You have just bitten into an apple. As you read this sentence, that piece has already begun one of the longest and most organized journeys that take place inside a human body. From the first contact with the teeth to the way out, food travels a path of roughly nine meters, full of stations where each part has an exact function.
Most of that journey happens without you noticing. You do not decide when the stomach releases acid or when the intestine contracts. An entire system works in silence, day and night, turning food into energy, into muscle, into thought. On this trip through your own body, you will get to know each station, understand the science behind it, and see why David wrote that we were made in a staggering way.
The mouth: where the journey already starts to count
Digestion does not wait for food to go down. It begins earlier, the moment food comes close and you catch the smell. The mouth fills with saliva, and this water that seems so ordinary already carries a chemical tool: amylase, an enzyme that attacks starch and begins to break it down into smaller sugars.
Try an experiment at the next Club meeting. Put a piece of bread in your mouth and hold it without swallowing for a minute. Little by little a faint sweet taste appears. That is the amylase in your saliva at work, turning starch into sugar right on your tongue. The teeth, meanwhile, cut and grind, increasing the surface of the food so the enzymes can reach more pieces at once.
Chewing may seem like a detail, but it is the foundation of everything that comes after. Well-chewed food reaches the stomach in small pieces, easy to process. Swallowing too fast throws all the work onto the organs that follow, which have no teeth. That is why eating slowly is biology working in your body's favor, well beyond good table manners.
The esophagus: food does not fall, it is pushed
After swallowing, you might imagine that food simply slides down by gravity. That is not how it works. The esophagus, the tube that connects the throat to the stomach, pushes food along with muscular waves called peristalsis.
Picture a squeezing motion that runs down the tube from top to bottom, like when you squeeze toothpaste from the bottom to the tip. The muscle contracts behind the ball of food and relaxes in front of it, nudging it forward centimeter by centimeter. That is why an astronaut can eat upside down in space, without gravity: peristalsis moves the food even against the force that would pull it back.
At the end of the esophagus there is a muscular ring, the sphincter, which opens to let food through and closes right afterward. When it fails and stomach acid rises, you get the burning sensation that many people know. The system is precise, and small failures in that control are enough to remind us how much every part matters.
The stomach: an acid cauldron that does not destroy itself
The stomach receives the food and does something that would sound dangerous in any laboratory: it bathes everything in hydrochloric acid. This acid is genuinely strong, with a pH that usually sits between 1.5 and 3.5, able to dissolve proteins and kill much of the bacteria that come in with food. At the same time, the stomach contracts and mixes, turning the meal into a liquid mush.
Here lies a puzzle that impresses scientists. If the acid dissolves meat, why does it not dissolve the stomach itself, which is also made of living tissue? The answer is a layer of thick mucus, rich in bicarbonate, that lines the wall from the inside and neutralizes the acid right at the surface of the cells. This protection is not permanent: the cells that produce the mucus renew themselves nonstop, replacing the barrier before the acid can overcome it.
When that balance breaks, ulcers appear, wounds in the stomach wall. The fine detail is what stands out: an organ that carries enough acid to digest meat lives with it for a whole lifetime because it was equipped with a defense that rebuilds itself continuously. Faced with an arrangement like this, the idea of design sounds like the most honest reading.
Read alsoThe ear and hearingThe small intestine: where absorption really happens
Food leaves the stomach and enters the most important station of the journey. The small intestine is the longest part of the whole route, several meters coiled inside your belly, and this is where almost all nutrients pass from food into the blood. Vitamins, sugars, amino acids, fats: everything is collected in this stretch.
The trick is in the surface. The inner wall is not smooth. It is covered by millions of tiny folds called villi, and each villus has, at the tip of its cells, even smaller projections, the microvilli. This layered texture multiplies the contact area in a way that is hard to imagine. If the wall were a smooth tube, the area would be small; with the villi and microvilli, the absorption surface reaches something around thirty square meters, close to the size of a large bedroom, all folded up inside you.
This is why the small intestine can capture so much nutrient in so little space. Each villus has, inside it, very thin blood vessels that receive what has been absorbed and carry it to the whole body. It is surface engineering taken to the extreme, hidden in a belly that fits under the shirt of a uniform.
Liver, gallbladder, and pancreas: the backstage team
Not all of digestion's work happens inside the tube. Three neighboring organs pour their help into the start of the small intestine, and without them absorption would stall, especially the absorption of fats.
The liver produces bile, a fluid that breaks fat into smaller droplets, the same way detergent dissolves grease on the dishes. The gallbladder is a little pouch that stores this bile and releases it at the right moment, when a fatty meal arrives. The pancreas, in turn, sends powerful enzymes that attack proteins, fats, and carbohydrates all at once, along with bicarbonate that neutralizes the acid coming from the stomach so it does not burn the intestine.
Notice the synchrony. The stomach acidifies, the pancreas alkalizes right afterward, the gallbladder releases bile at the exact moment the fat passes through. It is a timed team effort, in which each organ steps in at the right instant. The liver does even more: it receives the blood loaded with nutrients, filters toxins, and organizes what the body will use or store. It works like the chemical manager of the whole operation.
The large intestine and the trillions of invisible residents
What remains after the small intestine takes the nutrients moves on to the large intestine, the last big station. Here the task changes: instead of absorbing food, the body recovers water. Much of the liquid you drank and of the secretions of digestion is reabsorbed at this stage, which prevents dehydration and gives shape to what will be eliminated.
The large intestine holds the biggest surprise of the journey. It houses an immense population of bacteria, the so-called microbiome, with a number of microorganisms in the trillions. Many of these bacteria are allies: they ferment fibers your body cannot break down on its own, produce certain vitamins, such as part of vitamin K, and help train your defense system to recognize real threats.
Caring for these friendly bacteria means caring for yourself. A diet rich in fiber, with fruits, greens, vegetables, and whole grains, feeds the good microbiome. Too much ultra-processed food impoverishes that population. The link between what enters the mouth and the health of the whole intestine closes the circle of the journey, and connects science with daily choices.
A staggering body and the invitation to care for it
After following this journey, David's words gain concrete weight. In Psalm 139:14 he writes: "I praise you because I am fearfully and wonderfully made; your works are wonderful, I know that full well" (NIV). Anyone who knows the villi, the mucus that renews itself, and the synchrony of the organs understands that this admiration is not poetic exaggeration.
The Bible links this care for the body to practical decisions. In the book of Daniel, four young men taken to Babylon ask to eat vegetables and drink water instead of the king's rich food. After ten days of testing, they appeared healthier and better nourished than the others (Daniel 1:8-15). The story does not become a rigid rule. It shows young people taking their own bodies seriously, and it is from that kind of choice that the Adventist health message is born, the invitation to treat the body as something entrusted to you.
Paul sums up the principle in 1 Corinthians 10:31: "So whether you eat or drink or whatever you do, do it all for the glory of God" (NIV). Eating well, chewing calmly, drinking water, sleeping: none of this is too small to matter. Caring for the nine-meter machine that works for you in silence is a form of gratitude. If you want to go deeper into this theme, it is worth getting to know the origin of the Adventist health message and the Temperance honor.