It’s ALIVE!And it gets ulcers
Brandon W. Maister
Digestion is pretty gross. However, if you’re willing to look a bit more closely, this intricate process is fascinating.Your body takes anything and everything that you stick into your mouth and turns it into either a usable energy source or expels it as waste product. Your digestive system is basically one continuous tube that begins at your mouth and ends where you sit. This tube is divided into a bunch of different parts. In each area different chemicals called enzymes degrade different kinds of foods for use by your body systems.
Mom was right. Take care of your teeth. They are the first step in your digestive process (also, without them you’ll be sipping baby food peas and carrots through a straw at the end of your life). Teeth are also way less boring than they look.
Firstly, more than half of your tooth is not visible when you open your mouth. Also, whether the dentist has ever stuck his drill in your mouth or not, you’ve got cavities. Don’t worry though, they are supposed to be there. The holes that tunnel in at the base of your teeth inside your gums serve as entryways for all the various blood vessels and nerve endings.
The inside of your tooth is a tangle of tubes surrounded by a hard yellow tissue called dentin, which protects the inhabitants of the hollow space inside it. Even Rembrandt Deeply White TM isn’t going to change the color of that stuff, so you can stop brushing hard enough to skin an elephant, it’s not going to help. The final, outer covering of your tooth is the better known enamel, or cementum, the part of your tooth that rests under your gum.
Your body begins its breakdown of food the instant you put your fork (or fingers) into your mouth. As you masticate, or chew, the physical tearing apart of larger chunks of whatever it is you are eating into smaller chunks kicks off the digestion process, creating a larger surface area for the enzymes in your digestive organs to work with.
Once you’ve swallowed, food continues down your alimentary canal into your esophagus. This organ is basically a tube of muscle that pushes your chewed up edibles down towards your stomach through a repetitive undulating squeeze known as peristalsis. Gravity helps pull the food down, so your muscles don’t need to work too hard. However, when you toss your cookies, known in science-speak as reverse peristalsis (which sounds a lot more sanitary), the muscles of your food pipe work backwards to force the contents of your stomach upward and out.
In addition to being uncomfortable, reverse peristalsis can actually harm you. The food coming up is returning from the stomach, an extremely acidic environment that activates food-degrading enzymes. Inside your belly, the hydrochloric acid and enzymes turn all the food you eat into a terrible looking, burning mush known as chyme. Your stomach is equipped to handle this extreme acidity, which has a pH of about 2.0, because it is covered in a layer of mucous, a snot-like substance that shields your more sensitive tissues from harm. Your esophagus however, is not as well protected. Repeated or chronic vomiting can burn through the tissue causing pain and inhibited function, and even a change or loss of voice quality.
Even your stomach is not impervious to acid induced injury. If the mucous membrane of the stomach is compromised by a bacteria, or habits like frequent smoking and aspirin abuse, acid can reach the stomach tissue and cause the stomach wall to erode. This condition is commonly referred to as an ulcer.
Once the stomach has churned your food into a sufficiently yucky mess, the chyme is pushed out of the stomach and into the small intestine. This is where peristalsis begins to push it down the approximately twenty foot long intestinal tract, which reacts with a full-on “oh my god calm down!”
Or at least, it spends the first third of its distance de-acidifying (or neutralizing, if you want to sound scientific) the muck that it receives from the stomach.
Once it has neutralized the threatening acids, it is within the small intestine that your body actually starts absorbing the food that you began chewing an hour or more before. This entire process so far has simply been your body trying to get the chunks of flesh or vegetable you consumed small enough to rub along the walls of the intestine, so that the good, nutritional, parts of the food can get absorbed into the blood.
Your intestinal lining requires that food is as close to the consistency of blood as possible in order for it to be able to pass through the chyme/blood boundary. So, no, despite the fact that your body is actually absorbing meat into your blood from your small intestine, you can’t wear Lady Gaga’s meat dress and successfully avoid eating (although you might not be admitted to a restaurant).
In fact, millions of years of evolution have generated tiny grasping meat-fingers in your intestine, for the sole purpose of exposing even more blood vessels to the nutrient-rich slush passing along nearby. These meat-fingers coat the entirety of the inner small intestine and are so small that they look like hair. In other words, 1 millimeter (less than 0.04 inches) long hairs made out of muscle are continuously grasping for food in your intestine.
The small intestine successfully sucks most of the useful nutrients out of whatever you’ve eaten, and the large intestine is then left with the task of absorbing the water and producing vitamins from the leftovers. Unfortunately, while the colon can absorb moisture it cannot create vitamins. That task is left to the more than 700 species of bacteria living inside it. These bacteria, or “gut fauna,” eat what remains of your food and poop out vitamins which your body then absorbs.
From there it is a short trip to the colon, which doesn’t do very much, it’s mostly just a sack of... fecal matter, absorbing water and vitamins, ready and waiting for your next trip to the bathroom.