Name: The Integumentary System, Part 2 - Skin Deeper: Crash Course A&P #7
Uploaded: 2015-05-27T16:26:37.000Z
Duration: 9 min 57 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Look at all this stuff! Soaps, lotions, conditioners, polishes -- all

Relative clauses (Restrictive vs. nonrestrictive)

from that huge section of your local store that’s dedicated solely to the grooming

of your skin, hair, and nails. Some might see these things as the trappings

of vanity. But me? I see them as the tools for the care,

maintenance, and -- sure, sometimes decoration -- of the integumentary system.

Now, true, in spite of what the cosmetics industry may lead you to believe, your integumentary

system is more than just a place to put eye shadow and hair product in the hopes of attracting a mate.

This collection of resilient tissues, ranging from the sharp and hard to the soft and fluffy,

serve a whole panoply of functions, the majority of which you never even notice.

But, when you do notice what your integumentary system is doing, the results are often uncomfortable

or ugly or both, and that is what this stuff is mostly for.

Your skin can become either scaly or greasy, and -- in rare cases -- it can even change color.

And hair, well, let’s just say it takes a lot of science to tame this mane.

But each of these tissues -- frustrating as they may be at times -- has a purpose, and

without them you’d be cold and vulnerable and dead.

I’m not gonna lecture you on personal hygiene today. But hopefully by the end of this you’ll

understand the important functions of your integumentary system, and maybe why it’s

worth a little bit of time and effort to keep it healthy.

If you recall our recent run-ins with rogue

nails and tattoo needles, you’ll probably remember that the first and most vital purpose

of your integumentary system is to act as a protective barrier.

Your skin, hair, nails and sweat and oil glands all work together to shield you from all the

things out there that are out to get you: excessive sunlight, infections, abrasions,

and just, you know, getting poked by sharp sticks and stuff.

But beyond that, this system is also vital to how you sense the world around you.

Your skin is loaded with structures that are actually part of your nervous system -- called

cutaneous sensory receptors -- they’re what receive stimuli from the outside environment

These receptors, or corpuscles, as they’re sometimes called, register all of the different

sensations that you associate with touch.

Your tactile corpuscles, for instance, are what make you constantly aware of the tag

that’s scratching at the back of your neck, while your lamellar corpuscles register the

sense of pressure, like when someone puts their hand on your shoulder.

Your hair follicles have receptors, too, which is why you can feel a slight breeze on your

Now, on the less-sexy front, your integumentary system also plays a role in the excretion

of waste, though not as big as a role as we’re often led to believe.

Most nitrogen-containing wastes like urea, uric acid, and ammonia are disposed of through

your urine, but small amounts are eliminated through your skin in sweat.

But despite what you may be told at the beginning of your hot-yoga class, there isn’t much

evidence that suggests that heavy sweating actually rids your body of any extra toxins

-- if anything, you’re just losing more water.

When you do exercise, though, you call on another of your skin’s lesser-known functions

About 5 percent of your entire blood volume is retained in your skin at any given time.

And when you suddenly need more blood supplied to your organs, like when you’re working out,

your nervous system constricts your dermal blood vessels to squeeze that extra blood into circulation.

Now, during these times of exertion, both your blood and your sweat glands work together

to perform a key function: regulating your body temperature.

Even without exercise, your body oozes out about half a liter of sweat per day, in an

effort to keep you at a comfortable temperature. That’s just your normal, barely noticeable

But on a hot day, or if you’re on the dance floor exerting yourself, that sweat becomes

much more noticeable. Such sensible perspiration could produce as much as 12 LITERS of sweat per day!

Now, if the temperature gets chilly, the surface of your skin can lose a lot of heat, because

it has so much warm blood behind it. To regulate that heat loss, your dermal blood vessels

constrict, causing your blood to head deeper into your tissues and help keep your vital organs warm.

Once things warm up, those blood vessels in the skin gradually relax, and allow that blood

You’ve probably noticed that if you’re cold for too long, your skin may lose some

of its color -- or even turn pale blue if you’re light-skinned -- as that blood retreats

And in fact, like a litmus test for your body, changes in the color of your skin can indicate

Blue skin, or cyanosis, in Caucasian people may indicate heart failure, poor circulation,

or severe respiratory issues. That’s because blood that’s been depleted of oxygen turns

darker in color, and when seen through the tissue of lips or skin, it can look bluish.

A yellowing of the skin, called jaundice, usually signifies liver disorder, as yellow

bile starts accumulating in the blood stream.

Reddened skin, or erythema, could indicate a fever, inflammation, or allergy -- all of

these conditions cause blood vessels to expand and more blood to flow to the skin’s surface.

Of course, human skin color spans a pretty wide spectrum, so some of these conditions

are easier to diagnose by looking for discolorations of other tissues, like mucous membranes and

However light or dark your skin color is, though, you can thank your melanin for it.

You’ll remember that melanin is a pigment produced by the melanocyte cells in your epidermis.

Melanin has two forms, producing pigments that range in color from reddish yellow to

Because its main job is to protect us from the sun’s ultraviolet rays, it makes sense

that, in the distant past, the distribution of these different skin tones was not at all random.

Historically, where solar radiation is more intense, higher concentrations of deep-colored

melanin became an advantage for the protection it provided.

But closer to the poles, where those solar rays are weaker and more diffuse, lower concentrations

of melanin allowed people to collect what sunlight was available, to manufacture vitamin D.

‘Cause the fact is, we all need some level of sunlight to hit our skin to survive.

Your bones require vitamin D to keep producing new bone cells, and it’s the only vitamin

that your body can actually produce on its own. Your skin cells contain a molecule that

converts to vitamin D when it comes in contact with UV light.

From there the vitamin heads through your bloodstream to your liver and kidneys where

it truly becomes activated D, also called calcitriol, which is circulated to all the bones of your body.

But let’s not just be skin-deep here -- your integumentary system also involves your so-called

skin appendages -- your hair, nails, sweat and sebaceous, or oil glands, which can each

be fascinating as well as frustrating in its own way.

If you’re like some people I know and you spend a fortune on hair conditioner? That’s

because your cuticles are out of control.

All of your hairs, or pili, are basically just flexible strands of dead keratin protein