Thoracic Cavity & Lung Volume Changes — NEET Biology
📚 Practice ConceptThe lungs are situated in the thoracic chamber which is anatomically an air-tight chamber. The thoracic chamber is formed dorsally by the vertebral column, ventrally by the sternum, laterally by the ribs and on the lower side by the dome-shaped diaphragm. The anatomical setup of lungs in thorax is such that any change in the volume of the thoracic cavity will be reflected in the lung (pulmonary) cavity. Such an arrangement is essential for breathing, as we cannot directly alter the pulmonary volume.
Select the INCORRECT statement regarding the human respiratory system. S1: The trachea divides into primary bronchi at the level of the fifth thoracic vertebra. S2: The inner pleural membrane is in close contact with the lung surface, reducing friction between the lung and the thoracic cavity. S3: Cartilaginous rings are present in the trachea and bronchi, but not in the initial or terminal bronchioles. S4: The exchange part of the respiratory system is responsible for clearing air from foreign particles and humidifying it. S5: The thoracic chamber is an anatomically air-tight chamber, formed dorsally by the vertebral column and ventrally by the sternum.
View solution & NCERT explanation
Correct answer: B — Only S3 and S4 are incorrect
Let's evaluate each statement: S1: The NCERT states, 'Trachea is a straight tube... which divides at the level of 5th thoracic vertebra into a right and left primary bronchi.' This statement is correct. S2: The NCERT states, 'The outer pleural membrane is in close contact with the thoracic lining whereas the inner pleural membrane is in contact with the lung surface. The pleural fluid between them reduces friction on the lung-surface.' This statement accurately describes the inner pleural membrane's contact and the overall function of the pleural system. So, S2 is correct. S3: The NCERT clearly states, 'The tracheae, primary, secondary and tertiary bronchi, and initial bronchioles are supported by incomplete cartilaginous rings.' This statement claims cartilaginous rings are *not* present in initial bronchioles, which contradicts the NCERT text. So, S3 is incorrect. S4: The NCERT clarifies, 'The conducting part transports the atmospheric air to the alveoli, clears it from foreign particles, humidifies and also brings the air to body temperature. Exchange part is the site of actual diffusion of O2 and CO2...' This statement wrongly attributes the functions of clearing and humidifying air to the exchange part. So, S4 is incorrect. S5: The NCERT states, 'The thoracic chamber is formed dorsally by the vertebral column, ventrally by the sternum, laterally by the ribs and on the lower side by the dome-shaped diaphragm.' This statement is correct. Therefore, statements S3 and S4 are incorrect.
What does NCERT say about lungs are situated thoracic?
Has this concept appeared in NEET?
Which chapter is this from?
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