Asthma Is A Chronic Inflammatory Disorder Biology Essay

Asthma Is A Chronic Inflammatory Disorder Biology Essay Introduction Asthma is a chronic inflammatory disorder of the bronchial tubes that causes constriction and inflammation of the airways. This results in narrowing of the airways. Airways narrowing in asthma is caused by three major processes that act on bronchi. These are: inflammation, bronchospasm and hyperreactivity. As a result, symptoms of wheezing, coughing, and shortness of breath occur. (Womenfitness, 2004) This essay will aim to discuss the pathophysiology, epidemiology, aetiology and the various causes of asthma. Furthermore, it will compare recent prevalence rates and patterns that have arisen in recent years. It will also concentrate on the effects of asthma on children and exercise, and the long term effects this may have on lung function. Finally, it will present the hygiene hypothesis that has drawn great attention and speculation over recent years. C:UsersuserPicturesasthma2.jpg Figure 1 adopted from asthma.about.com//def_hyperresponsiveness.htm Phathopysiology: Asthma is known to be an inflammatory disease which is characterised by airway inflammation, airflow obstruction and bronchial hyperresponsivness.The mechanism of airway inflammation in asthma maybe acute, sub acute or chronic. Inflammation is the most important factor that causes narrowing of the bronchial tubes. It increases the thickness of the wall of the bronchial tubes and produces excess mucous that forms plugs and clogs the small airways resulting in a smaller passageway for air to flow through. In irregular air flow obstruction and bronchial airway reactivity, oedema and mucus secretion also contribute to further narrowing of the airways. Thus resulting in difficulty breathing. When asthmatic patients are exposed to triggers such as allergens, irritant and infections, the inflamed or constricted airways becomes more sensitive or reactive to those triggers leading to increase narrowing and inflammation of the airways. As a result an asthmatic person has to make a greater effo rt during expiration and inspiration. (Szeftel and Shiffman, 2009). Asthma is characterized by an increased number of mast cells, eosinophils, macrophages, activated T lymphocytes, dendritic cells and neutrophils in the bronchial tissues. During an asthma attack, antigen presenting cells e.g. (macrophages or dendritic cells) in the airways capture and process the inhaled allergen to T-lymphocytes which in turn becomes activated. Once T-lymphocyte becomes activated it produces TH1 cells and TH2 cells both secreting cytokines respectively. TH1 release (INF, lymphotoxin, IL-2) .TH2 release (IL-3, IL-4, IL-9, IL-13, IL-15).TH2cells (CD4 T-lymphocytes) has an important role in allergic response. Allergens drives the cytokine pattern towards TH2cells which in turn promotes B cells to produce immunoglobin E (IgE) and eosinophil recruitment .Then IgE binds to high affinity receptor for IgE, Fc-epsilon-R1 on the surface of mast cells and basophils. This leads to degranulation of the cells and the release of mediators such as histamine, leukotrienes and other enzymes. The production of histamine and leukotrienes result in bronchial hyperresponsivness and air way obstruction causing the symptoms of asthma. (Morris, 2009) Types of asthma: There are two main types of asthma: Extrinsic or allergy asthma: This type is more common and is responsible for 90%of all cases. It develops in children and is associated with features of atopy such as rhinitis or eczema. (Szeftel and Shiffman, 2009) Intrinsic asthma: This type is less common and presents for only 10%of all cases. It is more commonly found in women after the age of 30 and is typically not associated with allergies. (ibid 2009) Epidemiology 5.4million people in UK are currently receiving treatment for asthma. 1.1million children in UK are currently receiving treatment for asthma. There is a person with asthma in one in five household in the UK. (Asthma Uk,2008) The incidence of asthma has increased dramatically over the past 20 years. This is not due to the changes in our genetic makeup, however, due to environmental factors (allergens, infection, life style and diet) that influence on the development of asthma. The prevalence of asthma in Wales is amongst the highest in the world. With 260,000 people currently living with the condition and the rate of hospitalization for adults is 28%, it exceeds all other regions in the UK. (Asthma UK, 2009) Mortality and morbidity Asthma affects 5-10% of the population in United States or an estimated 22 million persons, including 6 million children. Asthma is common in industrial countries such as Canada, England, Australia, Germany and New Zealand. The prevalence rate of severe asthma in those countries ranges from 2-10% and is estimated to affect 300million people world wide. There are about 5000 deaths per year in U.S.and about 500 deaths per year in Canada. (Kelly, 2009) C:UsersuserPicturesasthm prevelance.gif Figure3: shows the high percentage of the population affected with asthma was reported in USA, Canada, UK, Australia and NewZeland (>10%). The lowest prevalence were reported in China and India (