Fig. 3.1 Fig. 3.1 shows the human breathing system, including the ribs, the intercostal muscles and the diaphragm. During breathing, coordinated movements o...
Question 1 Report
Fig. 3.1
Fig. 3.1 shows the human breathing system, including the ribs, the intercostal muscles and the diaphragm. During breathing, coordinated movements of these structures change the volume and pressure inside the thorax, causing air to move in and out of the lungs. The air travels through the trachea and bronchi before it reaches the alveoli, where gas exchange takes place.
(a) State the name of the muscular sheet that separates the thorax from the abdomen. [1]
(b) State the name given to the muscles found between the ribs. [1]
(c) Describe the changes that take place in the ribs and the diaphragm during inspiration. [3]
(d) Explain how these changes cause air to move into the lungs. [3]
(e) State one way in which the movements during expiration differ from those during inspiration. [1]
(f) Explain the function of the rings of cartilage in the wall of the trachea. [2]
(g) Describe how goblet cells and cilia in the airways protect the gas exchange surfaces. [3]
Answer Details
This question tests the mechanism of breathing and the protective structures of the airways.
(a) The muscular sheet separating the thorax from the abdomen is the diaphragm [1].
(b) The muscles between the ribs are the intercostal muscles [1].
(c) Changes during inspiration [3]: the ribs move up and out [1]; the diaphragm muscles contract [1]; so the diaphragm flattens and moves down [1].
(d) How this draws air in [3]: these movements increase the volume of the thorax [1]; so the pressure inside falls below atmospheric pressure [1]; and air then moves in from the higher pressure outside to the lower pressure in the lungs [1]. Air always flows down a pressure gradient.
(e) One difference during expiration [1]: the diaphragm relaxes and domes up (or the ribs move down and in, decreasing the thorax volume).
(f) The rings of cartilage keep the trachea open [1] and stop it collapsing when the air pressure inside falls during inspiration [1].
(g) How goblet cells and cilia protect the lungs [3]: goblet cells make mucus that traps pathogens and dust [1]; the cilia beat and sweep this mucus [1] upwards to the throat, where it is swallowed [1].
Exam tip: inspiration is an active process - muscles contract, volume up, pressure down, air in. Keep that chain in order and don't say the lungs "suck" air in.
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