BIOLOGY TOPIC 2 - structure & functions in living organisms

What happens in inhalation

• Intercostal muscles contract

• Ribcage is pulled upwards & outwards

• Diaphragm contracts & pulls downwards

• Thorax volume increases - pressure decreases

How are alveoli adopted for gas exchange?

• walls are one cell thick to reduce diffusion distance

• large surface area for the maximum exchange of gases

• moist surface to dissolve gases so they can diffuse

• Rich blood supply

Effects of smoking on the air passages

• cigarette smoke paralyzes the cilia on epithelial cells; mucus builds up, smoker’s cough

• Smoke irritates the bronchi - bronchitis

Effects of smoking on the alveoli

• damages walls; they break down & join together, causing larger air spaces than normal

• Reduces the ability of the blood to carry oxygen - increased strain on the heart risks coronary heart disease

Carbon monoxide from smoking

• Combines with hemoglobin in the red blood cells. Reduces the ability of the blood to carry oxygen - more strain on the heart is a risk of coronary heart disease 

Cancer from smoking

• tobacco smoke contains carcinogens e.g tar

• smoking increases the risk of lung cancer + mouth, throat & esophagus cancer