The Integumentary System, Part 2 - Skin Deeper: Crash Course Anatomy & Physiology #7

Today, Hank answers the question, "Why do we use lotion?" We'll take a look at your integumentary system and all the hard work it does to protect you from and help you interact with the world around you.

Pssst... we made flashcards to help you review the content in this episode! Find them on the free Crash Course App!

Chapters:
Introduction: Why Do We Use Lotion? 00:00
Protective & Sensory Functions of the Integumentary System 1:23
More Functions: removing waste, storing blood, and regulating body temperature 2:16
Skin Discoloration: Cyanosis, Jaundice, and Erythema 3:46
Melanin, Vitamin D, and Skin Tone 4:39
How Does Hair Conditioner Work? 5:40
How Do Hair, Skin, and Nails Grow? 6:17
Types of Sweat Glands: Eccrine, Apocrine, Mammary, and Ceruminous 6:55
Sebaceous (Oil) Glands 8:17
Review 9:05
Credits 9:33

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Notes for Integumentary System Part 2

When we notice what integumentary system is doing, results are often uncomfortable
sweat glands -> smell, oil glands -> zits
skin -> scaly or greasy


1st & most vital purpose of integumentary system = protective barrier
skin, hair, nails, sweat, & oil glands all work together to shield from excessive sunlight, infections, abrasions,
how you sense the world


Cutaneous sensory receptors/corpuscles - structures part of nervous system in skin
receive stimuli from outside environment & send stimuli to brain
part of nervous system
register diff sensations that associate w/ touch

Types of Corpuscles
tactile corpuscles - transmits sensations of light touch & low-frequency vibrations from periphery -> central nervous system

lamellar corpuscles - register sense of pressure

Hair follicles have receptors too -> why can feel slight breeze on skin or through hair


More Functions of Integumentary system: removing waste, storing blood, and regulating body temperature


Waste Removal
Integumentary system excretes small amounts of waste eliminated through skin via sweat
most nitrogen-containing wastes like urea, uric acid, and ammonia are disposed via urine
isn’t much evidence that suggests heavy sweating rids body of any extra toxins, just losing more water


Blood Storage Unit
~5% of entire blood volume retained in skin @ any given time
when need more blood supplied to organs, (i.e.) when working out -> nervous system constricts dermal blood vessels to squeeze extra blood into circulation



Body Temp Regulation
During times of exertion, both blood & sweat glands work together to perform a key function: regulating body temp

insensible perspiration = unnoticeable sweat
even w/out exercise, body oozes out about 1/2 a liter of sweat per day to keep comfy temp
No solute lost, just pure water


sensible perspiration = noticeable sweat
both solute & solvents lost
could produce as much as 12 L of sweat per day


To regulate heat loss dermal blood vessels constrict -> blood heads deeper into tissues & help keep vital organs warm
Once things warm up, blood vessels in skin gradually relax & allow blood to return to surface
Skin Discoloration: Cyanosis, Jaundice, and Erythema
Changes in the color of skin can indicate homeostatic imbalances

Cyanosis = Blue skin
in Caucasian people may indicate heart failure, poor circulation, or severe respiratory issues
cause blood that’s been depleted of oxygen turns darker in color, and when seen through lips/skin tissue, can look bluish


Jaundice = yellowing of the skin
usually signifies liver disorder
Yellow bile starts accumulating in bloodstream


Erythema = Reddened skin
could indicate fever, inflammation, or allergy
all of these conditions cause blood vessels to expand & more blood to flow to skin’s surface

Human skin color wide spectrum, so some of these conditions easier to diagnose by looking for discolorations of other tissues (i.e. mucous membranes & beds of finger & toenails)
Melanin, Vitamin D, and Skin Tone

Melanin - pigment produced by melanocyte cells in epidermis
2 forms: produces pigments that range reddish yellow -> brownish black
main job = protect from sun’s ultraviolet rays
Historically, where solar radiation more intense -> higher concentrations of deep-colored melanin
closer to poles, where solar rays weaker & more diffused, lower melanin concentrations allowed people to collect what sunlight was available, to manufacture vitamin D


Vitamin D - required by bones to keep producing new bone cells & only vitamin body can produce on its own
skin cells have a molecule that converts to vitamin D when it comes in contact w/ UV light
Vitamin path: skin -> bloodstream -> liver & kidneys
where vitamin D is activated (calcitriol)
Then calcitriol circulated to all bones of body



Skin appendages - hair, nails, sweat, & sebaceous/oil glands

Hairs/pili - flexible strands of dead keratin protein cells, like fingernails


Cuticle - outermost layer of dead keratin cells
looks like overlapping roof shingles
conditioner evens out rough surface between those cuticle cells to make hair look smooth


2 Main Regions of Hair

shaft - where keratinization is completed

root - part inside follicle where keratinization is still happening


follicle - tube of epidermal cells
just like in epidermis, cells @ bottom of each follicle are young & fresh, continually dividing & pushing older cells up through skin, into open air
Finger & toenails pretty much grow same way
start at @ back of nail bed where new cells divide @ root & get pushed forward
creates scaly-hard keratin top layer



2 Types of Sweat Glands
Up to 3 million tiny sudoriferous/sweat glands distributed throughout body & secrete salty, watery sweat

1. Eccrine glands - simple coiled tubes that start in dermis, extend through a duct, & open into a pore on skin’s surface
more abundant than apocrine
in palms, forehead, & soles


2. Apocrine glands
only have about 2000 apocrine sweat glands
Activated around puberty, empties into hair follicles around armpits & groin
secrete sweat w/ fats & proteins in it
More viscous & sometimes yellowish in color
when bacteria on skin combine with this sweat, it gets odorific- body odor
Deodorants don’t affect amount of sweat, but reduces smells by attacking stink-making bacteria,
antiperspirants are opposite, uses ingredients (i.e. aluminum) to block sweat glands & stop perspiration
Some researchers believe these glands are human equivalent of musky sex scent glands, might help w/ mate acquisition

Types of Apocrine Glands

Mammary glands - secrete milk in lactating people


Ceruminous glands - make cerumen/earwax


Sebaceous (Oil) Glands - found everywhere but thick skin in
ducts are smaller on limbs, but they’re pretty big on face, and neck, and upper chest
Most secrete sebum/oily substance into hair follicles where it can travel to skin’s surface- cause pimples
primary goal: soften & lubricate skin & hair
help slow water loss from skin in dry environments

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[sangheilientertainment]

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[prodrumer]

7:33 The sheer amount of joy at sweat that can appear yellowish in color.

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Love Crash Course...goes over the info way more in depth in 10 minutes than we do in my hour and a half class. One thing though - this video says your blood vessels constrict when you're working out in heat AND when you're cold. Your blood vessels dilate when you're exercising, bringing blood to the surface - that's why people get red when they're exercising. Might be a good idea to edit that part!

[rockercaterrorencountered]

I have vitiligo (white patches on my skin) and it was kind of cool to learn about skin and stuff. My patches are mostly on my head, so I have so white stripes in my hair, which is kind of cool. I have 1 next to my eye and 1 on my left ring finger, too.

[crashcourse]

Pssst... we made flashcards to help you review the content in this episode! Find them on the free Crash Course App!

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Damn those sebaceous glands..