22 Circulatory Anatomy & Physiology Practice Questions & Answers

1. 1. A phlebotomy student asks why the pulmonary artery is classified as an artery when the blood inside it is low in oxygen. What is the correct explanation?

   • A.Vessel names follow the direction of flow, so a vessel carrying blood away from the heart is an artery✓ Answer
   • B.Vessel names follow oxygen content, so the pulmonary artery is a rare exception to a firm rule
   • C.Vessel names follow wall thickness, so a thick-walled vessel is an artery whatever it carries
   • D.Vessel names follow internal pressure, so a low-pressure vessel leaving the heart counts as a vein

   Arteries and veins are defined by the direction of flow relative to the heart, not by oxygen content: an artery carries blood away from the heart. The pulmonary arteries carry oxygen-poor blood to the lungs and the pulmonary veins return oxygen-rich blood to the left atrium, which is the classic exception candidates miss.

   Source: NHA CPT Test Plan, Core Knowledge, cardiovascular anatomy and physiologyReport a problem with this question

2. 2. Blood has just been ejected from the right ventricle. Which sequence traces its route until it reaches the left atrium?

   • A.Pulmonary valve, then pulmonary arteries, then the lungs, then pulmonary veins, then left atrium✓ Answer
   • B.Aortic valve, then the aorta, then systemic capillaries, then superior vena cava, then left atrium
   • C.Mitral valve, then pulmonary arteries, then the lungs, then superior vena cava, then left atrium
   • D.Tricuspid valve, then pulmonary veins, then the lungs, then pulmonary arteries, then left atrium

   Blood leaving the right ventricle passes the pulmonary semilunar valve into the pulmonary arteries, is oxygenated in the lungs, and returns through the pulmonary veins to the left atrium. The tricuspid valve sits before the right ventricle and the mitral valve after the left atrium, so neither can appear on this segment of the circuit.

   Source: NHA CPT Test Plan, Core Knowledge, pulmonary and systemic blood flowReport a problem with this question

3. 3. A patient asks why the left side of the heart is described as the stronger side. Which explanation is accurate?

   • A.The left ventricle receives blood already under high pressure, so its wall thickens over time
   • B.The left ventricle fills with a much larger volume of blood on each beat than the right does
   • C.The left ventricle wall is thicker because it drives blood through the short pulmonary circuit
   • D.The left ventricle wall is thicker because it must push blood through the whole systemic circuit✓ Answer

   Both ventricles eject about the same stroke volume, but the left ventricle must overcome the high resistance of the systemic circuit while the right ventricle pumps only into the low-pressure pulmonary circuit. Greater workload, not greater volume, is what builds the thicker left ventricular myocardium.

   Source: NHA CPT Test Plan, Core Knowledge, anatomy and physiology of the heartReport a problem with this question

4. 4. During palpation an artery feels firm and round while a nearby vein flattens under the fingertip. Which structural difference explains this?

   • A.The artery has a thick tunica adventitia, while the vein has almost no outer connective layer
   • B.The artery contains one-way valves that brace it, while the vein has no valves to support it
   • C.The artery has a thick muscular tunica media, while the thin media of a vein lets it collapse✓ Answer
   • D.The artery has a double endothelial lining, while a single lining cannot hold the vein open

   The tunica media, made of smooth muscle and elastic tissue, is the thickest layer in arteries and keeps the lumen round and firm against high pressure. Veins have a thin media and a relatively thick adventitia, so they collapse easily, and the one-way valves formed by folds of the tunica intima are found in veins rather than arteries.

   Source: NHA CPT Test Plan, Core Knowledge, structure of blood vesselsReport a problem with this question

5. 5. Where in the circulatory system does the actual exchange of oxygen, nutrients, and wastes between blood and tissue take place?

   • A.In the large veins, where low pressure lets fluid and gases move freely through the wall
   • B.In the arterioles, whose muscular walls open pores that release oxygen into the tissue
   • C.In the capillaries, whose wall is a single endothelial cell thick and permits free diffusion✓ Answer
   • D.In the venules, where slowing blood flow lets wastes pass back across the vessel wall

   Capillaries are the only vessels thin enough for exchange: their wall is a single layer of endothelium (tunica intima alone), so gases, nutrients, and wastes diffuse across it between blood and interstitial fluid. Arterioles, venules, and veins are conduits whose walls are too thick for that exchange.

   Source: NHA CPT Test Plan, Core Knowledge, capillary exchangeReport a problem with this question

6. 6. A patient who has been lying down for two hours stands up, and blood is collected fifteen minutes later. Compared with the supine sample, how do the albumin and calcium results change?

   • A.Both rise, because standing shifts water out of the vessels and concentrates bound analytes✓ Answer
   • B.Neither changes, because posture affects cell counts alone and leaves plasma chemistry alike
   • C.Both fall, because standing pulls water into the vessels and dilutes the larger plasma proteins
   • D.Albumin rises but calcium falls, because only unbound analytes follow the shift in plasma water

   Standing moves plasma water out of the vessels into the tissues, and large protein-bound molecules cannot follow it, so albumin, calcium, cholesterol, and enzymes concentrate and can rise by roughly ten percent. Posture is a physiologic pre-analytical variable, not an analyzer error.

   Source: NHA CPT Test Plan, Core Knowledge, pre-analytical error: postureReport a problem with this question

7. 7. While palpating the medial aspect of the antecubital fossa, the phlebotomist feels a firm structure that pulses against the fingertip. What does this finding indicate and what should be done?

   • A.It is a well-filled median cubital vein, so it may be entered at a shallower angle than usual
   • B.It is the brachial artery, so another site should be selected instead of that structure✓ Answer
   • C.It is a sclerosed vein, so firm massage should be applied to restore flow before the puncture
   • D.It is a tendon, so the needle should be redirected slightly medial to it before the puncture

   A structure that pulses and feels firm is an artery, and the brachial artery runs through the medial antecubital area beneath the basilic vein. Nothing that pulsates is ever punctured for a routine venous specimen, so the phlebotomist moves to a different vein.

   Source: CLSI GP41 site selection; NHA CPT Test Plan, Core KnowledgeReport a problem with this question

8. 8. The median cubital vein cannot be palpated in either arm. Following CLSI vein-selection priority, which vein is chosen next and which is held back as a last resort?

   • A.The basilic is next; the cephalic is last because it rolls and lies over the median nerve
   • B.The cephalic is next; the basilic is last because the brachial artery and nerves lie beside it✓ Answer
   • C.The cephalic is next; the basilic is last because it is too deep to enter without a syringe
   • D.The basilic is next; the cephalic is last because it carries a higher risk of hematoma there

   CLSI GP41 ranks the veins by the risk of what lies beneath them: median or central veins first, then the lateral cephalic, and the medial basilic last because the brachial artery and the median and medial antebrachial cutaneous nerves run immediately alongside it. The cephalic rolls more but sits away from those structures.

   Source: CLSI GP41, vein selection priority (median, then lateral, then medial)Report a problem with this question

9. 9. A patient arrives visibly dehydrated after several days of vomiting. Which direction of change should be expected in the hematocrit and the total protein on that specimen?

   • A.Hematocrit is decreased and total protein is unchanged, because only cells react to fluid loss
   • B.Both are falsely decreased, because water from the tissues moves into the bloodstream
   • C.Both are falsely increased, because plasma water is lost and the remaining blood concentrates✓ Answer
   • D.Both are unchanged, because the body defends blood volume and keeps analyte levels constant

   Dehydration removes plasma water while cells and large proteins stay behind, so the blood is concentrated and hematocrit, total protein, and other large analytes read falsely high. This is hemoconcentration from a physiologic state rather than from the draw itself, and the direction of change is the tested point.

   Source: NHA CPT Test Plan, Core Knowledge, pre-analytical error: hemoconcentrationReport a problem with this question

10. 10. The structure the phlebotomist palpates in the antecubital area is hard and cord-like, does not roll or rebound, and stands out more when the patient clenches the hand. What is it most likely to be?

    • A.A vein in spasm, which will refill and become soft again if the tourniquet is retied
    • B.The brachial artery, which becomes firmer whenever the surrounding muscle contracts
    • C.A thrombosed vein, which will feel softer once the arm is warmed for several minutes
    • D.A tendon, which must be avoided because puncturing it is painful and yields no blood✓ Answer

    A tendon is hard and cord-like, does not have the soft bounce of a patent vein, and tightens with hand movement because it anchors muscle to bone. A healthy vein palpates soft and spongy and rebounds under the finger, and an artery pulses, so those two feel entirely different.

    Source: CLSI GP41, palpation and site assessment; Core KnowledgeReport a problem with this question

11. 11. In a patient with many previous draws, one vein feels hard and cord-like along its whole length with no springiness when pressed. What does this indicate and what should follow?

    • A.It is sclerosed and scarred, so flow through it is poor and another site should be chosen✓ Answer
    • B.It is simply a deep vein, so a longer needle will reach it and the draw can proceed there
    • C.It is a collapsed vein, so releasing the tourniquet briefly will let it refill and be used
    • D.It is a valve-rich segment, so entering just above a valve will still give an adequate flow

    Repeated punctures scar a vein: the wall becomes fibrotic and the lumen narrows, so the vessel palpates hard and cord-like and loses its normal spongy rebound. Blood flow through a sclerosed vein is inadequate and the specimen is likely to be compromised, so a different site is selected.

    Source: CLSI GP41, veins to be avoided (sclerosed or thrombosed); Core KnowledgeReport a problem with this question

12. 12. Why are the dorsal metacarpal veins of the hand considered a second-choice site rather than a first-choice site for venipuncture?

    • A.They carry partly arterial blood, so results from them cannot be compared with venous ones
    • B.They pass directly over the radial artery, so the risk of arterial entry there is too high
    • C.They are smaller and less anchored than antecubital veins, so they roll more and hurt more✓ Answer
    • D.They have no valves at all, so blood pools backward in them and hemolysis follows easily

    Hand veins are narrower and are supported by far less surrounding tissue than the antecubital veins, so they roll away from the needle and the puncture is more painful, and a winged set with smaller tubes is used when they must be entered. Anatomy, not oxygen content, is what makes them a second choice.

    Source: CLSI GP41, alternate venipuncture sites; Core KnowledgeReport a problem with this question

13. 13. Two specimens from the same patient are centrifuged: one was allowed to clot completely, the other was anticoagulated. What is the physical difference between the fluid layers obtained?

    • A.Both tubes give the same fluid, since fibrinogen stays dissolved however blood is handled
    • B.The clotted tube gives serum, which lacks fibrinogen because the protein was used in the clot✓ Answer
    • C.The clotted tube gives serum, which holds more fibrinogen than the anticoagulated tube does
    • D.The clotted tube gives plasma, which keeps fibrinogen because clotting removes no protein

    When blood is allowed to clot, fibrinogen is converted to fibrin and trapped in the clot, so the fluid left above the cells is serum, which contains no fibrinogen or other consumed clotting factors. An anticoagulated tube blocks that conversion, so its supernatant is plasma and still contains fibrinogen.

    Source: NHA CPT Test Plan, Core Knowledge, blood components: serum versus plasmaReport a problem with this question

14. 14. A tube of anticoagulated whole blood has been centrifuged. What occupies the thin layer between the plasma above and the red cell mass below, and what does that lower layer represent?

    • A.White cells and platelets form the buffy coat, and the red layer below is the hematocrit✓ Answer
    • B.Fibrin strands sit in the middle layer, and the lower layer is what is called the hematocrit
    • C.Serum proteins settle in the middle layer, and the lower layer is the total blood volume
    • D.Reticulocytes gather in the middle layer, and the lower layer is the plasma protein share

    Centrifuged anticoagulated blood separates into about 55 percent plasma on top, a buffy coat of white cells and platelets that is less than 1 percent, and roughly 45 percent packed red cells at the bottom. That packed red cell fraction is what the hematocrit reports.

    Source: NHA CPT Test Plan, Core Knowledge, composition of whole bloodReport a problem with this question

15. 15. A differential count is reported on a healthy adult. Which white cell type should appear in the greatest proportion, and which in the smallest?

    • A.Monocytes are the most numerous, and eosinophils are the fewest in a normal adult
    • B.Eosinophils are the most numerous, and lymphocytes are the fewest in a normal adult
    • C.Lymphocytes are the most numerous, and monocytes are the fewest in a normal adult
    • D.Neutrophils are the most numerous, and basophils are the fewest in a normal adult✓ Answer

    In a normal adult differential the neutrophils dominate at roughly half to seventy percent because they are the front-line phagocytes against bacteria, while basophils, which release histamine and heparin, make up one percent or less. Lymphocytes are second in number and monocytes are the largest cells, not the most abundant.

    Source: NHA CPT Test Plan, Core Knowledge, formed elements: leukocytesReport a problem with this question

16. 16. Which statement correctly describes platelets and the part they play when a vessel wall is injured?

    • A.They are the largest formed element and engulf bacteria at the site of the injured vessel
    • B.They are fragments of megakaryocytes and clump together to form the first plug at the injury✓ Answer
    • C.They are whole cells with a nucleus and release the fibrin that seals the injured vessel
    • D.They are immature red cells and carry oxygen to the tissue around the injured vessel

    Platelets are not whole cells but cytoplasmic fragments shed from megakaryocytes in the bone marrow, and they are the smallest formed element. They adhere to the damaged vessel wall and aggregate into the temporary platelet plug of primary hemostasis, before the fibrin clot is built.

    Source: NHA CPT Test Plan, Core Knowledge, thrombocytes and primary hemostasisReport a problem with this question

17. 17. Place the phases of hemostasis in the order the body carries them out after a small vessel is cut.

    • A.Vasoconstriction, then the platelet plug, then the fibrin clot, then breakdown of the clot✓ Answer
    • B.Platelet plug, then vasoconstriction, then breakdown of the clot, then the fibrin clot
    • C.Fibrin clot, then vasoconstriction, then the platelet plug, then breakdown of the clot
    • D.Vasoconstriction, then the fibrin clot, then breakdown of the clot, then the platelet plug

    Hemostasis runs in four fixed steps: the vessel constricts to slow flow, platelets adhere and aggregate into a temporary plug, the coagulation cascade converts fibrinogen to fibrin and stabilizes that plug, and finally fibrinolysis dissolves the clot as the vessel heals. Each step depends on the one before it.

    Source: NHA CPT Test Plan, Core Knowledge, hemostasis: four phasesReport a problem with this question

18. 18. Which pathway of coagulation does each test evaluate: the prothrombin time with INR, and the activated partial thromboplastin time?

    • A.The PT evaluates the intrinsic pathway, and the aPTT evaluates the extrinsic pathway
    • B.The PT evaluates platelet function, and the aPTT the firmness of the fibrin clot formed
    • C.The PT evaluates the extrinsic and common pathways, and the aPTT the intrinsic pathway✓ Answer
    • D.The PT evaluates fibrinolysis, and the aPTT evaluates the common pathway on its own

    The prothrombin time with INR measures the extrinsic pathway (tissue factor and factor VII) as it feeds the common pathway, which is why it monitors warfarin. The aPTT measures the intrinsic pathway (factors XII, XI, IX, and VIII) into the common pathway and is the test used to follow heparin.

    Source: NHA CPT Test Plan, Core Knowledge, coagulation pathways and monitoring testsReport a problem with this question

19. 19. Calcium is designated factor IV of the coagulation system. What role does it play, and what happens when a chelating agent binds it in a specimen?

    • A.It carries the clotting factors in plasma, so binding it releases them and speeds the cascade
    • B.It is required at several steps of the cascade, so binding it stops the specimen from clotting✓ Answer
    • C.It is the substance converted into fibrin, so binding it makes the clot form even faster
    • D.It dissolves clots once healing begins, so binding it leaves the specimen clotted and unusable

    Calcium (factor IV) is an obligatory cofactor at several points in both the intrinsic and extrinsic pathways and in the common pathway. Chelating agents work by binding that calcium so the cascade cannot proceed, which is exactly how an anticoagulated specimen is kept liquid.

    Source: NHA CPT Test Plan, Core Knowledge, coagulation cascade; calcium as factor IVReport a problem with this question

20. 20. A patient with type AB blood and a patient with type O blood are compared. Which statement about their red cells and their plasma is correct?

    • A.Type O is the universal red cell donor, and type AB is the universal plasma donor✓ Answer
    • B.Type O carries both A and B antigens, and type AB carries both A and B antibodies
    • C.Type AB plasma holds anti-A and anti-B, and type O plasma holds neither antibody
    • D.Type AB is the universal red cell donor, and type O is the universal plasma donor

    Type O red cells carry neither the A nor the B antigen, so they can be given to any ABO recipient, which makes O the universal red cell donor. The roles reverse for plasma: AB plasma contains no anti-A or anti-B antibody, so it is the universal plasma donor while AB red cells can go only to AB recipients.

    Source: NHA CPT Test Plan, Core Knowledge, ABO blood group systemReport a problem with this question

21. 21. An Rh-negative patient has never been transfused and has never been pregnant. What should be true of her plasma with respect to anti-D antibody?

    • A.Anti-D is absent, because it forms only after exposure to D-positive red cells✓ Answer
    • B.Anti-D is present but too weak to matter until a first transfusion is given later
    • C.Anti-D is present from birth, in the same way anti-A and anti-B occur in ABO groups
    • D.Anti-D is absent, because Rh-negative people are unable to make that antibody at all

    Unlike the ABO antibodies, anti-D does not occur naturally: an Rh-negative person makes it only after immune exposure to D-positive red cells through transfusion or pregnancy. That is why Rh status matters for transfusion compatibility and for hemolytic disease of the newborn.

    Source: NHA CPT Test Plan, Core Knowledge, Rh blood group systemReport a problem with this question

22. 22. The tourniquet stays in place for more than a minute while a difficult vein is located. In which direction should the potassium and total protein results move, and why?

    • A.Both are unaffected, because tourniquet time changes cell counts without altering chemistry
    • B.Both rise, because stasis drives plasma water into the tissue and concentrates all that remains✓ Answer
    • C.Both fall, because blood stagnating in the vein loses its solutes to the surrounding tissue
    • D.Potassium rises but protein falls, because only the smaller ions are trapped by stalled flow

    Venous stasis raises the pressure inside the vein and forces plasma water out into the tissue, leaving potassium, total protein, calcium, and other large or cell-associated analytes concentrated in the sample. This is why CLSI limits tourniquet application to no more than one minute.

    Source: CLSI GP41 (tourniquet no more than 1 minute); Core Knowledge, hemoconcentrationReport a problem with this question

Concept-focused practice questions based on CLSI GP41 (venous blood collection), the CLSI order of draw, and the OSHA Bloodborne Pathogens Standard (29 CFR 1910.1030). Not affiliated with the NHA, ASCP, or CLSI, and not medical advice. Facility protocols and current CLSI standards take precedence — always follow your employer's procedures. About the CPT exam →