Course Hero Logo

ON RESPIRATORY DISEASES.docx - ON RESPIRATORY DISEASES...

Course Hero uses AI to attempt to automatically extract content from documents to surface to you and others so you can study better, e.g., in search results, to enrich docs, and more. This preview shows page 1 - 2 out of 8 pages.

ON RESPIRATORY DISEASESAllergic RhinitisAsthmaCOPDRESEARCH ON THE FF :1. Explaining the pathophysiology of the disorderALLERGIC RHINITISIn allergic rhinitis, numerous inflammatory cells, including mast cells, CD4-positive T cells, Bcells, macrophages, and eosinophils, infiltrate the nasal lining upon exposure to an incitingallergen (most commonly airborne dust mite fecal particles, cockroach residues, animaldander, moulds, and pollens). In allergic individuals, the T cells infiltrating the nasal mucosaare predominantly T helper 2 (Th2) in nature and release cytokines (e.g., interleukin [IL]-3, IL-4, IL-5, and IL-13) that promote immunoglobulin E (IgE) production by plasma cells.Crosslinking of IgE bound to mast cells by allergens, in turn, triggers the release of mediators,such as histamine and leukotrienes, that are responsible for arteriolar dilation, increasedvascular permeability, itching, rhinorrhea, mucous secretion, and smooth muscle contraction inthe lung. The mediators and cytokines released during the early phase of an immune responseto an inciting allergen trigger a further cellular inflammatory response over the next 4–8 h(late-phase inflammatory response) which results in recurrent symptoms (usually nasalcongestion) that often persist.ASTHMAAirflow obstruction in asthma is due to bronchoconstriction that results from contraction of bronchialsmooth muscle, inflammation of the bronchial wall, and increased secretion of mucus (Figure 29.2).The underlying inflammation of the airways contributes to airway hyperresponsiveness, airflowlimitation, respiratory symptoms, and disease chronicity. Asthma attacks may be triggered byexposure to allergens, exercise, stress, and respiratory infections. Unlike COPD, cystic fibrosis, andbronchiectasis, asthma is usually not a progres- sive disease (that is, it does not inevitably lead toincapacitated air- ways). However, if untreated, asthma may cause airway remodeling, resulting inincreased severity and incidence of asthma exacerbations and/or death.COPDCOPD results from the combined processes of peripheral airway inflammation and narrowing of theairways. This leads to airflow limitation and the destruction and loss of alveoli, terminal bronchiolesand surrounding capillary vessels and tissues, which adds to airflow limitation and leads to decreasedgas transfer capacity (Fig 1). The extent of airflow limitation is determined by the severity ofinflammation, development of fibrosis within the airway and presence of secretions or exudates.Reduced airflow on exhalation leads to air trapping, resulting in reduced inspiratory capacity, whichmay cause breathlessness (also known as dyspnoea) on exertion and reduced exercise capacity.Abnormalities in gas transfer occur due to reduced airflow/ventilation and as a result of loss ofalveolar structure and pulmonary vascular bed. Low blood oxygen levels (hypoxaemia) and raised

Upload your study docs or become a

Course Hero member to access this document

Upload your study docs or become a

Course Hero member to access this document

End of preview. Want to read all 8 pages?

Upload your study docs or become a

Course Hero member to access this document

Term
Fall
Professor
N/A
Tags
bronchial asthma

Newly uploaded documents

Show More

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture