The Respiratory System 0.0 / 5 ? BiologyHealth, illness and diseaseASAQA Created by: ernilyCreated on: 21-04-15 20:03 Lung Function Ventilation: Breathing in and out. Inspiraton: The intercostal and diaphragm muscles contract. This causes the ribcage to move upwards and outwards, and the diaphragm to flatten. The volume of the thorax increases, and lung pressure decreases. This causes air to flow into the lungs. Expiration: The intercostal and diaphragm muscles relax. The ribcage moves downwards and inwards. The volume of the thorax decreases, and lung pressure increases. This causes air to be forced out of the lungs. Factors Affecting Gas Exchange: Large Surface Area: There are a huge number of alveoli in the lungs. The alveoli are surrounded by a network of capillaries. Short Diffusion Pathway: Oxygen diffuses out of the alveoli, across the alveolar and capillary endothelium, and into haemoglobin. Carbon Dioxide diffuses into the alveoli from the blood and is breathed out. Steep Concentration Gradient: Increases the rate of diffusion. 1 of 4 How Lung Disease Affects Function Pulmonary Ventilation: The volume of air taken into the lungs in one minute. Tidal Volume: The volume of air in each breath. Ventilation Rate: The number of breaths per minute. PV (dm3min-1) = TV (dm3) x VR (min-1) Pulmonary Tuberculosis: Caused by mycobacterium tuberculosis. When infected, the immune system cells build a wall around the bacteria. This forms hard lumps called tubercles. The infected tissue in the tubercles dies, damaging the gas exchange surface. The tidal volume decreases. TB also causes fibrosis, which further reduces the tidal volume. Symptoms include: cough, chest pains, shortness of breath, and fatigue. TB is transmitted by droplet infection; sneezing, coughing, etc. It's spread in areas with poor hygiene and crowded living. 2 of 4 How Lung Disease Affects Function Fibrosis: Scar tissue forms on the surface of the lungs as a result of infection or exposure to toxic substances. The scar tissue is thicker and less elastic than normal tissue. This means that the lungs are less able to expand, and they can't hold as much air. This causes the tidal volume to decrease. It is harder to ventilate the lungs due to the loss of elasticity. Diffusion is slower, therefore gas exchange is slower. Symptoms include shortness of breath, dry cough, chest pain, fatigue, and weakness. A person with pulmonary fibrosis will have a faster breathing rate in order to try to get enough air into the lungs to oxygenate their blood. Asthma: A person's airways become inflamed due to an allergic reaction. The bronchioles contract and mucus is produced. The airways constrict, so airflow is severely reduced. This makes it difficult to breathe properly, so gas exchange is reduced. Symptoms include wheezing, a tight chest, and shortness of breath. 3 of 4 How Lung Disease Affects Function Emphysema: This is a lung disease caused by smoking or air pollution. It causes inflammation, which attracts phagocytes that break down the elastin of the lungs. Loss of elastin means that the alveoli can't recoil, so air remains trapped in them. The alveoli walls are destroyed, which reduces the surface area of the lungs, and so the rate of gas exchange decreases. Symptoms include wheezing, shortness of breath, and increased breathing rate as the patient attempts to ventilate their lungs. 4 of 4
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