The Cellular Mechanisms of Respiratory System - Essay Example

The Cellular Mechanisms of Respiratory System The respiratory system mainly provides gaseous exchange between the blood and the environment. It absorbs oxygen is from the atmosphere into the body while carbon dioxide is expelled from the body. When a human breathe blood is delivered to all parts of the body. 1. What are the cellular mechanisms behind its functioning?  The respiratory system of mammal makes use of lungs to respire oxygen. The air makes up its way from the trachea to bronchi to bronchioles to alveolar sac to alveolar duct and finally to alveolus where the gaseous exchange takes place. There are about 700 million alveoli present in the lungs and its lining consists of a very thin layer of squamous epithelium cells. Each alveolus is surrounded by a dense network of capillaries which replace carbon dioxide in place of oxygen. Collagen and elastic fibers allow the expansion and recoiling of the alveoli during breathing. Special cells in the alveolus wall secrete detergent-like chemical on the inside lining of the alveolus. It is called surfactant, it lowers the surface tension of the fluid layer lining and thereby reduces the amount of effort needed to breathe in and inflate the lungs. Surfactant also speeds up the transport of carbon diode and oxygen between the air and the liquid lining the alveolus and helps to kill bacteria which reach the alveoli. Oxygen diffuses across the thin barrier of the epithelium of the alveolus to the endothelium of the capillary. It passes first into the blood plasma and then combines with hemoglobin in the red blood cells to form oxyhameoglobin. Carbon dioxide diffuses in the reverse direction i.e. from the blood to the alveoli. The diameter of the blood capillaries is smaller than the diameter of the red blood cells passing through them. This means that the red blood cells have to be squeezed through the capillaries by pressure. During this process they curve into an umbrella shape, revealing more of their surface area to the surface of the alveolus and allowing greater uptake of oxygen. Progress of the cells is also relatively slow, thus increasing the time available for gaseous exchange to take place. When blood leaves the alveolus it possesses the same concentration of oxygen and carbon dioxide as the air in the alveoli. References: - ENCognitive. 11th March 2008. Respiratory System. 25th November 2008. http://www.encognitive.com/systems/respiratory-system-2008-mar-11.html - McGowan, Pippa & Jefferies, Angus. Respiratory System: Respiratory System. Published by Elsevier Health Sciences, 2003. 2. What characteristics it has that makes it suited for the function it performs?  The respiratory surface of the mammal consists of many air sacs called alveoli inside the pair of lungs. The lungs are located next to the heart in the thoracic cavity and are linked to the atmosphere by tubes. Air passes into lungs through these tubes. Twelve pairs of bony ribs surround and protect the lungs and heart. Intercostal muscles are attached to the ribs, and a large diaphragm separates the thorax from the abdomen. These are involved in the ventilation mechanism. Air is passed in and out of the lungs by movements of the intercostals and diaphragm muscles which alter volume of the thoracic cavity. There are two sets of intercostals muscles between each pair of ribs. The external intercostals are outside the internal intercostals. The muscle fibers run diagonally but in opposite directions in the two set of muscles. The diaphragm consists of circular and radial muscle fibres arranged around the edge of a circular inelastic sheet of white fiber. Inspiration (breathing in) is an active process it works when the external intercostals muscles contract and the internal intercostals relax. This pulls the rib cage up and out. At the same time, the diaphragm muscles contract. This flattens the diaphragm. Both actions increase the volume of the thorax. As a result the pressure in the thorax, and hence the lungs, is reduced to less than atmospheric pressure. Air therefore enters the lungs, inflating the alveoli, until the air pressure in the lungs is equal to that of atmosphere. Expiration (breathing out) is a largely a passive process under resting conditions, and is brought about by the elastic recoil of the lung tissue, respiratory muscles and the weight of the rib cage. The respiratory muscles act follows: The external intercostals muscle relax and internal intercostals contract. The rib cage drops, mainly due to its own weight. At the same time, the diaphragm relaxes. The dropping rib cage forces the diaphragm into a domed shape, pushing it up into the thoracic cavity. Theses events reduce the volume of the thorax and raise its pressure above that of the atmosphere. Consequently air is forced out of lungs. References: - Roush, J. Role of the internal intercostals and external intercostals during breathing: A Kinesiological Model. The Cardiopulmonary Physical Therapy Journal. . FindArticles.com. 25 Nov. 2008. http://findarticles.com/p/articles/mi_qa3953/is_200312/ai_n9318786 - Kean University. updated July 30, 2002 Lab 7 Respiration and Circulation. 25th November 2008. http://eve.kean.edu/~breid/respiration/respir.html - Simon, S eymour. Lungs: Your Respiratory System. Published by Collins, 2007. 3. What tasks/duties it performs in the normal functioning of our bodies?  Normally we are not conscious of our breathing because it is controlled involuntarily. We can take over some voluntary control, and this will be discussed after considering involuntary control. Involuntary control of breathing is carried out by a breathing center located in the medulla of the brain (the medulla is a part of hindbrain). The ventral rate and depth of inspiration and is called the inspiratory centre. The dorsal (top) and lateral (side) portion inhibit inspiration and stimulate expiration. These regions form the expiratory center. The breathing center communicates with the intercostals muscles by way of the intercostals nerve. The bronchial tree (the mass of bronchioles and the bronchi) is connected to the brain by the vagus nerve. Rhythmic nerve impulses to the diaphragm and intercostals muscles bring about the ventilation movements. Inspiration inflates the lungs, and, as they inflate, stretch receptors located in the bronchial tree are stimulated to send more and more nerve impulses via the vagus nerve to expiratory centre. This temporarily inhibits the inspiratory center and inspiration. The external intercostals muscles therefore relax, elastic recoil of the lung tissues occurs and expiration rakes place. On the other side within the limits, the rate and depth of breathing are also under voluntary control as an ability to hold the breath. Voluntary control is also used during forced breathing, speech, singing, sneezing and coughing. When such control is being exerted, impulses originating in the cerebral hemisphere pass to breathing center which then carries out appropriate action. References: Davies, Andrew & Moores, Carl. The Respiratory System: Systems of the Body. Illustrated by Robert Britton. Published by Elsevier Health Sciences, 2003 4. If it malfunctions (i.e due to a disease) how other tissues, organs, systems will be affected?  Although "respiratory disease" is often thought of as only a lung problem, malfunction of any component of the respiratory system can cause a breathing problem. For example, if the brain stem center is depressed which controls the breathing, can caused by overdose of a drug, which may result in the failure of the respiratory system (and the victim can die because of it) even if the lungs are normal. Polio, got very common disease before the discovery of its vaccine, it can cause serious damage to the respiratory system which can damage the nerves which leads to the thoracic cage muscles. This is a normal situation for the brain and lungs but for the chest it may not be able to expand to move air into the lungs; as a result, a respiratory failure can be caused by a polio patient. Thus all parts of the respiratory system must function properly for normal breathing. In spite of the significance of all respiratory system mechanism, there is fine reason why the lungs are usually create an impression of respiratory disease when one hears. Lung disease accounts for the vast majority of respiratory illness. Diseases like emphysema, bronchitis, asthma, pneumonia and lung cancer all are originates in the lungs. Our lungs are the only internal organ directly in contact with the atmosphere, making them vulnerable to all pollutants, including cigarette smoke, as well as airborne viruses and bacteria. Our lungs are also the only internal organ in direct contact with the increased ambient pressure of daily life activities, makes it uniquely vulnerable to changes in pressure. References: - Robert Silverstein, Robert & Silverstein, Virginia. Respiratory System. Published by Millbrook Press, 1997. - Shea. A. Steven. 1996. Behavioral and arousal-related influences on breathing in humans. Physiology Program, Harvard University, School of Public Health. 25th November 2008. http://ep.physoc.org/cgi/reprint/81/1/1.pdf 5. Assume you are an investigator, what would be your research about (the organ or tissue or system you selected) and why?  As I have read about many diseases and seen people experiencing many problems, but, for me Asthma, Emphysema, Bronchitis and Lung Cancer seemed most dreadful to me. These diseases are linked to emotions and needs constant will power to keep fighting against them. Smoking is the most common thing which can cause short term on breathing and gaseous exchange as well as long term affects on the respiratory system. Nicotine causes constriction of the finer bronchioles, increasing resistance to the flow of air, nicotine paralyses the cilia which remove dirt and bacteria: the accumulation of extra material in the air passages can restrict air flow. Smoke acts as an irritant; this causes secretion of excess mucus from goblet cell and excess fluid into the airways, making it more difficult for air to pass through them. Asthma is a complex problem and more research is needed to establish who are most at risk and why. Emotional disturbance may provoke the attack, while other triggers cold air, exercise and smoking. Emphysema is also very common especially in Britain. About 1 person in 100 suffers from it and it is 10 times more common in men than women. Death is typically preceded by years of increasing disability. It is mostly cause by smoking or air pollution. Bronchitis is also serious and common disease. Britain has the highest death rate from this disease (one person in 2000 every year, about 30000 people per year). About 1 million others are affected, three times as many men as women. Death rate is higher among smoker. As an investigator I will further study to find out how the exposure to ammonium nitrate and carbon particles can cause injury to the lungs. Moreover, cellular injuries are seen even in healthy people. There are particle-induced lung injuries like damages to airway, bifurcations, centriacinar regions and causing respiratory bronchioles. References: Kent E. Pinkerton, Ph.D. Mechanisms of Particle, Toxicity: Effects on the Respiratory System. University of California at Davis. 2003. 25th November 2008. www.co.mendocino.ca.us/aqmd/pdf_files/PM%20Report/PM_toxics.pdf Roca, N, Bosch. Serrano,Marta. & Tenllado, A. Antonio. The Respiratory System, the Breath of Life. Illustrated by Antonio Munoz Tenllado. Published by Chelsea House Publishers, 1995 Read More