The anatomy of skin and how skin reacts to the environment

Skin Consists of Three Layers:

• epidermis
• dermis
• subcutaneous fat

The skin is made up of three distinct layers as listed above states.
The top layer is reffered to as the epidermis.
The epidermis is translucent, meaning light can be seen through. The epidermis does not contain any blood vessels but gets its oxygen and nutrients from the deeper layers of the skin.

At the bottom of the epidermis is a very thin membrane, called the basement membrane, which attaches the epidermis firmly, though not rigidly, to the layer below.
The second layer lies deeper and is called the dermis. It contains blood vessels, nerves, hair roots and sweat glands.
Below the dermis lies a layer of fat, the subcutaneous fat. The depth of this layer differs from one person to another. It contains larger blood vessels and nerves, and is made up of clumps of fat-filled cells called adipose cells.
The subcutaneous fat lies on the muscles and bones, to which the whole skin structure is attached by connective tissues. The attachment is quite loose, so the skin can move fairly freely. If the subcutaneous tissues fill up with too much fat the
areas of attachment become more obvious and the skin cannot move as easily.

A series of finger-like structures called "rete pegs" project up from the dermis, and similar structures project down from the epidermis. These projections increase the area of contact between the layers of skin, and help to prevent the epidermis from being sheared off. They are not present in the skins of unborn babies but rapidly develop after birth, and are very noticeable in a young person's skin when it is examined under the microscope. As skin ages they get smaller and flatter.

Networks of tiny blood vessels run through the rete pegs, bringing food, vitamins and oxygen to the epidermis. If the blood carries plenty of oxygen it will be pink and the skin will tend to have a rosy color. If the blood is running sluggishly and has lost most of its oxygen the skin will look bluer. These blood vessels respond to temperature changes. They open up in hot weather, bringing lots of red blood cells, and hence a pink flush to the skin.

The epidermis around the eye is not only very thin, it also contains many blood vessels; so therefore the dermal/blood vessels below show through the epidermis. Dark undereye 'circles' or dark shadows under the eyes are possibly due to slow blood flow and the resulting build-up of lymph.

Below the epidermis is the dermis, which serves as a foundation for the epidermis and makes up the principal mass of the skin. This layer produces collagen, elastin and reticulin, the substances that lend structure and support to your largest organ. The dermis also houses nerve endings, blood vessels, oil glands and sweat glands — the various engine parts that keep the skin in working order. Nerve endings allow you to feel the sun on your face and the sand between your toes; they also tell you when to put on more sunscreen or get out of the water because it’s too cold. Sweat glands help keep your skin cool; oil glands produce sebum, which keeps your skin soft, pliable and waterproof. And all the while, blood vessels are working to supply the skin with the nutrients it needs to keep replenishing itself, and carry waste products to the lungs for oxygenation and renewal.