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CRL Quiz 1 2008

1

Which one of the following statements regarding the blood vessels is correct?


  Large arteries are important determinants of total peripheral resistance.

  The blood flow velocity is greatest in the capillaries.

  The large veins act as diastolic pumps.

  Blood in the pulmonary vein is red.


A is incorrect: The major determinants of TPR are the small arteries. B is incorrect: Because of the large total cross-sectional area at the level of the capillaries, flow velocity is slowest. C is incorrect: The large arteries are the diastolic pumps because elastic in their walls recoils during diastole and helps propel blood to the organs. The large veins act as reservoirs. D is correct: The pulmonary vein carries oxygenated blood to the right atrium.

2

Which one of the following statements regarding blood pressure is NOT CORRECT?


  If the small arteries constrict, the mean arterial pressure will rise.

  If the heart rate and stroke volume increase, the mean arterial pressure will rise.

  Pulse pressure is the difference between systolic blood pressure and diastolic blood pressure.

  Pulse pressure will be lower if the large arteries are less compliant.


A is correct: Small arteries determine TPR and MAP = CO x TPR. B is correct: HR and SV determine CO and MAP = CO x TPR. C is correct: PP = SBP - DBP D is incorrect: Reduced compliance will increase PP

3

Which one of the following statements regarding the diaphragm is correct?


  The diaphragm moves upwards when it contracts.

  The muscular portion of the diaphragm is pierced by the inferior vena cava.

  The right hemidiaphragm domes higher than the left hemidiaphragm.

  The superior surface of the diaphragm is covered by visceral pleura.


A is incorrect: The muscular fibres of the diaphragm pull the central tendon downwards during contraction. B is incorrect: The caval orifice at the level of T8 is through the central tendon and thus is pulled open during inspiration which promotes venous return. C is correct: The right hemidiaphragm domes higher than the left due to the underlying liver. D is incorrect: The diaphragmatic part of the parietal pleura lines the superior surface of the diaphragm.

4

Which one of the following statements regarding the right lung is correct?


  The mediastinal surface bears a deep impression created by the arch of the aorta.

  The right pulmonary artery usually enters the hilum above the right main bronchus.

  There is no horizontal fissure.

  The lower lobe is best auscultated via the posterior chest wall.


A is incorrect: The mediastinal surface of the right lung bears impressions of venous structures. B is incorrect: The right upper lobe bronchus and bronchus intermedius enter the hilum as 2 separate structures posterior to the corresponding branches of the right pulmonary artery. C is incorrect: The right lung has 3 lobes divided by oblique and horizontal fissures. D is correct: The lower lobe lies posteroinferior to the upper and middle lobes.

5

Which one of the following statements regarding the function of the lungs is correct?


  The lungs humidify inspired air and the water vapour subsequently passes into the alveolar capillaries by passive diffusion.

  The lungs exchange oxygen and carbon dioxide in equal amounts.

  The capacity of the lungs to exchange oxygen and carbon dioxide can increase markedly during exercise compared to rest.

  The main function of the lungs is to filter venous blood.


A is incorrect: 2 statements - neither correct - ie the air is humidified, but in the upper airway not the lungs and it is not the function of the lungs to diffuse water vapour from the alveoli into the capillaries. B is incorrect: The amount of O2 and CO2 exchanged depends on the respiratory exchange ratio (or respiratory quotient) ie the rate of CO2 production divided by the rate of O2 consumption. It depends on metabolism - at rest approx 0.8 and during heavy exercise 1.2 or higher. D is incorrect: Not the main function.

6

Which upper airway muscle dilates the glottis?


  Thyroarytenoid.

  Genioglossus.

  Posterior Cricoarytenoid.

  Geniohyoid.

  Tensor Palatini.


Posterior Croco-arytenoids abduct the vocal cords to dilate the glottis. There is pre-activation of these muscles just before the respiratory pump muscles commence inspiration. This is to stabilise the upper airway and reduce its resistance in preparation for the negative pressure of inspiration.

7

A 60 year old male smoker (50 pack years) complains of dyspnoea on exertion. You request lung function assessment. The least likely finding will be:


  Low static lung volumes.

  High resistive work of breathing.

  Low maximal flow rate.

  An obstructive ventilatory defect.

  Reduced FEV1.


In COPD and other obstructive lung diseases , the static lung volumes (TLC, FRC, RV) tend to be increased due to loss of elastic recoil (Emphysema) and gas trapping due to narrowing of small airways (Chronic Bronchitis). Hence reduced static lung volumes (A) is wrong.

8

Which one of the following statements regarding the pathology of allergic asthma is NOT CORRECT?


  Plugs composed entirely of cell break-down products may form in the bronchi.

  Psuedo thickening of the basement membrane is evident.

  Eosinophils and lymphocytes infiltrate the mucosa and submucosa.

  Increased smooth muscle is present.


Plugs are predominantly composed of mucus and plasma proteins.

9

Which one of the following does NOT influence airways resistance in asthmatics?


  The velocity of smooth muscle shortening.

  The stage of the respiratory cycle (inspiration/expiration).

  A recent deep inspiration.

  A short-acting beta2-adrenoceptor agonist.

  Endogenous adrenaline.


The velocity of shortening is significant as an influence on airways resistance. as the more rapidly the shortening of muscle , the greater the likelihood of airway closure during the expiratory phase of the respiratory cycle. The stage of cycle influences resistance as during expiration the load on smooth muscle is reduced as the parenchymal alveoli deflate and release the restraint that they apply to intra-thoracic airways to which they attach. Thus, resistance is greater during expiration than inspiration. In asthma the inhalation of a short-acting beta 2 agonist is expected to decrease airways resistance. In fact, one of the diagnostic features of asthma is the reversibility of the airway obstruction upon treatment with a short-acting bronchodilator. As adrenaline is the major endogenous ligand for the airway beta2 adrenoceptors and the asthmatic generally has some degree of elevated airway resistance, the resistance increase is partially offset by the action of adrenaline. Clearly, however, further effect is possible, as synthetic exogenous beta2 agonists are also able to decrease airways resistance. A recent inspiration has a detectable bronchodilator effect in non-asthmatic individuals but not in asthmatics. The reasons for this difference are the source of speculation but no broadly accepted explanation has yet been advanced.

10

With regard to chest radiography, which of the following statements is correct?


  The optimum patient position is erect AP (antero-posterior).

  The aetiology of the "silhouette sign" is the interaction of X-rays with body tissues of differing electron density.

  Normal oblique fissures can be visualized on the anterior view.

  The superior mediastinum is defined as being above the level of the pulmonary hila.

  The normal cardio-thoracic ratio in an adult (i.e. ratio of maximum transverse cardiac to thoracic cavity widths) is > 50% on an optimized chest radiograph.


A is incorrect. The optimum patient position is erect PA (postero-anterior). C is incorrect. The normal oblique fissure is only visible on the lateral view D is incorrect. The superior mediastinum is defined as being above a plane between the MSJ and T 4/5 disc which corresponds with the bifurcation of the trachea and therefore lies above the pulmonary hila. E is incorrect. The ratio is < 50%

11

Which one of the following statements concerning the alveolar capillary membrane is correct?


  It is formed mainly by type 2 alveolar cells.

  There is a layer of surfactant on the endothelial side.

  A sodium pump in the alveolar cells transports oxygen into the blood.

  Fluid normally passes from the capillaries into the lymphatics.


A is incorrect: Mainly type 1 cells. B is incorrect: On the epithelial (alveolar) side. C is incorrect: Transports Na (and water)

12

Which one of the following statements concerning gas exchange is correct?


  The FiO2 of air at sea level is 150mmHg.

  The PAO2 at sea level in a young person with a PaCO2 of 40mmHg is about 100mmHg.

  The PvCO2 in a normal person is about 60mmHg.

  High V/Q units occur in normal people at the lung bases.


A is incorrect: FiO2 of air is 0.21 (PiO2 is about 150 mmHg) C is incorrect: PvCO2 is about 46 mmHg D is incorrect: Lung apices

13

Which one of the following statements concerning blood carriage of oxygen and carbon dioxide is correct?


  Blood oxygen content in a normal person in the pulmonary veins is about 20 ml of oxygen per 100 ml of blood.

  CO2 is carried in blood mostly dissolved in serum.

  Haemoglobin concentration does not affect blood oxygen content.

  SaO2 is directly proportional to PaO2.


B is incorrect: Mostly as HCO3 but also as CO2 attached to proteins and CO2 dissolved in blood. C is incorrect: Yes it does. D is incorrect: No it isn't.

14

Which one of the following statements concerning diffuse alveolar damage (DAD) is correct?


  DAD is associated with decreased permeability of alveolar capillaries.

  Pulmonary infection and aspiration of gastric contents are common causes of DAD.

  Type 1 pneumocytes proliferate in response to DAD.

  A hyaline membrane accumulates within the alveolar wall in DAD.

  DAD does not progress to pulmonary fibrosis.


A is incorrect: As alveolar capillary permeability increases. C is incorrect: As type 2 pneumocytes proliferate, type 1 become necrotic. D is incorrect: As the hyaline membrane accumulates on the surface, rather than within the alveolar wall. E is incorrect: As DAD does progress to pulmonary fibrosis if the patient survives. B is correct: Pulmonary infection and gastric aspiration are amongst the most common causes of DAD.

15

Which one of the following statements regarding the external intercostal muscle is correct?


  Its fibres are directed posteroinferiorly.

  It is a muscle of expiration.

  The intercostal neurovascular structures lie superficial to it.

  In the anterior part of the intercostal space, external intercostal muscle fibres are replaced by membrane.


A is incorrect: The fibres are directed anteroinferiorly B is incorrect: When external intercostal contracts it elevates the ribs and hence is a muscle on inspiration. C is incorrect: The neurovascular plane lies between internal and innermost intercostal ie. deep to external intercostal. D is correct: The external intercostal membrane replaces external intercostal muscle fibres in the anterior part of the space.