Unit 9 Project – Fantastic Voyage

HS130 - 04
June 19, 2012

Fantastic Voyage
Good afternoon everyone! This is Lisa back again with another top health news story. Once again I will be taking my mini-sub through the miniaturization process making us only 8 microns long and traveling through the human body. Today we will be swallowed by a 55 year old man, Mr. Smith, who is currently eating a hamburger, French fries, and enjoying a nice cold root beer. Our goal today is to monitor the digestion of Mr. Smith’s meal through the gastrointestinal tract. As we progress through the body, I will be describing all the major structures that we go through as well as describing what happens to the meal as it goes through the digestion process. Let’s get started.
We are going to begin our journey by watching how the food is digested via the gastrointestinal pathway and the urinary pathway. Starting with the digestive system, the food will begin to be digested in the mouth where food is acted upon by saliva and enzymes like amylase (WiseGeek, Digestive System, 2012). The brain has a reflex that triggers the flow of saliva into our mouths when we see or even think of food (WiseGeek, Digestive System, 2012). There are three major salivary glands that are involved in this process: the parotid, submandibular, and sublingual glands. These glands function to secrete saliva into our mouths in order to keep it moist, lubricate and bind our food to begin the digestion process, and to maintain oral hygiene (WiseGeek, Salivary Glands, 2012). Our saliva moistens the food while our teeth chew it up and make it easier for us to swallow. As Mr. Smith swallows his food, the muscles in his tongue and mouth will move the food into his pharynx. The pharynx is divided into three parts: nasopharynx, oropharynx, and laryngopharynx (WiseGeek, Pharynx, 2012). The nasopharynx is located at the base of the skull next to the soft palate and is the most important part of the pharynx to the digestive and respiratory system. The oropharynx extends from the uvula to the epiglottis and allows for both food and air to pass through the body with the help of the epiglottis. The laryngopharynx is the part of the pharynx that connects to the esophagus and diverts our food to the stomach by temporarily ceasing air (WiseGeek, Pharynx, 2012). This prevents the body from choking. The epiglottis separates the two parts of the pharynx with a lid or flap so that food mistakenly does not enter the windpipe or trachea (WiseGeek, Epiglottis, 2012).
From the pharynx, Mr. Smith’s food will travel down a muscular tube in the chest called the esophagus which is also called the food pipe. There are a number of muscular contractions called peristalsis which propels the bolus of food forward and down the esophagus. At the lower end of esophagus, there is an esophageal sphincter which acts as a gateway and allows food to enter the stomach and then squeezes shut to keep food or fluid from flowing back up into the esophagus (Patton, Thibodeau, 2008). The stomach acts like a mixer grinder where the food churns and mixes with acids and enzymes like pepsin converting it into small digestible pieces. It leaves the stomach in the form of chime and enters the duodenum which is the first part of the small intestine. “The small intestine is the portion of the digestive system where most of the nutrient extraction takes place (WiseGeek, What is the Digestive System, 2012)”. The small intestine is a long, twisted tube that extends from the stomach to the large intestine and is separated into three parts: the duodenum, jejunum, and ileum. The duodenum is where our food enters first and where most of the digestion occurs. It is also where bile and pancreatic juices are secreted to aid in digestion. The jejunum and ileum are the second and third sections of the small intestine. (WiseGeek, Small Intestine, 2012) In the lining of the small intestine are many finger-like projections called villi through which nutrients can be absorbed into the body and work to finish breaking down carbohydrates and proteins. The small intestine is one of the longest organs in the human body measuring in at about 20 feet long. The ileum is the last part of the small intestine and is the part where absorption of bile salts and remnants of digested food that were not absorbed in the jejunum takes place. The final portion of the small intestine is the distal ileum which has many little folds containing tiny blood vessels. When nutrients of bile salts from our food come into contact with these folds, they get absorbed into the bloodstream. (WiseGeek, Small Intestine, 2012)
Upon the food being absorbed by the blood vessels in the distal ileum, it will pass through the mucosal membrane and drain into the superior mesenteric vein. Once in the superior mesenteric vein, the blood will unite with the splenic vein to form the hepatic portal vein. The hepatic portal vein is responsible for pumping blood out of the spleen and the gastrointestinal tract. Almost all of the blood passing through the digestive tract will end up in the hepatic portal vein before being circulated back into the body which allows the liver to filter the blood and remove most of the toxins (WiseGeek, Hepatic Portal Vein, 2012). Now in order to get to the kidney, we must first trace the blood flow through the heart and the lungs.
Upon leaving the liver, the blood enters the inferior vena cava via the iliac vein and moves into the right atrium of the heart. From the right atrium, the blood will pass into the right ventricle via the tricuspid valve and then into the pulmonary artery. The de-oxygenated blood from the pulmonary artery moves into the lungs where it leaves the carbon dioxide and starts carrying oxygen. The oxygen-rich blood now gets carried from the lungs via the pulmonary vein towards the left atrium. We will now travel from the left atrium via the bicuspid valve and get pumped into the left ventricle down towards the abdominal aorta. Oh wow….can you see the kidneys now? They are the two organs that are shaped like a large bean. Let’s keep traveling through the abdominal aorta and head into the superior mesenteric artery. I want to go into the kidneys to see what is happening so let’s keep flowing into the left renal artery. Now that we have entered the kidney, the blood that we are traveling with is fully oxygenated and has plenty of glucose to help the kidney function properly and help it produce urine. The blood in the renal artery has enough pressure for the success of blood filtration. Now there is some blood with urea that has entered the kidney via the nephrons. Urea is produced when foods containing protein are broken down in the body. Urea is carried in the bloodstream to the kidney. This urea is captured by the kidneys from the blood through tiny filtering units called nephrons (WiseGeek, Urea, 2012). The nephron is a tiny funnel with a very long stem that is highly convoluted. The nephron is composed of two components called the renal corpuscle and the renal tubule. The renal corpuscle can be subdivided into two more parts called Bowman’s capsule and the Glomerulus (Patton, Thibodeau, 2008). The more pressurized blood forced its way through the Glomerulus which is a network of blood capillaries. The Bowman’s capsule is the initial step in blood filtration to help form urine. The urine passes through proximal convoluted tubule which is highly folded to maximize the re-absorption of water and salts before it leaves the body. It will then pass through the loop of Henley, the distal convoluted tubule, and then into the collecting duct system (Patton, Thibodeau, 2008).
From the kidneys, urine travels down two thin tubes called ureters to the bladder which is a balloon like organ. The bladder stores urine until it if full and then it expands and sends impulses to the brain through autonomic nervous system that tells us when we need to empty it. The bladder has circular muscles which prevent urine from leaking before we are ready to release it. Signals from the brain cause the bladder muscles to tighten and thus squeeze the urine out of the bladder via the urethra. (WiseGeek, Urinary System, 2012; Patton, Thibodeau, 2008)
Now, Homeostasis can be defined as “the tendency of biological systems to maintain relatively constant conditions in the internal environment while continuously interacting with and adjusting to changes originating within or outside the system (Farlex, Homeostasis, 2012)”. Therefore we have learned that the consumption of Mr. Smith’s hamburger resulted in absorption of large quantities of amino acids at the distal ileum which then traveled into the blood stream. The blood stream which is part of the circulatory system took the amino acids from the digestive system and passed them to the kidneys where the urinary system took over and helped get the waste out of the body via the urethra. So today we learned that the digestive system works in synergy with the circulatory system and the urinary system to get the foods that we eat absorbed, distributed, and passed through our body and help keep us healthy and growing.
Thank you everyone for listening to today’s top news story. I hope you enjoyed our journey through Mr. Smith’s body and learned a lot about the way our food travels though the digestive system and ends up exiting via the urethra. Have a great day and be sure to tune in tomorrow for the next great adventure.

References:
Farlex. (2012). Digestive System. The Free Medical Dictionary. Retrieved from: http://medical-dictionary.thefreedictionary.com/digestive+system
Farlex. (2012). Homeostasis. The Free Medical Dictionary. Retrieved from: http://medical-dictionary.thefreedictionary.com/homeostasis
Patton, K., Thibodeau, G. (2008). Structure & Function of the Body. St. Louis. Mosby Elsevier.
WiseGeek. (2012). Digestive System and Homeostasis. WiseGeek. Retrieved from: http://www.wisegeek.com/what-is-the-relationship-between-the-digestive-system-and-homeostasis.htm WiseGeek. (2012). How Does the Digestive System Work? WiseGeek. Retrieved from: http://www.wisegeek.com/how-does-the-digestive-system-work.htm WiseGeek. (2012). Relationship Between the Digestive System and Circulatory System. WiseGeek. Retrieved from: http://www.wisegeek.com/what-is-the-relationship-between-the-digestive-system-and-circulatory-system.htm WiseGeek. (2012). Types of Digestive Enzymes. WiseGeek. Retrieved from: http://www.wisegeek.com/what-are-the-different-types-of-digestive-system-enzymes.htm WiseGeek. (2012). What is the Epiglottis? WiseGeek. Retrieved from: http://www.wisegeek.com/what-is-an-epiglottis.htm WiseGeek. (2012). What is the Hepatic Portal Vein? WiseGeek. Retrieved from: http://www.wisegeek.com/what-is-the-hepatic-portal-vein.htm WiseGeek. (2012). What is the Pharynx? WiseGeek. Retrieved from: http://www.wisegeek.com/what-is-the-pharynx.htm WiseGeek. (2012). What are the Salivary Glands? WiseGeek. Retrieved from: http://www.wisegeek.com/what-are-salivary-glands.htm WiseGeek. (2012). What is the Small Intestine? WiseGeek. Retrieved from: http://www.wisegeek.com/what-is-the-small-intestine.htm WiseGeek. (2012). What is the Splenic Vein? WiseGeek. Retrieved from: http://www.wisegeek.com/what-is-the-splenic-vein.htm WiseGeek. (2012). What is the Urea? WiseGeek. Retrieved from: http://www.wisegeek.com/what-is-urea.htm WiseGeek. (2012). Urinary System. WiseGeek. Retrieved from:
http://www.wisegeek.com/what-is-the-urinary-system.htm