Special Sub-Topic: Take a Deep Breath and Have a Go Click Here To Play: Take a Deep Breath and Have a Go

In the lungs, oxygen is absorbed into the blood. In which part of the lungs does this mainly happen?

alveoli. The lungs contain around 700 million alveoli, with a total surface area of about 70 square metres.

What name is given to the maximum volume of air that can be breathed in or out of the lungs in one breath?

vital capacity. Tidal volume is the volume a (normal) breath. Residual capacity is the volume of air left in the lungs after breathing out as much as one can. Inspiratory reserve volume is the extra air that could still be breathed in after a normal inspiration.

Many of the airways in the lungs have goblet cells in their walls. What do these do?

secrete mucus. The goblet cells secrete mucus to trap bacteria and dust that may be breathed in. The mucus is then moved up, away from the lungs, by cilia.

What muscular movements cause air to be drawn into the lungs?

diaphragm and external intercostal muscles contract. Contraction of these muscles causes expansion of the thorax (chest), due to the ribs being raised and the diaphragm moving down. This expansion of the thorax causes a reduction of pressure, allowing air to enter.

Which blood vessels carry deoxygenated blood towards the lungs?

pulmonary arteries. The pulmonary arteries bring deoxygenated blood to the lungs from the right ventricle of the heart. Then the pulmonary veins return the oxygenated blood to the left atrium.

What is the function of surfactant in the lungs?

to prevent the alveoli collapsing. The surfactant is a detergent, which lowers the surface tension of the moisture on the surface of the alveoli, preventing the alveoli sticking together.

Some of the airways are reinforced by cartilage, and this helps to keep the airways open. Which airways are reinforced in this way?

trachea and bronchi. Only the larger airways are reinforced in this way - the trachea (windpipe), bronchi and the larger bronchioles.

What is the correct description of the epithelium of the alveoli?

squamous. The alveolar wall is very thin, for efficient exchange of gases. It is a squamous (or "pavement") epithelium, which means that the cells are broader than they are tall.

Smokers may develop a condition known as emphysema. What is this?

breakdown of the alveolar walls. In this form of emphysema, inhalation of cigarette smoke stimulates production of excess elastase, an enzyme that breaks down the elastic material in the walls of the alveoli. The resulting reduction of the surface area of the alveoli means that the lungs are unable to absorb sufficient oxygen.

Cystic fibrosis is an inherited lung disorder, where the sufferer is unable to transport ions across cell membranes. Which ions cannot be transported?

chloride. Inability to transport chloride ions out from the epithelial cells results in an excessively sticky mucus, which blocks the lungs.