BLO 251 Final Exam Questions with Correct
Answers (VerifiedAnswers) Plus Rationales
2026 Q&A Instant Download PDF
BLO 251 Final Exam Practice Questions
Question 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
Correct Answer: D. Left ventricle
The left ventricle is the major pumping chamber of the systemic
circuit. It receives oxygenated blood from the left atrium and
ejects it through the aortic valve into the aorta. Because
systemic circulation requires blood to be propelled throughout
the entire body, the left ventricular myocardium is substantially
thicker than that of the right ventricle.
,Question 2
Which structure normally serves as the pacemaker of the
heart?
A. Atrioventricular node
B. Sinoatrial node
C. Bundle of His
D. Purkinje fibers
Correct Answer: B. Sinoatrial node
The sinoatrial node, located in the right atrium, normally
generates spontaneous electrical impulses at the fastest
intrinsic rate in the cardiac conduction system. These impulses
spread through the atria and initiate atrial contraction. The
atrioventricular node, bundle branches, and Purkinje fibers
conduct the impulse afterward but normally do not determine
the resting heart rate.
Question 3
What is the primary function of the atrioventricular node?
A. Initiating ventricular repolarization
B. Producing red blood cells
C. Delaying the electrical impulse before it enters the ventricles
D. Closing the semilunar valves
,Correct Answer: C. Delaying the electrical impulse before it
enters the ventricles
The atrioventricular node introduces a brief delay between
atrial and ventricular depolarization. This delay gives the atria
sufficient time to complete their contraction and move blood
into the ventricles before ventricular contraction begins.
Without this coordination, ventricular filling and cardiac
efficiency would be reduced.
Question 4
Which valve prevents backflow of blood from the left ventricle
into the left atrium?
A. Tricuspid valve
B. Pulmonary semilunar valve
C. Aortic semilunar valve
D. Mitral valve
Correct Answer: D. Mitral valve
The mitral, or bicuspid, valve lies between the left atrium and
left ventricle. It opens when ventricular pressure is lower than
atrial pressure, allowing blood to enter the ventricle. When
ventricular pressure rises during systole, the valve closes and
prevents blood from returning to the atrium.
, Question 5
Which blood vessels are the primary sites of exchange between
blood and tissues?
A. Arteries
B. Veins
C. Capillaries
D. Arterioles
Correct Answer: C. Capillaries
Capillaries have extremely thin walls, generally consisting of a
single layer of endothelial cells. Their structure permits efficient
movement of oxygen, carbon dioxide, nutrients, hormones, and
metabolic wastes between blood and surrounding tissues.
Arteries and veins are primarily responsible for transporting
blood rather than direct exchange.
Question 6
Which component of blood is primarily responsible for oxygen
transport?
A. Platelets
B. Plasma proteins
C. Erythrocytes
D. Leukocytes
Answers (VerifiedAnswers) Plus Rationales
2026 Q&A Instant Download PDF
BLO 251 Final Exam Practice Questions
Question 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
Correct Answer: D. Left ventricle
The left ventricle is the major pumping chamber of the systemic
circuit. It receives oxygenated blood from the left atrium and
ejects it through the aortic valve into the aorta. Because
systemic circulation requires blood to be propelled throughout
the entire body, the left ventricular myocardium is substantially
thicker than that of the right ventricle.
,Question 2
Which structure normally serves as the pacemaker of the
heart?
A. Atrioventricular node
B. Sinoatrial node
C. Bundle of His
D. Purkinje fibers
Correct Answer: B. Sinoatrial node
The sinoatrial node, located in the right atrium, normally
generates spontaneous electrical impulses at the fastest
intrinsic rate in the cardiac conduction system. These impulses
spread through the atria and initiate atrial contraction. The
atrioventricular node, bundle branches, and Purkinje fibers
conduct the impulse afterward but normally do not determine
the resting heart rate.
Question 3
What is the primary function of the atrioventricular node?
A. Initiating ventricular repolarization
B. Producing red blood cells
C. Delaying the electrical impulse before it enters the ventricles
D. Closing the semilunar valves
,Correct Answer: C. Delaying the electrical impulse before it
enters the ventricles
The atrioventricular node introduces a brief delay between
atrial and ventricular depolarization. This delay gives the atria
sufficient time to complete their contraction and move blood
into the ventricles before ventricular contraction begins.
Without this coordination, ventricular filling and cardiac
efficiency would be reduced.
Question 4
Which valve prevents backflow of blood from the left ventricle
into the left atrium?
A. Tricuspid valve
B. Pulmonary semilunar valve
C. Aortic semilunar valve
D. Mitral valve
Correct Answer: D. Mitral valve
The mitral, or bicuspid, valve lies between the left atrium and
left ventricle. It opens when ventricular pressure is lower than
atrial pressure, allowing blood to enter the ventricle. When
ventricular pressure rises during systole, the valve closes and
prevents blood from returning to the atrium.
, Question 5
Which blood vessels are the primary sites of exchange between
blood and tissues?
A. Arteries
B. Veins
C. Capillaries
D. Arterioles
Correct Answer: C. Capillaries
Capillaries have extremely thin walls, generally consisting of a
single layer of endothelial cells. Their structure permits efficient
movement of oxygen, carbon dioxide, nutrients, hormones, and
metabolic wastes between blood and surrounding tissues.
Arteries and veins are primarily responsible for transporting
blood rather than direct exchange.
Question 6
Which component of blood is primarily responsible for oxygen
transport?
A. Platelets
B. Plasma proteins
C. Erythrocytes
D. Leukocytes
