Question

1. Why is it so difficult for people with COPD to breathe? How does the disease affect the rate of diffusion and why does it affect the rate of diffusion?

2. Why can you not put a fresh water fish in a salthwater tank? Why can't you put a saltwater fish in fresh water fish?

Answer 1

1) COPD is Chronic Obstructive Pulmonary Disease. It is a group of progressive lung disorders. It has two aspects- Chronic bronchitis and emphysema. Most often it is a combination of both. Emphysema is the permanent and destructive enlargement of airspaces distal to the terminal bronchioles without fibrosis and loss of normal architecture. Chronic bronchitis is the presence of productive cough with sputum on most days for atleast 3 months over 2 consecutive years, not due to any other cause. COPD involves clinically significant airflow limitation. It is the result of inflammatory processes in the airways and distal airspaces. Narrowing is seen in the small and large airways. There is squamous metaplasia, atrophy of cilia and hypertrophy of mucus glands. The smaller airways are the major site of occlusion. Goblet cell hyperplasia, edema, peribronchial fibrosis, intraluminal mucus plugs and increased smooth muscle occlude the lumen. There is also marked inflammatory infiltration. Emphysema begins as increased size and number of alveolar fenestrae which gradually results in destruction of the alveolar septae and their attachment to terminal and respiratory bronchioles. Airflow limitation and increased airway resistance combined with decrese in alveolar area results in breathing difficulty or dyspnoea. Small airway narrowing causes decrease in ventilation of the distal alveolar acini. If the alveolar capillaries are intact, there will be mismatched ventilation and blood flow, reduced ventilation-perfusion ratio qnd mild to moderate hypoxemia. In emphysema, when the alveolar walls are destroyed there will be decreased alveolar perfusion with preserved v-p ratio. Hence, there is a decrease in the rate of diffusion in COPD patients.

2) Saltwater fish when put in fresh water will have more salt inside their body cells when compared to the external environment. Hence this will draw in water into the cell by the principle of osmosis. The homeostatic condition would be disrupted causing its organs to malfunction and the fish would die. Similarly, when a freshwater fish is put in saltwater, water would flow out into the surrounding saltwater by osmosis and the fish would die of dehydration.