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20 Cards in this Set
- Front
- Back
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What are platelets? |
-Discoid "cells" lacking a nucleus -Small - 2-3 um -Produced in the bone marrow from megakaryocytes |
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Where do megakaryocytes develop? |
- There are multiple stages of megakaryocytes as they develop from stem cells. - Polypoid in the in the marrow |
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What is development of megakaryocytes stimulated by? |
- Thrombopoietin |
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What are the characteristics of megakaryocytes? |
-Multilobulated nuclei -Lots of cytoplasm -Demarcation membrane system in mature cytoplasm -Platelets are shed from the megakaryocytes |
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What is the normal range of platelets? |
150-450 x 10^9/L |
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What is the life span of platelets in Peripheral Blood? |
7-10 days |
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What is the percentage of platelets in circulation, in comparison to the percentage that is sequestered in the spleen? |
-67% of platelets in circulation -33% sequestered in the spleen |
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What are the 4 zones platelet structure? |
-Peripheral -Structural -Organelle -Membrane Systems |
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What is involved in the peripheral zone? |
-Glycocalyx (Glycoproteins, proteins, and glycolipids) - Responsible for negative charge - Receptors for platelet activation - GPIb - GPIIb/IIIa -Cytoplasmic membrane |
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What is GPIb? |
-Receptor for vonWillebrand Factor (vWF) -Bound with GPV & GPIX -GPIb/IX/V plays a large role in platelet adhesion |
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What is GPIIb/IIIa? |
-Receptor for fibrinogen -"Resting" until platelets are activated -Required for platelet aggregation |
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What's included in the cytoplasmic membrane of the peripheral zone? |
-Phospholipid Bilayer - once activated, serves as a surface for coagulation reactions -Integral proteins - Receptors for stimuli in platelet function. - Glycoproteins - GPIb - GPIIb/IIIa |
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What is the structural zone composed of? |
- Composed of microtubules, cytoskeleton, contractile proteins (actin/myosin) - Supports the membrane - Maintains platelet shape - Allows shape change upon activation - Anchor glycoproteins - Release granule contents |
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What is the organelle zone? |
- Mitochondria - Glycogen Particles - Support metabolism - Granules - Dense granules - Alpha granules - Lysosomal granules |
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What are alpha granules? |
- Most numerous - Contain proteins - vWF, Factor V, fibrinogen, platelet derived growth factor - Platelet Factor 4 (PF4): neutralizes heparin-like substances on endothelial cells -PDGF and Beta-thromboglobulin: proteins believed to attract fibroblasts and promote wound healing
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what are dense bodies? |
Delta granules - Contain non-protein components: ADP, ATP, Calcium, Serotonin |
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What do lysosomal granules contain? |
Hydrolytic enzymes |
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What are the two types of Membrane Systems? |
-Open Canalicular System -Dense Tubular System |
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What are Open Canalicular Systems? |
-Surface connected. - Channels from surface to interior of platelet - Alpha granules fuse to it when activated to allow content secretion - Provides more membrane surface area during activation |
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What are Dense Tubular Systems? |
-Storage site for calcium ions -Channels do not connect to platelet surface |
