clinical studies — skin science
select a topic
introduction
Your skin — your body's largest organ
As one of your body's vital organs, your skin plays a crucial role in keeping you alive and healthy. In many different ways, it regulates your "inner environment" — by conserving fluids, regulating body heat, providing sensory information, and protecting against microorganisms and other threats from the outside.
Your skin is complex, too. It's comprised of many different elements in 1 square inch, including:
- 9.5 million cells
- 650 sweat glands
- 95 to 100 oil glands
- 65 hair follicles
- 19 yards of blood vessels
- 78 yards of nerves
- 19,500 sensory cells at the end of nerve fibers
- 1,300 nerve endings to record pain
The skin is also very thin. It has an average thickness of one to two millimeters on our main body surfaces, four millimeters at the nape and three millimeters at the palms and soles. In addition, the skin contains cells that are responsible for producing melanin. Melanin, as you may know, gives the skin colour — even the uneven dark spots that concern so many people.
skin layers
The skin can be divided into three layers — the epidermis, dermis and subcutaneous tissue.
epidermis
The epidermis forms the outer covering of your body and can be divided into five sublayers: stratum corneum, or the horny celllayer, lucid cell, granular cell, spinous cell and basal cell. Each sub-layer represents successive states in the life cycle of epidermal cells. As they move outward from their original layer toward the surface, the cells progressively flatten and ultimately become the surface cells.
The epidermis is a thin, protective layer of cells that contains no blood vessels. Designed to provide protection, the epidermal layer is responsible for the appearance, colour, suppleness and texture of the skin.
The skin we see — the stratum corneum — acts as a protective barrier against the environment and moisture loss. If this structure is disrupted for any reason (i.e. lipid removal caused by detergents or harsh soaps), excessive moisture loss and skin dehydration results. This layer is the body's main barrier to water loss as well as to infection and trauma.
dermis
The dermis is a layer of tissue between the epidermis and subcutaneous tissue. It gives your skin strength and support through elastin fibers and collagen.
Collagen is the most abundant protein in the body and constitutes about 70% of the dry weight of the dermis. It serves as the major structural component of the skin, and also plays an essential role in healing wounds and scars. The production of collagen slows down in puberty, levels off in your twenties and thirties, and as you mature, it becomes very little. This accounts for the thin, frail, wrinkled appearance of aging skin. Additionally, chronic exposure to the sun and extreme weather weakens the strength and tone of collagen.
Without the dermis, the skin would be a soft, fragile layer of cells with little ability to provide protection. Alternately, the vascular system (blood supply) within the dermis is responsible for providing the epidermis with nutrients and oxygen.
subcutaneous tissue
The subcutaneous tissue — the deepest skin layer — consists of loose fatty tissue and elastin fibers. The thickness of subcutaneous tissue varies depending on where it is on your body. It may be thickest in the abdominal area, yet almost nonexistent on the eyelids. Wherever it is, it is nonetheless crucial to your body's ability to absorb shock, store calories and protect you against the cold.
references
- Sam WM, Lynch PJ, eds. Principles and Practice of Dermatology. New York, NY: Churchill Livingstone; 1990.
- Williams PI, Warwick R, eds. Gray's Anatomy of the Human Body. 36th ed. Philadelphia, PA: WB Saunders Company; 1980.
- Moschella SL, Hurley HJ, eds. Dermatology. 2nd ed. Philadelphia, PA: WB Saunders Company; 1985:I.
