In this first part of learning the structure of the skin, the focus will be on the basic building blocks of the skin. In many ways the cell layers that make up the skin are like bricks in a brick wall or stones that make up a cobblestone street.
The basic layers of the skin are 3 : the epidermis, the dermis, and the adipose or fat layer.
Think of the epidermis as the layer of skin you see directly. More specifically this layers is composed of 5 layers of cells progressing from the basal layer to the stratum corneum. These cells are called keratinocytes and form a barrier to the environment.
Keratinocytes have many functions. They are responsible for producing vitamin D for the body and converting it into its active form. They also produce a protein called keratin. If you have ever had a whitehead or blackhead or cyst and squeezed it and found cheesy white stuff that came out - that is keratin. It can have a bit of an odor if bacteria are present. This keratin actually plays a role in forming an effective barrier from the environment and preventing pathogens from getting through the skin.
The next layer is the dermis. This is where we find blood vessels that nourish the skin and play a role in thermoregulation. It is also where collagen and hyaluronic acid is found. This is the support that provides structure for the skin. We find many structures in the dermis.
The dermis is where we find hair follicles, sweat, glands, sebaceous glands, blood vessels, nerves, and lymphatic vessels. If you nick yourself and bleed, then you have gone past the epidermis into the dermis since there are no blood vessels in the epidermis itself. This can give a good sense of just how thin the epidermis can be while the dermis can be much thicker.
Below the dermis is the fat or adipose tissue. This layer is not just about insulation. It plays a role in wound healing and possible hormonal links as well.