Hema Lec #4: Coagulation Mechanism Flashcards
T or F. By the end of the promegakaryoblastic stage, the cell has reached its full RNA ploidy.
False.
Which of the following is a cellular change as megakaryoblasts mature into
megakaryocytes within the bone marrow?
I. A progressive increase in N:C ratio.
II. Dwindling basophilia of the cytoplasm.
III. Nuclear lobulation and fragmentation.
IV. Amplified delineation of the demarcation system.
II and IV only.
It encourages the differentiation of a common stem cell
precursor into the megakaryocytic lineage, except:
MYB
The following statements about platelets are false, except:
I. Platelets are anucleate blood cells consisting of a cytoskeleton
framework, several cytoplasmic organelles, three types of cytoplasmic
granules and a cell membrane.
II. Platelet dense bodies contain agonists such as serotonin, ADP, ATP
and other proteins that bring about activation such as calcium.
III. Platelets bear a limited number of cell surface proteins that often
serve as ligands.
IV. Platelets are normally smaller than red blood cells with a mean
platelet volume (MPV) of about about 10-30 fL.
III only.
T/F. A permanently anchored platelet plug still requires further consolidation
and stabilization, which is provided by fibrinogen.
True
True or False. Qualitative platelet disorders can be attributed to defects in any of the
steps in platelet activation and granule secretion defects; the latter
frequently able to cause Von Willebrands Disease (VWD), by preventing
alpha granule secretion of VWF.
False
Given the following automated CBC result of an apparently healthy albeit nervous 3-year old boy: WBC : 16.3 x 109 / microliter RBC : 5.0 x 106 / microliter Hemoglobin : 12.9 g/dL Hematocrit : 39% MCV : 86 fL MCHC : 34 % RDW (Red cell Distribution Width) : 13 MPV : 8 fL Platelet count : 56 x 109 / microliter Differential count: Segmenters 87% Lymphocytes 2% Monocytes 8% Eosinophils 2% Atypical lymphocytes 1% What is the best assumption to make?
A blood smear cannot be used as
a cross-check of the automated platelet count.
Given the following automated CBC result of a 36 year old postpartum woman with complaints of vaginal bleeding: WBC : 2.8 x 109 / microliter RBC : 3.1 x 106 / microliter Hemoglobin : 12.5 g/dL Hematocrit : 37.5% MCV : 89 fL MCHC : 34 % RDW (Red cell Distribution Width) : 16 MPV : 10 fL Platelet count : 77 x 109 / microliter Differential count: Segmenters 31% Lymphocytes 60% Monocytes 7% Eosinophils 1% Basophils 1% What is the best assumption to make? She was previously given 10 units of platelet concentrate transfusion because of moderate to severe thrombocytopenia of 50,000 per microliter?
Further transfusions with
any kind of platelet products will likely be non-beneficial.
What is the dilution used in the manual platelet count using the
Brecker-Cronkite method if a patient is severely thrombocytopenic?
1:100 or 1:20
What cofactor activates a zymogen coagulation factor which in turn when activated, accelerates the conversion of the first contact factor to be activated to its active form?
High Molecular Weight Kininogen
Who act as a bridge for the vitamin K-dependent coagulation factors to
attach on the negatively charged platelet membrane?
Calcium
This substance facilitates primarily the adhesion of platelets to
sub-endothelial collagen. Who is this important substance?
von Willebrand factor
Who facilitate the aggregation of the ADP-stimulated platelets?
GP IIb/IIIa
Fibrinogen
What clotting factor is most abundant in the plasma?
Fibrinogen
Who facilitate the response of vascular system to endothelial cell injury?
Smooth muscle cells
What substance is produced in the pathway where the most potent platelet agonist is generated that opposes the action of the cells responsible for the initial response of vascular system to injury and further causes the platelets to perform adhesion because it exposes well the sub-endothelial collagen?
Prostacyclin
When a patient is on aspirin medication and gets himself an injury, what
is the expected bleeding time result of this patient?
Prolonged
To facilitate the formation of clot at the site of injury, this substance from the platelet neutralize the naturally-occurring anticoagulant in the lumen of the damaged blood vessel. What is this important component of the platelets alpha granules?
Platelet factor 4
Give the three (3) substances that can prolong the vascular response to
injury.
Serotonin
Thromboxane A2
Endothelin 1
Which active enzyme in the coagulation system clots the most abundant
coagulation factor in the plasma?
Thrombin
Which coagulation factor secreted as zymogen is important in the formation of a complex in the third pathway of coagulation and is activated by both complexes in the first and second pathways?
Factor X
The polymerization of fibrin monomer is initiated by what exact mechanism?
D-E contact
The formation of fibrin polymer produces an unstable clot. Who stabilizes
this already formed clot?
Factor XIIIa
Patients on aspirin medication may develop bleeding tendencies. What is
inhibited by this medication responsible for the manifestation mentioned?
Cyclo-oxygenase enzyme
