Fantastic Voyage
Desire Fleming
HS130, Section 03
Unit 9 Assignment
Kaplan University
6/13/2014
Fantastic Voyage This essay will discuss the travels of a hamburger, french fries, and a root beer through the gastrointestinal tract of a 55 year old man. There will be a lot of sights to explore along the way. A description of the entire digestive process will take place. After the description, the voyage will continue on through the distal ilium through the mucosal membrane. Then travels will resume in the bloodstream via the superior mesenteric vein. All major passageways and structures will be described going through the superior mesenteric vein all the way to the left renal artery. Once the voyage gets to the kidney, the nearest nephron will be entered. All structures will be discussed passing through on the way to the urinary tract where the voyage will exit out through the urethra. This journey is quite far but very interesting. The gastrointestinal tract is also known as the alimentary canal. Its main function is to digest food through various muscle movements and hormone and enzyme release. The tract is around 20-25 feet in length (wisegeek, 2014). The gastrointestinal tract consists of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus. It also consits of accessory organs which include the tongue, mouth glands, pancreas, liver, and the gallbladder. Each and every one of these parts work together to break down food so it can be easily digested. As this 55 year old man ingests his food and drink, it will first enter through his mouth. While he is chewing his food, the salivary glands will begin to produce saliva and amylase, produced by enzymes. This will in turn break down some of the carbohydrates. Also the chewing motion will break down the food and the tongue will form it into a small bolus for easy swallowing. The food will then travel into the pharynx, which is also known as the throat. When swallowing, the body will automatically shut down the windpipe and nasal cavities so that the food can easily go into the esophagus. The esophagus is a narrow tube that extends from the pharynx all the way down to the stomach (Collins, 2000). The body's muscle contractions are what help transport the food forward through the esophagus. These contractions are also known as peristalsis. At the bottom end of the esophagus there is a sphincter (lower esophagus sphincter) that will open and allow food to enter the stomach and then immediately close shut to keep the food from going back up. Occasionally this sphincter may malfunction and cause food in the stomach to reenter the esophagus which in turn can cause acid reflux. Symptoms of acid reflux include burning chest pain, burping, bloating, nausea, or regurgitation (WebMD, 2005). Now in the stomach, there is a very noticeable acidic environment. In the stomach there are different enzymes called pepsin and stomach acid that work to break down the food even further. The food then turns into a gravy like consistency called chyme when it is ready to leave the stomach (Barrett & Kroger, 2000). The next stop following the stomach is the small intestine. There are three parts to the small intestine. The duodenum is the first and shortest part. Next is the jejunum, and finally the ileum. The lining of the small intestine contains mucous and glands called intestinal glands, which produce intestinal digestive juices. The lining is also arranged into small circular folds known as plicae. The folds are lined with small finger like projections called villi (Thibodeau & Patton, 2008). The maximum digestion of foods happens while in the small intestine. The pancreas as well as the bile from the liver releases enzymes which work to further break down the chyme. The duodenum is mainly responsible for furthering the break down process while the jejunum and ileum are responsible for making sure the nutrients are absorbed into the bloodstream. After the nutrients from the food are absorbed into the bloodstream, the veins from the ileum drain into the superior mesenteric vein. This vein combines with the splenic vein to form the heptic portal vein which leads directly to the liver. The liver's main function is to filter the blood from the digestive tract before passing it to other parts of the body (WebMD, 2005). In the liver there is a portal venous system that delivers the blood to the capillary system. From there the blood flows into the inferior vena cava, right atrium, right ventricle, down the pulmonary artery, and then eventually to the lungs. The blood in the lungs then travels through the left atrium into the pulmonary vein. Next it travels through the left ventricle to the aorta. Moving on from the aorta, the next stop is the abdominal aorta. From there is the superior mesenteric artery and the left renal artery which leads straight to the kidney. The kidneys are very vital organs. Their main purpose is to form urine. The blood enters the kidney through the glomerular membrane in the nephrons. Nephrons are tiny filtering units in the kidney that remove many harmful toxins and excess fluids from the blood (Hilaire,2006). Blood then trickles down the bowman’s capsule to the renal tubule. The renal tubule is made up of the proximal convoluted tubule, loop of henle, distal convoluted tubule, and lastly the collecting tubule. From the collecting tubule, urine is formed and then drained into the renal pelvis. The urine is collected in the ureter which is then passed to the urinary bladder and exits the body out through the urethra. All of the body's systems work together to maintain equilibrium, which is known as homeostasis. The circulatory system maintains homeostasis by the small intestine telling the brain that the body has nutrients after eating. The body then knows to transport those nutrients. The digestive system maintains homeostasis by breaking down foods so the body can digest them into important nutrients to be absorbed for energy. This system breaks down all the foods so the nutrients can be absorbed while the waste will exit the body. Lastly, the urinary system maintains homeostasis by regulating body fluids by getting rid of the body's waste. All of the systems in the body rely on the circulatory system to get the job done.

References
Barrett, S., & Kroger, M. (2000). The Digestive Process. Retrieved from http://www.nutriwatch.org/01Basics/digestion.html
Collins, A. (2000). The Human Digestive System. Retrieved from http://www.annecollins.com/food-digestion-guide.htm
Hillaire, Rodger. (2006). Nephrons: The Kidney's Filtration System. Retrieved from http://www.comprehensive-kidney-facts.com/nephrons.html
Thibodeau, G., & Patton, K. (2008). Structure and Function of the Body. 13th Edition. St. Louis. MO:Mosby Elsevier
WebMD. (2005). What is Acid Reflux Disease. Retrieved from http://www.webmd.com/heartburn-gerd/guide/what-is-acid-reflux-disease