Respiratory-organ diversity and the steps of respiration
Question 1
The flow diagram shows the chapter's five respiratory steps with one step replaced by ?. Which step belongs in the blank?
(a)transport of O₂ and CO₂ by blood
(b)diffusion of O₂ and CO₂ across the alveolar membrane
(c)pulmonary ventilation
(d)diffusion of O₂ and CO₂ between blood and tissues
Show answer
(a) transport of O₂ and CO₂ by blood
The source sequence is pulmonary ventilation, alveolar diffusion, transport by blood, diffusion between blood and tissues, and cellular utilisation of O₂ with CO₂ release. The missing step is transport of O₂ and CO₂ by blood.
Question 2
A learner writes, ‘Breathing is the cellular use of O₂. After air enters, blood transports O₂ before it diffuses across the alveolar membrane.’ Which correction is complete?
(a)Breathing is distinct from cellular O₂ use, but blood transport occurs before alveolar diffusion.
(b)Breathing is the same as cellular O₂ use, but alveolar diffusion occurs before blood transport.
(c)Breathing is pulmonary ventilation, cellular O₂ use is distinct, and alveolar diffusion occurs before blood transport.
(d)Breathing is tissue diffusion, cellular O₂ use occurs in blood, and transport follows cellular release of CO₂.
Show answer
(c) Breathing is pulmonary ventilation, cellular O₂ use is distinct, and alveolar diffusion occurs before blood transport.
Breathing is pulmonary ventilation, whereas cellular O₂ use is a later cellular-respiration step. O₂ must diffuse from alveoli into blood before blood can transport it toward tissues.
Human airway, conducting and exchange parts, and pleura
Question 3
In the simplified airway diagram, ? marks one upper-airway structure. Which statement about its name and function is correct?
(a)Epiglottis — covers the glottis during swallowing and helps prevent food entering the larynx.
(b)Trachea — the flap that closes over the glottis during swallowing.
(c)Pharynx — a valve that seals the terminal bronchioles.
(d)Epiglottis — the cartilaginous sound box responsible for sound production.
Show answer
(a) Epiglottis — covers the glottis during swallowing and helps prevent food entering the larynx.
The marked flap is the epiglottis, which covers the glottis during swallowing. The larynx and epiglottis are adjacent but have distinct roles, so their functions must not be reversed.
Question 4
A learner writes, ‘The epiglottis is the sound box, while the larynx is the thin flap that covers the glottis during swallowing.’ Which correction is complete?
(a)The larynx is the sound box, while the epiglottis covers the glottis during swallowing.
(b)The larynx is the sound box, and it also covers the glottis while the epiglottis has no role.
(c)The pharynx is the sound box, while the trachea covers the glottis during swallowing.
(d)The epiglottis is the sound box, while the larynx covers the glottis during swallowing.
Show answer
(a) The larynx is the sound box, while the epiglottis covers the glottis during swallowing.
The two functions have been interchanged. The larynx is the cartilaginous sound box, and the epiglottis is the elastic flap that covers the glottis during swallowing.
Inspiration and expiration: thoracic volume and pressure mechanics
Question 5
The unlabelled thoracic schematic shows one normal breathing state. Which interpretation matches the diaphragm shape, rib/sternum arrows and thoracic-space change?
(a)External intercostals relax, the ribs fall, thoracic volume increases, and the state is inspiration.
(b)The diaphragm contracts but thoracic volume decreases, so the state is expiration.
(c)The diaphragm is relaxed and arched upward, thoracic volume increases, and the state is inspiration.
(d)The diaphragm is contracted, ribs and sternum rise, thoracic volume increases, and the state is inspiration.
Show answer
(d) The diaphragm is contracted, ribs and sternum rise, thoracic volume increases, and the state is inspiration.
Contraction of the diaphragm and external intercostals enlarges the thoracic chamber during inspiration. Muscle state and rib-cage movement change thoracic volume in a coordinated way.
Question 6
A learner writes, ‘The lungs directly expand without a thoracic-volume change. Their intra-pulmonary pressure then rises above atmospheric pressure and pulls air inward.’ Which correction is complete?
(a)Thoracic contraction increases pulmonary volume; intra-pulmonary pressure equals atmospheric pressure, so air enters.
(b)Thoracic expansion increases pulmonary volume; intra-pulmonary pressure rises above atmospheric pressure, so air enters.
(c)The lungs expand independently of the thorax; intra-pulmonary pressure falls below atmospheric pressure, so air enters.
(d)Thoracic expansion increases pulmonary volume; intra-pulmonary pressure falls below atmospheric pressure, so air enters.
Show answer
(d) Thoracic expansion increases pulmonary volume; intra-pulmonary pressure falls below atmospheric pressure, so air enters.
Lung volume changes follow thoracic-volume changes because the lungs occupy an air-tight thoracic chamber. Inspiration occurs when increased pulmonary volume lowers intra-pulmonary pressure below atmospheric pressure, allowing air to enter.
Respiratory volumes, pulmonary capacities and spirometry
Question 7
Which option correctly works backward from breathing endpoints and component expressions to all five pulmonary-capacity names?
(a)TV + IRV → IC. TV + ERV → EC. RV alone after normal expiration → FRC. ERV + TV + IRV → VC. VC + RV → TLC.
(c) TV + IRV → IC; TV + ERV → EC; ERV + RV → FRC; ERV + TV + IRV → VC; VC + RV → TLC.
After normal expiration, TV + IRV is IC and ERV + RV is FRC. After normal inspiration, TV + ERV is EC. VC excludes RV, while TLC equals VC + RV and contains all four respiratory volumes.
Question 8
A learner writes: “Tidal volume is the maximum air moved during forcible breathing.” Which replacement is completely correct?
(a)TV is normal breathing, but IRV is additional forced expiration and ERV is additional forced inspiration.
(b)TV is about 500 mL, so every volume measured by a spirometer must also equal 500 mL.
(c)TV is about 500 mL in a normal respiration; IRV and ERV are additional forced inspiratory and expiratory volumes, and a spirometer estimates these volumes.
(d)TV is the maximum volume of a forced breath; IRV and ERV are parts of normal quiet breathing.
Show answer
(c) TV is about 500 mL in a normal respiration; IRV and ERV are additional forced inspiratory and expiratory volumes, and a spirometer estimates these volumes.
TV is about 500 mL moved in a normal respiration. IRV and ERV are additional volumes moved by forcible inspiration and expiration respectively, while a spirometer estimates such volumes for clinical assessment.
Partial-pressure gradients, gas diffusion and the alveolar membrane
Question 9
The diagram gives alveolar and deoxygenated-blood partial pressures without showing diffusion arrows. Which account follows from the gradients?
(a)O2 and CO2 both diffuse from alveoli to blood because the two gases follow the same direction.
(b)O2 diffuses from blood to alveoli, while CO2 diffuses from alveoli to blood.
(c)Neither gas diffuses because only equal partial pressures can drive exchange.
(d)O2 diffuses from alveoli to blood, while CO2 diffuses from blood to alveoli.
Show answer
(d) O2 diffuses from alveoli to blood, while CO2 diffuses from blood to alveoli.
Alveolar pO2 is 104 mm Hg compared with 40 mm Hg in deoxygenated blood, so O2 enters blood. Deoxygenated-blood pCO2 is 45 mm Hg compared with 40 mm Hg in alveoli, so CO2 enters alveoli; the gases move oppositely.
Question 10
The diagram shows the three major components of the alveolar diffusion membrane from air to capillary blood. Which complete statement correctly identifies the band marked ?
(a)The marked band is the endothelium of the alveolar capillary.
(b)The marked band is an air-filled gap that replaces the basement substance between alveolus and capillary.
(c)The marked band is alveolar epithelium on the blood-facing side.
(d)The marked band is alveolar squamous epithelium, and it is the only component of the entire diffusion membrane.
Show answer
(a) The marked band is the endothelium of the alveolar capillary.
The marked band is the endothelium of the alveolar capillary. The barrier has three major components in sequence: thin alveolar squamous epithelium, intervening basement substance and capillary endothelium.
Oxygen transport, haemoglobin loading and dissociation curve
Question 11
The graph plots percentage haemoglobin saturation against pO2. Which statement best interprets the point marked ? on the single curve?
(a)The point lies in the low-pO2, low-saturation part before the curve rises strongly.
(b)The vertical coordinate represents pCO2, while the horizontal coordinate represents hydrogen-ion concentration.
(c)The point is on the high-pO2 plateau where saturation is already near its upper level.
(d)The curve should be read as a straight proportional line because haemoglobin saturation is linear and controlled by pO2 alone.
Show answer
(a) The point lies in the low-pO2, low-saturation part before the curve rises strongly.
The point lies in the low-pO2, low-saturation part before the curve rises strongly. The overall relation is sigmoid rather than a straight proportional line, and the curve approaches a plateau at high pO2.
Question 12
A learner proposes: “Haemoglobin saturation rises in a straight line with pO2 and no other factor affects binding.” Which correction is complete and source-supported?
(a)The curve is sigmoid; pCO2, H+ and temperature also affect binding, alveolar conditions favour oxyhaemoglobin formation, and tissue conditions favour O2 dissociation.
(b)Alveoli favour formation and tissues favour dissociation, but saturation rises linearly with pO2 alone and is unaffected by pCO2.
(c)The curve is sigmoid, but high pO2 and low pCO2 at tissues favour dissociation while low pO2 at alveoli favours formation.
(d)The curve is sigmoid and other factors matter, but low-pO2, high-pCO2 tissues still favour oxyhaemoglobin formation.
Show answer
(a) The curve is sigmoid; pCO2, H+ and temperature also affect binding, alveolar conditions favour oxyhaemoglobin formation, and tissue conditions favour O2 dissociation.
The oxygen dissociation curve is sigmoid, not linear. High pO2 with low pCO2, lower H+ and lower temperature at alveoli favours oxyhaemoglobin formation; the opposite tissue profile favours oxygen dissociation.
Carbon-dioxide transport and reversible bicarbonate formation
Question 13
The figure gives the site and gas conditions for a reversible carbonic-anhydrase reaction. Which net change is favoured?
(a)Bicarbonate must continue forming at both sites because the reaction cannot proceed back toward CO₂.
(b)CO₂ enters blood and net bicarbonate formation is favoured.
(c)Low tissue pCO₂ drives CO₂ loading, while high alveolar pCO₂ drives its release.
(d)No net change can occur because carbonic anhydrase acts only on oxygen transport.
Show answer
(b) CO₂ enters blood and net bicarbonate formation is favoured.
CO₂ enters blood and net bicarbonate formation is favoured. Carbonic anhydrase facilitates the sequence in both directions. High tissue pCO₂ drives CO₂ into blood and favours bicarbonate formation, whereas lower alveolar pCO₂ favours conversion back toward CO₂ and H₂O for release.
Question 14
Measurements show that one CO₂ route carries nearly 70%, another carries about 20–25% through RBC binding, and plasma contains only minute quantities of carbonic anhydrase. Which interpretation is supported?
(a)Bicarbonate is the main CO₂ route, and RBCs contain the high carbonic-anhydrase concentration.
(b)Bicarbonate is the main CO₂ route, but plasma contains the high carbonic-anhydrase concentration.
(c)Dissolved CO₂ is the main route, and the enzyme is equally concentrated in RBCs and plasma.
(d)Carbamino-haemoglobin is the main CO₂ route, and RBCs contain the high carbonic-anhydrase concentration.
Show answer
(a) Bicarbonate is the main CO₂ route, and RBCs contain the high carbonic-anhydrase concentration.
Bicarbonate is the largest CO₂ transport fraction, while carbamino-haemoglobin carries about 20–25%. The high carbonic-anhydrase concentration is in RBCs, not plasma; the dissolved plasma fraction does not locate most of the enzyme there.
Neural regulation of respiration and respiratory disorders
Question 15
Which comparison of asthma, emphysema and occupational dust injury is correct?
(a)Asthma and emphysema both have the same alveolar-wall injury; prolonged dust exposure can cause fibrosis.
(b)Asthma inflames bronchi and bronchioles; emphysema damages alveolar walls; industrial dust causes only temporary blockage.
(c)Asthma is caused only by cigarette smoking; emphysema is only temporary; masks reverse established fibrosis.
(d)Asthma inflames bronchi and bronchioles; emphysema damages alveolar walls; prolonged dust exposure can cause fibrosis.
Show answer
(d) Asthma inflames bronchi and bronchioles; emphysema damages alveolar walls; prolonged dust exposure can cause fibrosis.
Asthma causes wheezing and breathing difficulty through inflammation of bronchi and bronchioles. Emphysema damages alveolar walls and reduces respiratory surface. Long industrial dust exposure can lead to inflammation and fibrosis, and protective masks help reduce exposure.
Is moving air into the lungs the same as cellular respiration?
Wrong
Breathing air into the lungs is cellular respiration.
Why it feels right. Both processes involve oxygen and are described together.
Right
Ventilation moves air. Cellular respiration transfers energy from fuel to ATP.
Worked example
Oxygen path
Inhaled air in lungs→Blood→Muscle mitochondria→Supports ATP production
Ventilation moves air. Cellular respiration uses oxygen in energy transfer inside cells.
Trace oxygen from the inhaled air into the blood and then to a muscle cell.
The air movement occurs in the lungs.
In the muscle, mitochondria use oxygen in the reactions that support ATP production.
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