Page 8 - OASC February 2021 Newsletter

Skin-deep?
Our skin covers a surface area of around 2 square metres, give or take, representing about 15% of our body weight. Its heft varies with site and age. The thinnest stretches over eyelids, the thickest over the soles of the feet. It waxes and wanes: thin at birth, thickening
until age 40 or 50 then thinning again. The skin holds us
together, protects our insides while helping us sense the
outside, and regulates our core body temperature. The
secret of its strength is its many levels and layers which all
have a specific anatomy and function and work together.
A. The epidermis or outer skin contains 4-5 layers:
} The stratum corneum, also called the ‘horny skin’,
is a layer of keratin (15-20 compressed sublayers of
cells). While this layer constantly sheds dead cells
(contributing only marginally to your household
dust), it is live tissue that serves many vital functions.
Most notably it is our first line of defense against impact, pressure, infection, dehydration, radiation, and chemicals.
} The stratum lucidum is thin, clear, and found only in the thick skin of our palms and soles which endure a lot of friction.
} The stratum granulosum secretes chemicals that keep the skin ‘glued’ together.
} The stratum spinosum or ‘prickle cell’ layer contains dendritic cells: first-line defenders in the
immune system.
} The stratum basale produces keratinocytes (important to forming Vitamin D in sunlight plus keratin and lipids for a protective barrier) and contains melanocytes which produce melanin, a natural skin pigment.
B. Next comes the dermis, which nourishes the skin and gives it flexibility and strength. It houses the sweat glands, oil glands (sebaceous glands), hair, hair follicles, muscles, nerve endings, blood vessels and more dendritic cells. It has two layers: the papillary region of loose connective tissue whose bumpy surface give us our fingerprints, and the reticular region of more dense connective tissue supporting flexibility and strength.
C. Lastly, the hypodermis helps insulate and pad the body. While not exactly part of the skin, this layer helps attach it to muscle and bone. Also called the subcutaneous fascia or subcutaneous layer, it contains fat along with hair follicles, nerve endings and blood vessels. n
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Image credit: CC Mikael Häggström, based on work by Wbensmith, CC BY-SA 3.0 <https://creativecommons