4- Thorax MSQs Only (2)

Question 1

1- A 63 year old man is undergoing a right pneumonectomy for carcinoma of the bronchus. As the surgeons approach the root of the lung, which structure will lie most posteriorly (in the anatomical plane)?

Answer 1

Vagus nerve

The vagus nerve is the most posteriorly located structure at the lung root. The phrenic nerve lies
most anteriorly.

Question 2

3- How many valves lie between the superior vena cava and the right atrium?

Answer 2

None ( Right)

One

Two

Three

Four

There are no valves which is why it is relatively easy to insert a CVP line from the internal jugular vein into the right atrium.

Question 3

2- During a tricuspid valve repair the right atrium is opened, following establishment of cardiopulmonary bypass. Which of the following structures do not lie within the right atrium?

Answer 3

Trabeculae carnae

Structures within the right atrium:
· Musculi pectinati
· Crista terminalis
. Opening of the coronary sinus
· Fossa ovalis

The trabeculae carnae are located in the right ventricle.

Question 4

4- A 63 year old man is undergoing an upper GI endoscopy for dysphagia. At 33 cm (from the incisors) a malignant looking stricture is encountered. The endoscopist attempts a balloon dilatation.Unfortunately the tumour splits through the oesophageal wall. Into which region will the oesophageal contents now drain?

Answer 4

Posterior mediastinum

At this position the oesophagus is still likely to be intrathoracic and located in the posterior mediastinum.

Question 5

5- The thebesian veins contribute to the venous drainage of the heart. Into which of the following structures do they primarily drain?

Answer 5

Atrium

The thebesian veins are numerous small veins running over the surface of the heart they drain into the heart itself. Usually this is to the atrium directly.

Question 6

6- During a gangland gunfight a man is shot in the chest. The bullet passes through the posterior mediastinum (from left to right). Which of the following structures is least likely to be injured

Answer 6

Arch of the azygos vein

The arch of the azygos vein lies in the middle mediastinum.

Question 6

7- What is embryological origin of the pulmonary artery?

Answer 6

Sixth pharyngeal arch

The proximal part of the sixth right pharyngeal arch gives origin to the right pulmonary artery. The distal part gives origin to the left pulmonary artery and the ductus arteriosus.

Question 7

8- A 72 year old man with carcinoma of the lung is undergoing a left pneumonectomy. The left
main bronchus is divided. Which of the following thoracic vertebrae lies posterior to this structure?

Answer 7

T6

The left main bronchus lies at T6. Topographical anatomy of the thorax is important as it
helps surgeons to predict the likely structures to be injured in trauma scenarios (so popular
with examiners)

Question 8

9- Which of the following structures accompanies the posterior interventricular artery within the
posterior interventricular groove?

Answer 8

Middle cardiac vein

Question 9

10- Which nerve directly innervates the sinoatrial node?

Answer 9

Superior cardiac nerve
Right vagus nerve
Left vagus nerve
Inferior cardiac nerve
None of the above (Right)

No single one of the above nerves is responsible for direct cardiac innervation (which those who have handled the heart surgically will appreciate).
The heart receives its nerves from the superficial and deep cardiac plexuses. The cardiac plexuses send small branches to the heart along the major vessels, continuing with the right and left coronary arteries. The vagal efferent fibres emerge from the brainstem in the roots of the vagus and accessory nerves, and run to ganglia in the cardiac plexuses and within the heart itself.

The background vagal discharge serves to limit heart rate, and loss of this background vagal tone accounts for the higher resting heart rate seen following cardiac transplant.

Question 10

11- Which of the following is not contained within the middle mediastinum?

Answer 10

Thoracic duct

The thoracic duct lies within the posterior and superior mediastinum.

Question 11

12- A 28 year old man is shot in the right chest and develops a right haemothorax necessitating a thoracotomy. The surgeons decide to place a vascular clamp across the hilum of the right lung. Which of the following structures will lie most anteriorly at this point?

Answer 11

Phrenic nerve

The phrenic nerve lies anteriorly at the root of the right lung.

Question 12

13- How many fissures are present within the right lung?

Answer 12

Two

The right lung has an oblique and horizontal fissure. The upper oblique fissure separates the inferior from the middle and upper lobes. The short horizontal fissure separates the superior and middle lobes.

Question 13

14- A 23 year old man is due to undergo a mitral valve repair for mitral regurgitation. Which of the following is a feature of the mitral valve?

Answer 13

Its closure is marked by the first heart sound

The mitral valve is best auscultated over the cardiac apex, where its closure marks the first heart sound.
It has only two cusps. These are attached to chordae tendinae which themselves are linked to the wall of the ventricle by the papillary muscles.

Question 14

15- During the repair of an atrial septal defect the surgeons note that blood starts to leak from the coronary sinus. Which structure forms the largest tributary of the coronary sinus?

Answer 14

Great cardiac vein

The great cardiac vein runs in the anterior interventricular groove, and is the largest tributary of the coronary sinus. The thebesian veins drain into the heart directly.

Question 15

15- Which of the following overlies the outer muscular layer of the intrathoracic oesophagus?

Answer 15

Loose connective tissue

The oesophagus has no serosal covering and hence holds sutures poorly. The Auerbach’s and Meissner’s nerve plexuses lie in between the longitudinal and circular muscle layers and submucosally.
The sub mucosal location of the Meissner’s nerve plexus facilitates its sensory role.

Question 16

17- Which of the following types of epithelium lines the lumenal surface of the normal oesophagus?

Answer 16

Non keratinised stratified squamous epithelium

The oesphagus is lined by non keratinised stratified squamous epithelium. Changes to glandular type
epithelium occur as part of metaplastic processes in reflux.

Question 17

18- Which of the following is true in connection with the phrenic nerves?

Answer 17

They both lie anterior to the hilum of the lungs

C3,4,5
Keeps the diaphragm alive!

They both lie anterior to the hilum of the lung. The phrenic nerves have both motor and sensory functions. For this reason sub diaphragmatic pathology may cause referred pain to the shoulder.

Question 18

19- A 23 year old man is shot in the chest during a robbery. The left lung is lacerated and is bleeding. An emergency thoracotomy is performed. The surgeons place a clamp over the hilum of the left lung. Which of the following structures lies most anteriorly at this level?

Answer 18

Phrenic nerve

The phrenic nerve lies anteriorly at this point. The vagus passes anteriorly and then arches backwards immediately superior to the root of the left bronchus, giving off the recurrent laryngeal nerve as it does so.

Question 19

20- A 43 year old man is reviewed in the clinic following a cardiac operation. A chest x-ray is performed and a circular radio-opaque structure is noted medial aspect of the 4th intercostal space on the left. Which of the following procedures is the patient most likely to have undergone?

Answer 19

Mitral valve replacement with metallic valve

Question 20

21- Which structure is least likely to be found at the level of the sternal angle?

Answer 20

Left brachiocephalic vein

The left brachiocephalic vein lies posterior to the manubrium, at the level of its upper border. The sternal angle refers to the transition between manubrium and sternum and therefore will not include the left brachiocephalic vein.

Question 21

22- A 72 year old man presents with haemoptysis and undergoes a bronchoscopy. The carina is noted to be widened. At which level does the trachea bifurcate?

Answer 21

T5

The trachea bifurcates at the level of the fifth thoracic vertebra. Or the sixth in tall subjects.

Question 22

23- Which of the following pairings are incorrect?

Answer 22

Termination of dural sac and L4

Vena cava T8 (eight letters)
Oesophagus T10 (ten letters)
Aortic hiatus T12 (twelve letters)

It terminates at S2, which is why it is safe to undertake an LP at L4/5 levels. The spinal cord itself terminates at L1.

Question 22

24- An 18 year old lady with troublesome hyperhidrosis of the hands and arms is due to undergo a sympathectomy to treat the condition. Which of the following should the surgeons divide to most effectively treat her condition?

Answer 22

Sympathetic ganglia at T2 and T3

To treat hyperhidrosis the sympathetic ganglia at T2 and T3 should be divided. Dividing the other structures listed would either carry a risk of Horners syndrome or be ineffective.

Question 23

26- The right and left pulmonary arteries are derived from which of the following embryological aortic arches?

Answer 23

Sixth

Pulmonary vessels develop from the sixth arch

Question 24

25- A 53 year old man with a carcinoma of the lower third of the oesophagus is undergoing an oesophagogastrectomy. As the surgeons mobilise the mid part of the oesophagus, where are they most likely to encounter the thoracic duct?

Answer 24

Posterior to the oesophagus

The thoracic duct lies posterior to the oesophagus and passes to the left at the level of the Angle of Louis. It exits the thorax at T12 together with the aorta.

Question 25

28- A patient has a chest drain insertion. There is fresh blood at the chest drain insertion area. Which vessel has been damaged?

Answer 25

Intercostal artery

The intercostal vein is more superior than the artery and is thus slightly less susceptible to injury.

Within the intercostal spaces there are thin, strong muscles, intercostal vessels, nerves and lymphatics.
There are 3 intercostal muscle layers corresponding to the lateral abdominal wall; external, internal, innermost intercostals. At the mid axillary line there are thin intracostals which is an extension of the internal intercostal muscle. In each intercostal space lies the neurovascular bundle, comprising, from superior to inferiorly; the posterior intercostal vein, artery and nerve, lying protected in the subcostal groove of the rib above and situated between the second and third layer of the intercostal muscles.
These blood vessels anastomose anteriorly with the anterior intercostal vessels, which arise from the internal thoracic artery and vein.

Question 26

27- A 72 year old man is undergoing a left pneumonectomy for carcinoma of the bronchus. As the surgeons approach the root of the lung, which structure will lie most anteriorly (in the anatomical plane)?

Answer 26

Phrenic nerve

The phrenic nerve is the most anteriorly located structure in the lung root. The vagus nerve lies most
posteriorly.

Question 27

29- Which of the following are not generally supplied by the right coronary artery?

Answer 27

The circumflex artery

The circumflex artery is generally a branch of the left coronary artery.

Question 28

30- During an Ivor Lewis Oesophagectomy for carcinoma of the lower third of the oesophagus which structure is divided to allow mobilisation of the oesophagus?

Answer 28

Azygos vein

The azygos vein is routinely divided during an oesophagectomy to allow mobilisation. It arches anteriorly to insert into the SVC on the right hand side.

Question 29

31- A 34 year old male is being examined in the pre-operative assessment clinic. A murmur is identified in the 4th intercostal space just next to the left side of the sternum. From where is it most likely to have originated?

Answer 29

Tricuspid valve

The tricuspid valve is generally referred to being best auscultated adjacent to the sternum. The plane of projected sound from the mitral area is best heard in the region of the cadiac apex.

Question 30

32- What are the boundaries of the ‘safe triangle’ for chest drain insertion?

Answer 30

Bounded by latissimus dorsi, pectoralis major, line superior to the nipple and apex at the axilla

Question 31

A 63 year old man is undergoing a coronary artery bypass procedure. During the median sternotomy which structure would routinely require division?

Answer 31

Interclavicular ligament

The interclavicular ligament lies at the upper end of a median sternotomy and is routinely divided to provide access. The pleural reflections are often encountered and should not be intentionally divided, if they are, then a chest drain will need to be inserted on the affected side as collections may then accumulate in the pleural cavity. Other structures encountered include the pectoralis major muscles, again if the incision is truly midline then these should not require formal division. The close relationship of the brachiocephalic vein should be borne in mind and it should be avoided, iatrogenic injury to this structure will result in considerable haemorrhage.

Question 32

34- Which of the following statements relating to the right phrenic nerve is false?

Answer 32

It lies deep to the prevertebral layer of deep cervical fascia

Crosses posterior to the 2nd part of the subclavian artery (Right)

It runs on the anterior surface of the anterior scalene muscle

On the right side it leaves the mediastinum via the vena cava hiatus at a level of T8

The right phrenic nerve passes over the right atrium

Question 33

35- Where is the centre of the ‘safe triangle’ for chest drain insertion located?

Answer 33

5th intercostal space, mid axillary line

‘Safe Triangle’ for chest drain insertion:
5th intercostal space, mid axillary

Question 34

36- Following an oesophagogastrectomy the surgeons will anastomose the oesophageal remnant to the stomach, which of the following is not part of the layers that comprise the oesophageal wall?

Answer 34

Serosa

The oesophageal wall lacks the serosa layer
The wall lacks a serosa which can make the wall hold sutures less securely.

Question 35

37- A 23 year old lady with troublesome axillary hyperhidrosis is undergoing a thorascopic sympathectomy to treat the condition. Which of the following structures will need to be divided to access the sympathetic trunk?

Answer 35

Parietal pleura

The sympathetic chain lies posterior to the parietal pleura. During a thorascopic sympathectomy this structure will need to be divided. The intercostal vessels lie posteriorly. They may be damaged with troublesome bleeding but otherwise are best left alone as deliberate division will not improve surgical access

Question 36

38- Inspection of the left ventricle reveals all except which of the following?

Answer 36

Conus arteriosus

The conus arteriosus (infundibulum) is the smooth walled outflow tract of the right ventricle leading to the pulmonary trunk.

Question 37

39- A 22 year old man is stabbed in the chest at the level of the junction between the sternum and manubrium. Which structure is at greatest risk?

Answer 37

Aortic arch

Mneumoic for lower sternal angle:
Red, white, blue and air 2
Aortic orifice of diaphragm red- arch of aorta
white- the thoracic duct crosses at the midline
blue- azygous joins the svc
air- tracheal bifurcation
2- costal cartilage of the second rib

At the level of the Angle of Louis (Manubriosternal angle), is the surface marking for the aortic arch. The oesophagus is posteriorly located and at less risk.

Question 38

40- Which of the structures listed below are not located within the mediastinum?

Answer 38

Vertebral bodies

The vertebral bodies lie outside of the mediastinum, as do the lungs.

Question 39

41- An individual is noted to have a left sided superior vena cava. By which pathway is blood from this system most likely to enter the heart?

Answer 39

Via the coronary sinus

Persistent left superior vena cava is the most common anomaly of the thoracic venous system. It is
prevalent in 0.3% of the population and is a benign entity of failed involution during embryogenesis.

Question 40

42- A 33 year old man is stabbed in the right chest and undergoes a thoracotomy. The right lung is mobilised and the pleural reflection at the lung hilum is opened. Which of the structures listed below does not lie within this region?

Answer 40

Pulmonary artery

Azygos vein ( Right)

Pulmonary vein

Bronchus

None of the above

The pleural reflections encase the hilum of the lung and continue inferiorly as the pulmonary ligament. It encases the pulmonary vessels and bronchus. The azygos vein is not contained within it.

Question 41

43- Where are the greatest proportion of musculi pectinati found?

Answer 41

Right atrium

The musculi pectinati are found in the atria, hence the reason that the atrial walls in the right atrium are
irregular anteriorly.
The musculi pectinati of the atria are internal muscular ridges on the anterolateral surface of the chambers and they are only present in the area derived from the embryological true atrium.

Question 42

44- During a neck dissection, a nerve is noted to pass posterior to the medial aspect of the first rib. Which of the nerves listed below is this most likely to be?

Answer 42

Phrenic nerve

The key point is that the phrenic nerve runs posterior to the medial aspect of the first rib. Superiorly, it lies on the surface of scalenus anterior.

Question 43

45- A patient presents with superior vena caval obstruction. How many collateral circulations exist as alternative pathways of venous return?

Answer 43

Four

There are 4 collateral venous systems:
· Azygos venous system
· Internal mammary venous pathway
. Long thoracic venous system with connections to the femoral and vertebral veins (2 pathways)

Despite this, venous hypertension still occurs.

Question 44

46- Which of the structures listed below accompanies the aorta as it traverses the aortic hiatus?

Answer 44

Thoracic duct

The aorta is accompanied by the thoracic duct as it traverses the aortic hiatus. The vagal trunks accompany the oesophagus which passes through the muscular part of the diaphragm on the right. The right phrenic nerve accompanies the IVC as it passes through the caval opening. The left phrenic nerve passes through the muscular part of the diaphragm anterior to the central tendon on the left.

Question 45

47- A 5 year old boy is playing with some small ball bearings. Unfortunately, he inhales one. To which of the following lung regions is the ball most likely to settle?

Answer 45

Right lower lobe

As the most dependent part of the right lung a small object is most likely to lodge here. Most objects will preferentially enter the right lung owing to the angle the right main bronchus takes from the trachea.

Question 46

48- Which of the following fascial structures encases the apex of the lungs?

Answer 46

Sibsons fascia

Sibson’s fascia overlies the apices of both lungs
The suprapleural fascia (Sibson’s fascia) runs from C7 to the first rib and overlies the apex of both lungs.It lies between the parietal pleura and the thoracic cage.