Our skin has three distinct layers, which make it tough. The skin cells are tightly layered into sheets creating a protective and rugged barrier.
Hi. I’m Dr. McGuire. To understand more about our skin, let’s take a closer look at this very “visible” organ.
Our skin has three distinct layers, which make it tough. The skin cells are tightly layered into sheets creating a protective and rugged barrier. The thin, top and outermost layer is called the epidermis, the inner supportive layer made mostly of fibrous material is called the dermis, and the final cushiony layer is made up of fat is called the subcutaneous layer.
Each layer of skin has special structures and functions. The superficial or top layer of the epidermis is the stratum corneum. The two main types of cells found in the stratum corneum are called keratinocytes and melanocytes. Keratinocytes produce a tough and fibrous protein called keratin, which is the main substance of our hair, nail and skin cells. Melanocytes, usually found at the base of the epidermis produce melanin, a substance that gives the skin its color and also provides a shield against ultraviolet radiation.
In a constant process, the skin sheds its outermost layer of dead cells while constantly producing new cells in sub layers. Squamous cells are flat thin cells that make up the lining of many organs like the heart, lungs, blood vessels, mouth and our skin. Squamous cells are the cells that are shed while basal cells, formed at the base of the epidermis are the new cells that are generated and eventually move up, dry, flatten and die. The epidermis is completely replaced every 30 days and annually people shed about a pound of skin!
Both basal cells and squamous cells play an important role in the ongoing renewal of the skin.
The inner, supportive, second layer of skin called the dermis, is made up of several types of fibrous connective tissue which allow it to move, stretch and contract with our body’s movements. It also contains blood vessels, lymph vessels and glands. One of the primary functions of the dermis is to provide circulation and nutrition to the skin through the vessels and glands. Some glands make sweat and others produce sebum, an oily substance that helps keep the skin moist. Sweat and sebum reach the skin’s surface through tiny openings called pores.
A third fatty layer of the skin is called the subcutaneous layer and is made primarily of fat cells. The fat in this layer acts as a storage house for energy, a source of insulation and aids in protection of underlying structures by providing substantial cushioning.
Human skin is comparable to that of many other mammals, but it is not protected by a pelt and often looks as if it is hairless. However, most of our skin is actually covered with hair follicles.
Our skin separates the inside of the body from the outside world. It acts as a thermostat to regulate body temperature and guards the underlying ligaments, muscles, bones and internal organs. The skin also protects from viruses and bacteria that can cause infections. It helps us sense the outside world, such as whether it is wet or dry, or cold or hot.
Because it interacts with the environment, our skin plays a key role in protecting the body against germs, diseases and excessive water loss. Additional functions of the skin are insulation, production of vitamin D and formation of scar tissue to heal damaged skin.
In humans, skin pigmentation or color varies among different people. And skin types can range from dry to oily.