells secrete lamellar bodies
(containing lipids and proteins) into the extracellular space. This results in the formation of the hydrophobic lipid envelope responsible for the skin's barrier properties. Concomitantly, cells lose their nuclei
and organelles causing the granular cells to become non-viable corneocytes in the stratum corneum.
Stratum spinosum
The stratum spinosum is a layer of the epidermis found between the stratum granulosum and stratum basale. This layer is also referred to as the "spinous" or "prickle-cell" layer. This appearance is due to desmosomal connections of adjacent cells. Keratinization begins in the stratum spinosum....
become known as granular cells in this layer. These cells contain keratohyalin
Keratohyalin
Keratohyalin is a protein structure found in granules in the stratum granulosum of the epidermis, which may be involved in keratinization, and in Hassall corpuscles in the thymus....
granules, protein structures that promote hydration and crosslinking of keratin.
At the transition between this layer and the stratum corneum
Stratum corneum
The stratum corneum is the outermost layer of the epidermis, consisting of dead cells that lack nuclei and organelles. The purpose of the stratum corneum is to form a barrier to protect underlying tissue from infection, dehydration, chemicals and mechanical stress...
, cells secrete lamellar bodies
Lamellar bodies
Lamellar granules are secretory organelles found in type II pneumocytes and keratinocytes. They are oblong structures, appearing about 300-400 nm in width and 100-150 nm in length in transmission electron microscopy images...
(containing lipids and proteins) into the extracellular space. This results in the formation of the hydrophobic lipid envelope responsible for the skin's barrier properties. Concomitantly, cells lose their nuclei
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
and organelles causing the granular cells to become non-viable corneocytes in the stratum corneum.