Human Bioscience Essay Example | Topics and Well Written Essays - 1250 words - 1

Human Bioscience - Essay Example Gas exchange occurs in the alveoli. There are about 300 million alveoli running to about 160m2 area. Lungs expand when there is increase in the volume of thoracic cavity. During inspiration, there is contraction of the external intercostal muscles which lift the ribs up and out and there is contraction of the diaphragm which draws the ribs down. During expiration, these processes are reversed. The elastic recoil of the lungs makes them to come back to their resting volume. At rest, a normal adult human being breathes about 15- 18 times exchanging 500ml of air each time. To diagnose a patient as having chronic bronchitis, the patient must suffer from chronic cough for atleast 3 months in one year for 2 consecutive years. The cough is accompanied by sputum expectoration, but there is no other cause for sputum production. There is enlargement of the mucus glands in the lungs, inflammation of the airways and thickening of the bronchial walls. Because of these pathological changes, there is loss of supporting alveolar attachments leading to deformity of the airway walls, which inturn results in narrowing of the airway lumen and decrease of airflow through it (Sharma, 2006) In emphysema, the alveoli are enlarged abnormally and permanently. There is also destruction of the alveolar walls and loss of elastic recoil. There are 3 types of emphysema: centriacinar emphysema, panacinar emphysema, and distal acinar emphysema or paraseptal emphysema (Sharma and Graham, 2005). Patients with emphysema typically suffer from breathing difficulty. The most common cause of COPD is smoking in the form of cigarette smoking or exposure to tobacco smoke either due to passive smoking or environmental tobacco smoke. Other causes include air pollution, airway hyperresponsiveness and alpha1- antitrypsin deficiency. COPD can occur either due to chronic bronchitis or