28 Questions
What triggers primary hemostasis upon blood vessel injury?
Endothelial cell inflammatory proteins
What is the normal range of platelets in women?
250-500x10^9/L
What factor recruits megakaryocyte progenitors from common myeloid progenitors?
Thrombopoietin (TPO)
Which cells act to balance megakaryocytopoiesis and erythropoiesis through their opposing actions?
GATA-1 and MYB
What is the role of megakaryocytes in the bone marrow?
Produce platelets
In what type of patients are platelets slightly lower?
Those over 65 years old
Which progenitor stage is the most immature in the megakaryocyte lineage?
BFU-Meg
What characterizes the progenitor stage of CFU-Meg Diploids?
Undergoes endomitosis
Which transcription factors are associated with endomitosis in the megakaryocyte lineage?
RUNX1 and NF-E2
What is a key feature of the terminal differentiation of a Promegakaryocyte into a Megakaryocyte (MK-I)?
Formation of proplatelet processes
Where do Megakaryocytes release platelets from during terminal differentiation?
Proplatelet processes into circulation
What is the alternative name for the Eicosanoid synthesis pathway?
Prostaglandin pathway
Which enzyme converts arachidonic acid to prostaglandin G2 and prostaglandin H2?
Cyclooxygenase
What effect does TXA2 have on adenylate cyclase activity?
Decelerates it
What is the function of Prostacyclin in endothelial cells?
Raises cyclic CAMP levels
Which pathway is triggered by G-proteins and involves phospholipase C activation?
IP3-DAG activation pathway
What binds guanosine diphosphate (GDP) when G-proteins are inactive?
Cyclooxygenase
What is the approximate size of a mature megakaryocyte (MK-III)?
20-90 um
Which transcription gene product suppresses megakaryocyte differentiation?
MYB
What is the main growth factor responsible for inducing thrombocytopoiesis?
Thrombopoietin
Where are sequestered platelets mainly found?
Spleen (white pulp)
Which platelets compensate for thrombocytopenia and have diameters larger than ordinary mature platelets?
Reticulated platelets
Which zone of the platelet contains glycoproteins related to the coagulation and fibrinolytic systems?
Peripheral zone
What is the function of phospholipase C in the context described?
It cleaves membrane phosphatidylinositol 4,5-bisphosphate to form IP3 and DAG, which are second messengers for intracellular activation.
What is the primary role of IP3 in the context described?
It promotes the release of ionic calcium from the dense tubular system (DTS), which triggers actin microfilament contraction.
What is the function of DAG in the context described?
It triggers a multistep process involving the activation of phosphokinase C, which triggers phosphorylation of the protein pleckstrin, which regulates actin microfilament contraction.
What is the purpose of using EDTA in the platelet counting procedure described?
To prevent clotting of the blood sample during the counting process.
What is the purpose of using a phase-contrast microscope in the platelet counting procedure described?
To visualize and count the platelets in the sample.
This quiz covers the basic concepts related to platelets in hematology, including their role in primary hemostasis, origin from megakaryocytes, normal values in blood, and characteristics of megakaryocytes.
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