Speaker 1: Welcome to Brainstuff, a production of iHeartRadio. Hey brain Stuff,
Speaker 1: Lauren vogelbaumb here. The warm sun can feel so good
Speaker 1: on your skin, and getting a bit of color from
Speaker 1: it can be beautiful. But we all know it's important
Speaker 1: to protect ourselves from the damage that the sun can do.
Speaker 1: Our planet does a fairly good job of protecting us.
Speaker 1: You might remember from our Sunburns in Space episode that
Speaker 1: Earth's ozone layer absorbs nearly all of the damaging ultraviolet
Speaker 1: light that the sun puts off. Sunscreen, sunglasses, and appropriate
Speaker 1: clothing can help us defend against the UV light that
Speaker 1: does get through. But today let's talk about our first
Speaker 1: line of defense, our skin. Skin is one of the
Speaker 1: most amazing organs of the human body. It's weird to
Speaker 1: think of it as an organ because we tend to
Speaker 1: think of organs as these sort of boxy things. Your heart, liver, kidneys,
Speaker 1: those are obviously organs. But an organ, by definition, is
Speaker 1: a structure made up of cells and tissues that performs
Speaker 1: or helps perform some function in our body, which definitely
Speaker 1: applies to skin. Skin is made up of very specific
Speaker 1: cells and tissues, and their collective purpose is to act
Speaker 1: as the boundary between you and the world. Most of
Speaker 1: our organs don't directly interface with the world around us,
Speaker 1: but the skin does, which is why it's loaded with
Speaker 1: sensors and has a very tough layered design so that
Speaker 1: it can handle things like abrasion and sunlight. Our skin
Speaker 1: is made up of three main layers, the epidermis on
Speaker 1: the outside, the dermis in the middle, and the hypodermis
Speaker 1: on the inside. The epidermis is the barrier. The dermis
Speaker 1: contains all of the equipment, things like nerve endings, sweat glands,
Speaker 1: hair follicles, and so on, and the hypodermis provides structural support,
Speaker 1: also called the subcutaneous layer. The hypodermis contains fat to
Speaker 1: insulate and protect are underlying muscles and organs, plus blood
Speaker 1: vessels to supply the equipment in the dermis. But today
Speaker 1: let's focus in on the epidermis. The epidermis itself has
Speaker 1: two main layers, the inner of which is living and
Speaker 1: the outer of which is dead. The dead skin cells
Speaker 1: of the outer layer are what we see and touch,
Speaker 1: and it's called the stratium corneum. The cells in this
Speaker 1: layer are filled with a protein called keratin. Keratin is
Speaker 1: interesting because it's tough. Horns, hair, hoofs, fingernails, and feathers
Speaker 1: all gain their strength from keratin. Yes, the same stuff
Speaker 1: that your fingernails are made of actually forms your visible skin,
Speaker 1: but in a much thinner and more flexible layer. That
Speaker 1: is what makes your skin so tough. In parts of
Speaker 1: the body that get a lot of wear, like the
Speaker 1: palms of the hands and soles of the feet, the
Speaker 1: stratium cornium is thicker to handle the abrasion. The cells
Speaker 1: of this layer are constantly flaking off and being replaced
Speaker 1: by newer, dead skins being pushed outward. Those cells are
Speaker 1: created in the living inner layer of the epidermis, which
Speaker 1: is called the malpigean layer. It sidles up to the dermis,
Speaker 1: which feeds and supports it, and this is where the
Speaker 1: sun affects our skin When we ten. The innermost part
Speaker 1: of the malpagean layer, called the basal layer, is where
Speaker 1: we produce those new tough outer skin cells, and also
Speaker 1: where we produce melanin. Melanins are a group of pigments
Speaker 1: found in several places in our bodies, but most relevant
Speaker 1: today in our eyes, skin, and hair. The two main
Speaker 1: types of melanin found there are eumelanin, which can be
Speaker 1: brown to black in color, and fiamelanin, which can be
Speaker 1: yellow to red. They're produced by cells called melanocytes, and
Speaker 1: no matter what color your skin is, it contains about
Speaker 1: one thy two hundred melanocytes per square millimeter, which is
Speaker 1: four hundreds of an inch, which is really small, which
Speaker 1: means that we have a lot of melanocytes. Our skin
Speaker 1: color is determined by how much and what types of
Speaker 1: melanin those cells produce. So okay, when your skin tans
Speaker 1: or deepens in color, what's happening is that your melanocytes
Speaker 1: are producing eumelanin pigment in reaction to the ultraviolet light.
Speaker 1: In sunlight, ev light can damage our cells, and our
Speaker 1: bodies evolved the ability to mitigate that with eumelanin. Eumelanin
Speaker 1: absorbs ultraviolet light and thus protects our cells from damage.
Speaker 1: So our bodies developed this technique that when we're exposed
Speaker 1: to UV light that stimulates the production of melanin. A
Speaker 1: melanin production takes a fair amount of time. That's why
Speaker 1: most people can't get a ten in a single day.
Speaker 1: First you have to expose yourself to UV light for
Speaker 1: a short period of time to activate the melanocytes. They
Speaker 1: produce melanin over the course of a few hours, and
Speaker 1: by repeating this process over five to seven days, pigment
Speaker 1: builds up in your cells to a level that's more
Speaker 1: protective than your baseline. Of course, people's baseline of melanin
Speaker 1: can vary wildly. People with darker skin are lucky to
Speaker 1: have elevated protection from UV radiation all the time. That
Speaker 1: doesn't mean you shouldn't wear sun protection though. Also your
Speaker 1: balance of types of melanin matters. Again. Eumelanin is what
Speaker 1: creates a tan, so people whose skin produces more feomelanin
Speaker 1: and less eumelanin, like many light skinned redheads, don't tan
Speaker 1: very well. This is caused by variations in a particular gene,
Speaker 1: the MC one R gene, to be specific. This gene
Speaker 1: also controls whether you freckle. Freckles are spots of hyperpigmentation
Speaker 1: where for some reason, your skin clusters production of eumelanin
Speaker 1: instead of spreading it out. People with albinism have no
Speaker 1: melanin in their skin, hair, or eyes. The chemical pathway
Speaker 1: that produces melanin can't proceed because an enzyme called tyrosinase
Speaker 1: is missing. But no matter what your skin color or
Speaker 1: whether it deepens with sun exposure, getting too much sun
Speaker 1: can cause damage to your skin. In the short term,
Speaker 1: too much sun can cause a sunburn, leaving your skin
Speaker 1: red and painfully tender, and sometimes even blistered. When you
Speaker 1: get a sunburn, what you're really getting is cellular damage
Speaker 1: from ultraviolet light. The body responds to the damage with
Speaker 1: increased blood flow to the capillary bed of the dermis
Speaker 1: in order to bring in cells to repair that damage.
Speaker 1: The extra blood in the capillaries is what causes redness.
Speaker 1: That's why if you press on sunburned skin, that will
Speaker 1: turn white and then return to red as the capillaries refill.
Speaker 1: In the long term, uv light can break down elastin
Speaker 1: fibers in your skin, which help give skin its bouncy structure.
Speaker 1: The cells throughout your skin's layers can be damaged too,
Speaker 1: of forcing them to repair themselves over time. This stress
Speaker 1: can affect the cell's DNA, which makes them less able
Speaker 1: to produce new cells and function properly. All of this
Speaker 1: can cause visible signs of aging, like wrinkles in sunspots,
Speaker 1: but more importantly can cause pancers like melanoma or basal
Speaker 1: cell carcinoma, but which start with damage in the melanocytes
Speaker 1: and those basal layer cells, respectively. All of this is
Speaker 1: why it's really good to wear protection when you're going
Speaker 1: to be outside during daylight hours, especially if it's sunny.
Speaker 1: But even if it's cloudy, BEUV light is still there. Hats, sunglasses,
Speaker 1: and long sleeves and pants or skirts can all help
Speaker 1: block it. But let's talk about the layer you put
Speaker 1: on first. Sunscreen sunscreens are designed to either physically block
Speaker 1: or chemically absorb UV light before it can reach your skin.
Speaker 1: Creams that go on white are usually physical blockers. That
Speaker 1: white tint is from fine particles of minerals like a
Speaker 1: titanium dioxide or zinc oxide, that reflect UV light. They
Speaker 1: can look a little chalky on your skin, but they
Speaker 1: usually don't cause any irritation. Chemical sunscreens absorb UV light
Speaker 1: and in doing so, emit a very low level of heat.
Speaker 1: Usually it's too low to notice, but these sunscreens are
Speaker 1: more lightly to cause irritation or an allergic reaction. Some
Speaker 1: formulas contain both physical and chemical elements. Look for broad
Speaker 1: spectrum sunscreens that means that they block a wider range
Speaker 1: of types of ultraviolet light, and look for waterproof or
Speaker 1: sport formulas. Find one that's SPF thirty or higher. SPF
Speaker 1: stands for sun protection factor, and the number refers to
Speaker 1: how much UV light the product blocks SPF ten, For example,
Speaker 1: let's one tenth of UV light through or ten percent
Speaker 1: SPF thirty only, let's one thirtieth of UV light through
Speaker 1: or three percent. After that, you get diminishing returns because
Speaker 1: of how fractions work. It can be worth it, though,
Speaker 1: if your skin is light and you don't tan in
Speaker 1: any case, you want to apply sunscreen generously about half
Speaker 1: an hour before you'll be outside to give it time
Speaker 1: to settle into your skin. Reap every couple hours or
Speaker 1: more often if you think that you might have swam
Speaker 1: or sweat or toweled your initial application off. Interestingly, in
Speaker 1: people who do tan, the stimulation of melanin production can
Speaker 1: happen when UV light hits your skin or your eyes.
Speaker 1: Melanocytes are prompted to produce more melanin when they receive
Speaker 1: a hormone called appropriately melanocyte stimulating hormone. This hormone can
Speaker 1: be produced locally by skin cells that are exposed to
Speaker 1: UV light, but it's also produced by the pituitary gland,
Speaker 1: where many of our hormones are produced. The pituitary gland
Speaker 1: is tied into the optic nerve, which means that it
Speaker 1: responds to light that comes in through your eyes. So
Speaker 1: when you wear sunglasses in bright sunlight and block some
Speaker 1: of that UV light from hitting your eyes, your petuitary
Speaker 1: gland produces less of the melanocyte stimulating hormone and you
Speaker 1: won't tan as much, which is why a sun blocking
Speaker 1: system of eye protection, appropriate clothing and sunscreen is the
Speaker 1: best way to prevent sun damage. Today's episode is based
Speaker 1: on the article how Sunburns and suntan's work on HowStuffWorks
Speaker 1: dot Com, written by Marshall Brain Brain Stuff is production
Speaker 1: by Heart Radio in partnership with HowStuffWorks dot Com and
Speaker 1: is produced by Tyler Klang. For more podcasts my heart Radio,
Speaker 1: visit the iHeartRadio app, Apple Podcasts, or wherever you listen
Speaker 1: to your favorite shows.