Well, we're heading into holiday season which means snacks, treats, candies, sweets, feasting... and then the holiday bloat begins. (Why are these goodies so irresistible?!) So it's appropriate that this month we'll focus on the inner workings of our digestive system. I know that it will help keep me more aware of what I am eating during this year's festivities!
Let's dive right in. We're all aware of our basic digestive processes. We eat, we digest and absorb nutrients, and we eliminate. However, when we start to look at this body system, we cannot really separate it from anything else that is happening in our body. We eat to live and nourish ourselves on a cellular level. Our food feeds every cell in our body, and thus has a direct impact on every single process, function, and part of our being.
In the digestive system, we have (of course) our mouth and salivary glands. This is where it all begins- enzymes in our saliva begin to break down our food into simpler complexes. (For instance, our saliva contains amylase which breaks down starches and carbohydrates into maltose).
Next along the pathway to digestion is the stomach, where gastric juices are produced to begin the breakdown of proteins. The stomach acts as a time-release holding tank for your food. It allows it time for the food to be broken down properly so your body can absorb nutrients properly. Your stomach itself does not absorb any nutrients, but can absorb alcohol (including tinctures), water, and some fruit and vegetable juices. The majority of nutrient absorption is actually happens in the intestines.
That brings us to the small intestine, which is the first portion of the bowels. This part of the digestive tract is over 30-40 feet in length, intricately folded! The small intestine is a marvel at its job. The walls of the small intestines are made up of villi, which are circular folds that help expand
the surface area of the intestines and allow for maximum digestion and absorption. Villi have both lymph vessels to carry away waste as well as capillaries which help absorb substances directly into the blood stream. Our small intestine is comprised of three sections (with incredibly fun names), each with a specific function: the duodenum, the jejunum, and the ileum.
The duodenum receives alkalizing substances from other organs- bile from the liver/gallbladder and sodium of bicarbonate from the pancreas. These help further break down foods. It also excretes specific hormones and enzymes which aid in digesting different types of food substances.
The jejunum is roughly 8 feet in length! Thanks to the digestive enzymes from the duodenum, the jejunum is where nutrient absorption happens.
The last section of the small intestine is the ileum. This is the longest section, and can be 15-30 feet in length! By the time food reaches this section, it has been expertly broken down into the components that the body needs- amino acids, monosaccharides, fatty acids, glycerol, vitamins, and minerals. In the ileum, these substances are mixed with water before continuing on into the large intestine.
At this point, most of the actual digestive process has already occurred. Once food reaches the beginning of the large intestine, the process of elimination is beginning. The digestive system and eliminatory system are intrinsically linked- they are nearly inseparable when it comes to bodily function.
The large intestine is comprised of multiple parts- the cecum, colon, rectum, and anus.
The ileum of the small intestine connects to the cecum of the large intestine through the ileocecal valve. The cecum acts as a reservoir and is the widest part of the colon. When it is full, it stimulates the smooth muscle of the bowels to move.
Food then travels through the colon. The colon has three identifiable parts:
The ascending colon
The transverse colon
The descending colon
The ascending and transverse colon frame the small intestines. In these sections of the bowels, water and electrolytes are absorbed out of the colon. By the time that the remaining food reaches the descending colon, it is nearly completely waste. The only digestion that is happening at this point occurs from the gut bacteria breaking down any remaining carbohydrates into vitamins such as B & K.
The descending colon secretes mucous to help the now solid, dehydrated waste pass smoothly into the rectum. This waste is now mostly indigestible matter and cell waste with only small amounts of water. When waste enters the rectum, it triggers defecation and waste leaves the body through the anus.
There it is! The whole process of digestion. It's truly amazing that the body can take what we eat, break it down into exactly what it needs, and eliminate the rest! It's a process that is continually at work within us, keeping us healthy on a cellular level. Everything we eat has to pass through our whole digestive tract, touching nearly every other organ system as it goes! The digestive system consists of smooth muscle that is controlled by the autonomic nervous system. It is fueled by enzymes and hormones that are produced in part by the endocrine system (and in fact, the hormones created in the digestive tract make it part of the endocrine system). It interplays with the eliminatory functions, such as that of the liver. The digestive system's cells are fed by the circulatory system and in turn, use the blood as a direct transporter to nourish the rest of the body's systems! So the next time you hear the old adage "You are what you eat" I hope you'll think of the interconnectedness of this system with the rest of the body- how every morsel you intake is intended fuel and nourishment for the system as a whole. I know I'm going to try to keep this in mind as I go about the holiday season!