CCT Cardiovascular Anatomy and Physiology 2 — Questions and Answers

Question 1: Which layer of the heart wall is responsible for the contractile function of the heart?

Myocardium (Correct answer)
Epicardium
Endocardium
Pericardium

Correct answer: Myocardium

The myocardium is the middle muscular layer of the heart wall composed of cardiac muscle cells (cardiomyocytes) that are responsible for generating the force needed to pump blood.

The heart wall consists of three layers: the epicardium (outer layer, visceral pericardium), the myocardium (middle muscular layer), and the endocardium (inner lining). The myocardium contains the specialized cardiac muscle cells that contract in response to electrical stimulation. The thickness of the myocardium varies — the left ventricle has the thickest myocardium because it must generate enough pressure to propel blood through the systemic circulation.

Question 2: What is the primary function of the tricuspid valve?

Prevent backflow of blood from the right ventricle into the right atrium during systole (Correct answer)
Prevent backflow from the left ventricle into the left atrium
Control blood flow from the left atrium to the left ventricle
Regulate flow from the aorta back into the left ventricle

Correct answer: Prevent backflow of blood from the right ventricle into the right atrium during systole

The tricuspid valve is located between the right atrium and right ventricle. It opens during diastole to allow blood to flow into the right ventricle and closes during systole to prevent backflow.

The tricuspid valve (right atrioventricular valve) has three leaflets and is supported by chordae tendineae attached to papillary muscles. During ventricular diastole, the valve opens passively as atrial pressure exceeds ventricular pressure, allowing blood to fill the right ventricle. During ventricular systole, rising ventricular pressure forces the valve closed, preventing regurgitation into the right atrium. Tricuspid regurgitation causes a holosystolic murmur heard best at the left sternal border.

Question 3: The sinoatrial (SA) node is located in which cardiac structure?

Right atrium, near the superior vena cava junction (Correct answer)
Left atrium, near the pulmonary veins
Interventricular septum
AV junction between the atria and ventricles

Correct answer: Right atrium, near the superior vena cava junction

The SA node is located in the posterior wall of the right atrium, near the junction with the superior vena cava, at the sulcus terminalis.

The SA node (sinoatrial node), the heart's primary pacemaker, is a small cluster of specialized cardiac cells located in the right atrium near the entry point of the superior vena cava. It typically fires at a rate of 60-100 beats per minute in adults at rest. The SA node is supplied by the SA nodal artery, which in most people (55-60%) arises from the right coronary artery. Damage to this area (e.g., during cardiac surgery or from infarction) can cause sick sinus syndrome.

Question 4: Which coronary artery primarily supplies the left ventricle's anterior wall and interventricular septum?

Left anterior descending (LAD) artery (Correct answer)
Right coronary artery (RCA)
Left circumflex artery (LCX)
Posterior descending artery (PDA)

Correct answer: Left anterior descending (LAD) artery

The left anterior descending artery travels in the anterior interventricular groove and is the primary blood supply to the anterior wall of the left ventricle and the anterior two-thirds of the interventricular septum.

The LAD (left anterior descending), also called the 'widow maker' due to the severity of events caused by its occlusion, is a branch of the left main coronary artery. It supplies the anterior left ventricular wall, the apex, and the anterior two-thirds of the interventricular septum. It also gives off diagonal branches to the lateral wall and septal perforators to the septum. LAD occlusion causes anterior STEMI, which is typically the largest and most hemodynamically significant type of MI.

Question 5: During the cardiac cycle, what occurs during ventricular diastole?

The ventricles relax and fill with blood from the atria (Correct answer)
The ventricles contract and eject blood into the arteries
The atrioventricular valves close
The semilunar valves open

Correct answer: The ventricles relax and fill with blood from the atria

Diastole is the relaxation phase of the cardiac cycle. During ventricular diastole, the myocardium relaxes, ventricular pressure falls, the AV valves open, and the ventricles fill with blood.

The cardiac cycle consists of systole (contraction and ejection) and diastole (relaxation and filling). During diastole, ventricular muscle relaxation causes intraventricular pressure to drop below atrial pressure, allowing the mitral and tricuspid valves to open and blood to flow passively into the ventricles (early diastolic filling). The atria then contract (atrial kick) to contribute an additional 15-30% of ventricular filling volume. Diastolic dysfunction — impaired ventricular relaxation — is a common cause of heart failure with preserved ejection fraction (HFpEF).

Question 6: What is the normal range for cardiac output at rest in a healthy adult?

4 to 8 liters per minute (Correct answer)
1 to 2 liters per minute
10 to 15 liters per minute
0.5 to 1 liter per minute

Correct answer: 4 to 8 liters per minute

Normal resting cardiac output in a healthy adult is approximately 4-8 liters per minute, calculated as heart rate multiplied by stroke volume (CO = HR × SV).

Cardiac output (CO) is the volume of blood pumped by the heart per minute and equals heart rate (HR) multiplied by stroke volume (SV). At rest, a typical adult has HR ≈ 60-80 bpm and SV ≈ 60-80 mL, giving CO ≈ 4-8 L/min. The cardiac index (CI = CO/body surface area) normalizes for body size and is normally 2.5-4.0 L/min/m². During maximal exercise, CO can increase 4-7 fold in trained athletes. Reduced CO is a hallmark of cardiogenic shock and heart failure.

CCT Cardiovascular Anatomy and Physiology 2

Which layer of the heart wall is responsible for the contractile function of the heart?