MRCS a Paper 1 SBAs Applied Basic Sci 2e

MRCS Part A: Paper 1 SBAs in Applied Basic Science Second Edition Shahzad G Raja BSc, MBBS, MRCS, FRCS(CTh) Specialist Registrar in Cardiothoracic Surgery Department of Paediatric Cardiothoracic Surgery Great Ormond Street Hospital London

Introduction This revised and updated second edition of Intercollegiate MRCS: 300 Single Best Answer Questions in Applied Basic Sciences not only has a new title but also includes 60 new questions that conform to the current IMRCS examination format. The revised edition has been updated to remain current with the syllabus and with the subtle changes in the examination philosophy. There are many single best answer guides available for the IMRCS candidates. However, MRCS Part A Paper 1: Single Best Answer Questions in Applied Basic Sciences is the only title that provides ‘real’-type practice questions at the appropriate level for candidates, similar to the exam. The 360 questions in this book are divided into three major sections, namely Anatomy, Physiology, and Pathology; each section has 120 questions with answers and detailed teaching notes. The questions in the book are designed to enable candidates to master large amounts of information in a limited amount of time as well as review important topics quickly and easily. There is a natural tendency to avoid the harder and more confusing topics, but rather than avoiding these, I have deliberately included them so that the candidates can use these to their advantage; everyone will get the easy questions right, but the students who enter the examination having done the more difficult questions should not just pass, but pass well. I am hopeful that this revised edition will prove more useful for the IMRCS candidates as it has been prepared in direct response to the feedback from the candidates who have sat the IMRCS examination. It is expected that I will be guided by constructive criticism and useful suggestions in the future as well. Last but not the least, I take this opportunity to acknowledge the numerous sources and resources which have been used in the preparation of this revised edition. Shahzad G Raja

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anatomy

Section 1: Anatomy Questions For each question given below choose the SINGLE BEST option.

1.1

Following tonsillectomy, a patient noted loss of general sensation and taste from the posterior one-third of the tongue. It could be assumed that the nerve that was injured was a branch of the:

m m m m m

A

Facial nerve

B

Glossopharyngeal nerve

C

Hypoglossal nerve

D

Lingual nerve

E

Vagus nerve

1.2

Which one of the following arteries can be felt pulsating at the lower border of the mandible just anterior to the masseter muscle?

m m m m m

A

Facial artery

B

Lingual artery

C

Maxillary artery

D

Superficial temporal artery

E

Transverse facial artery

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MRCS Part A: Paper 1 SBAs in Applied Basic Science, Second Edition

anatomy

1.3

Which one of the following structures lies parallel and immediately deep to the carotid sheath in the neck?

m m m m m

A

Internal jugular vein

B

Superior ramus of the ansa cervicalis

C

Sympathetic trunk

D

Trachea

E

Vagus nerve

1.4

While mobilising the second part of the duodenum a vital structure got injured. Which one of the following structures is it most likely to be?

m m m m m

A

Gallbladder

B

Hilum of the right kidney

C

Left lobe of the liver

D

Superior mesenteric artery

E

Transverse colon

1.5

Injury to which one of the following nerves will result in an inability to dorsiflex and evert the foot?

m m m m m

A

Common peroneal nerve

B

Deep peroneal nerve

C

Femoral nerve

D

Superficial peroneal nerve

E

Tibial nerve

4

Questions

Which one of the following is the most superficial structure encountered while performing dissection in the popliteal fossa?

m m m m m

A

Popliteal artery

B

Popliteal vein

C

Posterior tibial artery

D

Profunda femoris artery

E

Tibial nerve

1.7

A 43-year-old woman was diagnosed as having a meningioma that was compressing the neural contents within the right jugular foramen. Which one of the following clinical features is most likely to be seen in this patient?

m m m m m

A

Inability to elevate soft palate

B

Inability to protrude tongue

C

Inability to turn chin upwards and to the left

D

Loss of pain from the anterior two-thirds of the tongue

E

Sensory loss from skin overlying the zygomatic bone

1.8

A 56-year-old man was found to have enlarged submental lymph nodes. Enlargement of the submental lymph nodes is suggestive of pathology of which one of the following structures?

m m m m m

A

Hard palate

B

Maxillary incisors

C

Palatine tonsils

D

Soft palate

E

Tip of the tongue

anatomy

1.6

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MRCS Part A: Paper 1 SBAs in Applied Basic Science, Second Edition

anatomy

1.9

A 26-year-old motorcyclist was brought to the Emergency Department with a fractured right humeral shaft. Which one of the following nerves is most likely to be injured in a fracture of the humeral shaft?

m m m m m

A

Axillary nerve

B

Median nerve

C

Musculocutaneous nerve

D

Radial nerve

E

Ulnar nerve

1.10

A 36-year-old builder falls from the ladder resulting in the entire greater tubercle of the left humerus being torn away. Which one of the following movements of the humerus would be affected as a result of this injury?

m m m m m

A

Abduction and lateral rotation

B

Extension and medial rotation

C

Flexion and medial rotation

D

Flexion, abduction and adduction

E

Flexion and abduction

1.11

Clinical examination of a 56-year-old man reveals absent vibratory sensation in the toes. Absent vibratory sensation in the toes may indicate a lesion in the:

m m m m m

A

Anterior nerve roots

B

Anterior spinothalamic tract

C

Lateral columns of the spinal cord

D

Posterior white columns of the spinal cord

E

Spinotectal tract

6

1.12

A 67-year-old patient with atrial fibrillation has an embolic stroke. A computed tomography (CT) scan reveals extensive infarction of the medial surface of the frontal, parietal and limbic lobes. Embolic occlusion of which one of the following arteries will affect the blood supply to the medial surface of the frontal, parietal and limbic lobes?

m m m m m

A

Anterior cerebral artery

B

Anterior choroidal artery

C

Anterior communicating artery

D

Middle cerebral artery

E

Posterior cerebral artery

1.13

Which one of the following structures is most likely to be damaged if a lesion in the caudal medulla resulted in ipsilateral loss of perception of pain over much of the face?

m m m m m

A

Dorsal trigeminothalamic tract

B

Lateral spinothalamic tract

C

Medial lemniscus

D

Spinal trigeminal tract

E

Ventral trigeminothalamic tract

1.14

Which one of the following pairs of nerves supplies the biceps femoris muscle?

m m m m m

A

Femoral and common peroneal nerves

B

Femoral and obturator nerves

C

Obturator and tibial nerves

D

Tibial and common peroneal nerves

E

Tibial and femoral nerves

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anatomy

Questions

MRCS Part A: Paper 1 SBAs in Applied Basic Science, Second Edition

anatomy

1.15

Patients with myocardial infarction usually experience excruciating pain running down the left upper extremity. This referred pain is relayed by the:

m m m m m

A

Left intercostobrachial nerve

B

Left musculocutaneous nerve

C

Left phrenic nerve

D

Left recurrent laryngeal nerve

E

Left vagus nerve

1.16

Which one of the following structures forms the lateral boundary of the superior mediastinum?

m m m m m

A

Lateral border of the sternum

B

Mediastinal pleura

C

Roots of the lungs

D

Sternal angle

E

T1–T4 vertebrae

1.17

Which one of the following parts of the heart will be damaged as a result of occlusion of the circumflex branch of the left coronary artery?

m m m m m

A

Apex of the heart

B

Left atrium and left ventricle

C

Left ventricle and interventricular septum

D

Right atrium and left ventricle

E

Right and left ventricles

8

Questions

An FY doctor, while performing a posterolateral thoracotomy injures the posterior intercostal artery in the fifth intercostal space on the left side. The posterior intercostal artery in the fifth intercostal space arises from the:

m m m m m

A

Costocervical trunk

B

Internal thoracic artery

C

Musculophrenic artery

D

Subclavian artery

E

Thoracic aorta

1.19

The site of the cloacal membrane (which is also the point of demarcation between the endodermal and ectodermal epithelium) is represented in the adult anal canal by the:

m m m m m

A

Anal valves (pectinate/denate line)

B

External anal sphincter

C

Rectal columns

D

Transition zone

E

White line

anatomy

1.18

1.20 A newborn baby is diagnosed as having a vitelline duct anomaly. Which one of the following is a vitelline duct anomaly?

m m m m m

A

Duodenal stenosis

B

Gastroschisis

C

Omphalocele

D

Umbilical fistula

E

Umbilical hernia

9

2.19 A 38-year-old man undergoes lung volume studies using the helium dilution method. The test begins at the end of a normal expiration. The initial fraction of helium in the spirometer is 0.05, and the helium fraction after equilibration with the lungs is 0.03. The volume of gas in the spirometer is kept constant at 4 L during the procedure by the addition of O2. According to a spirogram, this patient’s vital capacity is 5 L and his expiratory reserve volume is 2 L. What is this patient’s functional residual capacity?

m m m m m

A

1.0 L

B

1.7 L

C

2.7 L

D

3.0 L

E

5.0 L

2.20 A 38-year-old man undergoes lung volume studies using the helium dilution method. The test begins at the end of a normal expiration. The initial fraction of helium in the spirometer is 0.05, and the helium fraction after equilibration with the lungs is 0.03. The volume of gas in the spirometer is kept constant at 4 L during the procedure by the addition of O2. According to a spirogram, this patient’s vital capacity is 5 L and his expiratory reserve volume is 2 L. What is this patient’s residual volume?

m m m m m

A

0.7 L

B

1.0 L

C

1.7 L

D

2.7 L

E

3.0 L

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physiology

Questions

MRCS Part A: Paper 1 SBAs in Applied Basic Science, Second Edition

2.21 Insulin is produced by the β cells of the islets of Langerhans in the pancreas. Insulin secretion from endocrine pancreas is inhibited by:

m m m m m

A

Glucagon

B

α2-Adrenergic agonists

C

β2-Adrenergic agonists

D

Cholecystokinin

E

Muscarinic agonists

physiology

2.22 Vasopressin is released from the posterior pituitary gland when there is a decrease in plasma:

m m m m m

A

Potassium concentration

B

Sodium concentration

C

pH

D

Volume

E

Calcium concentration

2.23 The second heart sound is produced by the closure of the aortic and pulmonic valves. Closure of the aortic valve occurs at the onset of:

m m m m m

54

A

The rapid ejection phase of the cardiac cycle

B

The isovolumetric contraction phase of the cardiac cycle

C

The protodiastole

D

The rapid filling phase of the cardiac cycle

E

The isovolumetric relaxation phase of the cardiac cycle

Questions

2.24 Turbulence in a blood vessel is more likely to occur if:

m m m m m

A

The velocity of blood within the vessel increases

B

The diameter of the vessel decreases

C

The viscosity of blood within the vessel increases

D

The density of blood decreases

E

The length of the vessel increases

m m m m m

A

The arterial PCO2 is increased

B

The pH is decreased

C

The blood temperature is increased

D

The H+ concentration is increased

E

2,3-Diphosphoglycerate (DPG) levels in the red blood cells (RBCs) are decreased

physiology

2.25 The affinity of haemoglobin for oxygen will increase if:

2.26 A patient with persistent diarrhoea will have an increased:

m m m m m

A

Anion gap

B

Filtered load of bicarbonate

C

Production of ammonia by the distal tubule

D

H+ secretion by the distal tubule

E

Production of new bicarbonate by the proximal tubule

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MRCS Part A: Paper 1 SBAs in Applied Basic Science, Second Edition

2.27 A patient in the Emergency Department with profuse haemorrhage from a severed limb artery will have increased:

m m m m m

A

Sodium excretion

B

Sympathetic nerve activity

C

Vagal nerve activity

D

Arteriolar diameter in skin

E

Water excretion

physiology

2.28 Intestinal peristalsis results in the movement of food through the gut. Intestinal peristalsis:

m m m m m

A

Is controlled by extrinsic innervation

B

Is inhibited by vagotomy

C

Is inhibited by sympathectomy

D

Requires an intact myenteric nerve plexus

E

Is inhibited by cholecystokinin

2.29 Secretin was the first substance that was identified to cause a physiological effect in the body after being transported via the blood. Which of the following statements about secretin is true?

m m m

A

It is a polypeptide hormone made up of 17 amino acids

B

It increases gallbladder emptying

C

It is released by the presence of long-chain fatty acids in the chyme

m m

D

It stimulates bicarbonate release from the pancreas

E

It inhibits pepsinogen secretion

56

Questions

m m m m m

A

Increased PCO2

B

Increased PO2

C

Decreased alveolar dead space

D

Decreased right ventricular afterload

E

Increased pulmonary vascular resistance

2.31

What will be the interstitial osmotic pressure in a skin capillary if fluid is being forced out of it with a net filtration pressure of 8 mmHg when the capillary hydrostatic pressure is 24 mmHg, interstitial hydrostatic pressure 7 mmHg and capillary colloid osmotic pressure 17 mmHg? (Assume that both the filtration coefficient and reflection coefficient in this case are 1.)

m m m m m

A

8 mmHg

B

6 mmHg

C

9 mmHg

D

–9 mmHg

E

–6 mmHg

physiology

2.30 A 72-year-old woman developed an acute pulmonary embolism 3 days after her total hip replacement. Which of the following features is most likely to be seen in this patient?

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MRCS Part A: Paper 1 SBAs in Applied Basic Science, Second Edition

2.32 When air enters the intrapleural space (pneumothorax), the most likely response is for:

physiology

m

A

The lung to expand outwards and the chest wall to spring inwards

m

B

The lung to expand outwards and the chest wall to spring outwards

m

C

The lung to collapse inwards and the chest wall to collapse inwards

m

D

The lung to collapse inwards and the chest wall to spring outwards

m

E

The lung volume to be unaffected and chest wall to spring outwards

2.33 Haemodynamic changes in response to obstruction of venous return to the right side of heart include:

m

A

Cardiac output will fall and systemic arterial blood pressure will fall

m

B

Cardiac output will rise and systemic arterial blood pressure will rise

m

C

Cardiac output will fall and systemic arterial blood pressure will rise

m

D

Cardiac output will fall and systemic arterial blood pressure will remain unchanged

m

E

Cardiac output will remain unchanged and systemic arterial blood pressure will fall

58

Questions

2.34 Common features of a tumour of the right atrium and cardiac tamponade include: A

Pulmonary oedema, pulmonary hypertension and pulmonary venous congestion

m

B

Pulmonary venous congestion, systemic venous congestion and systemic hypotension

m m

C

Systemic oedema, high cardiac output and ascites

D

Systemic oedema, congestion of the systemic veins and ascites

m

E

Pulmonary oedema, systemic hypertension and low cardiac output

physiology

m

2.35 Voltage-gated sodium channels are an example of a protein embedded in the plasma membrane of nerve and muscle cells that is used in the rapid electrical signalling found in these cells. Voltagegated sodium channels:

m

A

Are formed by co-assembly of five identical or similar α subunits

m

B

Have specialised transmembrane domains (S4) that sense transmembrane voltage

m m m

C

Are equally permeable to K+ and Na+

D

Are activated by binding of glycine

E

Are activated by a decrease in intracellular ATP concentration

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MRCS Part A: Paper 1 SBAs in Applied Basic Science, Second Edition

2.36 Cells within the sinoatrial (SA) node are the primary pacemaker site within the heart. These cells are characterised as having no true resting potential, but instead generate regular, spontaneous action potentials. Phase 0 of an SA nodal action potential results from:

physiology

m m m m m

A

Activation of sodium channels

B

Activation of the pacemaker current

C

Influx of Ca2+ ions

D

Inactivation of K+ channels

E

Influx of Na+ ions

2.37 What should the myeloid:erythroid ratio in your bone marrow be if you want to be a voluntary bone marrow donor?

m m m m m

A

1:1

B

1:3

C

3:1

D

1:10

E

10:1

2.38 Substances with high oil:water partition coefficients readily permeate cell membranes. Which group has high oil:water partition coefficients?

m m m m m

60

A

Peptides, steroid hormones, oxygen

B

Steroid hormones, oxygen, ions

C

Oxygen, ions, carbon dioxide

D

Ions, carbon dioxide, steroid hormones

E

Carbon dioxide, steroid hormones, oxygen