Basic Skin Anatomy I

Basic Skin Anatomy I


I would like to begin with the basics. This information will teach you how your skin works, and therefore how you can help it to be at its best.

Skin has three basic layers: epidermis, dermis, and subcutaneous tissue. Each layer of skin has many different cells that are crucial for our skin’s health.
 
Epidermis
The epidermis is the top layer of skin and is in direct contact with the environment. It is thinnest on the eyelids (.05 mm) and thickest on the palms and soles (1.5 mm).
The epidermis contains four layers (except in the palms and soles, in which there is one extra layer). Below is a list of skin layers, from the deepest layer to the surface layer:
    •    Basal Layer
    •    Spiny Layer
    •    Granular Layer
    •    Horny Layer

Basal Layer:
Connected to the dermis, this layer primarily contains keratinocytes (90-95%). It also consists of melanocytes and Langerhans cells.

This is the only truly living layer of the epidermis. This layer contains stem cells that divide and push already formed cells into higher layers. As they move into layers nearer to the skin’s surface, they have less nourishment, which causes them to flatten and die. Keratinocytes are responsible for constantly renewing epidermal cells. Keratinocytes carry pigment granules, which gives colour to the skin and helps with UV protection.

Melanocytes provide protection by absorbing as much UV light as possible to prevent deeper penetration of these rays into the growing layers of the skin. This protective mechanism results in a tan, which is an overproduction of melanin.

Langerhans cells repair damaged cells, and seek out cells that could turn cancerous and destroy them. Unfortunately, these cells are very sensitive to UV irradiation; if damaged or destroyed, the skin will have difficulty repairing itself.


Spiny Layer:
This is the thickest layer of the epidermis. It consists of cells that are already changing in their metabolism and shape and are beginning to die.


Granular Layer:
This is a thin layer of flattened cells that are becoming dried out and are starting to die. As the cells die, their contents are transformed into the waterproofing layer of ceramides and keratins, which accumulate on the edges of the cells and are extruded from the cells into the intercellular space. The granular layer forms the most important waterproofing layer of the skin.


Horny Layer:
This is the outer layer of skin, which is made of dead, flat skin cells that shed about once every two weeks. It acts as the main protective layer of the skin against UV irradiation and both physical and chemical trauma. It is also part of the waterproofing barrier that keeps moisture in the skin and obstructs the penetration of bacteria and other substances. Normally, a layer of oils is secreted from various glands that helps to form the “acid mantle” of the skin. This has a pH level of between 4.5 to about 6.5, and its acid nature inhibits the growth of bacteria and fungi.