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
