Lessons:
- Lesson 1: Your Body’s Wrapper: Not Just Pretty Paper
- Lesson 2: Glands Gone Wild: When Your Skin Can’t Stop, Won’t Stop
- Lesson 3: The Conveyor Belt Catastrophe: When Skin Cells Forget How to Behave
- Lesson 4: Melanocytes: The Pigment Police (and When They Go Rogue)
- Lesson 5: Healing Heroes vs. Healing Zeros: When Wounds Win (and Lose)
- All Minilectures
Lesson 1: Your Body’s Wrapper: Not Just Pretty Paper
Let’s talk about your largest organ. No, not your ego—your SKIN. You’re literally wearing 20 square feet of it right now, and it’s doing about seven jobs simultaneously while you sit there ignoring it. Your skinThe body’s largest organ, providing protection and regulation. is the overachiever of organs—it’s waterproof, self-healing, comes with its own climate control system, AND manufactures vitamins using nothing but sunlight like some kind of biological solar panel. Oh, and it’s also trying to kill off about a million dead cellsThe basic structural and functional units of life. right now while you’re reading this. You’re basically a walking snow globe of your own dead skin. Attractive, right? Let’s find out why this is actually amazing.
Key Concepts:
- The epidermisThe outermost layer of the skin, made of stratified squamous epithelium. is a stratified squamous epithelial tissue with 4-5 layers functioning as a protective barrier (layers, thick vs thin skinSkin found on most of the body, lacking a stratum lucidum., the “conveyor belt” of keratinocytesThe most abundant cells in the epidermis, responsible for producing keratin.)
- The dermisThe thick inner layer of the skin that contains blood vessels, nerves, and connective tissue. is the structural foundation containing blood vessels, nerves, and glands that support the epidermis
- The hypodermisThe layer beneath the dermis, composed of connective and adipose tissue, providing insulation and cu anchors skin to underlying structures and provides insulation/energy storage
MiniLectures to Watch Before Class
Introduction to the Integumentary System
12 minutes
Epidermal Layers
13 minutes
MiniLectures to Watch After Class
Epidermal Cells
8 minutes
Innervation and Vascularization
11 minutes
Lesson 2: Glands Gone Wild: When Your Skin Can’t Stop, Won’t Stop
Pop quiz: What do a teenager’s pizza face and a nervous dental hygienist with swamp hands have in common? GLANDS THAT DIDN’T GET THE MEMO ABOUT MODERATION. Your skin is absolutely COVERED in tiny factories—some pump out oil like an OPEC nation, others produce enough sweat to fill a swimming pool (literally—you make about a liter a day). Today we’re meeting Maya, whose sebaceous glandsOil-producing glands in the skin that secrete sebum. think they’re preparing for an apocalypse, and Jordan, whose eccrine glands turn every handshake into a slip-n-slide. Spoiler alert: both conditions are treatable, but first you need to understand why your skin insists on being so… moist.
Key Concepts:
- Sebaceous glands produce sebumAn oily secretion that helps keep the skin and hair moisturized. to lubricate hair and skin but can overproduce leading to acne (location, function, dysfunction)
- Eccrine glands regulate body temperature through sweat but can become overactive in hyperhydrosis (distribution, mechanism, control)
- Apocrine glands serve unclear functions related to scent/pheromones (location, secretionThe process of moving substances from the blood into the nephron tubule to be excreted in urine. differences)
MiniLectures to Watch Before Class
Sweat and Oil Glands
11 minutes
The Dermis
8 minutes
MiniLectures to Watch After Class
Hair and Nails
9 minutes
Lesson 3: The Conveyor Belt Catastrophe: When Skin Cells Forget How to Behave
Imagine a factory where the conveyor belt is supposed to take 28 days to move products from start to finish. Now imagine that same factory decides ‘LOL, let’s do this in 3 days instead!’ and just DUMPS a massive pile of half-finished products at the end. That’s psoriasis. OR imagine the conveyor belt is moving at normal speed, but every single product coming off is DEFECTIVE and leaking everywhere. That’s eczema. Today we meet Sarah, whose skin can’t hold waterThe universal solvent essential for life. like a dollar-store Tupperware, and Marcus, whose skin is in such a hurry it’s literally piling up on itself. These two conditions are confused ALL THE TIME, but by the end of today, you’ll never mix them up again. I promise.
Key Concepts:
- The epidermal “conveyor belt” normally takes 28 days from stratum basaleThe deepest layer of the epidermis, where new skin cells are formed. to stratum corneumThe outermost layer of the epidermis, consisting of dead, keratinized cells. (review of layers, keratinocyte maturation)
- Psoriasis = hyperproliferation (3-4 day cycle) due to autoimmune T-cell activation—TOO FAST
- Eczema = barrier dysfunction due to defective keratinA strong, fibrous protein that forms the structure of skin, hair, and nails./filaggrin—NORMAL SPEED, DEFECTIVE PRODUCT
MiniLectures to Watch Before Class
Epidermal Layers
13 minutes
Epidermal Cells
8 minutes
MiniLectures to Watch After Class
Lesson 4: Melanocytes: The Pigment Police (and When They Go Rogue)
Your melanocytesCells in the stratum basale that produce melanin, the pigment responsible for skin color. have ONE JOB: make melaninA brown-black pigment made by melanocytes in the stratum basal and given to keratinocytes as melanos and share it with all the neighboring keratinocytes like generous little pigment Santa Clauses. But what happens when the immune system decides melanocytes are the ENEMY and starts hunting them down? You get vitiligo—patches of skin that look like someone spilled bleach on you. OR what if your melanocytes decide ‘You know what? I’m going to make SO MUCH melanin that your face looks like you’re wearing a brown mask’? That’s melasma. Same cells, opposite problems, both emotionally devastating. Meet Alicia, who’s watching her pigment disappear, and Grace, who can’t get her pregnancy-triggered pigment to LEAVE. Let’s talk about why skin color is way more complicated than you think.
Key Concepts:
- Melanocytes in the stratum basale produce melanin which protects DNA from UV damage and determines skin color (melanin production, transfer to keratinocytes, UV response)
- Individual skin color differences result from melanin TYPE and AMOUNT, not melanocyte number (eumelaninA brown-black pigment responsible for darker skin and hair colors. vs pheomelaninA reddish-yellow pigment found in lighter skin and red hair., genetic factors)
- Vitamin D3 production occurs in skin when UV light converts 7-dehydrocholesterol (mechanism, why darker skin needs more sun exposure, dietary sources)
MiniLectures to Watch Before Class
Skin Pigmentation
13 minutes
MiniLectures to Watch After Class
Vitamin D3 Synthesis: Your Skin’s Solar Power
Skin Pigmentation (rewatch for reinforcement)
13 minutes
Lesson 5: Healing Heroes vs. Healing Zeros: When Wounds Win (and Lose)
Let me tell you about two wounds. David burned his arm on a hot pan three days ago. Right now, his body has deployed an entire ARMY of cells—platelets, neutrophils, macrophages, fibroblasts—all working in a precisely choreographed dance to rebuild his skin. In about 3 weeks, he’ll have new skin. Now meet Monica. She has a wound on her leg that’s been there for SIX MONTHS. Same wound-healing army showed up, but it’s like they’re trying to build a house with no blueprints, no materials, and the construction site keeps flooding. What’s the difference? Blood flow, diabetes, and the dermis’s ability to do its job. Today you’re going to learn the three phases of wound healing, why burns are classified by depth, and why some wounds just refuse to heal. Bonus: You’ll finally understand why your scars don’t tan.
Key Concepts:
- Wound healing occurs in three overlapping phases: inflammatory (0-3 days), proliferative (4-21 days), and remodeling (21 days-2 years)
- Burn classification depends on depth: 1st degree (epidermis only), 2nd degree (partial dermis), 3rd degree (full thickness)—affecting regeneration potential
- Chronic wounds (diabetic ulcers) fail to progress through healing phases due to poor vascularization, infection, and impaired cellular function
MiniLectures to Watch Before Class
Introduction to the Integumentary System
12 minutes
Innervation and Vascularization
11 minutes
MiniLectures to Watch After Class
The Three Phases of Wound Healing
Hair and Nails
9 minutes
All MiniLectures
- Intro to the Integumentary System 12 Minutes
- Epidermal Cells 8 Minutes
- Epidermal Layers 13 Minutes
- The Dermis 8 Minutes
- Innervation and Vascularization 11 Minutes
- Sweat and Oil Glands 11 Minutes
- Skin Pigmentation 13 Minutes
- Hair and Nails 9 Minutes
- The Epidermal Conveyor Belt: Speed vs Quality Minutes
- The Three Phases of Wound Healing Minutes
- Vitamin D3 Synthesis Your Skins Solar Power Minutes
Intro to the Integumentary System
12 Minutes
How do we assess the extent of burns?. You’ll discover why your skin is actually an organ (not just the system itself!), learn the fascinating “Rule of Nines” used to assess burn victims. Plus, there’s an explanation of skin layers that includes comparisons to candy shells and gelatinous stockings. Warning: You’ll never look at your skin the same way again—and you’ll actually understand why some burns heal while others don’t.
Epidermal Cells
8 Minutes
Did you know your skin is literally shedding right now? This page reveals how your epidermis works like a conveyor belt, constantly replacing itself every 7 days. You’ll meet the different cell types living in your skin—including waterproofing warriors, immune system spies that “drink” your fluids, and your personal pigment factories. Plus, discover where the borderline between living and dead skin cells actually is (hint: it’s not where you think!).
Epidermal Layers
13 Minutes
Think your skin is one solid layer? Think again. This page breaks down the five layers of your epidermis—from the stem cell factory at the bottom to the dead cell graveyard on top. You’ll discover why your palms and feet have “thick skin” with an extra layer, learn the real science behind blisters, and find out why toilet paper is actually a perfect analogy for skin thickness. Plus, there are some pretty relatable comparisons involving fried eggs and new sneakers.
The Dermis
8 Minutes
Your dermis is basically a gelatinous water reservoir. This page reveals the two-layer structure of your dermis and explains why drinking water beats expensive face creams. Discover why stretch marks are literally torn collagenA structural protein in the dermis that provides strength and elasticity. fibers, learn about the “eating cells” patrolling your skin, and find out the surprising truth about wrinkles and dehydrationA condition in which fluid loss exceeds intake, leading to a decrease in total body water.. Plus, there’s a relatable chicken analogy that’ll make you never look at skin the same way again.
Innervation and Vascularization
11 Minutes
Why do third-degree burns never heal, but second-degree burns do? This page reveals how nerve endings positioned at different depths sense different things (temperature vs. pain), why inflammation is actually your friend, and process that turns blood clots into scabs and eventually into remodeled scar tissue. Plus, there’s an insect exoskeleton comparison you won’t forget.
Sweat and Oil Glands
11 Minutes
Why don’t nicotine patches work on your palms or forehead? Learn about the surprising locations of your skin’s glands—from oil glands that cause acne to the mysterious glands in your armpits that might be secreting pheromones. You’ll discover why soaps that make your skin feel “tight” are actually stripping away your unique acid mantleA thin, slightly acidic film on the skin that acts as a barrier to bacteria and contaminants., learn about “cradle cap” in babies, and find out why your hypothalamusA small but vital brain region controlling hormones, temperature, and autonomic functions. has direct control over each individual sweat gland. Plus, there’s science about attraction you didn’t know existed.
Skin Pigmentation
13 Minutes
Can you really turn orange from eating too many carrots? This page dives into melanin, skin cancerAbnormal growth of skin cells, often due to UV exposure. detection, and the wild variety of pigments that make your skin change colors. Discover how melanocytes sacrifice themselves to protect your DNA from UV damage, learn the warning signsObjective clinical findings observable by a provider (e.g., edema, fever). that distinguish a harmless mole from melanomaA dangerous form of skin cancer that originates in melanocytes., and explore bizarre conditions like “bronzing” and carotenosis (yes, babies can actually turn orange).
Hair and Nails
9 Minutes
You’re shedding 90 hairs per day right now—so why aren’t you bald? This page explains the surprising facts about hair growthAn increase in size and number of cells., including why pregnant women develop extra-thick hair that all falls out after delivery (thanks, progesteroneA hormone that supports pregnancy and regulates the menstrual cycle.!). Learn about the involuntary smooth muscles that make your hair stand up when you’re scared, just like a fluffed cat. Seriously.
The Epidermal Conveyor Belt: Speed vs Quality
Minutes
Ever wonder why some skin conditions pile up thick scales while others just leak and itch? This lecture reveals the shocking truth: your epidermis is a factory conveyor belt that can fail in two completely opposite ways! Watch as we expose psoriasis (running 7 times too fast, spitting out immature cells every 3-4 days) versus eczema (normal speed but producing defective, leaky products). By the end, you’ll diagnose skin conditions like a detective by asking one simple question: Is this a SPEED problem or a QUALITY problem?
The Three Phases of Wound Healing
Minutes
Healing isn’t magic—it’s a precisely orchestrated cellular symphony with dozens of players performing at exactly the right time! Journey through the 2-year transformation from bloody wound to mature scar as platelets, neutrophils, macrophages, fibroblasts, and keratinocytes each take the stage when their cue arrives. See why granulation tissue (that pink, bumpy stuff) is actually a GOOD sign, learn why scars will never tan or grow hair, and discover the heartbreaking truth about chronic wounds: they’re not just “slow healers”—they’re stuck in an endless inflammatory loop that dressings alone can never fix. This is wound healing like you’ve never seen it before!
Vitamin D3 Synthesis Your Skins Solar Power
Minutes
Your skin is secretly a solar panel producing hormones from sunlight—and you never even knew it! Discover the mind-blowing 4-step transformation from a cholesterolA lipid molecule that is a key component of cell membranes and a precursor for bile acids and steroi molecule sitting in your epidermis to a powerful hormone controlling 200+ genes in your body. We’ll reveal why melanin is evolution’s ultimate double-edged sword: it protects your DNA from UV damage but also blocks the exact same UV rays you desperately need to avoid bone disease. Find out why dark-skinned people in Minnesota face a Vitamin D crisis and how your body balances sun protection with hormone production!
By the End of This Module
You Will be Able to:
- Describe the main structural features of the epidermis, and explain the functional significance of each.
- Explain what accounts for individual differences in skin color, and discuss the response of melanocytes to sunlight exposure.
- Describe the interaction between sunlight and vitamin D3 production.
- Describe the structure and functions of the dermis.
- Describe the structure and functions of the hypodermis.
- Describe the mechanisms that produce hair, and explain the structural basis for hair texture and color.
- Discuss the various kinds of glands in the skin, and list the secretions of those glands.
- Describe the anatomical structure of nailsHard, keratinized structures that protect the fingertips and enhance fine motor skills., and explain how they are formed.
- Explain how the skin responds to injury and repairs itself.
List of terms
- skin
- cells
- epidermis
- thin skin
- keratinocytes
- dermis
- hypodermis
- sebaceous glands
- sebum
- secretion
- water
- stratum basale
- stratum corneum
- keratin
- melanocytes
- melanin
- eumelanin
- pheomelanin
- collagen
- dehydration
- acid mantle
- hypothalamus
- skin cancer
- signs
- melanoma
- growth
- progesterone
- cholesterol
- nails