Studied by 41 people
Megakaryocytes
Platelets arise from unique bone marrow cells called?
GATA-1
Megakaryocyte progenitors arise from the common myeloid progenitor under the influence of this transcription gene product.
Endomitosis
A partially characterized form of mitosis unique to megakaryocytes in which DNA replication and cytoplasmic maturation are normal but cells lose their capacity to divide.
It is a form of mitosis that lacks telophase and cytokinesis
Terminal differentiation
A series of stages in which microscopists become able to recognize unique Wright-stained morphology in bone marrow aspirate films.
MK-I stage / megakaryoblast
This is called the least differentiated megakaryocyte precursor
DMS
A series of membrane-lined channels that invade from the plasma membrane and grow inward to subdivide the entire cytoplasm
MK-II stage
The promegakaryocyte reaches its full ploidy level by the end of what stage?
MK-III stage
In this stage, the megakaryocyte is easily recognized at 103 magnification on the basis of its 30- to 50-mm diameter
2000-4000
During thrombocytopoiesis, a single megakaryocyte may shed how many platelets?
TPO growth factor
It is a 70,000 Dalton molecule that possesses 23% homology with the red blood cell-producing hormone erythropoietin
MPL
It is a viral oncogene associated with murine myeloproliferative leukemia
IL-6 and IL-11
These cytokines act in the presence of TPO to enhance endomitosis
IL-3
This cytokine acts in synergy with TPO to induce the early differentiation of stem cells
Reticulated platelets
Also known as stress platelets, they appear in compensation for thrombocytopenia
Cholesterol
It stabilizes the membrane, maintains fluidity, and helps control the transmembranous passage of materials through the selectively permeable plasma membrane
Surface-Connected Canalicular System (SCCS)
This enables the platelet to store additional quantities of the same hemostatic proteins found on the glycocalyx
It is the route for endocytosis and for secretion of a-granule contents upon platelet activation.
Dense Tubular System (DTS)
It is a condensed remnant of the rough endoplasmic reticulum.
It sequesters Ca2+ and bears a number of enzymes that support platelet activation including phospholipase A2, cyclooxygenase, and thromboxane synthetase.
Actin
It is contractile in platelets (as in muscle) and anchors the plasma membrane glycoproteins and proteoglycans
FcyIIA (CD32)
A low-affinity receptor for the immunoglobulin Fc portion that plays a role in a dangerous condition called heparin-induced thrombocytopenia
P-selectin (CD62)
It is an integrin that facilitates platelet binding to endothelial cells, leukocytes, and one another.
ADAMTS13
The interaction between platelet and VWF remains localized by a liver-secreted plasma enzyme
Blood vessel injury
This exposes tissue factor expressed on subendothelial smooth muscle cells and fibroblasts
Microparticles
These are membrane-derived vesicles that form in response to an activating stimulus that increases the platelet intracellular concentration of calcium
Vascular System
Platelets (Thrombocytes)
Blood Coagulation Factors
Fibrinolysis and ultimate tissue repair
4 Major Components of Hemostasis
Vasoconstriction
It is a reflex in which blood vessels narrow to increase blood pressure.
Epinephrin and serotonin
These hormones promote vasoconstriction
Endothelium
It regulates the permeability of the inner vessel wall and provides the principal stimulus to thrombosis following injury to a blood vessel.
Involved in the clotting process by producing or storing clotting components.
Prostacyclin
It strongly inhibits platelet aggregation and adhesion
Endothelins
They act as modulators of vasomotor tone, cell proliferation, and hormone production
Endothelin-1
It is the only family member produced in endothelial cells and is also produced in vascular smooth muscle cells
Endothelin-2
It is produced predominantly within the kidney and intestine, with smaller amounts produced in the myocardium, placenta, and uterus.
Endothelin-3
It has been found in high concentrations in the brain and may regulate important functions, such as proliferation and development in neurons and astrocytes
It also is found throughout the gastrointestinal tract and in the lung and kidney
Endothelial Dysfunction
It plays an important role in the initiation, progression, and clinical complications of various forms of inflammatory and degenerative vascular diseases
First phase of Endothelial Dysfunction
Rapid vasoconstriction for up to 30 minutes reduces blood flow and promotes contact activation of platelets and coagulation factors
Second phase of Endothelial Dysfunction
Platelets adhere immediately to the exposed subendothelial connective tissue, particularly collagen.
Third phase of Endothelial Dysfunction
Coagulation is initiated through both the intrinsic and extrinsic systems
Fourth phase of Endothelial Dysfunction
Fibrinolysis occurs following the release of tissue plasminogen activators (t-PAs) from the vascular wall.
Fibrinolytic removal of excess hemostatic material is necessary to reestablish vascular integrity.
Circulating functional platelets
Adrenocorticosteroids
Ascorbic Acid
Essential Factors for Vascular Integrity
Veins
They may rupture with a slight increase in hydrostatic pressure
Megakaryocytopoiesis
Proceeds initially through a phase characterized by mitotic division of a progenitor cell, followed by a wave of nuclear endoreduplication.
Endoreduplication
It is the process in which chromosomal material (DNA) and the other events of mitosis occur without subsequent division of the cytoplasmic membrane into identical daughter cells
Thrombopoietin
It is the hormone thought to stimulate the production and maturation of megakaryocytes, which in turn produce platelets, has recently been purified and cloned
TRUE
Platelets have no nucleus. TRUE OR FALSE
FALSE
Nuclei are still visible in megakaryocytes. TRUE OR FALSE
Inactive or unstimulated platelet
It circulates as a thin, smooth-surfaced disc
Glycocalyx or fluffy coat
It surrounds the cellular membrane of the platelet externally
Composed of plasma proteins and carbohydrate molecules that are related to the coagulation, complement, and fibrinolytic systems
Microfilaments and Microtubules
Located directly beneath the cell membrane of platelet
Provide structure of the platelet to maintain its discoid shape
Maintains the position of the organelles
Alpha
Most abundant type of granules in a mature platelet
Dense or delta
Type of granules that contain serotonin, adenosine diphosphate (ADP), adenosine triphosphate (ATP), and calcium.
Lysosomes
They store hydrolase enzymes
Contractile proteins
Actomyosin (thrombosthenin),
Myosin
Filamin
1000-2000
An average megakaryocyte produces about how many platelets?
2 days
Platelets initially enter the spleen & remains for how many days?
5 days
Marrow transit time / maturation period of megakaryocyte
G-proteins
Type of proteins that control cellular activation for all cells at the inner membrane surface
LD-CFU-Meg
REVIEW QUESTION:
The megakaryocyte progenitor that undergoes endomitosis is:
Thrombopoietin
REVIEW QUESTION:
The growth factor that is produced in the kidney and induces growth and differentiation of committed megakaryocyte progenitors is:
Dense tubular system
REVIEW QUESTION:
What platelet organelle sequesters ionic calcium and binds a series of enzymes of the eicosanoid pathway?
GP IIb/IIIa
REVIEW QUESTION:
What platelet membrane receptor binds fibrinogen and supports platelet aggregation?
Phosphatidylserine
REVIEW QUESTION:
What platelet membrane phospholipid flips from the inner surface to the plasma surface on activation and serves as the assembly point for coagulation factors?
Prostacyclin
REVIEW QUESTION:
What is the name of the eicosanoid metabolite produced from endothelial cells that suppresses platelet activity?
Serotonin
REVIEW QUESTION:
Which of the following molecules is stored in platelet dense granules?
VWF
REVIEW QUESTION:
What plasma protein is essential for platelet adhesion?
Increased platelet production in response to need
REVIEW QUESTION:
Reticulated platelets can be enumerated in peripheral blood to detect:
Are largely composed of platelets and von Willebrand factor
REVIEW QUESTION:
White clots:
The surface connected canalicular system
REVIEW QUESTION:
Upon activation, platelets secrete their a-granule contents via:
Bud off of platelets after their exposure to strong agonists
REVIEW QUESTION:
Microparticles:
Thiazole orange
This nucleic acid dye binds the RNA of the endoplasmic reticulum
50 to 80
How many α-granules are there in each platelet?
2 to 7
How many dense granules are there per platelet?
GP IV
It is a key collagen receptor that binds thrombospondin
Thrombin
It cleaves two STRs, PAR1and PAR4.
TXA2
TPα and TPβ bind?
Platelet aggregation
Platelet-to-platelet binding referred to as?
Red clot
This type of clot is essential to wound repair, but may also be characteristic of inappropriate coagulation.
White clot
This type of clot is composed primarily of platelets and Von Willebrand factor (VWF).
Arachidonic acid
5,8,11,14-eicosatetraenoic acid is commonly called?
Cyclooxygenase
It converts arachidonic acid to prostaglandin H2 to produce TXA2
IP3-DAG pathway
This is the second G-protein dependent platelet activation pathway.
