This article is not medical advice. If you have concerns, please consult your physician or medical professional.
Movie superheroes have flashy, form-fitting outfits with accessible weapons and devices to save the planet, or at least the city. Reflecting cosmic rays, their shields block incoming laser beams and projectiles.
The inventive gear could come in handy for average earthbound people, as we fight off attacks by germs, bites, allergens, cuts and many more intrusions. But we have something even better than a shiny shield. We have skin.
Our largest organ, weighing about 3.5 kilograms, the three layers of skin cover the entire human body to create a delicate but durable defence. It is part of the integumentary system. (The integumentary system includes skin, hair, nails, glands and nerves.) The epidermis, dermis and hypodermis act like a barrier to prevent intrusion from the toxins and germs of the external world. Skin guards the body against wintry weather and rays of summer sun. It sends warning signals to cover up against the cold and heat to ensure a regulated body temperature.
The visible outer skin of humans is called the epidermis. Similar in thickness to a sheet of paper, the epidermis is made of several types of cells — keratinocytes, melanocytes, lymphocytes, Langerhans cells and Merkel cells.
A tight layer of keratinocytes makes up about 90 per cent of the epidermis. A type of structural fibrous protein supplying the surface skin’s structural and barrier functions, keratin also helps to form the tissues of nails and hair.
Melanocytes produce melanin, a substance related to pigmentation. “The amount of melanin you have determines the colour of your skin, hair and eyes,” Cleveland Clinic states. “People who make more melanin have darker skin and may tan more quickly.”
Located close by, Langerhans cells are a part of the body’s immune system, a defence against infection and germs. The cells determine dangers and send out troops to meet the pathogenic enemy. Merkel cells are responsible for the ability to sense pressure and a light touch.
The epidermis constantly renews itself, replaced in about four weeks’ time. “New cells are made in the lower layers of the epidermis,” according to Institute for Quality and Efficiency in Healthcare. “This constant renewal serves to replace cells that are lost and fall to the ground as tiny flakes of skin when the skin is rubbed.” If the skin is rubbed often, such as palms gripping a shovel handle for digging, the skin surface will thicken and develop a callus to protect the area. The soles of feet also develop calluses where shoes cause repeated friction.
Under the epidermis, the dermis is home to an operating network of tiny blood vessels (capillaries), nerves, sebaceous glands and sweat glands. The thicker dermis layer “is a dense network of tough, elastic collagen fibres,” IQEH noted. It’s what every crusader needs — a strong and stretchy covering. However, the dermis can be pulled too far. It will tear, resulting in permanent stretch marks.
Dermal capillaries carry oxygen and nutrients to cells. Capillaries help your body cool down when you get too hot and the opposite happens in cold conditions, causing vessels constrict to prevent heat loss.
The innermost layer of skin closest to muscles is the hypodermis, also called subcutaneous tissue or superficial fascia. Mainly composed of fat cells — adipocytes in adipose tissue — the hypodermis “insulates the body from cold and helps absorb shock and damage to the internal organs,” Medical News Today stated. The third layer also has connective tissue plus more blood vessels and nerves.
Ranging in thickness depending on the body’s fat composition, the hypodermis may be a slim one millimetre on the eyelids or “up to three centimetres in depth” in the abdominal region. Injections into subcutaneous areas of thigh, abdomen and upper arm permit medication such as insulin, allergy medication, blood thinners and more to absorb slowly into the body’s system.
Unlike the champion’s shield of impervious materials, skin may be damaged by burns or abscesses. Hard-to-treat pressure sores may develop, cancer may create tumours, or injuries could damage the skin, from bruising to scrapes and cuts.
Beyond action hero talents, healthy skin has the extraordinary ability to mend itself, something that we often take for granted. Cuts into the first layer of skin repair quickly; deeper cuts take longer and require more magical cell work.
Cuts heal from the inside to the outside, and from the outer edges inward. Repair cells are on the job almost immediately, with blood vessels constricting to reduce flow. “Platelets — sticky blood cells — flood the area and aggregate into clumps,” Alicia Ault said in Smithsonian Magazine, Sept. 3, 2015. Special proteins combine with platelets to form clots.
The team of macrophages arrives at the site (white blood cells), “scavenging for infectious invaders. Over the next few days, macrophages also make growth factors to help repair the wound.” Scabs develop, and underneath, collagen cells work hard to rebuild skin tissue and capillaries. Deep cuts almost always result in a scar.
The human armour needs support to be at its optimal strength to prevent illness. Bathing or showering and then moisturizing prevents dry skin that could crack and allow germs to enter. Drinking adequate water and enjoying good nutrition helps keep skin in good condition. Avoid tanning, both inside and outside. Broad-spectrum sunscreen with SPF 30 or higher will protect against the sun’s piercing rays. Check skin regularly for moles and signs of changes.
“Quit smoking and using tobacco products,” Cleveland Clinic stated. “Nicotine and other chemicals in cigarettes and electronic cigarettes age skin faster.” Causing blood vessels to narrow and reduce oxygen to skin cells, nicotine contributes to premature aging of the skin and encourages wrinkles.
Aging is also responsible for skin wrinkles, even though the epidermis regularly renews itself. Skin loses elasticity as we age, and “the subcutaneous layer thins so it has less insulation and padding,” Medline Plus mentioned. “This increases your risk of skin injury and reduces your ability to maintain body temperature.” The capacity to sense heat and cold, pressure and touch with skin is also hampered.
Our human shield doesn’t need the gleam of superhero gear to impress. To stay healthy and strong, skin just needs tender loving care.
Susanna McLeod is a writer living in Kingston.
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