BIOS 255 Anatomy & Physiology III Exam 1
(2025/2026) | 100+ Practice Questions with
Answers & Rationales – Guaranteed Exam Prep
1. Which layer of the heart wall is responsible for contraction?
Answer: Myocardium
Rationale: The myocardium is composed of cardiac muscle fibers that contract to pump
blood. The epicardium is the outer layer, and the endocardium lines the inner chambers.
2. The heart’s pacemaker is located in the:
Answer: Sinoatrial (SA) node
Rationale: The SA node generates electrical impulses that initiate each heartbeat, setting
the rhythm for the heart.
3. Which valve prevents backflow from the right ventricle to the right atrium?
Answer: Tricuspid valve
Rationale: The tricuspid valve has three cusps and ensures unidirectional flow from
atrium to ventricle.
4. During ventricular systole, which valves are open?
Answer: Semilunar valves (aortic and pulmonary)
Rationale: Ventricular contraction pushes blood into the arteries, opening semilunar
valves while atrioventricular valves remain closed.
,5. Which blood vessels have the highest blood pressure?
Answer: Arteries
Rationale: Arteries are closer to the heart and have thick muscular walls to withstand
high pressure from ventricular contraction.
6. Cardiac output is the product of:
Answer: Heart rate × Stroke volume
Rationale: Stroke volume is the amount of blood pumped per beat; multiplying by heart
rate gives cardiac output (CO = HR × SV).
7. Which ion is critical for cardiac muscle contraction?
Answer: Calcium (Ca²⁺)
Rationale: Calcium influx during the plateau phase triggers actin-myosin interaction in
cardiac muscle.
8. The P wave on an ECG represents:
Answer: Atrial depolarization
Rationale: P wave corresponds to the electrical activity that causes atria to contract. QRS
represents ventricular depolarization.
9. Which condition results from narrowing of coronary arteries?
Answer: Myocardial ischemia
Rationale: Reduced blood flow through coronary arteries limits oxygen delivery to
cardiac tissue, causing ischemia.
10. Which factor increases venous return?
Answer: Skeletal muscle pump
, Rationale: Contraction of skeletal muscles compresses veins, pushing blood toward the
heart, aided by venous valves.
Lymphatic and Immune System
11. The largest lymphatic organ is the:
Answer: Spleen
Rationale: The spleen filters blood, removes old RBCs, and houses lymphocytes for
immune response.
12. Lymph is returned to the venous system via the:
Answer: Thoracic duct and right lymphatic duct
Rationale: Lymphatic trunks drain into these ducts, which empty lymph into subclavian
veins.
13. Which cells produce antibodies?
Answer: B lymphocytes (plasma cells)
Rationale: B cells differentiate into plasma cells that secrete antibodies against specific
antigens.
14. The primary function of T helper cells (CD4⁺) is to:
Answer: Activate B cells and cytotoxic T cells
Rationale: T helper cells coordinate adaptive immunity by stimulating other immune
cells.
15. Innate immunity includes all EXCEPT:
a) Skin
(2025/2026) | 100+ Practice Questions with
Answers & Rationales – Guaranteed Exam Prep
1. Which layer of the heart wall is responsible for contraction?
Answer: Myocardium
Rationale: The myocardium is composed of cardiac muscle fibers that contract to pump
blood. The epicardium is the outer layer, and the endocardium lines the inner chambers.
2. The heart’s pacemaker is located in the:
Answer: Sinoatrial (SA) node
Rationale: The SA node generates electrical impulses that initiate each heartbeat, setting
the rhythm for the heart.
3. Which valve prevents backflow from the right ventricle to the right atrium?
Answer: Tricuspid valve
Rationale: The tricuspid valve has three cusps and ensures unidirectional flow from
atrium to ventricle.
4. During ventricular systole, which valves are open?
Answer: Semilunar valves (aortic and pulmonary)
Rationale: Ventricular contraction pushes blood into the arteries, opening semilunar
valves while atrioventricular valves remain closed.
,5. Which blood vessels have the highest blood pressure?
Answer: Arteries
Rationale: Arteries are closer to the heart and have thick muscular walls to withstand
high pressure from ventricular contraction.
6. Cardiac output is the product of:
Answer: Heart rate × Stroke volume
Rationale: Stroke volume is the amount of blood pumped per beat; multiplying by heart
rate gives cardiac output (CO = HR × SV).
7. Which ion is critical for cardiac muscle contraction?
Answer: Calcium (Ca²⁺)
Rationale: Calcium influx during the plateau phase triggers actin-myosin interaction in
cardiac muscle.
8. The P wave on an ECG represents:
Answer: Atrial depolarization
Rationale: P wave corresponds to the electrical activity that causes atria to contract. QRS
represents ventricular depolarization.
9. Which condition results from narrowing of coronary arteries?
Answer: Myocardial ischemia
Rationale: Reduced blood flow through coronary arteries limits oxygen delivery to
cardiac tissue, causing ischemia.
10. Which factor increases venous return?
Answer: Skeletal muscle pump
, Rationale: Contraction of skeletal muscles compresses veins, pushing blood toward the
heart, aided by venous valves.
Lymphatic and Immune System
11. The largest lymphatic organ is the:
Answer: Spleen
Rationale: The spleen filters blood, removes old RBCs, and houses lymphocytes for
immune response.
12. Lymph is returned to the venous system via the:
Answer: Thoracic duct and right lymphatic duct
Rationale: Lymphatic trunks drain into these ducts, which empty lymph into subclavian
veins.
13. Which cells produce antibodies?
Answer: B lymphocytes (plasma cells)
Rationale: B cells differentiate into plasma cells that secrete antibodies against specific
antigens.
14. The primary function of T helper cells (CD4⁺) is to:
Answer: Activate B cells and cytotoxic T cells
Rationale: T helper cells coordinate adaptive immunity by stimulating other immune
cells.
15. Innate immunity includes all EXCEPT:
a) Skin
