Lecture: Thrombocytes Flashcards
Earliest cell in the megakaryocytic series
BFU-Meg
BFU-Meg and CFU-Meg undergo what type of cell division?
Mitosis
What precursor/hematopoietic stem cell undergo meiosis/endomitosis?
LD-CFU-Meg
Nucleus: fine chromatin; multiple nucleoli that generally stain blue; Begins development of alpha and dense granules
Megakaryoblast / MK-1
Cytoplasm: more abundant but less basophilic; granules begin to form; Demarcation Membrane System (DMS) develops – gives rise to membrane bsystem/compartments of platelets
Promegakaryocyte / MK-II
Nucleus is intensely indented or lobulated, and the degree of lobulation is imprecisely proportional to ploidy; Cytoplasm: abundant; pinkish-blue; diffusely granular and has an irregular peripheral border
Granular Megakaryocyte / MK-III
Cytoplasm: contains coarse clumps of granules aggregating into bundles which bud off from the periphery to become platelets (2000-4000 platelets) known as platelet shedding
Mature Megakaryocyte / Metamegakaryocyte
Not a true cell; Size: 1-4 µm; Cytoplasm: light blue to purple; very granular; consists of two parts: chromomere and hyalomere; Cellular/cytoplasmic fragments
Thrombocytes
Non-granular pale blue
that surrounds the centromere
Outer hyalomere
Resting platelets are in what shape?
Biconvex/discoid
Platelets in blood collected using EDTA tend to _
“round up” / spherical
Platelets Turnover Rate
35,000 ± 4,300
Cytokine that Induces early differentiation of stem cells
IL-3
Cytokines that enhances endomitosis,
megakaryocyte maturation
IL-6 and IL-11
Platelet Distribution
2/3 in the blood; 1/3 in the spleen
Circulating Life Span of Platelets
8-9 days
Exterior fluffy coat rich in glycoproteins (Gp) which serves as membrane receptors/adhesion or aggregating agents and physiological agonists
Glycocalyx
Von Willebrand’S Factor Receptor
Gp Ib
VWF and fibrinogen receptor
Gp IIb and IIIa
Thrombin receptor
Gp Va
Collagen receptor
Gp VI
Phospholipids are the source of ?
Arachidonic acid
Structural support; Composed of CHON tubulin which maintains the discoid shape of platelets
Microtubules
Composed of actin and myosin which upon stimulation are converted into actomyosin, a contractile CHON important in clotting retraction
Microfilaments
Other term for actomyosin
Thrombostenin
Intermediate Filaments; Connect with actin at tubules – maintaining shape
Desmin and vimentin
α-granules proteins that supports mitosis
PDGF
Endothelial GF
Transforming GF-Beta
α-granules proteins that are adhesion molecules
Fibronectin
Thrombospondin
α-granules protein that acts in heparin neutralization
Platelet factor 4
Protein that is only found in α-granules
β-thromboglobulin
α-granules protein that promotes fibrinolysis
Plasminogen
α-granules proteins that control fibrinolysis
Plasminogen activator inhibitor-1
alpha 2-antiplasmin
α-granules protein that controls coagulation
Protein C inhibitor
α-granules stains what color in osmium dye?
Medium gray
Delta Granules (δ-granules) stain what color in osmium dye?
Black (opaque)
A δ-granule that is a potent vasoconstrictor
5-hdyroxytryptamine – 5-HT-serotonin
Hydrolytic enzyme that is for clot lysis
Lysozymes
Provides direct communication between intracellular and extracellular environment; Intracellular compounds are released into the external environment
Open Canalicular System
Acts as Ca-sequestering pump which maintains cytoplasmic Ca level; Important for arachidonic acid metabolism
Dense Tubular System
Serves as a link from platelet to platelet
Fibrinogen
Serves as the link from damaged vessel to platelet
Von Willebrand Factor
Enhances the binding of platelet to platelet
Pseudopods
Irreversible second wave of aggregation by changing conformation of IIb-IIa complex
ADP
Promotes ADP release; stimulates ADP-induced secondary aggregation and promotes release of phospholipase
Thrombin
Promotes aggregation; Potent vasoconstrictor; End product of arachidonic acid; Main mediator of aggregation
TxA2 – thromboxane A2
Large molecule coagulation proteins that participate in secondary hemostasis
α-granule contents
Small molecule vasoconstrictor and platelet agonists that amplify primary hemostasis
Dense granules contents
GpIb is for platelet _?
Adhesion
GpIIb and GpIIIa is for platelet _?
Aggregation
If GpIb is absent, what may be the disease that develop?
Bernard-Soulier Syndrome
If GpIIb and GpIIIa si absent, what may be the disease that develop?
Glanzman’s Disease or Thrombasthenia
Phospholipid is converted into arachidonic acid via?
Phospholipase
Prostacyclin is then converted to PGI2 via?
COX1-cyclooxygenase
PGI2 is then converted into thromboxane A2 via?
Thromboxane synthase
