The Life Is in the Blood

We can’t see it, but we know it’s there, under our skin. If it weren’t, we’d be dead!

Our blood—the rich, red stuff of life—flows continuously throughout our circulatory system, keeping us alive. But just how does it do this? Why is blood so important, and what exactly does it accomplish for us?

Blood plays multiple roles in making life possible—one substance ingeniously designed to serve many purposes. Perhaps an imaginary scenario can help us to understand them.

Imagine a young boy on the playground, playing a “pick up” game of basketball with some friends in the summer. Having been passed the ball by a teammate, he rushes through defenders toward the basket for a layup. On his way, he and another player collide and fall to the ground. The boys around offer their two friends a hand up and a pat on the back. Before resuming play, he notices he’s bleeding a bit at his elbow, but not much. He wipes off the blood, unworried, and rushes back into the game, grinning all the while.

The young man may not realize it, but the remarkable design of human blood has played a crucial role in making his game (and his life) possible in at least five different ways—five tasks we all need blood to accomplish for us every day.

Moving Goods and Making Trades

Blood serves as the body’s transport system. Each of its cells—20 to 40 trillion of them—receives oxygen and vital nutrients continuously, and has waste products removed, by blood flowing through the vast, fibrous network of veins, arteries, and capillaries that run throughout the body.

Our basketball player’s muscle cells are fed by the nutrients blood carries from the digestive system, as are the hormones that regulate and motivate his body. Adrenaline to increase his heart rate and ready his muscles, proteins to build and maintain his bones and tissues, and fuel derived from the breakfast he enjoyed earlier are all carried to his hungry cells, non-stop, every moment as he drives himself toward the basket.

As he makes more demands on his muscles, they cry out for more oxygen to burn their fuel. His lungs take in air, and it is the blood—specifically, the highly specialized cells called erythrocytes or, more simply, red blood cells—that brings the oxygen where it is needed. These erythrocytes, manufactured in our bone marrow, look like smooth, symmetric disks, with a bowl-shaped indentation in the middle of each side. Unlike other cells in the body, erythrocytes have no central nucleus. They contain the protein hemoglobin, which “grabs” oxygen from the lungs and “gives” oxygen to other cells it contacts in its journey through the body, passing through even the most microscopic blood vessel so no cell is deprived of the oxygen it continually needs.

Upon reaching a cell, the erythrocyte exchanges its oxygen for carbon dioxide, which the body’s cells produce as a waste product, and carries it to the lungs, which release it to be exhaled and deliver a fresh load of oxygen for the next trip. And along with carbon dioxide, blood carries other waste products to the liver and the kidneys, which “scrub” waste from the blood so that it can continue on its journey, transporting more material.

Sealing Leaks, Mobilizing Troops, and Keeping Things Cool

Two more key roles served by our blood kicked in as soon as our promising young basketball player hurt his elbow.

The moment blood vessels were broken, blood began doing its job to seal that breach. Structures in the blood such as platelets, also called thrombocytes, began to accumulate on the lining of the blood vessels at the injury site. Also made in your bone marrow, platelets respond to signals from a damaged blood vessel by extending “branches” of sorts that allow them to adhere together and “patch” the opening. As they do so, they send additional signals into the blood to bring more platelets to the task, eventually forming a blood clot and sealing the opening—keeping your blood inside and giving your body the opportunity to heal.

The functioning of blood platelets is highly regulated by the body. Should your blood clot too slowly, you risk not only infection but bleeding to death. Yet, if your blood coagulates too quickly or easily, it can create dangerous clots that can damage other parts of the body or cause a stroke. Human blood clotting is an astonishingly fine-tuned mechanism that demonstrates the precision of a loving Creator and ingenious Designer!

But our basketball player isn’t out of danger yet. The moment he cut his elbow, invasive organisms outside his body—such as various microscopic bacteria—were able to enter, potentially causing life-threatening infection.

His blood, however, is already on the job! Next come the white blood cells, or leukocytes, dedicated to destroying invaders and keeping you safe from out-of-control infection. White blood cells form a crucial part of one of the great marvels of creation: your human immune system—discussed in far more detail in our previous article “The War Beneath Your Skin” (March-April 2018). Suffice it to say that your blood carries a microscopic army on constant alert for the presence of anything that should not be there. Without this ever-mobilized army, our lives would be short and painful!

Finally, as our promising basketball star is helped from the ground, he wipes some sweat from his brow. He’s hot! Here, too, we see blood serving us in a way we almost never consider. Where we sweat, our skin cools. Blood cells, carrying heat from the interior of our bodies, pass through these cooler areas of our sweating skin—releasing their store of heat and taking colder temperatures back into the body’s core, cooling it. On cold days our circulatory system does the reverse, moving blood further away from the skin to help the body retain more of its heat.

Keeping his ravenous cells constantly fed and fueled, carrying away toxins and waste products, immediately patching and sealing any cuts, flooding breach sites with defensive armies, and keeping his body at a safe temperature—the blood of our young basketball player is hard at work, continually doing all it can to keep him in the game.

Deeper Lessons

We have yet to be able to fully replicate everything blood is able to accomplish for us. The red fluid flowing through our veins is a marvel of engineering and design, and nothing mankind can create comes anywhere close to rivaling this astonishing substance.

God states that life is in the blood (Leviticus 17:11)—not surprising when we see just how vital blood is to our survival! Yet more important is the spiritual reality this points to in Jesus Christ. For while our own blood is at the heart of our hold on physical life, it is the spilled blood of our Savior that allows us to grasp hold of eternal life as it cleanses us of our sins (1 John 1:7), carrying away from us the ultimate “waste product.”

Even beyond the ingenuity of its design and its astounding ability to accomplish so many different functions, blood holds deeper lessons for us and points us beyond this physical life—to the spiritual and eternal things of the One who created it.