What are the three major layers of the skin and the layers of the epidermis?
The three major layers of the skin are the epidermis, dermis, and hypodermis (subcutis or panniculus).
The layers of the epidermis from proximal to distal are the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.
The stratum basale, or basal layer rests upon the basement membrane and is responsible for the production of new epidermal cells.
In the spinous or prickle cell layer, the keratinocyte cytoskeleton is produced.
In the stratum granulosum or granular layer, keratohyalin is produced and deposited. Cells in this layer are flattened and basophilic, and ‘granules’ can be seen in the cytoplasm.
Cells in the stratum lucidum or ‘clear layer’, are anuclear, and this layer is rich in protein-bound lipids. This layer is best developed in footpads and can also be seen in the nasal planum. It is not seen in other areas of the skin.
The most distal layer or stratum corneum, is the skin layer in contact with the environment. It is the fully cornified layer and is made of flattened, anuclear, densely packed keratinocytes.
The skin produces hairs and hair follicles, sebaceous glands, sweat glands, specialized glands (i.e. anal sacs, tail gland, glands of the external ear canal, and circumanal glands), claws, nails, and the horny layer of the skin.
What are tylotrich hairs, and where are they located?
Tylotrich hairs are large hair follicles scattered throughout the body.
The hairs are larger than normal hairs and contain one large hair surrounded by a complex of neurovascular tissue at the level of the sebaceous gland. They are believed to be rapid adapting mechanoreceptors.
