1. Which chamber of the heart pumps oxygenated blood into the systemic circulation?
A. Right atrium
B. Right ventricle
C. Left atrium
D. Left ventricle
Answer: D. Left ventricle
Rationale: The left ventricle has the thickest myocardium because it must generate sufficient pressure
to propel oxygenated blood through the entire systemic circulation. The right ventricle only pumps
blood to the lungs, requiring less force.
2. Which blood vessel carries oxygenated blood from the lungs to the heart?
A. Pulmonary artery
B. Superior vena cava
C. Pulmonary vein
D. Aorta
Answer: C. Pulmonary vein
Rationale: Pulmonary veins are unique because they carry oxygen-rich blood from the lungs to the
left atrium. Most veins carry deoxygenated blood.
3. The sinoatrial (SA) node is located in the:
A. Left ventricle
B. Right atrium
C. Interventricular septum
D. Left atrium
Answer: B. Right atrium
Rationale: The SA node is the natural pacemaker of the heart and initiates electrical impulses that
establish heart rhythm. It is located in the wall of the right atrium.
4. Which component of blood is primarily responsible for clotting?
A. Erythrocytes
B. Leukocytes
C. Platelets
D. Plasma proteins
Answer: C. Platelets
,Rationale: Platelets, or thrombocytes, initiate hemostasis by forming platelet plugs and releasing
clotting factors that help stop bleeding.
5. Which white blood cell is most abundant in normal blood?
A. Basophil
B. Eosinophil
C. Neutrophil
D. Monocyte
Answer: C. Neutrophil
Rationale: Neutrophils account for approximately 50–70% of circulating leukocytes and serve as the
primary defenders against bacterial infections.
6. Hemoglobin is found within:
A. Plasma
B. Leukocytes
C. Platelets
D. Erythrocytes
Answer: D. Erythrocytes
Rationale: Hemoglobin is the oxygen-carrying protein found inside red blood cells. It binds oxygen in
the lungs and transports it to tissues.
7. Which valve prevents backflow from the left ventricle into the left atrium?
A. Tricuspid valve
B. Pulmonary valve
C. Mitral valve
D. Aortic valve
Answer: C. Mitral valve
Rationale: The mitral (bicuspid) valve ensures one-way blood flow from the left atrium to the left
ventricle and prevents regurgitation during ventricular contraction.
8. The largest artery in the body is the:
A. Pulmonary artery
B. Coronary artery
C. Aorta
D. Carotid artery
Answer: C. Aorta
, Rationale: The aorta receives blood directly from the left ventricle and distributes oxygenated blood
to systemic tissues.
9. Which blood type is considered the universal donor?
A. AB+
B. O−
C. A+
D. B−
Answer: B. O−
Rationale: Type O-negative blood lacks A, B, and Rh antigens, minimizing the risk of transfusion
reactions in recipients.
10. Which blood type is considered the universal recipient?
A. O−
B. AB+
C. A−
D. B+
Answer: B. AB+
Rationale: Individuals with AB-positive blood possess all major antigens and therefore do not produce
antibodies against A, B, or Rh antigens.
11. Gas exchange in the lungs occurs within the:
A. Bronchi
B. Trachea
C. Alveoli
D. Pleura
Answer: C. Alveoli
Rationale: Alveoli have thin walls and extensive capillary networks that facilitate oxygen and carbon
dioxide diffusion.
12. Which muscle is the primary muscle of inspiration?
A. External intercostal
B. Diaphragm
C. Internal intercostal
D. Rectus abdominis
Answer: B. Diaphragm