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Score — click each question to reveal the answer
Q1
The heart is situated in the:
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A. Middle mediastinum
B. Superior mediastinum
C. Inferior mediastinum
D. Posterior mediastinum
✅ Answer: A — Middle mediastinum
The heart lies in the middle mediastinum, the central compartment of the thorax. It is enclosed by the pericardium and flanked on each side by the pleural cavities. The middle mediastinum is bounded anteriorly by the sternum, posteriorly by the vertebral column, and superiorly by the plane of the sternal angle.
⚠ Trap: The superior mediastinum is above the sternal angle — it contains the great vessels, trachea, and oesophagus, not the heart itself.
Q2
The base of the heart is formed mainly by:
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A. Right atrium
B. Left atrium
C. Left ventricle
D. Right ventricle
✅ Answer: B — Left atrium
The base of the heart is its posterior surface. It is formed mainly by the left atrium, which receives the four pulmonary veins. A small part is formed by the right atrium. The base faces posteriorly toward the vertebral column (T6–T9 level) and is not resting on the diaphragm.
⚠ Trap: Students confuse "base" with the bottom. Anatomically, the base of the heart is posterior (not inferior). The apex points inferolaterally to the left. "Base at the back" — remember this.
Q3
The apex of the heart is formed by the:
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A. Right atrium
B. Right ventricle
C. Left ventricle
D. Left atrium
✅ Answer: C — Left ventricle
The apex is the blunt inferior tip of the heart formed by the left ventricle. It is located at the left 5th intercostal space, midclavicular line — the site where the apex beat (cardiac impulse) is felt. The apex points downward, forward, and to the left.
⚠ Classic T/F question: "The apex is formed by the right ventricle" = FALSE. It is always the LEFT ventricle. Apex location (5th ICS, MCL) is also a standalone MCQ.
Q4
The heart is enclosed in a fibroserous sac called the:
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A. Pleura
B. Peritoneum
C. Endocardium
D. Pericardium
✅ Answer: D — Pericardium
The pericardium is the fibroserous sac enclosing the heart. It has two layers: (1) outer fibrous pericardium (tough, attached to diaphragm inferiorly and great vessels superiorly) and (2) inner serous pericardium (with parietal and visceral/epicardium layers separated by pericardial cavity containing lubricating fluid).
Pleura = lung covering · Peritoneum = abdominal cavity · Endocardium = inner heart lining. All different structures.
Q5
The pericardial cavity is the space between:
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A. Parietal and visceral layers of serous pericardium
B. Fibrous pericardium and heart
C. Fibrous and serous pericardium
D. Epicardium and myocardium
✅ Answer: A — Parietal and visceral layers of serous pericardium
The pericardial cavity is the potential space between the parietal serous pericardium (lines the fibrous sac) and the visceral serous pericardium (epicardium) (covers the heart). It normally contains 15–50 mL of lubricating fluid. In cardiac tamponade, this space fills with blood, compressing the heart.
⚠ The pericardial cavity is NOT between the fibrous pericardium and the heart — that would be the entire serous pericardium, not just the cavity. Know the layers precisely.
Q6
The right atrium receives blood from the:
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A. Pulmonary veins and superior vena cava
B. Superior and inferior vena cava and coronary sinus
C. Aorta and pulmonary trunk
D. Only from the inferior vena cava
✅ Answer: B — SVC + IVC + coronary sinus
The right atrium receives deoxygenated blood through three inlets: (1) Superior vena cava (SVC) — from the upper half of the body; (2) Inferior vena cava (IVC) — from the lower half; (3) Coronary sinus — venous drainage from the heart muscle itself. This is a classic TMU define question structure.
⚠ Pulmonary veins open into the LEFT atrium (oxygenated blood). Aorta and pulmonary trunk are OUTFLOWS (arteries), not inflows.
Q7
The crista terminalis is a muscular ridge in the:
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A. Right ventricle
B. Left atrium
C. Right atrium
D. Left ventricle
✅ Answer: C — Right atrium
The crista terminalis is a C-shaped muscular ridge on the interior of the right atrium. It separates the smooth-walled posterior part (sinus venarum — formed from the embryonic sinus venosus) from the rough anterior part (bearing pectinate muscles). The SA node lies at its upper end, near the SVC opening.
Q8
The fossa ovalis is a depression in the:
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A. Interventricular septum
B. Right ventricle
C. Left atrium
D. Interatrial septum (right atrium side)
✅ Answer: D — Interatrial septum (right atrium side)
The fossa ovalis is an oval depression on the right side of the interatrial septum. It is the remnant of the fetal foramen ovale — the opening through which blood bypassed the non-functional fetal lungs. It normally closes shortly after birth. A patent foramen ovale (PFO) persists in ~25% of adults.
⚠ The fossa ovalis is in the INTERATRIAL septum (not interventricular), and visible from the RIGHT side. The limbus (raised margin) surrounds it.
Q9
The tricuspid valve is located between the:
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A. Right atrium and right ventricle
B. Left atrium and left ventricle
C. Right ventricle and pulmonary trunk
D. Left ventricle and aorta
✅ Answer: A — Right atrium and right ventricle
The tricuspid valve (right atrioventricular valve) guards the right atrioventricular orifice between the right atrium and right ventricle. It has three cusps: anterior, posterior, and septal. Each cusp is attached to papillary muscles via chordae tendineae. Prevents regurgitation of blood from RV → RA during systole.
Q10
The bicuspid (mitral) valve is located between the:
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A. Right atrium and right ventricle
B. Left atrium and left ventricle
C. Left ventricle and aorta
D. Right ventricle and pulmonary trunk
✅ Answer: B — Left atrium and left ventricle
The bicuspid (mitral) valve is the left atrioventricular valve, with two cusps (anterior and posterior). It guards the left atrioventricular orifice. The mitral valve is the most frequently diseased valve (rheumatic fever preferentially damages it). Mitral stenosis → diastolic murmur; mitral regurgitation → systolic murmur.
Q11
The pulmonary valve is located at the:
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A. Opening of pulmonary veins
B. Opening of superior vena cava
C. Origin of pulmonary trunk from right ventricle
D. Origin of aorta
✅ Answer: C — Origin of pulmonary trunk from right ventricle
The pulmonary valve is a semilunar valve at the outlet of the right ventricle, at the origin of the pulmonary trunk. It has three semilunar cusps: anterior, right, and left. Semilunar valves (pulmonary + aortic) open during ventricular systole and close at the start of diastole, producing the S2 heart sound ("dub").
Q12
The aortic valve is located at the:
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A. Origin of pulmonary trunk
B. Opening of coronary sinus
C. Junction of atria and ventricles
D. Origin of aorta from left ventricle
✅ Answer: D — Origin of aorta from left ventricle
The aortic valve is a semilunar valve at the outlet of the left ventricle, at the origin of the ascending aorta. Three cusps: posterior (non-coronary), right, and left. The right coronary artery opens from the right aortic sinus; the left coronary artery from the left aortic sinus. Aortic stenosis → systolic murmur + syncope + angina.
Q13
Papillary muscles are connected to the cusps of the atrioventricular valves by:
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A. Tendinous cords (chordae tendineae)
B. Trabeculae carneae
C. Pectinate muscles
D. Septomarginal trabecula
✅ Answer: A — Chordae tendineae
Chordae tendineae ("heart strings") are fibrous cords connecting papillary muscles to the free edges and ventricular surfaces of AV valve cusps. When papillary muscles contract during ventricular systole, the chordae are pulled taut, preventing the cusps from inverting into the atrium. Rupture → acute severe valve regurgitation.
Trabeculae carneae = muscular ridges on ventricular walls · Pectinate muscles = atrial wall ridges · Septomarginal trabecula (moderator band) = carries right bundle branch. All different from chordae.
Q14
The moderator band (septomarginal trabecula) is found in the:
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A. Left ventricle
B. Right ventricle
C. Left atrium
D. Right atrium
✅ Answer: B — Right ventricle
The moderator band (septomarginal trabecula) is a prominent muscular band that crosses the cavity of the right ventricle from the interventricular septum to the base of the anterior papillary muscle. It carries the right bundle branch of the conducting system, preventing it from being stretched during ventricular filling. It is an important landmark in the RV.
Q15
The interventricular septum is supplied by:
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A. Only the right coronary artery
B. Only the left coronary artery
C. Anterior and posterior interventricular arteries
D. Only the circumflex artery
✅ Answer: C — Anterior and posterior interventricular arteries
The interventricular septum has a dual supply: (1) Anterior 2/3 → by the anterior interventricular artery (LAD), a branch of the left coronary artery; (2) Posterior 1/3 → by the posterior interventricular artery, usually from the right coronary artery (right dominance in ~70% of people). The bundle branches run within the septum, so LAD occlusion can cause bundle branch block.
Q16
The coronary sinus drains into the:
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A. Left atrium
B. Right ventricle
C. Left ventricle
D. Right atrium
✅ Answer: D — Right atrium
The coronary sinus is the main venous channel of the heart, lying in the posterior atrioventricular groove. It collects blood from: great cardiac vein, middle cardiac vein, small cardiac vein, and oblique vein of left atrium. It drains into the right atrium through an opening guarded by the Thebesian valve, between the IVC orifice and the right AV orifice.
Q17
The right coronary artery typically arises from the:
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A. Right coronary sinus of aorta
B. Left coronary sinus of aorta
C. Anterior coronary sinus
D. Posterior coronary sinus
✅ Answer: A — Right coronary sinus of aorta
The right coronary artery (RCA) arises from the right aortic sinus (right sinus of Valsalva). The left coronary artery arises from the left aortic sinus. The posterior (non-coronary) aortic sinus gives rise to no coronary artery. The sinuses of Valsalva are the slight dilations of the aorta just above each cusp of the aortic valve.
⚠ There is no "anterior coronary sinus." The three aortic sinuses are: right, left, and posterior (non-coronary). "Coronary sinus" = venous structure in the AV groove, NOT an aortic sinus.
Q18
The left coronary artery divides into:
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A. Right marginal and posterior interventricular arteries
B. Anterior interventricular and circumflex arteries
C. Only circumflex artery
D. Posterior interventricular and marginal arteries
✅ Answer: B — Anterior interventricular (LAD) + circumflex arteries
The left coronary artery (LCA) arises from the left aortic sinus and divides into two main branches: (1) Anterior interventricular artery (LAD — left anterior descending) — runs in the anterior interventricular groove, supplies anterior ventricles and anterior 2/3 of septum; (2) Circumflex artery — runs in the left AV groove, supplies left atrium and posterior left ventricle. LAD occlusion = "widow-maker" MI.
Q19
The sinoatrial (SA) node is located in the:
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A. Interventricular septum
B. Right ventricle
C. Posterior wall of right atrium near superior vena cava opening
D. Left atrium
✅ Answer: C — Posterior wall of RA near SVC opening
The SA node (sinoatrial node / sinus node) is located at the upper end of the crista terminalis in the posterior wall of the right atrium, near the opening of the SVC. It is the cardiac pacemaker, generating impulses at 60–100/min. It is supplied by the SA nodal artery, which arises from the RCA in 60% and the LCA in 40% of people.
Q20
The atrioventricular (AV) node is located in the:
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A. Lateral wall of right atrium
B. Left ventricle
C. Apex of heart
D. Interatrial septum near coronary sinus opening
✅ Answer: D — Interatrial septum near coronary sinus opening
The AV node lies in the floor of the right atrium at the apex of the Triangle of Koch, bounded by: (1) tendon of Todaro, (2) attachment of the septal leaflet of tricuspid valve, and (3) coronary sinus orifice. The AV node delays the impulse by ~0.1 second, allowing the atria to finish contracting before ventricular contraction begins.
Q21
The right border of the heart is formed mainly by the:
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A. Right atrium
B. Left ventricle
C. Right ventricle
D. Left atrium
✅ Answer: A — Right atrium
Heart borders: Right border = right atrium · Left border = left ventricle (+ left auricle superiorly) · Inferior border = right ventricle + apex · Superior border = atria + great vessels. The right border projects slightly to the right of the sternum and is visible on a chest X-ray as the right cardiac silhouette.
Q22
The left border of the heart is formed mainly by the:
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A. Left atrium
B. Left ventricle
C. Right ventricle
D. Pulmonary trunk
✅ Answer: B — Left ventricle
The left border is formed mainly by the left ventricle, with a small contribution from the left auricle superiorly. On a chest X-ray, the left cardiac border is formed from top to bottom by: (1) aortic knuckle, (2) pulmonary trunk, (3) left auricle, (4) left ventricle. Cardiomegaly (left ventricular enlargement) displaces the left border laterally.
Q23
The inferior border of the heart is formed mainly by the:
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A. Left ventricle and apex
B. Left atrium
C. Right ventricle and apex
D. Right atrium
✅ Answer: C — Right ventricle and apex
The inferior border (diaphragmatic border) rests on the central tendon of the diaphragm and is formed mainly by the right ventricle with a small part of the left ventricle at the apex. The sternocostal (anterior) surface is also predominantly right ventricle — hence "RV is the most anteriorly placed chamber."
Q24
The sound of the heart beat 'lub' (S1) is produced by:
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A. Opening of semilunar valves
B. Opening of AV valves
C. Closure of semilunar valves
D. Closure of atrioventricular valves
✅ Answer: D — Closure of atrioventricular valves
S1 ("lub") = simultaneous closure of mitral (M1) and tricuspid (T1) valves at the start of ventricular systole. S2 ("dub") = closure of aortic (A2) and pulmonary (P2) valves at the end of systole. Memory: "Lub = Low-pitched = Long = start of systole = AV valves shut." Auscultation: S1 loudest at apex (5th ICS MCL).
Q25
The sound of the heart beat 'dub' (S2) is produced by:
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A. Closure of semilunar valves
B. Closure of atrioventricular valves
C. Opening of AV valves
D. Opening of semilunar valves
✅ Answer: A — Closure of semilunar valves
S2 ("dub") = simultaneous closure of aortic and pulmonary semilunar valves at the end of ventricular systole / start of diastole. S2 is higher-pitched and shorter than S1. It is loudest at the base of the heart (2nd ICS left = pulmonary area; 2nd ICS right = aortic area). Physiological splitting of S2 on inspiration (P2 delayed) is normal.
Click any term to expand the full definition. Source: TMU Anatomy Question Bank V2 — Lecture 10.
Model answers from TMU Anatomy Question Bank V2 — Lecture 10. Structure your essay answers with headings for full marks.
Essay 1
Describe the chambers of the heart and the blood flow through them.
Essay Q
Blood Flow Through the Heart
The heart has four chambers: two atria (receiving chambers) and two ventricles (pumping chambers).
Right Side (Pulmonary Circuit)
Right atrium receives deoxygenated blood from the body via: superior vena cava (upper body), inferior vena cava (lower body), and coronary sinus (heart muscle). Blood passes through the tricuspid valve (3 cusps: anterior, posterior, septal) into the right ventricle, which pumps it through the pulmonary valve into the pulmonary trunk → lungs for oxygenation.
Left Side (Systemic Circuit)
Oxygenated blood returns from the lungs via four pulmonary veins to the left atrium. Blood passes through the bicuspid (mitral) valve (2 cusps: anterior, posterior) into the left ventricle (thickest walled chamber — 3× RV wall thickness), which pumps it through the aortic valve into the ascending aorta for systemic distribution.
Key Structural Points
- Interventricular septum separates right and left ventricles
- Interatrial septum contains fossa ovalis (remnant of foramen ovale)
- Crista terminalis in RA separates smooth sinus venarum from rough pectinate part
- Moderator band in RV carries right bundle branch
- Left ventricle has fine trabeculae; right has coarse trabeculae carneae
Marking guide: Define four chambers (1 mark each) · Valves named correctly (2 marks) · Blood flow sequence correct (2 marks) · Structural features (2 marks) · Clinical note (1 mark) = ~10 marks total
Essay 2
Describe the conducting system of the heart and explain how it coordinates cardiac contraction.
Essay Q
Components of the Conducting System
1. Sinoatrial (SA) node — located at the upper end of the crista terminalis in the posterior wall of the right atrium, near the SVC opening. It is the cardiac pacemaker generating impulses at 60–100/min. Supplied by the SA nodal artery (from RCA in 60%, LCA in 40%).
2. Atrioventricular (AV) node — located in the floor of the right atrium at the apex of the Triangle of Koch (bounded by: tendon of Todaro, septal tricuspid leaflet, coronary sinus orifice). Delays impulse ~0.1 second to allow complete atrial contraction before ventricles fire. Supplied usually by RCA.
3. AV bundle (Bundle of His) — runs from AV node through the membranous part of the interventricular septum. Divides into right and left bundle branches at the upper muscular septum. The only electrical connection between atria and ventricles (fibrous skeleton electrically insulates them).
4. Right bundle branch — runs in the interventricular septum, continues via the moderator band to the anterior papillary muscle of the RV, then fans out as Purkinje fibres.
5. Left bundle branch — divides into anterior and posterior fascicles, supplies the LV.
6. Purkinje fibres — terminal branches that rapidly conduct impulses to the ventricular myocardium from endocardium outward, triggering coordinated ventricular contraction.
Coordination Mechanism
The SA node fires → impulse spreads through both atria via internodal pathways → atria contract → impulse reaches AV node → delayed 0.1s → spreads through bundle of His → bundle branches → Purkinje fibres → ventricular myocardium contracts from apex upward, ejecting blood efficiently.
Clinical Significance
Damage to the SA node → sick sinus syndrome. AV node damage → heart block (1°, 2°, 3°). LAD occlusion → RBBB (moderator band affected). Complete heart block → ventricular escape rhythm at 30–40/min → pacemaker required.
Marking guide: Each node/component with location (1 mark each) · Impulse sequence correct (2 marks) · Clinical significance (2 marks) = ~10 marks total