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 MCQs on blood physiology with their answers

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مُساهمةموضوع: MCQs on blood physiology with their answers    الإثنين فبراير 07, 2011 8:58 pm

Question1:
Blood group antigens (agglutinogens) are:
A. Carried on the haemoglobin molecule.
B. Beta globulins.
C. Equally immunogenic.
D. Not present in fetal blood.
E. Inherited as recessive Mendelian characteristics.

Answer1:
A. False They are part of the red cell membrane.
B. False They are glycoproteins.
C. False A, B and D antigens are more immunogenic than the others.
D. False Fetal blood may elicit immune responses if it enters the maternal circulation.
E. False They are Mendelian dominants.

Question2:
Breakdown of erythrocytes in the body:
A. Occurs when they are 6–8 weeks old.
B. Takes place in the reticulo-endothelial system.
C. Yields iron, most of which is excreted in the urine.
D. Yields bilirubin which is carried by plasma protein to the liver.
E. Is required for the synthesis of bile salts.

Answer2:
A. False The normal erythrocyte lifespan is 16–18 weeks.
B. True The RES removes effete RBCs from the circulation.
C. False Most of the iron is retained for further use.
D. True The protein makes the bilirubin relatively water-soluble.
E. False Bile salts are synthesized from sterols in the liver.

Question3:

A person with group A blood:

A. Has anti-B antibody in the plasma.
B. May have the genotype AB.
C. May have a parent with group O blood.
D. May have children with group A or group O blood only.
E. Whose partner is also A can only have children of groups A or O.

Answer3:
A. True This appears about the time of birth.
B. False This would make them blood group AB.
C. True They could inherit an A gene from the other parent to give genotype AO.
D. False B or AB are possible depending on the partner’s genes.
E. True In this case, neither parent has the B gene.

Question4:

Blood platelets assist in arresting bleeding by:

A. Releasing factors promoting blood clotting.
B. Adhering together to form plugs when exposed to collagen.
C. Liberating high concentrations of calcium.
D. Releasing factors causing vasoconstriction.
E. Inhibiting fibrinolysis by blocking the conversion of plasminogen to plasmin.

Answer4:
A. True e.g. Thromboplastin, part of the intrinsic pathway.
B. True Vascular leaks are sealed by such platelet plugs.
C. False High Ca2+ levels are not needed for hemostasis; normal levels are adequate.
D. True e.g. Serotonin (5-hydroxytryptamine).
E. False Serotonin from platelets can release vascular plasminogen activators.

Question5:

Erythrocytes:
A. Are responsible for the major part of blood viscosity.
B. Contain the enzyme carbonic anhydrase.
C. Metabolize glucose to produce CO2 and H2O.
D. Swell to bursting point when suspended in 0.9 per cent (150 mmol/litre) saline.
E. Have rigid walls.

Answer5:
A. True Blood viscosity rises exponentially with the haematocrit.
B. True It catalyses the reaction CO2+H2O→H++HCO3-.
C. True Glycolysis generates the energy needed to maintain electrochemical gradients
across their membranes.
D. False This is isotonic with their contents.
E. False The walls deform easily to squeeze through capillaries.

Question6:

Human plasma albumin:
A. Contributes more to plasma colloid osmotic pressure than globulin.
B. Filters freely at the renal glomerulus.
C. Is negatively charged at the normal pH of blood.
D. Carries carbon dioxide in blood.
E. Lacks the essential amino acids.

Answer6:
A. True Its greater mass and lower molecular weight provide more osmotically active particles.
B. False Only a small amount is filtered normally and this is reabsorbed by the tubules.
C. True Blood pH is well above albumin’s isoelectric point so negative charges (COO-)
predominate.
D. True As carbamino protein.
E. False It is a first class protein containing essential and non-essential amino acids.

Question7:

Neutrophil granulocytes:
A. Are the most common leukocyte in normal blood.
B. Contain proteolytic enzymes.
C. Have a lifespan in the circulation of 3–4 weeks.
D. Contain actin and myosin microfilaments.
E. Are present in high concentration in pus.

Answer7:
A. True They comprise 60–70 per cent of circulating leukocytes.
B. True Their granules contain such enzymes, which, with toxic oxygen metabolites, can
kill and digest the bacteria they engulf.
C. False Less than a day.
D. True Responsible for their amoeboid motility.
E. True Pus consists largely of dead neutrophils.

Question8:

Antibodies:
A. Are protein molecules.
B. Are absent from the blood in early fetal life.
C. Are produced at a greater rate after a first, than after a second, exposure to an antigen
six weeks later.
D. Circulating as free immunoglobulins are produced by B lymphocytes.
E. With a 1 in 8 titre are more concentrated than ones with a 1 in 4 titre.

Answer8:
A. True They are made by ribosomes in plasma cells.
B. True Immunological tolerance prevents the fetus forming antibodies to its own proteins.
C. False The response to the second exposure is greater since the immune system has been
sensitized by the first exposure.
D. True T lymphocytes are responsible for cell-mediated immunity.
E. True Antibody with a 1 in 8 titre is detected at greater dilution than one with a 1 in 4
titre.

Question9:

Circulating red blood cells:
A. Are about 1 per cent nucleated.
B. May show an intracellular network pattern if appropriately stained.
C. Are distributed evenly across the blood stream in large blood vessels.
D. Travel at slower velocity in venules than in capillaries.
E. Deform as they pass through the capillaries.

Answer9:
A. False Nucleated red cells are not normally seen in peripheral blood.
B. True Reticulocytes, the most immature circulating RBCs, show this pattern when stained with certain dyes.
C. False They form an axial stream away from the vessel wall.
D. False The capillary bed has a greater total cross-sectional area than the venular bed.
E. True Normal cells, around 7 microns in diameter, become bullet-shaped as they pass through 5 micron diameter capillaries.

Question10:

Lymphocytes:
A. Constitute 1–2 per cent of circulating white cells.
B. Are motile.
C. Can transform into plasma cells.
D. Decrease in number following removal of the adult thymus gland.
E. Decrease in number during immunosuppressive drug therapy.

Answer10:
A. False About 20 per cent of leukocytes are lymphocytes.
B. True They migrate by amoeboid movement to areas of chronic inflammation.
C. True As plasma cells they manufacture humoral antibodies.
D. False The thymus is atrophied and has little function in the adult.
E. True Lymphocytes and immune responses are closely linked.

Question11:

Blood:
A. Makes up about 7 per cent of body weight.
B. Forms a higher percentage of body weight in fat than in thin people.
C. Volume can be calculated by multiplying plasma volume by the haematocrit (expressed as a percentage).
D. Volume rises after water is drunk.
E. Expresses serum when it clots.

Answer11:
A. True For example, 5 kg (about 5 litres) in a 70 kg man.
B. False Since fat tissue is relatively avascular, the reverse is true.
C. False It can be calculated by multiplying plasma volume by 1/1 minus haematocrit
(expressed as a decimal).
D. True The water is absorbed into the blood.
E. True Serum is plasma minus its clotting factors.

Question12:

Normal blood clotting requires:
A. Inactivation of heparin.
B. Inactivation of plasmin (fibrinolysin).
C. Calcium ions.
D. An adequate intake of vitamin K.
E. An adequate intake of vitamin C.

Answer12:
A. False The anticoagulant effects of heparin are overwhelmed.
B. False Blood clots in spite of the fibrinolytic system.
C. True Removal of calcium ions prevents clotting.
D. True Vitamin K is needed by the liver for synthesis of prothrombin and other factors.
E. False The spontaneous bleeding from the gums etc. seen in scurvy is due to capillary abnormality, not a clotting defect.

Question13:

Antibodies (agglutinins) of the A and B red cell antigens (agglutinogens):
A. Are present in fetal plasma.
B. Cause haemolysis of RBCs containing the A and B antigens when added to a suspension of red cells in saline.
C. Do not normally cross the placental barrier.
D. Have a molecular weight in excess of 500 000.
E. Are monovalent.

Answer13:
A. False They form shortly after birth, possibly in response to A and B antigens carried into the body by invading bacteria.
B. False They cause agglutination (clumping) of A, B and AB cells.
C. True Unlike Rh antibodies which have a smaller molecular size.
D. True Around 1000000.
E. False They are divalent and hence cause red cells to adhere to one another during
agglutination.

Question14:

Blood platelets:
A. Are formed in the bone marrow.
B. Are normally more numerous than white cells.
C. Have a small single-lobed nucleus.
D. Increase in number after injury and surgery.
E. Alter shape when in contact with collagen.

Answer14:
A. True They are formed from megalokaryocytes.
B. True By a factor of 20 or more.
C. False No nucleus but the cytoplasm contains electron dense granules, lysosomes and mitochondria.
D. True This increases the tendency of blood to clot.
E. True They put out pseudopodia and adhere to the collagen and to one another.

Question15:

The conversion of fibrinogen to fibrin:
A. Is effected by prothrombin.
B. Involves the disruption of certain peptide linkages by a proteolytic enzyme.
C. Is followed by polymerization of fibrin monomers.
D. Is inhibited by heparin.
E. Is reversed by plasmin (fibrinolysin).

Answer15:
A. False It is effected by thrombin; prothrombin is the inactive precursor of thrombin.
B. True Thrombin breaks off the solubilizing end groups.
C. True Polymerized fibrin monomers form the strands of the clot meshwork.
D. True This is a rapidly acting anticoagulant.
E. False Plasmin does not convert fibrin back to fibrinogen, it degrades both fibrin and fibrinogen to products which can inhibit thrombin.

Question16:

Haemolytic disease of the newborn:
A. Affects mainly babies of Rh-positive mothers.
B. Occurs mainly in babies who lack D agglutinogen.
C. Causes jaundice which clears rapidly after birth.
D. Can be treated by transfusing the affected baby with Rh-positive blood.
E. Can be prevented by injecting the mother with anti-D agglutinins just after delivery.

Answer16:
A. False It affects babies of Rh-negative mothers when the child’s red cell membranes carry the D antigen.
B. False It occurs in Rh-positive babies.
C. False The jaundice deepens rapidly after birth as bilirubin is no longer excreted by the maternal liver.
D. False This would be attacked by maternal Rh antibodies in the infant’s blood; Rh negative blood is given.
E. True These destroy fetal Rh-positive cells in the maternal circulation before such cells
can sensitize her to D antigen.

Question17:

Iron deficiency:
A. Frequently follows persistent loss of blood from the body.
B. Is more common in men than in women.
C. May cause anaemia by inhibiting the rate of multiplication of RBC stem cells.
D. May cause large pale erythrocytes to appear in peripheral blood.
E. Anaemia should normally be treated by injections of iron

Answer17:
A. True Especially if dietary intake of iron is limited.
B. False It is more common in women due to menstrual blood loss.
C. False It causes anaemia by limiting the rate of haemoglobin synthesis.
D. False In iron deficiency anaemia, RBCs are small and pale due to lack of haemoglobin.
E. False Oral iron is avidly absorbed in iron deficiency states.

Question18:

Severe reactions are likely after transfusion of blood group:
A. A to a group B person.
B. O to a group AB person.
C. A to a group O person.
D. A to a group AB person.
E. O Rh-negative to a group AB Rh-positive person.

Answer18:
A. True The recipients have anti-A antibody.
B. False Group O people are ‘universal donors’.
C. True The recipients have anti-A antibody.
D. False Group AB persons, ‘universal recipients’, lack anti-A and anti-B antibodies.
E. False The recipients lack anti-A, anti-B and anti-Rh antibodies.

Question19:

The haematocrit (packed cell volume):
A. May be obtained by centrifugation of blood.
B. May be calculated by multiplying the mean cell volume by the red cell count.
C. Rises in a patient who sustains widespread burns.
D. Rises following injections of aldosterone.
E. Rises in macrocytic megaloblastic anaemias such as pernicious (B12 deficiency) anaemia.

Answer19:
A. True Since red cells are heavier than plasma.
B. True This gives a slightly lower value than centrifugation which traps a little plasma between cells.
C. True Due to loss of plasma and interstitial fluid.
D. False It falls as extracellular fluid and hence plasma volume increases.
E. False Though individual RBCs are large, total red cell mass is decreased.




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MCQs on blood physiology with their answers

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