Question
▶️Answer/Explanatio
Question
What causes the expansion of the thorax during inspiration?
A. Air entering the lungs
B. An increase in tidal volume
C. An increase in pressure inside the lungs
D. The contraction of the diaphragm and external intercostal muscles
▶️Answer/Explanation
Ans. D
The thorax expands during inspiration, or inhalation, due to the contraction of the diaphragm and the muscles between the ribs:
Diaphragm
The diaphragm is a dome-shaped muscle that contracts and moves downward during inhalation, which flattens the diaphragm and increases the vertical diameter of the thorax.
Intercostal muscles
The muscles between the ribs contract and pull the rib cage upward and outward, which also enlarges the chest cavity.
The increased size of the thoracic cavity and decreased pressure inside draw air in through the nose or mouth, down the trachea, and into the lungs.
Question
Which type of cell is specialized to facilitate gas exchange?
A. Type I pneumocytes
B. Type II pneumocytes
C. Internal intercostal muscle fibres
D. External intercostal muscle fibres
▶️Answer/Explanation
Ans:A
Question
Which process results in the exchange of gases across the membrane of pneumocytes?
A. Active transport
B. Simple diffusion
C. Facilitated diffusion
D. Mass flow
▶️Answer/Explanation
Ans:B
Question
The diagram shows a section through an alveolus.
What are the functions of the following labelled structures?
Answer/Explanation
Ans:C