#7 The integumentary System, Part 2 - Skin Deeper

<Protective & Sensory Functions of the Integumentary System>

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 wokr together to shield you from all the things out there that are out to get you: excessive sunlight, infections, abrasions.

The system is also vital to how you sense the world around you.

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 senese 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 skin or through your hair.

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<More Functions: removing waste, stroing blood, and regulating body temperature>

Your integumentary system also plays a role in the excretion of waste.

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

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

Those blood vessels in the skin gradully relax, and allow that blood to return to the surface.

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<SkinDiscoloration: Cyanosis, Jaundice, and Erythema>

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

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<Melanin, Vitamin D, and Skin Tone>

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.

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.

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<Types of Sweat Glands>

You've got up to three million tiny sudoriferous, or sweat glands, distributed throughout your body.

Your eccrine sweat glands are more abundant - they're in your palms, forehead, and in the soles of your feet.

You only have about 2000 of these, and they start cookin' around puberty, empthing into the hair follicles around tyour armpits and groin.

Mammary glands, which secrete milk in lactating people, and ceruminous glands, the ones that make your cerumen, or earwax, are two other types of modified apocrine sweat glands.

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<Sebaceous (oil) Glands>

Most of your sebaceous glands secrete their sebum, an oily substance, into hair follicles where it can travel to the surface of your skin.