The Integumentary System: Our Living Interface

Our integumentary system is made of our skin, hair, nails, and glands. Our skin is our first interaction with the world around us, really from the moment we are born. It is our body’s largest organ and serves as both a physical shield from harm, and a sensory gateway to experience everything from hugging our families, petting our dogs, and touching hot stoves. It also serves as a sort of ‘storyteller’ of our internal world (how our liver is processing things) and external world (if we spent too much time in the sun that day). It is a beautiful, complicated organism that goes underappreciated and underlooked in medicine and life.

Right now, take an inventory of everything your body is touching. Maybe you’re sitting on a couch. Is it soft? Rough? Firm? Are your feet on the floor? What’s the texture of the clothes you’re wearing? Are they tight or loose? Is your hair resting on your shoulders? Is your watch too tight or too loose? What’s the temperature like? Do you have a blanket over you? Are you in a bathing suit on the beach?

Your skin is your messenger of ALL of this information, ALL the time. It also is processing it instantaneously, deciding if you’re too hot, or too cold, and performing actions you never have to think about that are essential to keeping you alive. If you’re on the beach and it’s hot, you might be sweating. Thank your integumentary system. If your fingers are cold and you turned the heat up, thank your integumentary system for that signal. If you’re outside at a soccer game and the sun goes down, thank your integumentary system for the goosebumps and shivering you do to keep warm.

ALL of these mechanisms are a product of this system evolving and adapting to an internal and external environment over thousands of years and generations.

Story time - I’m a terrible flirt. Always have been. It’s something I’m not naturally good at, and never really cared enough to get better at until I started seriously dating. I’m awkward and uncomfortable. I had to make it a point, since I was bad at flirting with my words and would often find myself muttering something I thought would be flirty, only to have to say it with clear articulation (which I’m sure made me REAL attractive) again, I relied significantly on touch as a way to show dates I was interested in them. I’m a student of body-language anyway, but I always found a touch to either be a great indicator to my date that I liked him, and offputting to me if I didn’t like him but he touched my arm or shoulder or face.

My husband will tell you, within the first month of us dating, we were on the couch watching a show, and he put his hand on my leg and glided his thumb back and forth across my thigh. I hated it. Something about the repetitive motion drove me crazy. I didn’t say anything at first because I liked him and he was trying to show affection. But after a few minutes I had to tell him that it was like nails on a chalkboard to me. Something in my nervous system did not like that type of touch or feeling. He has since learned, and will now put his hand on my leg and just keep it there.

Touch: The First Language

Good thing he learned, because we got married a few years later, and a few years after that, I was pregnant with our daughter. It was 2023, and all of the instagram influencers talked about the importance of ‘skin to skin’ contact right after birth. One of my favorite data-driven moms is Emily Oster, author of Expecting Better and Cribsheet, who a neighbor of ours introduced me to, and is NOT an instagram ‘influencer’, but an economist and professor at Brown. She speaks and writes in such a way that is practical, sensible, and humorous, and has a way of explaining and calming down the ‘panic headlines’ that get people to buy the article for $2.99.

While ‘Cribsheet’ doesn’t have a robust chapter on skin to skin, she does mention that it can improve breastfeeding success and helps to regulate the baby’s temperature. We know that it helps regulate the baby’s heart rate, and releases hormones like oxytocin, the bonding and love hormone. This doesn’t happen (or doesn’t happen as effectively) when mom or dad has clothes on. We have to conclude that there’s something about our skin touching another person’s skin that signals relevant information.

Our skin has 3 main layers, and within each there are specialized cells that have various functions. There are cells that produce proteins and hormones, synthesize vitamin D, sense touch, temperature, pain, release immune responses and clean up waste products.

I heard another PT explain it at some point in my career, that when we touch someone’s skin, we’re talking to their nervous system, and ultimately touching their brain. That hit me. Our skin is our body’s sense of the world around us, and is a living breathing organ that deserves our attention and respect.

One of my mentors uses a “4 Ts” framework when interacting with patients.

1. Talk

2. Touch

3. Teach

4. Thank

He makes sure that his employees use this framework in order to establish rapport with their patients and build trust.

As a PT, I touch a dozen people a day. I use my hands to feel their skin, muscles, bones, tendons and ligaments. My hands then help them move, stretch, breathe, and exercise. It’s always amazing to me how when I shut my mouth and simply touch the muscles I want them to use (or tap, or rub), their form improves and I don’t have to say a word. As a matter of fact, often my words INHIBIT the type of movement I want to see. Touch is a powerful stimulus, and I’m grateful my patients trust me to touch and move their body in a really intimate way.

OUTPUT OF OUR SKIN :

Our skin can also be a really helpful indicator of overall health or if there’s a problem with our INSIDE environment. Think of anyone you’ve ever seen who is battling cancer. Their skin sags. It’s often pale and poorly colored. You can often tell by looking at someone if they’re acutely ill.

Story time - when my daughter was 2 days old, we took her to our pediatrician’s office for the first time. I’d been breastfeeding as best I could but didn’t know what I was doing, and our doctor (in a VERY roundabout way) was concerned about her skin color and noticed jaundice, so she basically insisted that we formula feed her to “get the jaundice out.” As I understood it…it took her about 10 minutes to ‘explain’ this, but I digress.

The point is, as I learned (thanks to Professor Emily Oster and Dr. Google), jaundice is a symptom of a condition where a newborn’s bilirubin levels accumulate. In an incredible process (which I won’t explain fully in this book, but we’ll touch on your organ’s responsibilities) , our spleen, liver, and intestines break down red blood cells and excrete the byproduct (bilirubin) in our stool. In an infant, their spleen and liver often cannot process the bilirubin quickly enough (since mom’s body had been doing it throughout the pregnancy), and the result can be the buildup of bilirubin and subsequently, a yellowish coloring of the skin and eyes. One of the ways to help excrete the bilirubin is to ensure the baby is eating well and enough to produce wet and poopy diapers. (Hence, the insistence on formula feeding to ‘get the jaundice out’).

My baby’s body was telling us something through her SKIN, that otherwise is undetectable unless bloodwork is done. Her SKIN told that story. We ended up giving her a small amount of formula that night, and I drove myself mad trying to pump enough breastmilk to feed her enough to ‘get the jaundice out’. She was fine and is healthy as can be now, two years later. We’ve had friends who have put their babies under the special lights at the hospital to improve their bilirubin to safe levels.

But do you want to know something ABSOLUTELY MINDBLOWING? When you put a baby who has symptoms of jaundice in sunlight (or blue light), their SKIN CHANGES THE CHEMICAL STRUCTURE OF THE BILIRUBIN IN THEIR BODY to a different form that the liver can process more easily and then can be excreted. That’s why you’ll hear doctors (or your parents or grandparents) say, ‘take them outside’ or ‘feed them near a window’.

COME ON. That’s a miracle.

Everyone I know has had some kind of skin reaction to an allergy they have, or to poison ivy, or a medication. Our skin tells us a full story of our health if we listen, while providing the rest of our body with important inputs from the world around us.

Story time - Hank’s skin and gut health

INPUT OF THE SKIN

Our skin has specialized cells called ‘mechanoreceptors’ which connect to our nerves and give us information about the environment around us. These mechanoreceptors have individual specialties. They detect hot/cold, sharp/dull, vibration and stretch or pressure.

Think for a moment how amazing it is that you can feel a tight squeeze of a hug, and also that there’s a small bug crawling on you, and also that the stove is hot, and also that the leaves on that bush are prickly, and the blanket around you is soft. Your skin gives the first line of information to your nervous system, and it’s incredibly important to your safety and survival that it receives and transmits an accurate signal.

Story time - my niece is a monkey bar whiz. She’s 7, and I can confidently say that if we stuck her on an ‘American ninja warrior’ course, she’d cruise through it. Any playground we’ve been to, she has no problem clambering and climbing every structure quickly and with ease.

My parents have this great Japanese maple tree right outside their back door. It’s PERFECT for climbing, and about 2 years ago, I asked my niece to scale it. She (claims) to never have climbed a tree before. But she was a climbing girl, and was up for the challenge.

Almost immediately, she noticed a difference between this tree and her monkey bars. ‘It hurts my hands’.

Every surface she’d climbed on prior to this tree was plastic, metal, PVC, etc. It was smooth. It’s temperature was controlled to some degree. It was predictable, uniform, sturdy and steady.

The skin on her hands had a completely different perception of this surface than every other one she’d ever climbed. And it told her so in the form of discomfort. AND , most importantly, SHE LISTENED to the signal it sent. She had to take a break after a few minutes. After a few tries, she reached a point on the tree that was sharp, and actually got a cut on her hand. She was upset and scared, and she cried as we cleaned it and put a bandaid on it.

I hadn’t thought at all about the points I just made about the surface being different from her monkey bars until that moment. It hit me like a ton of bricks that not only was the task itself different from a playground, but the SURFACE her skin had to interact with was completely foreign.

She has since recovered from her scraped hand, and now is an actual monkey. Girl can climb trees barefoot and with 1 hand tied behind her back.

My daughter, who is 2, loves to climb that tree, and I actually have her do it barefoot so she can more accurately feel the branches, their texture, and their sturdiness, since I learned from her cousin how important it is to expose her to those kinds of surfaces and challenges.

Why your skin matters in your rehab journey:

First off, if you’re having or have had a surgery, your surgeon is going to cut through your skin to get to whatever they’re working on. The ABOSOLUTE highest priority post operatively, is ensuring that there’s no infection to the skin or structures underneath it. (This is part of why surgeries are done in sterile environments).

If your skin gets infected, we have a whole other slew of problems before we can even consider the rehab process. So, keep it clean, dry, and safely mobile.

The scar that forms on your body will be nearly a direct reflection of how well you’ve healed from that procedure. If your surgeon does a good job stitching you back up, and you’ve adequately hydrated, slept, ate well, and moved appropriately, your skin will not be a limiting factor in your recovery. But if that scar is raised, infected, or prolonged in it’s healing, it can impact the mobility of the skin, fascia, muscles, tendons, and ligaments underneath it, and significantly impact your progress in rehab.

I’m going to have ChatGPT explain to you how M.O.V.E impacts skin health .

Stress:

Chronic stress affects skin through hormones and inflammation.

• Cortisol increases sebum (oil) production → acne, rosacea flare-ups.

• Inflammation increases sensitivity and slows wound healing.

• Barrier breakdown makes the skin more reactive, dry, and less able to protect against bacteria.

• Stress also worsens autoimmune skin issues like psoriasis and eczema.

🧘‍♀️ Calming your nervous system is a skin-care strategy — breathwork, prayer, journaling, sunlight, or nature literally show up on your face over time.

💤 SLEEP — The Skin’s Night Shift

When you sleep, your body switches into repair and regeneration mode.

• Cellular repair: Growth hormone (GH) spikes during deep sleep → boosts collagen synthesis, tissue repair, and cell turnover.

• Reduced inflammation: Sleep regulates cortisol and cytokines — less puffiness, redness, and breakouts.

• Barrier recovery: The skin barrier heals faster overnight, which means better moisture retention.

• Lack of sleep: Raises cortisol → breaks down collagen and hyaluronic acid → fine lines, dullness, and “tired” skin.

🧠 Think of sleep as your skin’s night crew — quietly rebuilding, replenishing, and restoring while you rest.

🏃‍♀️ MOVEMENT & BLOOD FLOW — The Circulatory Glow

Movement = circulation = nourishment.

• Increased blood flow delivers oxygen and nutrients to skin cells and removes CO₂ and metabolic waste.

• Lymphatic movement helps drain excess fluid and prevent puffiness.

• Sweating opens pores and eliminates waste while promoting natural exfoliation.

• Regular exercise boosts collagen production and improves insulin sensitivity — both vital for youthful, resilient skin.

🚴‍♀️ When you move, you’re irrigating your skin from within — like giving it a gentle daily facial through circulation.

💧 HYDRATION — The Inner Moisturizer

Skin hydration starts inside-out.

• Water balance: The outermost layer (stratum corneum) depends on internal hydration to maintain elasticity and smoothness.

• Lymph flow: Water helps flush metabolic waste and toxins that can otherwise stagnate in tissues.

• Blood viscosity: Proper hydration improves circulation — nutrients get delivered and waste gets removed efficiently.

• Dehydration: Skin appears dull, tight, flaky, and fine lines become more visible.

💦 Hydration isn’t just about drinking water — it’s about keeping electrolytes balanced (sodium, potassium, magnesium) so the water stays where it belongs in your cells.

🥦 NUTRITION — The Skin’s Building Material

Your skin literally builds itself from what you eat.

• Proteins: Provide amino acids for collagen, keratin, and elastin — structural integrity and resilience.

• Healthy fats: Omega-3s and 6s maintain the lipid barrier, preventing dryness and inflammation.

• Micronutrients:

  • Vitamin C → collagen synthesis, antioxidant

  • Vitamin A (retinoids) → cell turnover, acne control

  • Zinc → wound healing, inflammation regulation

  • Polyphenols (berries, greens) → protect from UV and oxidative stress

• Sugar & processed foods: Glycation cross-links collagen fibers → loss of elasticity and premature aging.

🥗 Food is literally skin care — from the inside out.

In conclusion - appreciate your skin. It is a miracle organ that protects you, heals you, and allows you to interact safely with the physical world around you.