Question

List the five layers of the epidermis from most internal to most external and describe the function of each layer.

Answer 1

The epidermis has five layers from most internal to most external: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. They are responsible for generating new skin cells, providing structural strength, forming a waterproof barrier, and protecting the body's surface.

Step-by-step explanation:

Layers of the Epidermis from Most Internal to Most External

The epidermis is the outermost layer of the skin, comprised of several distinct layers of cells. Each layer has a unique function and contributes to the protective qualities of the skin. Listed from the most internal to the most external, the five layers of the epidermis in thick skin are the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

1. Stratum Basale: This single layer of basal cells is where new keratinocytes are generated. Basal cells divide through mitosis, and the newly formed keratinocytes begin their journey to the surface.
2. Stratum Spinosum: Also known as the " layer", keratinocytes in this layer start to produce keratin and become more flattened as they push upward.
3. Stratum Granulosum: In this layer, keratinocytes begin to degrade and release lipids, contributing to the waterproof barrier of the skin.
4. Stratum Lucidum: This layer is found only in thick skin—like on the palms and soles—and consists of dead, translucent keratinocytes.
5. Stratum Corneum: The most external layer is composed of several layers of dead, flattened keratinocytes which form the tough, protective outer surface of the skin.

The epidermis provides protection against pathogens, regulates the amount of water released from the body, and gives the skin its tone through melanin produced by melanocytes.

Answer 2

The most internal layer of the epidermis is the stratum basale which contains melanocytes. Melanocytes produce melanin to protect the DNA. The cells of the stratum basale are the only cells that are capable of cell division. The stratum basale is attached to the underlying dermis. The stratum spinosum is superficial to  the stratum basale.  Stratum granulosum is superficial to the struatum spinosum. The stratum granulosum is three to five layers thick and contains keratohyalin granules, which produce keratin, a water proof protein.Stratum lucidum is superficial to stratum granulosum, but only in thick skin, which is on the palms and soles. Stratum corneum is about 25 cells thick and is the most superficial layer. It is dead and the cells are completely filled with keratin, which is waterproof. The many layers of dead skin protect from abrasion and are the first line of defense against any foreign bacteria, debris or virus.