Integration of Cardiovascular/Gastrointestinal Systems
Integration of gastrointestinal and cardiovascular systems within the human body
The integration of the gastrointestinal and cardiovascular systems allow for nutrients to be introduced, broken down, and absorbed by body to maintain and promote healthy bodily functions. Independently, these systems serve separate functions, but when working in conjunction, help to transport necessary nutrients throughout the body, while maintaining and promoting homeostasis within the systems. Any imbalance within these systems will greatly affect the body, as a whole, and can lead to potentially fatal results.
Integration of gastrointestinal and cardiovascular systems within the human body
The gastrointestinal and cardiovascular systems of the human body help to breakdown and transport items that are ingested, such as food and medication, to the necessary parts of the body, expelling wastes that are not needed. Separately, the gastrointestinal and cardiac systems have different functions, but when the systems work in conjunction with each other, will help to distribute nutrients and enzymes, among other things, throughout the body.
The gastrointestinal system is essentially a long tube that runs throughout the body and has specialized sections that are capable of digesting materials inserted at the beginning of the tract, extracting useful components from said materials, and subsequently expelling waste materials at the end (University of Leicester 2001). The digestive system is comprised of the following organs and tubes: the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus. The entire digestive system is approximately nine meters long; digestion within a human adult can take anywhere from 24 to 72 hours. The mouth is designed to aid in breaking down pieces of food that are introduced into the human body while the esophagus will take in food, from the mouth, and push it down the gastrointestinal tract via peristalsis to the stomach (Cleveland Clinic 2005). The stomach is a hollow organ that holds food and mixes it when chemicals and enzymes to be further broken down in the digestive process. The small intestine is a 22-foot long muscular tube where digestion continues to occur. The pancreas secretes digestive enzymes into the first section of the small intestine; the pancreas also makes insulin that is secreted directly into the bloodstream (Cleveland Clinic 2005). The liver helps to process nutrients that are absorbed by the small intestine. The gallbladder sits below the liver and helps the duodenum, the first section of the small intestine, digest and absorb fats. The large intestine is used to process and digest unwanted solid wastes from the body. The colon, on average, is 6-feet long and connects the small intestine to the rectum. The rectum is an 8-inch tube that connects the large intestine to the anus; this is also where stool is held until it is evacuated from the body. The anus is a two-inch canal that aids in the evacuation of stool; it is comprised of a series of pelvic muscles and two anal sphincters (Cleveland Clinic 2005).
The cardiovascular system is comprised of the heart, blood, and blood vessels. The cardiovascular system's main duties include the transport of materials including gasses, nutrients, wastes, and hormones; housing cells that help to combat infections; the stabilization of pH and ionic concentration of bodily fluids; and the maintenance of body temperature through the transportation of heat (Gregory n.d.). The heart is comprised of two separate pumps; the left side of the heart pumps blood to the body while the right side of the heart pumps blood to the lungs; both sides of the heart are made up of an atrium and ventricle (Gregory n.d.). At rest, the heart will beat, on average, 60 to 80 times per minute. Blood cells can be subdivided into three different types: erythrocytes (red blood cells), leukocytes (white cells), and thrombocytes (platelets) (Cotterill 2000). Plasma is composed of water that contains proteins, nutrients, hormones, antibodies, and waste products (Cotterill 2000). Nutrients, and blood, must pass through the body's various veins into the ascending aorta and then to the heart (Thibodeau 1992). At rest, the cardiovascular will supply all organs of the body with blood and oxygen that ensure that these organs do not fail and help maintain the entire body healthy. While at rest, or prior to digestion, the cardiovascular system is triggered by the parasympathetic nervous system to increase blood flow to the digestive system and its organs. Due to the increased blood flow to the digestive system, and in preparation for the digestive process, heart rate will increase slightly.
The digestive processes begin even before food, or any other materials, are introduced to the body. One of the initial reactions that the digestive system has to the introduction of materials to the mouth is salivation. Salivation controlled by the autonomic nervous system that controls both the volume and type of saliva that is produced (University of Leicester 2001). Saliva production may be stimulated parasympathetically or potently. Potent stimuli may include the presence of food, thoughts about food, or the presence of an irritating substance in the mouth (Bowen 2002). Within the mouth, saliva serves several important functions that include the providing lubrication for food within the esophagus and binding masticated food for facilitated passage down the esophagus, solubilizes dry food, helps to regulate oral hygiene, initiates digestion, provides alkaline buffering and fluid, and aids in evaporative cooling (Bowen 2002). In order for food to be passed down to the esophagus, it must first be masticated. The mouth is also comprised of the tongue, the hard and soft palates, and the uvula, which hangs at the back of the mouth from the soft palate (Thibodeau 1992). At the back of the mouth, before food is passed down to the esophagus, is the pharynx. The esophagus is approximately 25.4 cm, or 10 inches, in length and pushes food down the upper abdominal cavity into the stomach (Thibodeau 1992). As food is pushed into the stomach and into the fundus, the cardiac sphincter will close up behind the food in order to prevent food from being reintroduced into the esophagus once stomach contractions begin. When the stomach contracts, food will mix with gastric juices and be broken down into chyme (Thibodeau 1992). Stomach contractions, known as peristalsis, will further propel food down the digestive tract. The stomach is lined with thousands of gastric glands which secrete gastric juice and hydrochloric acid into the stomach; partial digestion will occur in the stomach and last approximately three hours (Thibodeau 1992). Partially digested food is then passed through the pyloric sphincter into the first portion of the small intestine to be further broken down.
The small intestine is also covered in a mucosal wall; intestinal glands within these walls secrete digestive juice, as opposed to gastric juice and hydrochloric acid; digestive juice helps to advance the digestive process (Thibodeau 1992). The small intestine is covered with circular folds called plicae and are covered with villi and microvilli; villi and microvilli help to absorb nutrients as food is passed through the digestive system (Thibodeau 1992). Most of the digestive process will occur in the duodenum, the first section of the small intestine. Two ducts within the duodenum empty pancreatic digestive juices and bile into the intestine which further aid in digestion. The pancreas will secrete digestive enzymes and bicarbonate that neutralizes stomach acid (Farabee 2010). The digestion of carbohydrates, proteins, and fats continues in the small intestine; "Starch and glycogen are broken down into maltose by small intestine enzyme…[while] proteases are enzymes secreted by the pancreas that continue the breakdown of protein into small peptide fragments and amino acids" (Farabee 2010). Bile, secreted by the gall bladder, will emulsify fats before they are acted upon by lipases; bile contains cholesterol, phospholipids, bilibrubin, and a mixture of salts (Farabee 2010). The last two sections of the small intestine are the jejunum and the ileum. Solid wastes, from which most nutritionally useful products have been removed, are moved into the large intestine where they will be eventually be expelled from the body via the rectum (University of Leicester 2001). It is at the ileum that nutrients can pass from the digestive system into the cardiovascular system (Thibodeau 1992).
It is at this point in the digestive process, when food and nutrients have found their way into the ileum, that nutrients can pass from the digestive system to the cardiovascular system. In the ileum, nutrients pass through the ileum lumen to the simple columnar cells of the villi and through to the villi's interstitial fluid (Thibodeau 1992). From the interstitial fluid, nutrients are passed through to the ileum's capillaries to venules and through the ileum's small and medium veins to the superior mesenteric vein (Thibodeau 1992). Capillaries within the cardiovascular system provide for the transportation and the absorption of nutrients, oxygen, and wastes through the blood by way of capillary walls. As blood is pumped to and from various parts of the body, the nutrients and insulin that have been passed into the bloodstream are transported throughout the rest of the body.