Pre Clinical Medical Science SBAs
Pre Clin Respiratory: (59 questions)

Questions

• 1
  What is the effect of a local decrease in ventilation:perfusion ratio?
  Difficulty: Easy     Topic: Ventilation: perfusion ratio 2
  a

  Bronchoconstriction and vasoconstriction

  b

  Bronchoconstriction and vasodilatation

  c

  Bronchodilatation and vasoconstriction

  d

  Bronchodilatation and vasodilatation

  e

  Bronchodilatation and no effect on vasculature
  Explanation: A local decrease in V:Q met by an attempt to correct it by the pulmonary vasculature an airways. To raise the ventilation there is bronchodilatation and to reduce the perfusion there is vasoconstriction, the net effect is to increase V:Q. This becomes a problem in patients who have chronically reduced V:Q across the whole lung (e.g. COPD), which results in pulmonary vasoconstriction, raise pulmonary artery pressures and ultimately right heart failure (cor pulmonale).
• 2
  What is anatomical dead space?
  Difficulty: Easy     Topic: Dead space
  a

  Where airways have collapsed

  b

  Where gas exchange does not occur

  c

  Where gas exchange does not occur above the respiratory bronchioles

  d

  Where gas exchange does not occur below respiratory bronchioles

  e

  Where there is no flow of gas within the airways
  Explanation: Dead space is all the volume of the respiratory system where gaseous exchange does not occur. Anatomical dead space is the volume of the conducting airways - all above the respiratory bronchioles - gas exchange never occurs in these areas. Alveolar dead space is the volume in the respiratory bronchioles or below where gas exchange should occur but does not.
• 3
  At the end of normal expiration what is (approximately) the intrapleural pressure?
  Difficulty: Hard     Topic: Intrapleural pressure
  a

  +10mmH20

  b

  +5 mmH20

  c

  0 mmH20

  d

  -5 mmH20

  e

  -15mmH20
  Explanation: Intrapleural pressure is the pressure between the parietal and visceral pleura - it is always negative (relative to atmospheric pressure). It is generated by the natural elastic recoil of the chest wall outwards and the lungs inwards. At the end of normal expiration, functional residual capacity, transmural pressure is zero i.e. there is no distending or collapsing force on the airways. Intrapleural pressure is at its least negative (approximately -5mmHg). At maximum inspiration intrapleural pressure may reach -15mmHg. During forced exhalation from TLC, intrapleural pressure may reach +5mmHg.
• 4
  At functional residual capacity, what is the relationship between compliance and airway transmural pressure?
  Difficulty: Easy     Topic: Functional residual capacity
  a

  Compliance is 1 with maximum distending pressure

  b

  Compliance is 1 with zero distending pressure

  c

  Compliance is zero with maximum distending pressure

  d

  Maximum compliance with zero distending pressure

  e

  Moderate compliance with moderate distending pressure
  Explanation: FRC is at the end of normal expiration and it is when the lung is most compliant. Compliance = 1/resistance. Therefore for normal breathing there is the minimum resistance (and maximum compliance). FRC is when there is zero distending pressure (or collapsing pressure) on the airways. The aim is to make normal breathing as efficient as possible.
• 5
  How does chest wall elasticity relate to total lung capacity (TLC)?
  Difficulty: Medium     Topic: Elasticity
  a

  Elastic limit must be passed to reach TLC

  b

  Elastic limit prevents TLC from being reached

  c

  Higher elasticity means less energy is required to reach TLC

  d

  There is minimum potentially elastic energy at TLC

  e

  TLC is the furthest volume away from chest wall elastic limit
  Explanation: The chest wall's elastic properties are such that it has a tendency to expand towards TLC. Conversely, the lung's elastic properties are such that it will collapse to a very low volume unless held open. TLC is above the chest wall's elastic limit, so energy must be expended to reach TLC - there is low compliance at high lung volumes. However there is a lot of elastic energy stored when the chest wall is above its elastic limit - this facilitates maximum exhalation force.
• 6
  Why do smaller alveoli have a higher internal pressure than larger alveoli?
  Difficulty: Medium     Topic: Small & large alveoli
  a

  Greater effect of intrapleural pressure

  b

  Greater surface tension forces

  c

  Greater tissue elasticity

  d

  Less distending force from air

  e

  Less support from tethering forces
  Explanation: Laplace's law states that the internal pressure of a sphere is inversely proportional to its radius. Surface tension forces in alveoli have tangential (circumferential) and radial (collapsing) components. Internal pressure must equal and oppose radial forces to keep alveoli open. Smaller spheres have greater interaction between their radial forces, which results in greater collapsing forces. Intrapleural pressure, tethering forces and elasticity should be equal for small and large alveoli. Air distending force equals the collapsing force.
• 7
  What is the action of surfactant?
  Difficulty: Medium     Topic: Surfactant 1
  a

  Increases compliance in small alveoli more than large alveoli

  b

  Increases radial collapsing forces across the whole lung

  c

  Increases surface tension in small alveoli more than large alveoli

  d

  Increases tangential forces across the whole lung

  e

  Reduces distending forces across the whole lung
  Explanation: Surfactant is a phospholipid that inserts between water molecules over the surface of alveoli to interrupt surface tension forces. The effect is to reduce the resistance from surface tension and increase lung compliance. The density of surfactant molecules is higher in smaller alveoli, which means that there is more interruption of collapsing forces than in large alveoli. By reducing collapsing forces, there is a net increase in distending forces across the lung.
• 8
  Which cell produces surfactant?
  Difficulty: Easy     Topic: Surfactant 2
  a

  Alveolar macrophages

  b

  Fibroblasts

  c

  Respiratory epithelial cells

  d

  Type 1 pneumocytes

  e

  Type 2 pneumocytes
  Explanation: Surfactant is produced by type 2 pneumocytes, which are polyhedral cells that sit on the surface of alveoli. They begin producing surfactant under the action of corticosteroids in the 3rd trimester. Alveolar macrophages phagocytose debris in alveoli. There are few fibroblasts in lung parenchyma. Respiratory epithelial cells form the psuedostratified epithelium of the conducting airways. Type 1 pneumocytes are thin cells that line the exchange airways.
• 9
  What is the pathophysiology of surfactant deficient lung disease?
  Difficulty: Medium     Topic: Surfactant 3
  a

  Alveolar collapse with difficulty of inflation

  b

  Excessive positive intrapleural pressure

  c

  Excessive positive intrapleural pressure

  d

  Loss of negative intrapleural pressure

  e

  Bronchiolar airway obstruction during expiration
  Explanation: Surfactant normally helps to: stabilise alveoli, reduce collapsing forces, increase compliance and reduced the energy required for breathing. In the absence of surfactant small alveoli collapse and empty into larger ones. The whole lung is much stiffer and a lot of energy is required to re-inflate the alveoli. Neonates present with acute respiratory distress and become extremely fatigued. Loss of alveolar surface area occurs in emphysema. Loss of negative intrapleural pressure occurs in pneumothoraces. Obtruction at the level of the bronchioles during exhalation occurs in COPD.
• 10
  Ligation of which receptor results in bronchodilatation?
  Difficulty: Medium     Topic: Bronchodilatation
  a

  Alpha-1-adrenoreceptor

  b

  Beta-2-adrenoreceptor

  c

  H1-receptor

  d

  Muscarinic acetylcholine-receptor

  e

  Nicotinic acetylcholine-receptor
  Explanation: Bronchodilatation is caused by beta-2-adrenoreceptor ligation by circulating adrenaline and by a low ventilation:perfusion ratio. Bronchoconstriction is caused by histamine (at H1-R), ACh from the vagus (at muscarinic-AChR), bradykinin, leukotrienes and a high ventilation:perfusion ratio. Alpha-adrenoreceptors cause vasoconstriction. Nicotinic-ACh-R are found on motor end plates, not in the lungs.
• 11
  What is the relationship between alveolar ventilation and gas partial pressure?
  Difficulty: Medium     Topic: Alveolar ventilation 1
  a

  Increasing alveolar ventilation gives an exponential increase in alveolar O2

  b

  Increasing alveolar ventilation gives a hyperbolic increase in alveolar CO2

  c

  Increasing alveolar ventilation gives a linear increase in alveolar CO2

  d

  Reducing alveolar ventilation gives a hyperbolic increase in alveolar O2

  e

  Reducing alveolar ventilation gives a linear increase in alveolar CO2
  Explanation: Alveolar ventilation (VA) removes CO2, which is being produced at a constant rate by the body. It also provides oxygen, which is at a fixed concentration that is dependent on the partial pressure of inspired oxygen. Therefore, reducing VA allows CO2 to accumulate in the alveoli and there is a linear increase in partial pressure. Increasing VA increases O2 partial pressure but levels plateau because they are limited by the fraction of inspired oxygen. Reduction in VA causes a marked, sharp drop in O2 partial pressure as O2 leaves the alveoli for the blood and is not replaced.
• 12
  Which blood gas measurement gives the most information regarding ventilation efficiency?
  Difficulty: Easy     Topic: Alveolar ventilation 2
  a

  Arterial carbon dioxide

  b

  Arterial oxygen

  c

  Capillary oxygen

  d

  Venous carbon dioxide

  e

  Venous oxygen
  Explanation: Arterial carbon dioxide is the marker of ventilation efficiency because it is dependent on only VCO2 (CO2 production rate) and alveolar ventilation (VA). Whereas oxygen is also dependent upon the fraction of inspired oxygen. Furthermore, the 'alveolar gas equation' describes the relationship between alveolar O2 partial pressure, arterial CO2 and the fraction of inspired oxygen - so O2 is partly dependent upon arterial CO2. Capillary and venous measurements are more affected by tissue metabolic levels so are less reliable.
• 13
  Why is carbon dioxide a perfusion limited gas?
  Difficulty: Hard     Topic: Perfusion limited gas
  a

  Increasing cardiac output has minimal effect on gas transfer

  b

  It dissolves from gaseous to liquid phase rapidly

  c

  It does not reach equilibrium before the end of the pulmonary capillary

  d

  It has high protein binding in blood

  e

  There is a large alveolar-capillary diffusion gradient
  Explanation: A perfusion limited gas is one that reaches equilibrium between the alveoli and pulmonary blood before the end of the pulmonary capillary. Therefore increasing blood flow raises (raising cardiac output) the total amount of gas transfer. For a gas to reach equilibrium it must either have a large concentration gradient (e.g. oxygen) or dissolve very rapidly (e.g. CO2). However it shows high protein binding it would be a diffusion limited gas (e.g. carbon monoxide) as protein-bound gas does not exert a partial pressure and cannot reach equilibrium.
• 14
  What pathology most likely to cause oxygen to become a diffusion limited gas?
  Difficulty: Hard     Topic: Diffusion limited gas
  a

  Cardiac failure

  b

  Lobar pneumonia

  c

  Pneumothorax

  d

  Pulmonary embolus

  e

  Pulmonary fibrosis
  Explanation: Oxygen is normally a perfusion limited gas because there is a large partial pressure difference between alveoli and pulmonary capillaries, and oxygen diffuses easily into the blood. However if pathology makes diffusion much more difficult then oxygen can become diffusion limited. In pulmonary fibrosis there is excessive connective tissue deposition that increases the diffusion barrier for gas exchange, which slows oxygen transport. In the other pathologies listed above patients may be hypoxic but this is primarily due to a ventilation-perfusion mismatch.
• 15
  How does the ventilation-perfusion ratio change across a normal lung?
  Difficulty: Easy     Topic: Ventilation:perfusion ratio 1
  a

  Overall the lung has a ventilation:perfusion ratio of 1.5

  b

  The apex has a ventilation:perfusion ratio of 0

  c

  The base has a ventilation:perfusion ratio of 1

  d

  The base has the lowest ventilation perfusion ratio

  e

  There are areas with higher alveolar ventilation pressure than perfusion pressure
  Explanation: There is a ventilation-perfusion gradient across the normal lung. The base receives much more perfusion than the apex due to the effects of gravity. It also receives more ventilation than the apex due to tethering forces but relatively the base has more perfusion than ventilation (a low V:Q ratio). Conversely the apex has a high V:Q as it receives relatively more ventilation than perfusion. Over the whole lung has a V:Q of 0.8. A V:Q of zero is always abnormal and suggests no ventilation. A V:Q of 1 may happen in a few areas around the mid-zone of the lung.
• 16
  How is tidal ventilation calculated?
  Difficulty: Easy     Topic: Lung volumes 2
  a

  (Tidal volume + residual volume) x respiratory rate

  b

  Inspiratory capacity x respiratory rate

  c

  Tidal volume x respiratory rate

  d

  Total lung capacity x respiratory rate

  e

  Vital capacity x respiratory rate
  Explanation: Tidal ventilation (VT) is the volume of air inspired and expired during a minute. This is the volume breathed in/out with each breath (tidal volume) multiplied by the respiratory rate. Residual volume is the volume remaining after maximum exhalation. Inspiratory capacity is maximum volume that can be inspired from FRC. Total lung capacity is the anatomical volume of the lungs. Vital capacity is the maximum that can be breathed in/out. TLC = residual volume + vital capacity.
• 17
  The ratio between which two measurable factors determines arterial pH?
  Difficulty: Medium     Topic: Acid-base 1
  a

  H+ and Cl-

  b

  HCO3- and Cl-

  c

  HCO3- and H2CO3

  d

  H+ and HCO3-

  e

  HCO3- and PaCO2
  Explanation: The Henderson-Hasselbalch equation, states that the pH of a system containing a weak acid can be predicted by the relative concentrations of the weak acid and its base. For the blood, the most important system is that of carbonic acid, which comes from dissolved CO2 in blood. HCO3- and H2CO3 are technically the two factors that determine pH, however H2CO3 is not measurable due to its rapid dissociation. Therefore PaCO2 is measured as a surrogate marker. Normal serum pH is present when the ratio of HCO3-:PaCO2 is 20:1.
• 18
  In a chronic respiratory acidosis what will be found on blood gas analysis?
  Difficulty: Medium     Topic: Acid base 2
  a

  High pH, high CO2, high HCO3-

  b

  High pH, low CO2, low HCO3-

  c

  Low pH, high CO2, high HCO3-

  d

  Low pH, high CO2, low HCO3-

  e

  Low pH, low CO2, low HCO3-
  Explanation: Respiratory acidosis occurs when inadequate ventilation results in retention of CO2, which causes the acidosis. The response of the kidneys is to reabsorb and generate HCO3- to compensate for the acidosis, therefore HCO3- also rises. Renal compensation takes 2-3 days to occur, so HCO3- may not be high in an acute respiratory acidosis. "A" is a partially compensated metabolic alkalosis. "B" is a compensated respiratory alkalosis. "D" would be a complicated mixed picture. "E" is a compensated metabolic acidosis.
• 19
  In a case of metabolic acidosis (e.g. DKA), what will be found on blood gas analysis?
  Difficulty: Medium     Topic: Acid base
  a

  High pH, high CO2, high HCO3-

  b

  High pH, low CO2, low HCO3-

  c

  Low pH, high CO2, high HCO3-

  d

  Low pH, high CO2, low HCO3-

  e

  Low pH, low CO2, low HCO3-
  Explanation: In a metabolic acidosis, the gain of acidic ions or loss of basic ions causes a low HCO3-. The acidosis stimulates hyperventilation at the peripheral chemoreceptors, which results in low CO2 that partially compensates the pH change. Respiratory compensation for a metabolic change occurs very quickly, within hours. "A" is a partially compensated metabolic alkalosis. "B" is a compensated respiratory alkalosis. "C" represents a chronic, compensated respiratory acidosis. "D" would be a complicated mixed picture.
• 20
  What group of causes of respiratory failure is most likely to cause type 2 failure?
  Difficulty: Medium     Topic: Respiratory failure
  a

  Central (neuromuscular)

  b

  Fibrotic

  c

  Infective

  d

  Malignant

  e

  Vascular causes
  Explanation: Respiratory failure (PaO2 <8KPa) can be divided into Type 1 (with PaCO2 <6KPa) or type 2 (with PaCO2). Given that CO2 is a marker of efficiency of alveolar ventilation, type 2 failure represents reduced ventilatory capacity. Central & neuromuscular causes always result in hypercapnia because they involve weakness in moving the rib cage (e.g. myasthenia gravis) or reduced respiratory rate (e.g. brainstem injury). The other causes listed may cause type 2 failure if severe but often impair perfusion or oxygen diffusion and cause type 1 failure.
• 21
  What constitutes a strong risk factor for pulmonary embolism?
  Difficulty: Hard     Topic: Pulmonary embolism
  a

  3 hour car journey

  b

  Middle age

  c

  Oral contraceptive pill

  d

  Recent femoral fracture

  e

  Underweight
  Explanation: Pulmonary embolism is a common, life-threatening condition affecting the respiratory system. An embolus (often from a deep vein thrombosis) occludes part of one of the pulmonary arteries. The result is infarction of an area of lung. The risk factors for venous thrombo-embolism are describes by Charcot's triad: blood stasis, endothelial injury & hypercoagulability. Lower limb fractures are a major risk factor. The OCP is a minor risk factor. All the other options are not significant risk factors.
• 22
  Where is the origin for the neurones that activate inspiration?
  Difficulty: Easy     Topic: Control of breathing
  a

  Medulla

  b

  Olivary nucleus

  c

  Pons

  d

  Red nucleus

  e

  Thalamus
  Explanation: Inspiration is caused by activation of the phrenic nerve, which begins in the medullary inspiratory centres (dorsal and ventral). There is also a pontine inspiratory centre but this is most involved in the timing of respiration. The Botzinger complex is another area in the medulla involved in inspiration, however its main role is initiating the medullary areas to trigger inspiration.
• 23
  What is the brainstem output following a fall in CSF pH?
  Difficulty: Easy     Topic: Central chemoreceptors
  a

  Increased activity in the carotid body

  b

  Increased activity in the nucleus ambiguus

  c

  Increased action potential frequency on the nerves to internal intercostal muscles

  d

  Increased action potential frequency on the phrenic nerve

  e

  Reduced action potential frequency on the phrenic nerve
  Explanation: CSF pH is the most important factor in determining ventilation. A rise in serum CO2 results in a fall in CSF pH. CO2 diffuses across the blood brain barrier and forms H+ and HCO3- in the CSF. Chemoreceptors respond to levels of H+, but they are specific to respiratory acidosis and do not respond to metabolic acidosis. In order to correct the raised CO2 ventilation must be increased, this occurs by raising the frequency of action potentials on the phrenic nerve. The carotid body is the site of peripheral chemoreceptors. The nucleus ambiguus is the origin of the vagus.
• 24
  What is the most important stimulus in controlling alveolar ventilation?
  Difficulty: Medium     Topic: Chemical control of breathing 1
  a

  CSF O2

  b

  CSF pH

  c

  Serum CO2

  d

  Serum O2

  e

  Serum pH
  Explanation: Alveolar ventilation is most closely related to PaCO2 levels. There is a strong positive linear correlation between PaCO2 and alveolar ventilation. The central chemoreceptors provide 80% of this response and they are only stimulated by changes in CSF pH, not serum CO2 per se. Central chemoreceptors don't respond to oxygen levels. The response of peripheral chemoreceptors to oxygen is non-linear - levels need to fall significantly before an increase in ventilation is stimulated. The peripheral chemoreceptors will respond to a change in serum pH, thus can respond to a metabolic acidosis.
• 25
  What mediates hyperventilation in metabolic acidosis?
  Difficulty: Easy     Topic: Chemical control of breathing 2
  a

  High CO2 - at carotid sinus

  b

  High pH - in CSF

  c

  Low CO2 - at carotid bodies

  d

  Low HCO3- - at carotid sinus

  e

  Low pH - at carotid bodies
  Explanation: In metabolic acidosis there is a gain of H+ or loss of HCO3- through a mechanism separate to respiratory CO2, for example acidic ketones in diabetic ketoacidosis. The reduced pH is sensed at the carotid bodies - the carotid sinus detects changes in blood pressure. Low CO2 would be either from a respiratory alkalosis or respiratory compensation for a metabolic acidosis.
• 26
  How does the carotid body respond to hypoxia?
  Difficulty: Hard     Topic: Carotid bodies
  a

  Potassium channel closure in type 1 glomus cells

  b

  Potassium channel closure in type 2 glomus cells

  c

  Potassium channel opening in type 1 glomus cells

  d

  Sodium channel closure in type 2 glomus cells

  e

  Sodium channel opening in type 1 glomus cells
  Explanation: The type 1 glomus cell is the oxygen-sensitive cell in the carotid bodies. They respond to hypoxia by increasing the frequency of action potentials along the glossopharyngeal nerve, which in tern activates the medullary inspiratory centre. Hypoxia is transduced via an unknown mechanism, this results in potassium channel closure that depolarises the glomus cell. Depolarisation causes opening of voltage gated calcium channels. The calcium influx stimulates neurotransmitter release, which activates the glossopharyngeal nerve. Type 2 glomus cells are supporting, glial-type cells.
• 27
  What is the key pathological feature of asthma?
  Difficulty: Medium     Topic: Asthma
  a

  Collapse of small airways on exhalation

  b

  Increased connective tissue deposition

  c

  Intermittent, inappropriate bronchoconstriction

  d

  Loss of alveolar surface area

  e

  Smooth muscle hyperplasia and increased mucus
  Explanation: Asthma is characterised by intermittent, reversible bronchoconstriction that can occur due to a variety of stimuli. Chronic, poorly controlled asthma may result in some degree of smooth muscle hyperplasia and increased mucus but these are more commonly associated with COPD; small airway collapse is also seen in COPD. Connective tissue is deposited in pulmonary fibrosis. Emphysema causes loss of alveolar surface area.
• 28
  What are the key pathological features of chronic bronchitis?
  Difficulty: Medium     Topic: Chronic bronchitis
  a

  Increased connective tissue deposition

  b

  Intermittent, inappropriate bronchoconstriction

  c

  Loss of alveolar surface area

  d

  Raised pulmonary artery pressure

  e

  Smooth muscle hyperplasia and increased mucus
  Explanation: Chronic bronchitis is characterised by small airway inflammation that results in increased mucus and smooth muscle hyperplasia. This causes increased resistance to airflow. Chronic bronchitis is almost always related to cigarette smoking and is very often associated with emphysema - causing loss of alveolar surface area. Pulmonary fibrosis causes increased connective tissue deposition. Intermittent bronchoconstriction is a feature of asthma. Raise pulmonary artery pressure may occur due to chronic hypoxia.
• 29
  What is the Hering-Breuer reflex?
  Difficulty: Easy     Topic: Hering-Breuer reflex
  a

  Cough stimulation due airway irritant receptors activation

  b

  Inhibition of expiration following carotid sinus pressure

  c

  Inhibition of inspiration due to airway stretch receptor activation

  d

  Phrenic nerve inhibition during dorsal inspiratory group activation

  e

  Stimulation of inspiration following activation of trigeminal afferents
  Explanation: The Hering-Breuer nerve is an afferent branch of the vagus that is activated by slowly-adapting stretch receptors in the walls of small airways. During inspiration the stretch receptors become activated, which increases the frequency of action potentials along vagal afferents. This causes termination of inspiration and activation of expiratory centres. Cough may be stimulated by irritant receptors in the lungs. Carotid sinus massage may cause hypotension by activating the baroreflex. Dorsal inspiratory group activation would increase phrenic nerve activity. The 'diving reflex' is an expiratory apnoea caused by activation of trigeminal afferents from cold water on the face.
• 30
  How does aerobic respiration change the ventilatory response to arterial O2?
  Difficulty: Medium     Topic: Exercise reflex
  a

  Increased alveolar ventilation due to increase in PaCO2

  b

  Increased alveolar ventilation due to raised lactate

  c

  Increased alveolar ventilation without change in PaO2

  d

  Increased respiratory rate but reduced tidal volume due to reduced PaCO2

  e

  Reduced alveolar ventilation due to reduced PaCO2
  Explanation: The exercise reflex involves several systems, but the initial respiratory response to aerobic exercise is hyperpnoea. Hyperpnoea is an increase in alveolar ventilation to exactly match the increased oxygen use and CO2 production such that arterial blood gases do not change. The stimulus for this is not entirely understood but may be linked to joint receptors and metaboreceptors. Past the anaerobic threshold, hyperventilation occurs where there is a disproportionate increase in alveolar ventilation, which causes a reduction in arterial CO2.
• 31
  In the pulmonary hila, which structures lie most posteriorly?
  Difficulty: Hard     Topic: Hila
  a

  Bronchi

  b

  Bronchial arteries

  c

  Lymphatics

  d

  Pulmonary arteries

  e

  Pulmonary veins
  Explanation: From anterior to posterior lies: pulmonary veins, pulmonary arteries, bronchi. The bronchial arteries are the vessels that supply oxygenated blood to the conducting airways, they are small vessels and lie within the hila. Lymphatic vessels and lymph nodes also lie within the hila.
• 32
  Where on a rib is a fracture most likely to occur?
  Difficulty: Hard     Topic: Ribs 1
  a

  Angle

  b

  Body

  c

  Head

  d

  Neck

  e

  Tubercle
  Explanation: The angle of the rib is its weakest point and where patients are most likely to sustain rib fractures. The head of the rib forms the cost-vertebral joint with thoracic vertebrae. The rib's tubercle forms an articulation with the lateral process of thoracic vertebrae. The neck lies between the head and tubercle. this is followed by the angle, which is the most curved part of the rib and lies approximately in the posterior axillary line. The body of the rib is the main curved part of the bone.
• 33
  Where does the 2nd rib attach to the sternum?
  Difficulty: Easy     Topic: Ribs 2
  a

  Body of sternum

  b

  1st fused costal cartilage

  c

  Manubrium

  d

  Manubro-sternal junction

  e

  Xiphoid process of sternum
  Explanation: The sternum is divided into the manubrium, sternum and xiphisternum (xiphoid process). The 1st rib attaches to the manubrium only. The2nd rib attaches at the junction between the manubrium and sternum. With a patient at 45 degrees this is at T4 and is the same level as the right atrium; it is known as the angle of Louis. Ribs 3-7 attach to the sternum via their own costal cartilages. Ribs 8-10 attach to fused costal cartilage of the 7th rib (known as false ribs). Ribs 11 & 12 are 'floating' - they do not attach to any other parts of the ribcage.
• 34
  Where does the main intercostal neurovascular bundle lie?
  Difficulty: Easy     Topic: Intercostal anatomy
  a

  Inferior to rib and between innermost and internal intercostal muscles

  b

  Inferior to rib and between internal and external intercostal muscles

  c

  Inferior to rib and inside innermost intercostal muscles

  d

  Superior to rib and between internal and external intercostal muscles

  e

  Superior to rib and outside external intercostal muscles
  Explanation: There is a large neurovascular bundle that lies immediately underneath each rib and between the two deepest layers of intercostal muscles. There are three layers of intercostal muscles: outer (inspiration), internal (expiration) and innermost. The innermost runs across many ribs on their inner surface. There is a smaller neurovascular bundle that lies immediately superior to each rib.
• 35
  What movements occur during inspiration?
  Difficulty: Easy     Topic: Respiratory movements
  a

  Ribs depress and diaphgram contracts

  b

  Ribs depress and diaphgram relaxes

  c

  Ribs elevate and diaphragm contracts

  d

  Ribs elevate and diaphragm relaxed

  e

  None of the above
  Explanation: During inspiration the ribs elevate and expand laterally in a similar method to lifting a bucket handle. The diaphragm contracts downwards to increase intrathoracic volume and reduce intrathoracic pressure, causing inspiration. Accessory muscles of inspiration may also contract: scalenes, trapezium, sternocleidomastoid. The opposite process occurs during expiration and may be aided by contraction of the abdominal wall musculature.
• 36
  At what vertebral level does the inferior vena cava pass through the diaphragm?
  Difficulty: Easy     Topic: Diaphragm
  a

  T6

  b

  T8

  c

  T10

  d

  T12

  e

  L2
  Explanation: There are three openings in the diaphragm; with descending vertebral level the openings also become more posterior. The IVC passes through at T8 along with the right phrenic nerve. The oesophagus passes through at T10 with the vagus nerves. At T12 the aorta, azygous vein and thoracic duct pierce the diaphragm. The sympathetic chain also passes through the diaphragm posteriorly.
• 37
  Where do the pulmonary ligaments lie?
  Difficulty: Medium     Topic: Pulmonary ligaments
  a

  Apices, extending superiorly

  b

  Bases, extending inferiorly

  c

  Costo-phrenic angle, extending infero-laterally

  d

  Hila, extending inferiorly

  e

  Hila, extending posteriorly
  Explanation: The pulmonary ligaments are fused double folds of pleura found at the hila. They enclose the pulmonary vasculature and support the hilar structures during respiration. The pulmonary ligaments extend inferiorly and provide attachment for the hila.
• 38
  On a chest x-ray, what pathology does ‘blunting of costo-phrenic angles’ suggest?
  Difficulty: Medium     Topic: Chest X-ray
  a

  Lobar collapse

  b

  Malignancy

  c

  Pleural effusion

  d

  Pneumonia

  e

  Pneumothorax
  Explanation: The costo-phrenic angles are formed from the most inferior point of the pleural cavity, where the parietal pleura lining the diaphragm and thoracic wall meet. This is usually a small potential space between the parietal pleura and the lung viscera. If there is fluid in the pleural space (an effusion) it will settle at the costo-phrenic angle and the normal sharp angle is lost on CXR. Malignancy and pneumonias may also cause effusions but angle blunting is primarily a sign of effusion.
• 39
  Where is the horizontal fissure located?
  Difficulty: Medium     Topic: Lung fissures
  a

  Left side, at level of 3rd-4th rib anteriorly

  b

  Left side, at level of 5th-6th rib anteriorly

  c

  Right side at level of 3rd-4th rib anteriorly

  d

  Right side, at level of 4th-5th rib anteriorly

  e

  Right side, at level of 5th-6th rib anteriorly
  Explanation: The horizontal fissure is found in the right lung - it separates the upper and middle lobes. It begins at the level of the 4th rib anteriorly and is almost horizontal, being at the level of 5th rib in the mid-axillary line. The oblique fissure is present bilaterally - separating the upper and lower lobes. It runs from the level of T3 posterior to the 6th costal cartilage anteriorly.
• 40
  What lies immediately posterior to the lingular lobe?
  Difficulty: Easy     Topic: Lingular lobe
  a

  Aortic arch

  b

  Azygous vein

  c

  Left ventricle

  d

  Oesophagus

  e

  Right hilum
  Explanation: The lingular lobe is a projection of the upper lobe of the left lung. It lies immediately anterior to the left ventricle and some believe it to be a remnant that is present instead of the middle lobe found in the right lung.
• 41
  What form of epithelium is present in the conducting airways?
  Difficulty: Easy     Topic: Epithelia 1
  a

  Pseudostratified, ciliated

  b

  Simple columnar, ciliated

  c

  Simple cuboidal

  d

  Simple cuboidal, ciliated

  e

  Stratified squamous
  Explanation: Respiratory epithelium is present in all the conducting airways (those where gaseous exchange does not occur). Pseudostratified epithelium comprises a single layer of cuboidal epithelial cells but their nuclei are at different levels, giving a stratified appearance (one of many levels). Cilia are present on the surface of the epithelium. They are motile projections that beat rhythmically to move mucus to the pharynx for swallowing. Many goblet cells are also present for mucus production.
• 42
  Following chronic smoke exposure respiratory epithelium may undergo metaplasia to which epithelium type?
  Difficulty: Hard     Topic: Epithelia 2
  a

  Pseudostratified, ciliated

  b

  Simple columnar, ciliated

  c

  Simple cuboidal

  d

  Simple cuboidal, ciliated

  e

  Stratified squamous
  Explanation: Cigarette smoke is toxic to the respiratory epithelium and stimulates metaplasia, which is the changing of one fully differentiated epithelium to another fully differentiated epithelium. Respiratory epithelium most often changes to stratified squamous (non-keratinised), similar to that found in the mouth and upper oesophagus. This is a pre-malignant change and this may facilitate transformation into squamous cell carcinoma - the most common form of lung cancer.
• 43
  Which nerve passes posterior to the right hilum and through the diaphragm at the level of T10?
  Difficulty: Easy     Topic: Thoracic nerves
  a

  Long thoracic nerve of Bell

  b

  Phrenic nerve

  c

  Recurrent laryngeal nerve

  d

  Right vagus nerve

  e

  Subcostal nerve
  Explanation: The vagus nerves pass posterior to the lung hila. The right vagus forms the oesophageal plexus and then pass through the diaphragm at the oesophageal hiatus to innervate the abdominal viscera. The left vagus forms the cardiac plexus and contributes to the oesophageal plexus. The long thoracic nerve innervates serratus anterior on the lateral chest wall. The phrenic nerves pass anterior to the lung hila. The recurrent laryngeal nerves ascend as vagal branches from the subclavian (right) and aortic arch (left). The subcostal nerve is the name for the intercostal nerve for rib 12.
• 44
  What name is given to the airway following one division from terminal bronchioles?
  Difficulty: Easy     Topic: Airway divisions
  a

  Alveolar ducts

  b

  Alveolar sacs

  c

  Alveoli

  d

  Respiratory bronchioles

  e

  Terminal alveoli
  Explanation: Airways, from large to small: trachea - bronchi - lobar bronchi - segmental bronchi - bronchioles - terminal bronchioles (end of conducting airways) - respiratory bronchioles (beginning of exchanging airways) - alveolar ducts - alveolar sacs - alveoli.
• 45
  What comprises the diffusion barrier for gaseous exchange?
  Difficulty: Easy     Topic: Diffusion barrier
  a

  1x cell, 1x basement membrane

  b

  2x cells, 1x basement membrane

  c

  2x cells 1x basement membrane, connective tissue

  d

  2x cells, 2x basement membranes

  e

  2x cells, 2x basement membranes, connective tissue
  Explanation: The barrier is formed from a type 1 pneumocyte (a thin epithelial cell lining exchange airways), which sits on a basement membrane. This membrane is fused with that of the pulmonary capillaries, upon which there are endothelial cells. Therefore the barrier comprises two cells and one basement membrane. There is very little connective tissue in between.
• 46
  At the level of which rib does the inferior margin of the lungs lie in the mid-axillary line?
  Difficulty: Medium     Topic: Surface anatomy 1
  a

  7th

  b

  8th

  c

  9th

  d

  10th

  e

  11th
  Explanation: Anteriorly the lungs extend from the 6th costal cartilage, descend to the 8th rib in the mid-axillary line and are at the level of the 10th rib posteriorly. The parietal pleura runs a similar course but 2 rib levels lower, giving space for lung expansion
• 47
  What structure does Little’s area overlie?
  Difficulty: Medium     Topic: Little's area
  a

  Ethmoid bone

  b

  Nasal bone

  c

  Palatine bone

  d

  Septal cartilage

  e

  Vomer
  Explanation: Little's area (= Keisselbach's area) is an area on the nasal septum where there is anastamosis of 4 arteries. The area overlies the septal cartilage, therefore is anterior on the septum - underlying the soft part of the nose. This is the area that should be compressed during anterior epistaxis (nosebleeds). The vessels involved are: anterior and posterior ethmoidal arteries, Sphenopalatine artery, septal branch of the labial artery and a branch of the greater palatine artery.
• 48
  Which blood vessel is most commonly implicated in posterior epistaxis?
  Difficulty: Hard     Topic: Epistaxis
  a

  Anterior ethmoidal artery

  b

  Facial artery

  c

  Greater palatine artery

  d

  Septal branch of superior labial artery

  e

  Sphenopalatine artery
  Explanation: The sphenopalatine artery is a large artery that runs on the posterior wall of the nasopharynx to supply parts of the nasal septum, it is joined by the posterior ethmoidal artery and then anastamoses in Little's area. Posterior epistaxis (nosebleeds) is that where the site of bleeding cannot be seen on nasoscopy. It can be severe and require blood transfusions.
• 49
  Which paranasal sinus does the superior meatus communicate with?
  Difficulty: Easy     Topic: Paranasal sinuses 1
  a

  Ethmoidal

  b

  Frontal

  c

  Mastoid

  d

  Maxillary

  e

  Sphenoidal
  Explanation: There are the three meati that drain the paranasal sinuses. The superior meatus drains the (posterior) ethmoidal air cells. The middle meatus drains the maxillary and frontal (plus the middle ethmoidal sinus). The inferior meatus is the opening of the naso-lacrimal duct. In addition, there is the spheno-ethmoidal recess that drains the sphenoid sinus.
• 50
  Which paranasal sinus lies immediately posterior to the superior nasal conchae and anterior to the sella turcia?
  Difficulty: Easy     Topic: Paranasal sinuses 2
  a

  Ethmoidal

  b

  Frontal

  c

  Mastoid

  d

  Maxillary

  e

  Sphenoidal
  Explanation: The sphenoidal sinuses lie postero-superior to the nasal cavity. They are immediately posterior to the superior conchae, anterior to the pituitary and medial to the cavernous sinus. The pituitary sits in the sella turcia, also known as the pituitary fossa. They are used as a route of surgical access to the pituitary gland, passing through the nasal cavity.
• 51
  What structure lies lateral to the ethmoidal air cells?
  Difficulty: Medium     Topic: Paranasal sinuses 3
  a

  Cavernous sinus

  b

  Middle conchae

  c

  Nasal cavity

  d

  Orbit

  e

  Superior conchae
  Explanation: The ethmoidal air sinuses are multiple interconnecting small sinuses located in the ethmoid bone. They are found supero-laterally in the nasal cavity and immediately lateral (and superior) to them are the orbits. During surgery on the ethmoidal air cells care must be taken not to damage the eyes. The cavernous (dural venous) sinus lies lateral the sphenoid (air) sinus. The conchae lie within the nasal cavity.
• 52
  Where is the ventricle of the larynx?
  Difficulty: Easy     Topic: Larynx 1
  a

  Between the tongue and the epiglottis

  b

  Between the vocal cords and the vestibular folds

  c

  Inferior to the vocal cords

  d

  Lateral to the epiglottis

  e

  Superior to the vestibular folds
  Explanation: The larynx can be divided into three areas by the true and false cords. The vestibule is the area above the false cords (also called the vestibular folds). Between the false cords and the inferior true (vocal) cords is the ventricle, also called the sinus. The area below the vocal cords is the trachea. These three regions can also be called the supra-, intra- and infra-glottic areas. The rima glottidis is the space lateral to the epiglottis at the base of the tongue.
• 53
  Between which three structures are the (true) vocal cords suspended?
  Difficulty: Easy     Topic: Larynx 2
  a

  Arytenoid cartilage, cricoid and thyroid cartilage

  b

  Arytenoid cartilage, thyroid cartilage and epiglottis

  c

  Arytenoid cartilage, epiglottis and cricoid cartilage

  d

  Cricoid cartilage, epiglottis and thyroid cartilage

  e

  Epiglottis, hyoid and thyroid cartilage
  Explanation: The vocal cords are formed from the free edge of the cricothyroid membrane, which is thickened and covered in mucosa. They are also attached to the arytenoid cartilage, which comprises up to 40% of the vocal cords. Movement of the arytenoid cartilages causes movement in the vocal cords.
• 54
  Which muscle contracts to cause closure of the laryngeal opening during swallowing?
  Difficulty: Medium     Topic: Larynx 3
  a

  Aryepiglotticus

  b

  Crico-thyroid

  c

  Inferior constrictor

  d

  Posterior crico-arytenoid

  e

  Thyro-arytenoids
  Explanation: The epiglottis is an elastic piece of cartilage that sits at the posterior of the tongue and is attached to the hyoid by a number of ligaments. It is bound to the arytenoid cartilage by the quadrangular membrane (aryepiglottic muscle). This muscle contracts during swallowing to close the epiglottis over the laryngeal inlet.
• 55
  In an emergency, when an upper airway is lost, which structure may be punctured to give a temporary airway?
  Difficulty: Easy     Topic: Larynx 4
  a

  Crico-thyroid membrane

  b

  Cricoid cartilage

  c

  Thyro-hyoid membrane

  d

  Thyroid cartilage

  e

  Trachea
  Explanation: The cricothyroid membrane is a ligament running between the two cartilages. It may be palpated on the anterior aspect of the neck and in an emergency it can be pierced to give a temporary airway. A tracheostomy is not performed as an emergency procedure and it is made over 2nd-4th cartilage rings on the trachea for a semi-permanent airway.
• 56
  What is the respiratory quotient?
  Difficulty: Easy     Topic: Respiratory quotient
  a

  Amount of ventilation needed to maintain oxygen levels

  b

  Percentage that one gas exerts in a mix of gases

  c

  Percentage of ventilation that results in gaseous exchange

  d

  Ratio between oxygen use and carbon dioxide production

  e

  Total gas exchange per minute
  Explanation: The respiratory quotient is the ratio between oxygen consumption (VO2) and carbon dioxide production (VCO2). The respiratory quotient, RQ = VCO2/VO2. This is dependent on the energy source used but is normally 0.8. The aim of the respiratory system is to match alveolar ventilation to metabolic rate and therefore CO2 production / O2 requirement.
• 57
  Which law describes the inversely proportional relationship between the volume and pressure of a closed system?
  Difficulty: Medium     Topic: Eponymous laws
  a

  Boyle

  b

  Dalton

  c

  Graham

  d

  Laplace

  e

  Pouiselle
  Explanation: The partial pressure of a gas is the force exerted by any one gas (alone or in a mixture) against the walls of its container. Boyle's law states that: P1 x V1 = P2 x V2, so that for one closed system, changing its volume causes an inversely proportional change in pressure. Dalton's law: total pressure is the sum of all partial pressures. Graham's law describes the factors affecting the diffusion of a gas through the gaseous phase. Laplace's law describes the relationship between internal pressure of a sphere and its diameter. Pouiselle's law describes the factors influencing resistance to laminar flow in a tube.
• 58
  What is the velocity and variance in partial pressure of gases in alveoli?
  Difficulty: Medium     Topic: Partial pressures and velocity
  a

  High velocity, moderate partial pressure changes

  b

  High velocity, near constant partial pressures

  c

  Moderate velocity, moderate partial pressure changes

  d

  Very low velocity, large partial pressure changes

  e

  Very low velocity, near constant partial pressures
  Explanation: At any one division in the respiratory system flow is equal. Flow = velocity x total cross-sectional area. Total cross-sectional area is very large at alveolar level, consequently the velocity is almost zero. The movement of gases is predominantly diffusion in alveoli. Therefore alveolar partial pressures of gases are almost constant throughout normal inspiration and expiration. The opposite is true in the upper airways, where there is: small total cross-sectional area, high velocity, high resistance and large partial pressure changes.
• 59
  What is the term given to the volume of air left in the lungs at the end of expiration of a normal, quiet breath?
  Difficulty: Easy     Topic: Lung volumes 1
  a

  Expiratory reserve volume

  b

  Functional residual capacity

  c

  Residual volume

  d

  Tidal volume

  e

  Vital capacity
  Explanation: Normally, the end of a quiet breath leaves functional residual capacity in the lungs. This is the term given to the volume present when transmembrane pressure is zero. Energy is expended to generate a positive (distending) transmembrane pressure for inspiration, and then the lungs recoil to FRC at the end of expiration. FRC = expiratory reserve volume + residual volume.