If you're like me, you’ve left the house before with an open cup of coffee in your hand, no lid. Of course, you're sure that this time not a drop will spill. You’ll surely have no problem rounding that sharp corner, and getting all the way to work with an open cup of hot coffee in your hand. Well, we all know how that turns out.

Having a lid on your cup is necessary for keeping everything from spilling out. It also works to keep out germs and other unwanted guests.

And the lid's final role is temperature control. With a wide open cup, a steaming hot coffee won't stay hot for very long.

Why all the focus on coffee cup lids? Well, we have something in our bodies that acts similar to that lid – but on a much greater scale. I’m referring to the largest organ of the human body – the skin.

Human skin is an absolutely marvelous organ, beautifully designed and engineered by our Creator. As with all things in life, we often learn to appreciate what we have only once they're gone. So let’s imagine that we had no skin. In fact, we don't even need to think that hard – unfortunately we can see something like this in a hospital: burn patients. A burn is one of the most heart-breaking, devastating conditions that we see. In third degree burns, the entire thickness of the skin’s layers are affected. Those patients have essentially lost their skin. Such patients are very hard to manage, and are often also in constant, excruciating pain.

Using the “coffee lid” analogy (the lid keeps coffee inside, keeps intruders outside, and maintains temperature), we can recognize that the issues that come up when skin is absent, are essentially the inverse of the three roles of the lid.

1. Without skin, a person will not be able to keep things inside. This is most apparent when it comes to fluid balance. Burn patients are essentially dehydrated, due to the mere fact that they can't keep their fluids inside. Keeping them hydrated becomes a very complex issue (especially because we don't want fluid to end up in unwanted places like the lungs).

2. Without skin, a person will not be able to keep out intruders. One of the saddest aspects of burn patients is that they often end up with horrible infections, simply because there is no barrier to keep these bugs out.

I had a professor in medical school that challenged us all to come up with the most important component of the immune system. We all began mentioning things like the white blood cells, antibodies, macrophages, and a number of other complex, immunological cells and proteins.

We were all wrong. The answer, he explained, is the skin. We don’t tend to think of the skin in that way, but it truly is amazing in its ability to keep things out. In fact, our skin is actually covered in highly destructive and powerful bacteria all the time. And yet we remain, for the most part, unaffected by them.

In order to prove to us that we were all covered in bacteria, our professors had us all take our fingertips and run them through a plate full of nutrients that allow bacteria to grow freely (known as an ‘agar plate’). If any bacteria were on our fingers at that moment in time, they would have the ability to sit on the plate and grow, unhindered. Those plates sat in a lab for three days and we then had the ability to go take a look and see what grew. Needless to say, most of us were quite grossed out by what was living on our fingertips! The simple ability of the skin to keep out harmful microbes, even as they sit on the surface of our bodies, is truly remarkable.

3. Without skin, we would not be able to properly control our body temperature. In 2020, we are accustomed to the idea of a thermostat - a device that automatically regulates temperature and maintains the temperature that we desire. However, when we stop and think about the human body and its ability to regulate temperature, it is quite astonishing. Our brain decides that a temperature of approximately 98.5F is the temperature to be at - and that’s where we remain. But think about a person running a marathon. As the muscles use more and more calories to perform work, a massive amount of heat is generated. Heat is increasing, however our brain is still telling our bodies to remain at 98.5F. Imagine trying to keep your house at 70F, while there is a massive bonfire in your living room. So what happens next? Why doesn’t body temperature rise to 107F after vigorous exercise?

The wonders of human physiology are evident in every single organ.

Here is where the skin comes into play. Ever notice how after a workout your skin looks flushed? The heat that is generated from the muscles ends up in our bloodstream. In an effort to get rid of that heat, the blood gets redirected to the surface of the skin, where the blood can release some of that heat, out of the body, and into the air. Moving that warm blood to the outermost layer of our body, enables us to cool off. In the cold, the opposite occurs. Our body tries its best to hold on to all that warm blood and keep it deep inside so that no heat can escape. (Hence, our skin in cold weather ends up looking pale and bloodless). All of these intricate mechanisms are taking place, behind the scenes, without us consciously contributing to the process at all!

The wonders of human physiology are evident in every single organ. It’s been shown that gratitude and the ability to pay attention to what we have (as opposed to what we don’t have) are linked to happiness. As Rabbi Noah Weinberg eloquently wrote: Just as every stroke of Picasso's brush has his signature on it, everything in this world has God's signature on it. We have to learn to appreciate it.

To hear more from Dr. Grubner about God’s creations and the inner workings of the human body, listen to his podcast at www.anchor.fm/arigrubner, or wherever you get your podcasts.