Skin Layers
It is divided into three layers: epidermis, dermis and hypodermis. Each of them has other sub-layers or strata.
Epidermis
The epidermis is the most superficial layer of the skin, in contact with the environment. It is formed by stratified keratinized epithelium and is avascular.
Its texture and thickness vary depending on the region of the body, being thinner on the palms of the hands and thicker on the soles of the feet.
It consists of five layers:
- Stratum corneum : Formed by dead, flattened, nucleated cells, which contain a large amount of keratin and are continually flaking off.
- Stratum lucidum : Formed by a layer of flattened, translucent cells. In some areas of the body, where the skin is very thin, its presence is not noticeable.
- Stratum granulosum : Formed by 3 to 5 layers of flattened polygonal cells and cytoplasm accumulated with keratin-hyaline granules, which will give rise to keratin.
- Stratum spinosum : Formed by 5 to 10 layers of cuboidal cells, slightly flattened and with a central nucleus. They present cytoplasmic projections with keratin filaments.
- Stratum germinativum : Deepest layer in contact with the dermis. The keratinocytes produced are pushed to the upper layers.
Dermis
The dermis is the middle layer of the skin, located between the epidermis and the hypodermis. It is formed by connective tissue and is more elastic and firm, due to the presence of collagen and elastin.
In this layer of the skin are found blood and lymphatic vessels, nerves, nerve endings, hair follicles, sweat and sebaceous glands .
It is divided into two layers:
- Papillary layer : Located below the epidermis, with papillae that increase adhesion between the dermis and the epidermis. It is made up of loose connective tissue.
- Reticular layer : This is a deeper and thicker layer, consisting of dense connective tissue.
Hypodermis
The hypodermis or subcutaneous tissue is the innermost layer, but it is not considered part of the skin. It is made up of fat cells, collagen fibers and blood vessels.
The amount of fat cells present varies from individual to individual and between parts of the body.
This layer performs important functions such as: isolating the body from external environmental variations and attaching the skin to adjacent organs and structures.
Find out more, read also:
- Human skin
- Integumentary System
- Organs of the human body