Unit 13 Question Bank
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Slide come from the TMU lecture. Items tagged Gray's are built from the textbook to cover
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0 / 20 answered
1The plane dividing the superior from the inferior mediastinum runs from the sternal angle to the ( ).
Answer: A
An imaginary horizontal plane from the sternal angle to the lower border of T4. The same plane marks the beginning and end of the aortic arch and the bifurcation of the trachea.TMU Lecture 15 Slide 3
2The middle mediastinum contains the ( ).
Answer: B
The heart within the pericardium, the roots of the great vessels, and a phrenic nerve on each side. The thymus is anterior; the aorta, oesophagus and duct are posterior.TMU Lecture 15 Slide 4
3The transverse pericardial sinus lies behind the ( ).
Answer: C
Behind the aorta and pulmonary trunk and in front of the superior vena cava and left atrium. Passing a ligature through it clamps both arterial outflows during bypass surgery.Gray's 4e p.172
4The three inlets of the right atrium are the orifices of the ( ).
Answer: D
SVC, IVC and coronary sinus. Its single outlet is the right atrioventricular orifice.TMU Lecture 16 Slide 11
5The crista terminalis separates the ( ).
Answer: A
A muscular ridge running from the SVC to the IVC orifice, separating the smooth-walled sinus venarum behind from the rough atrium proper with its musculi pectinati in front.TMU Lecture 16 Slide 12
6The tricuspid complex consists of the ( ).
Answer: B
All four components acting as one unit to prevent backflow from the right ventricle into the right atrium during systole. The bicuspid (mitral) complex is its counterpart on the left.TMU Lecture 16 Slides 13–14
7The left coronary artery arises from the ( ).
Answer: C
From the left aortic sinus, just above the aortic valve — which is why the coronaries fill during diastole. The right coronary arises from the right aortic sinus.TMU past paper · Gray's 4e p.186
8The apex of the heart is formed by the ( ) and lies in the ( ).
Answer: D
Formed by the left ventricle, in the 5th left intercostal space about 1–2 cm medial to the midclavicular line — the apex beat.TMU Lecture 16 Slide 5
9The base of the heart is formed mainly by the ( ).
Answer: A
Mainly the left atrium, with a small contribution from the posterior part of the right atrium. It faces backward, upward and to the right.TMU Lecture 16 Slide 6
10Normal pericardial fluid volume is about ( ).
Answer: B
About 50 mL. Because the fibrous pericardium does not stretch acutely, as little as 100–200 mL of blood accumulating rapidly can cause cardiac tamponade.Snell's 10e Ch.5
11Beck's triad of cardiac tamponade consists of ( ).
Answer: C
Falling blood pressure, rising jugular venous pressure and muffled heart sounds — the consequence of a rigid sac compressing the heart.Snell's 10e Ch.5 (clinical)
12The anterior interventricular (LAD) artery is a branch of the ( ).
Answer: D
The left coronary artery divides into the anterior interventricular (LAD) and circumflex arteries. The LAD supplies the anterior left ventricle, the anterior two-thirds of the septum and the apex.Gray's 4e p.186
13In about 80% of people the atrioventricular node is supplied by the ( ).
Answer: A
The right coronary artery — which is why an inferior infarct from right coronary occlusion often presents with heart block rather than pump failure.Gray's 4e p.186
14The coronary sinus drains into the ( ).
Answer: B
Into the right atrium, and its orifice is one of the atrium's three inlets. It lies in the posterior coronary groove.TMU Lecture 16 Slide 11
15The septomarginal trabecula (moderator band) is found in the ( ).
Answer: C
In the right ventricle, carrying part of the conducting system from the interventricular septum to the anterior papillary muscle.TMU Lecture 16 Slide 13
16The four inlets of the left atrium are the openings of the ( ).
Answer: D
The four pulmonary veins — two right and two left. Its outlet is the left atrioventricular orifice guarded by the mitral valve.TMU past paper · Gray's 4e p.184
17The atrioventricular crux is the junction of the ( ).
Answer: A
Where the coronary, posterior interventricular and posterior interatrial grooves meet on the posterior surface — an important landmark overlying the AV node.TMU past paper definition · Gray's 4e p.178
18The oblique pericardial sinus is a blind recess behind the ( ).
Answer: B
A cul-de-sac behind the left atrium, bounded by the serous reflections around the pulmonary veins and inferior vena cava.Gray's 4e p.172
19The wall of the left ventricle is approximately ( ) the thickness of the right.
Answer: C
About three times thicker, because it pumps against systemic rather than pulmonary resistance while ejecting the same volume.Snell's 10e Ch.5
20The coronary arteries fill mainly during ( ).
Answer: D
During diastole: the aortic valve closes, directing blood into the sinuses, and the relaxed myocardium is no longer compressing its own vessels. This is why tachycardia — which shortens diastole — worsens angina.Gray's 4e p.186
1 Mediastinum — 3′+
The bulky septum between the two mediastinal pleurae.
Boundaries: sternum and costal cartilages in front · thoracic vertebrae behind · mediastinal pleurae on each side · thoracic inlet above · diaphragm below.
Divisions: a plane from the sternal angle to the lower border of T4 separates the superior mediastinum above from the inferior below, which is further divided into anterior (in front of the pericardium), middle (the pericardium and heart) and posterior (behind the pericardium).TMU Lecture 15 Slides 2–4
Boundaries: sternum and costal cartilages in front · thoracic vertebrae behind · mediastinal pleurae on each side · thoracic inlet above · diaphragm below.
Divisions: a plane from the sternal angle to the lower border of T4 separates the superior mediastinum above from the inferior below, which is further divided into anterior (in front of the pericardium), middle (the pericardium and heart) and posterior (behind the pericardium).TMU Lecture 15 Slides 2–4
2 Transverse pericardial sinus — 3′+
A passage within the pericardial cavity lying behind the aorta and pulmonary trunk and in front of the superior vena cava and left atrium, between the arterial and venous reflections of serous pericardium.
Surgical use: a ligature passed through it can clamp both arterial outflow tracts at once when establishing cardiopulmonary bypass.Gray's 4e p.172
Surgical use: a ligature passed through it can clamp both arterial outflow tracts at once when establishing cardiopulmonary bypass.Gray's 4e p.172
3 Tricuspid complex — TMU past paper · 3′+
The right atrioventricular fibrous ring, the tricuspid valve cusps, the chordae tendineae and the papillary muscles, considered as a single functional unit.
Function: prevents backward flow of blood from the right ventricle into the right atrium during ventricular contraction. The papillary muscles contract with the ventricle and pull on the chordae, holding the cusps closed rather than allowing them to invert.
Its counterpart on the left is the bicuspid (mitral) complex.TMU Lecture 16 Slides 13–14
Function: prevents backward flow of blood from the right ventricle into the right atrium during ventricular contraction. The papillary muscles contract with the ventricle and pull on the chordae, holding the cusps closed rather than allowing them to invert.
Its counterpart on the left is the bicuspid (mitral) complex.TMU Lecture 16 Slides 13–14
4 Crista terminalis — 2′+
A muscular ridge on the interior of the right atrium, running from the orifice of the superior vena cava to that of the inferior vena cava.
It separates the smooth-walled sinus venarum posteriorly (of sinus venosus origin) from the rough atrium proper anteriorly, whose wall bears the musculi pectinati. The sinuatrial node lies at its upper end.TMU Lecture 16 Slide 12
It separates the smooth-walled sinus venarum posteriorly (of sinus venosus origin) from the rough atrium proper anteriorly, whose wall bears the musculi pectinati. The sinuatrial node lies at its upper end.TMU Lecture 16 Slide 12
5 Atrioventricular crux — TMU past paper · 2′+
The point on the posterior surface of the heart where the coronary groove, the posterior interventricular groove and the posterior interatrial groove all meet.
It is an important surface landmark and overlies the atrioventricular node.TMU past paper definition · Gray's 4e p.178
It is an important surface landmark and overlies the atrioventricular node.TMU past paper definition · Gray's 4e p.178
6 Fossa ovalis — 2′+
An oval depression on the interatrial septum in the right atrium, the remnant of the fetal foramen ovale, bounded above and in front by a raised margin, the limbus.
Clinical: failure of fusion leaves a probe-patent foramen ovale, a route for paradoxical embolism.TMU Lecture 16 Slides 11–12
Clinical: failure of fusion leaves a probe-patent foramen ovale, a route for paradoxical embolism.TMU Lecture 16 Slides 11–12
1
Describe the divisions of the mediastinum and their contents.
8′
Definition and boundaries
The mediastinum is the septum between the two mediastinal pleurae, bounded by the sternum and costal cartilages in front, the thoracic vertebrae behind, the mediastinal pleurae on each side, the thoracic inlet above and the diaphragm below.
Division
An imaginary horizontal plane from the sternal angle to the lower border of T4 separates the superior from the inferior mediastinum. The inferior is divided by the pericardium into anterior, middle and posterior parts.
| Division | Contents |
|---|---|
| Superior | Arch of the aorta and its three branches · brachiocephalic veins and SVC · trachea · oesophagus · thoracic duct · vagus, phrenic and left recurrent laryngeal nerves · thymus |
| Anterior | Thymus or its remnant · fat · lymph nodes · sternopericardial ligaments |
| Middle | Heart in the pericardial sac · roots of the great vessels · phrenic nerves and pericardiacophrenic vessels |
| Posterior | Descending thoracic aorta · oesophagus and oesophageal plexus · thoracic duct · azygos, hemiazygos and accessory hemiazygos veins · sympathetic trunks and splanchnic nerves |
The sternal angle plane is worth naming for its other landmarks: the start and end of the aortic arch, the tracheal bifurcation, and the level of the 2nd costal cartilage.
Marking guide: boundaries 2 · dividing plane 1 · four divisions named 1 · contents 4.
2
Describe the pericardium, including the pericardial sinuses, and explain cardiac tamponade.
8′
Structure
- Fibrous pericardium — a tough outer sac, fused below with the central tendon of the diaphragm and above with the adventitia of the great vessels
- Serous pericardium — in two layers: a parietal layer lining the fibrous sac, and a visceral layer (epicardium) adherent to the heart
- Pericardial cavity — the potential space between them, containing about 50 mL of fluid
The sinuses
- Transverse pericardial sinus — behind the aorta and pulmonary trunk, in front of the SVC and left atrium. Surgeons pass a ligature through it to clamp both arterial outflows during cardiopulmonary bypass.
- Oblique pericardial sinus — a blind cul-de-sac behind the left atrium, bounded by the reflections around the pulmonary veins and IVC.
Nerve supply
The fibrous and parietal serous pericardium are supplied by the phrenic nerve — so pericardial pain may be referred to the shoulder tip.
Cardiac tamponade
- The fibrous pericardium does not stretch acutely, so fluid or blood entering the cavity rapidly raises the pressure and prevents the heart filling
- As little as 100–200 mL accumulating quickly is enough; slowly accumulating fluid may reach a litre because the sac has time to stretch
- Beck's triad: hypotension, raised jugular venous pressure, muffled heart sounds
- Treated by pericardiocentesis — a needle inserted below the xiphoid process aimed toward the left shoulder
Marking guide: fibrous and serous layers 2 · fluid volume 0.5 · two sinuses 2 · nerve supply 0.5 · tamponade mechanism 2 · Beck's triad 1.
3
Describe the internal features of the right atrium and right ventricle.
8′
Right atrium
Three inlets: orifices of the superior vena cava, the inferior vena cava and the coronary sinus. One outlet: the right atrioventricular orifice.
Internal features:
- Crista terminalis — a muscular ridge from the SVC to the IVC orifice, separating the smooth sinus venarum behind from the rough atrium proper in front
- Musculi pectinati — parallel muscular ridges in the rough part and the right auricle
- Fossa ovalis — on the interatrial septum, the remnant of the fetal foramen ovale
- The sinuatrial node lies at the upper end of the crista terminalis
Right ventricle
Inlet: right atrioventricular orifice, guarded by the tricuspid valve. Outlet: the pulmonary orifice, guarded by the pulmonary valve.
Internal features:
- Trabeculae carneae — irregular muscular ridges
- Papillary muscles with chordae tendineae to the valve cusps
- Septomarginal trabecula (moderator band) — carrying part of the conducting system to the anterior papillary muscle
- Conus arteriosus (infundibulum) — the smooth-walled outflow tract
The tricuspid complex
The fibrous ring, cusps, chordae tendineae and papillary muscles together prevent regurgitation into the atrium: the papillary muscles contract with the ventricle and hold the cusps at exactly the closed position rather than letting them invert.
Marking guide: atrial inlets and outlet 2 · atrial features 2 · ventricular inlet and outlet 1.5 · ventricular features 1.5 · tricuspid complex 1.
4
What are the arteries of the heart? Where do they arise from, and what are their branches?
8′
A recurring TMU past-paper question.
Origin
The two coronary arteries are the first branches of the ascending aorta, arising from the aortic sinuses immediately above the cusps of the aortic valve. This position means they fill during diastole, when the valve closes and the myocardium is relaxed.
Right coronary artery — from the RIGHT aortic sinus
- Right conus branch
- Sinuatrial nodal branch (in about 60%)
- Right marginal artery — along the inferior border toward the apex
- Atrioventricular nodal branch (in about 80%)
- Posterior interventricular (posterior descending) artery
Left coronary artery — from the LEFT aortic sinus
- Anterior interventricular (left anterior descending) — anterior left ventricle, anterior two-thirds of the septum, apex
- Circumflex artery — left atrium and the lateral and posterior left ventricle, giving the left marginal branch
Venous drainage
The great, middle and small cardiac veins drain into the coronary sinus in the posterior coronary groove, which opens into the right atrium.
Clinical
- Occlusion of the LAD infarcts the largest territory — the "widow-maker"
- Right coronary occlusion often causes heart block, because it usually supplies the AV node
Marking guide: origin from aortic sinuses 1.5 · diastolic filling 0.5 · RCA branches 2 · LCA branches 2 · coronary sinus 1 · one clinical point 1.
5
Describe the external features of the heart.
6′
The heart has an apex, a base, two surfaces, three borders and four grooves.
Apex
Directed downwards, forwards and to the left; formed by the left ventricle; lies in the 5th left intercostal space about 1–2 cm medial to the midclavicular line. This is where the apex beat is palpated; displacement downward and laterally indicates left ventricular enlargement.
Base
Faces backward, upward and to the right; formed mainly by the left atrium, with a small contribution from the posterior part of the right atrium; receives the pulmonary veins.
Surfaces
- Anterior (sternocostal) — mainly right ventricle
- Inferior (diaphragmatic) — mainly left ventricle, resting on the diaphragm
Borders
- Right — right atrium
- Left — mainly left ventricle
- Inferior — right ventricle
Grooves
- Coronary (atrioventricular) — between atria and ventricles
- Anterior interventricular and posterior interventricular — between the ventricles
- Posterior interatrial — between the atria
Where the coronary, posterior interventricular and posterior interatrial grooves meet is the atrioventricular crux.
Marking guide: apex with chamber and position 1.5 · base 1 · two surfaces 1 · three borders 1 · four grooves 1.5.