Respiratory System Questions and Answers

Answer: D

The amount is about 4 ml of carbon dioxide.

Deoxygenated (mixed venous) blood carries about 52 ml of carbon dioxide per 100 ml, and arterial blood about 48 ml per 100 ml. As blood passes through the lungs it gives up the difference:

\[ 52 - 48 = 4 \text{ ml per 100 ml of blood} \]

This 4 ml is what physiology texts quote as the carbon dioxide delivered to the alveoli by each 100 ml of blood at rest. The smaller figures of 1, 2 and 3 ml understate this exchange.

Answer: A

It is called the pleura.

Each lung is covered by a double serous membrane: the visceral pleura sticks to the lung surface and the parietal pleura lines the chest wall. The thin film of fluid between the two layers lets the lungs glide smoothly during breathing. Inflammation of these layers is pleurisy.

The alveolar-capillary membrane is the thin barrier where gases are exchanged inside the lung. Infundibula are funnel-shaped passages leading to air sacs, and a bronchus is an airway. None surrounds the lungs.

Answer: B

The answer is inspiration, expiration.

During inspiration the diaphragm and the external intercostal muscles contract, enlarging the chest cavity. Pressure in the lungs falls below atmospheric pressure and air is drawn in. During expiration these muscles relax, the chest becomes smaller and air is pushed out.

The first option reverses the two. External and internal respiration are different processes: external respiration is gas exchange between the alveoli and the blood, and internal respiration is gas exchange between the blood and the tissues. Neither is the movement of air in and out.