Test 81    (physiology)

1. Bleeding time is increased in:

a. massive blood transfusion
b. vitamin K deficiency
c. von Willebrand's disease
d. disseminated intravascular coagulation (DIC)
e. haemophilia A

Answera.T   b.F  c.T   d.T  e.F
The bleeding time depends on the number and function of the platelets as well as the interaction between the 
capillary wall and the platelets. Therefore, the whole blood clotting system is not involved. 
In massive blood transfusion and DIC, the platelet 
count is reduced. In von Willebrand's disease, the function of the platelets is abnormal.

2. A shift in the oxygen-haemoglobin  dissociation curve to the right 
    occurs in :

a. hypothermia
b. carboxyhaemoglobin
c. acidosis
d. fetal haemoglobin
e. an increase in the 2-3-diphosphoglycerate (2,3-DPG)

Answera.F   b.F   c.T   d.F   e.T
Hyperthermia and not hypothermia causes an a shift of the curve to the right.

3. With regard to blood groups and blood products:

a. the ABO system is inherited in an autosomal dominant 
    pattern
b. group O and Rhesus positive is the universal donors'
    blood.
c. stored whole blood contains dextrose, phosphate and 
    citrate
d. stored blood becomes progressively more acidotic and
    hyperkalaemic with time
e. store blood contains a normal amount of clotting factors

Answera.T   b.F  c.T   d.T   e.F
Blood group O and Rhesus negative is the universal donors' blood. 
Stored blood contains reduced platelets and clotting 
factors and therefore rapid and large amount of transfusion can cause problem with clotting and bleeding time.
With time due to metabolism and haemolysis, the stored blood becomes more acidotic and hyperkalaemic.

4. The following are true about platelets:

a. they are formed in the bone marrow from 
    megakaryocytes.
b. their life span in circulation is about 30 days
c. in a normal person, 20% of the platelets are 
    found in the spleen.
d. they contain adenosine diphophate and 
    serotonin.
e. they produce prostacyclin 

Answera.T  b.F  c.T   d.T   e.F
Their life span is about 7 days.
Endothelium produces prostacyclin that inhibits aggregation of platelets.

5. Haemoglobin SC disease:

a. is common amongst Afro-carribean people
b. does not show sickle cells in the blood film.
c. causes severe anaemia
d. causes retinal vein occlusion
e. is associated with angioid streaks

Answera.T   b.F   c.F   d.T   e.T
Haemoglobin SC is a combination of sickle 
cell anaemia and haemoglobin C. 
Compared with sickle cell disease, the anaemia is mild.
Thrombosis is a known complication.

 
 

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