Blood and Circulation Practice Questions
20 free Blood and Circulation practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which component of blood is primarily responsible for the transport of oxygen to the body's tissues?
- A White blood cells
- B Platelets
- C Plasma
- D Red blood cells
Correct answer: Red blood cells
Red blood cells (erythrocytes) contain hemoglobin, a protein that binds to oxygen in the lungs and releases it in the tissues. Their biconcave shape increases surface area for efficient gas exchange.
Which chamber of the human heart receives oxygenated blood directly from the lungs via the pulmonary veins?
- A Right atrium
- B Right ventricle
- C Left ventricle
- D Left atrium
Correct answer: Left atrium
Oxygenated blood returns from the lungs and enters the left atrium. From there, it passes through the mitral valve into the left ventricle to be pumped to the rest of the body.
What is the primary function of platelets (thrombocytes) in the blood?
- A Fighting infections caused by bacteria
- B Maintaining blood pH balance
- C Transporting oxygen to body tissues
- D Initiating blood clot formation
Correct answer: Initiating blood clot formation
Platelets are cell fragments that stick to the site of a blood vessel injury and clump together. They release clotting factors that convert fibrinogen into fibrin, forming a mesh that seals the wound and stops bleeding.
Which blood vessel carries deoxygenated blood from the heart to the lungs?
- A Aorta
- B Pulmonary artery
- C Pulmonary vein
- D Superior vena cava
Correct answer: Pulmonary artery
The pulmonary artery is unique because it carries deoxygenated blood away from the right ventricle toward the lungs. Most other arteries in the body carry oxygenated blood.
In the ABO blood group system, which blood type is considered the 'universal donor'?
- A Type A
- B Type B
- C Type AB
- D Type O
Correct answer: Type O
Type O blood lacks both A and B antigens on the surface of the red blood cells. Because of this, it can be transfused into individuals of any other blood type without causing an immune reaction.
Which valve prevents the backflow of blood from the left ventricle into the left atrium?
- A Tricuspid valve
- B Pulmonary valve
- C Mitral valve
- D Aortic valve
Correct answer: Mitral valve
The mitral valve is located between the left atrium and left ventricle. It closes during ventricular contraction to ensure that blood is forced into the aorta rather than back into the atrium.
What is the normal average lifespan of a human red blood cell?
- A 5 to 7 days
- B 30 days
- C 120 days
- D 365 days
Correct answer: 120 days
Erythrocytes circulate for approximately 120 days before they become aged and fragile. They are then removed from circulation and broken down, primarily by the spleen and liver.
Which protein found in plasma is essential for maintaining osmotic pressure and preventing edema?
- A Transferrin
- B Serum albumin
- C Fibrinogen
- D Gamma globulin
Correct answer: Serum albumin
Serum albumin is the most abundant plasma protein and generates the oncotic pressure of blood. That pressure draws water back into the capillaries, balancing the hydrostatic pressure that pushes fluid out into the tissues, so a fall in albumin leads to edema.
The 'pacemaker' of the heart, which initiates the electrical impulses for contraction, is the:
- A Atrioventricular (AV) node
- B Bundle of His
- C Sinoatrial (SA) node
- D Purkinje fibers
Correct answer: Sinoatrial (SA) node
The SA node, located in the right atrium, spontaneously generates electrical signals at a regular rhythm. These signals spread through the atria, causing them to contract and send blood to the ventricles.
Which of the following describes the 'systolic' phase of blood pressure?
- A The pressure in the arteries when the heart is at rest
- B The pressure in the arteries during ventricular contraction
- C The pressure within the veins as blood returns toward the heart
- D The average pressure across a full cardiac cycle
Correct answer: The pressure in the arteries during ventricular contraction
Systolic pressure is the peak pressure in the arteries, occurring when the ventricles contract and pump blood into the aorta. It is the top number in a standard blood pressure reading.
Which blood vessels have the thinnest walls, allowing for the exchange of gases and nutrients with tissues?
- A Elastic arteries
- B Arterioles
- C Capillaries
- D Venules
Correct answer: Capillaries
Capillaries have walls that are only one cell thick, consisting of a single layer of endothelium. This minimal barrier allows oxygen, carbon dioxide, and nutrients to diffuse easily between the blood and interstitial fluid.
A person with Type AB blood is considered a 'universal recipient' because their plasma lacks:
- A Antibodies against the Rh (D) antigen
- B Anti-A and Anti-B antibodies
- C A and B surface antigens
- D Complement proteins
Correct answer: Anti-A and Anti-B antibodies
Individuals with Type AB blood have both A and B antigens on their red cells, so they do not produce antibodies against them. Therefore, they can receive blood from types A, B, AB, or O without a rejection response.
Which hormone, produced by the kidneys, stimulates the bone marrow to produce more red blood cells?
- A Insulin
- B Erythropoietin
- C Thyroxine
- D Antidiuretic hormone
Correct answer: Erythropoietin
When oxygen levels in the blood are low, the kidneys release erythropoietin. This hormone travels to the red bone marrow to accelerate the production of erythrocytes, enhancing the blood's oxygen-carrying capacity.
The 'lub-dub' sounds of a heartbeat are primarily caused by:
- A The contraction of the heart muscle
- B The flow of blood in the aorta
- C The closing of the heart valves
- D The electrical firing of the SA node
Correct answer: The closing of the heart valves
The first sound ('lub') is the closing of the AV valves, and the second sound ('dub') is the closing of the semilunar valves. These sounds are produced by the turbulence created when the valves snap shut.
Which of the following is an agranular leukocyte involved in the immune response?
- A Neutrophil
- B Eosinophil
- C Basophil
- D Monocyte
Correct answer: Monocyte
Monocytes and lymphocytes are agranulocytes, meaning they lack visible granules in their cytoplasm. Monocytes eventually leave the bloodstream to become macrophages in the tissues.
The hepatic portal vein carries nutrient-rich blood from the digestive tract to which organ?
- A Heart
- B Kidneys
- C Liver
- D Spleen
Correct answer: Liver
The hepatic portal system ensures that absorbed nutrients and potential toxins are processed by the liver before entering the general circulation. The liver detoxifies the blood and stores essential nutrients like glycogen.
Which metal ion is a central component of the heme group in hemoglobin?
- A Magnesium
- B Copper
- C Zinc
- D Iron
Correct answer: Iron
Each heme group contains an iron atom (Fe2+) at its centre, and that iron is what reversibly binds one oxygen molecule. This is why iron deficiency leads to anemia and reduced oxygen transport.
What is the primary difference between an artery and a vein?
- A Arteries carry only oxygenated blood, while veins carry only deoxygenated blood.
- B Arteries carry blood away from the heart; veins carry blood toward the heart.
- C Veins have thicker muscular walls than arteries.
- D Arteries contain valves to prevent backflow; veins do not.
Correct answer: Arteries carry blood away from the heart; veins carry blood toward the heart.
The definition of arteries and veins is based on the direction of blood flow relative to the heart. While most arteries are oxygenated, the pulmonary artery is a notable exception.
What condition is characterized by a lower-than-normal number of red blood cells or a reduced amount of hemoglobin?
- A Anemia
- B Leukemia
- C Hemophilia
- D Uremia
Correct answer: Anemia
Anemia results in fatigue and paleness because the blood cannot deliver enough oxygen to meet the body's needs. It can be caused by blood loss, nutritional deficiencies, or genetic disorders like sickle cell disease.
Which large vein returns deoxygenated blood from the lower half of the body to the right atrium?
- A Inferior vena cava
- B Superior vena cava
- C Jugular vein
- D Subclavian vein
Correct answer: Inferior vena cava
The inferior vena cava is the largest vein in the body. It collects deoxygenated blood from the legs, abdomen, and pelvis and delivers it to the right side of the heart to begin the pulmonary circuit.