Fantastic Voyage Essay Example for Free

Fantastic Voyage Essay Once again my mini sub and I will be miniaturized making us 8 microns long and witnessing another Fantastic Voyage in a human body. This time I will be swallowed by a 55 year old man, while he is eating his meal consisting of a hamburger, French fries, and a root beer. I will be piloting my sub through his gastrointestinal tract to monitor the digestion of his meal, I will be describing all major structures I go through. Digestion begins in the mouth. A brain reflex triggers the flow of saliva when we see or even think of food. Saliva moistens the food while the teeth chew it up and make it easier to swallow. Amylase, which is the digestive enzyme, found in saliva, starts to break down starch into simpler sugars before the food even leave the mouth. The nervous pathway involved in salivary excretion requires stimulation of receptors in the mouth, sensory impulses to the brain stem and parasympathetic impulses to salivary glands. Swallowing his food happens when the muscles in his tongue and mouth move the food into his pharynx. The pharynx, which is the passage way for food and air, a small flap of skin called the epiglottis closes over the pharynx to prevent food from entering the trachea and causing choking. For swallowing to happen correctly a combination of 25 muscles must all work together at the same time. After being chewed and swallowed the food enters the esophagus or gullet is the muscular tube in vertebrates through which ingested food passes from the throat to the stomach. It connects the pharynx, which is the body cavity that is common to both the digestive and respiratory systems behind the mouth, with the stomach, where the second stage of digestion is initiated. The esophagus is a long tube that runs from the mouth to the stomach. It uses rhythmic wave like muscle movements called peristalsis to force food from the throat into the stomach. At the end of the esophagus there is a sphincter that allows food into the stomach then closes back up so the food can not travel back up into the esophagus. The distal end of the esophagus is slightly narrowed because of the thickened circular muscles. This part of the esophagus is called the lower esophageal sphincter. Now I follow the food down the esophagus into the stomach. The stomach is a hallow saclike organ enclosed in a muscular wall. These flexible muscles allow the stomach to expand when you eat. The stomach has three tasks in digestion. Mixing foods with gastric juices, gastric juices are secretions from the stomach lining that contains hydrochloric acid and pepsin, an enzyme that digests protein. Hydrochloric acid I nteh stomach kills bacteria taken in with food and creates an acidic environment. Storing swallowed food and liquids, the stomach holds food and liquids Next is the pancreas, liver and gallbladder. The pancreas liver and gallbladder are essential for digestion. The pancreas produces enzymes that help digest proteins, fats, and carbohydrates, the liver produces bile that helps the body absorb fat, and the gallbladder stores the bile until it is needed. The enzymes and bile travel through special channels called ducts and into the small intestine where they help break down the food. After being in the stomach food enters the duodenum. The duodenum is a hollow jointed tube connecting the stomach to the jejunum. It is the first and shortest part of the small intestine. This is also where the bile and pancreatic juices enter the intestine. The jejunum is a part of the small bowel, located between the distal end of the duodenum and the proximal part of the ileum. The inner surface of the jejunum its mucous membrane, is covered in projections called villi, which increase the surface area of tissue available to absorb nutrients from the gut contents. The ileum its function is to absorb vitamin B12 and bile salts. The three main sections of the small intestine is the duodenum, the jejunum, the ileum. In the small intestine bile produced in the liver and stored in the gallbladder, pancreatic enzymes and other digestive enzymes produced by the inner wall of the small intestine help in the breakdown of food. After passing through the small intestine, food passes into the large intestine in the large intestine some of the water and electrolytes are removed from the food many microbes in the large intestine help in the digestion process. The first part of the large intestine is called cecum. The superior mesenteric vein drains blood from the small intestine jejunum and ileum. At its termination behind the neck of the pancreas the superior mesenteric vein combines with the splenic vein to form the hepatic portal vein. Before joining with the splenic vein, it lies next to the superior mesenteric artery wich arises from abdominal aorta. The portal vein drains blood to capillary beds in the liver. From here the hepatic vein arises and drains into the inferior cava where it enters the right atrium of the heart. From here he deoxygenated blood enters the right ventricle via the tricuspid valve. From the right ventricle it enters the pulmonary artery via the pulmonary valve and enters the lungs. From here the deoxygenated blood enters the left atrium of heart via the pulmonary vein and then the left ventricle via the mitral valve. From the left ventricle blood enters he aorta the ascending aorta. Thoracic aorta and ultimately abdominal aorta. The abdominal aorta divides into the left renal artery which enters the kidneys and supplies blood over there. Each renal artery divides into segmental arteries dividing further into interlobar arteries which penetrate the renal capsule and extend through the renal columns between the renal pyramids. These interlobular arteries supply blood to the accurate arteries that run through the boundary of the cortex and the medulla. Each arcuate artery supplies several interlobular arteries that feed into the afferent arterioles that supply the glomeruli and hence the kidneys. The urinary tract from bowmans capsule is, the blood then enters the kidney via glomerular membrane in the nephrons. The blood trickles from bowman’s capsule to renal tubule, that is proximal convoluted tubule, loop of Henley, distal convoluted tubule and then into collecting duct system. The blood from the cortex is passed to medulla of kidneys. The urine formed is collected via ureter. The urine from the ureter then passes to urinary bladder and leaves the body from the urethra. Homeostasis in the body is only possible if the cardiovascular system is working properly. This means that the system needs to deliver oxygen and nutrients to the tissue fluid that surrounds the cells and also take away the metabolic waste, the heart is composed of arteries that take blood from the heart, and vessels that return blood to the heart. Blood is pumped by the heart into two circuits the pulmonary and systemic circuits. The pulmonary circuit carries blood through the lungs where gas exchange occurs and the systemic system transports blood to all parts of the body where exchange with tissue fluid takes place. The cardiovascular system works together with all other systems to maintain homeostasis. Homeostasis and the urinary system, toxic nitrogenous wastes accumulate as proteins and nucleic acids are broken down and used for other purposes. The urinary system rids the body of these wastes. The urinary system is also directly involved in maintaining proper blood volume and ion concentration within the blood. One other contribution is that the kidneys produce a hormone that stimulates red blood cell production. The kidneys also play an important role in maintaining the correct water content of the body and the correct salt composition of extracellular fluid. External changes that lead to excess fluid loss trigger feedback mechanisms that act to inhibit fluid loss.