Aggregation Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Aggregation and links to relevant pages within the course.
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| Each of the following has been shown to induce platelet aggregation except: | View Page |
| What is the composition of basophilic stippling? | View Page |
| Which of the following is not true in terms of platelet characteristics? | View Page |
| All of the following activities are associated with platelets except | View Page |
| Primary Hemostasis – The Vascular System Overview of Vascular System Involvement in Primary Hemostasis:
Vasoconstriction
Reroute blood flow
Platelet aggregation
Contact activation of coagulation system (start of secondary hemostasis at this point) | View Page |
| Primary Hemostasis – The Vascular System & Platelet Involvement As discussed earlier, a break in the vessel endothelium leads to exposure of collagen and the vessel's subendothelial surface. Ruptured endothelial cells leak ADP and Serotonin, which are the chemical triggers that induce platelet adhesion, the next step in the sequence of hemostatic events. Circulating platelets are drawn to the area by those liberated chemical signals, and begin to physically attach themselves to the rough, damaged surfaces of the breach. As platelets continue to arrive and bind to the exposed collagen and basement membrane, a rudimentary barrier begins to form, as the platelets themselves serve to fill in the breached vessel wall. Platelets possess an inherent “sticky” property which enables them to adhere to one another, and not just to the damaged vessel endothelium. The process by which platelets bind to one another is referred to as platelet aggregation, and is vital because it allows for a platelet plug to be formed. The platelet plug is the structure responsible for plugging the hole in the vessel wall. | View Page |
| Primary Hemostasis – The Vascular System & Platelet Involvement Platelet aggregation is essential to platelet plug formation because the platelets are now able to span the center of the breach, where there was obviously no exposed collagen to bind to before, as well as clumping behind one another to buttress or strengthen the barrier.
The formation of the platelet plug signals the end of primary hemostasis, and serves to initiate upcoming processes associated with secondary hemostasis.
| View Page |
| Primary Hemostasis – Characteristics of the Platelet Platelets play a significant role in primary hemostasis, as they are the “bricks”, or building blocks of the developing platelet plug, the forerunner to the end stage fibrin clot. Platelets have inherent adhesive properties which are essential for adherence to the site of vascular damage, and for binding to one another in aggregation activities. Platelets must be present in sufficient number, and be functionally active for optimal clotting to occur. Platelet functionality tends to be more crucial than the number of platelets available, however, as patients with lower platelet counts can still clot relatively effectively as compared to those patients with intrinsic platelet defects. | View Page |
| Primary Hemostasis – Platelet Kinetics Kinetic Processes Specific to Platelets. Adhesion – When platelets adhere to exposed collagen, they take on a characteristic “spiny” shape. Their inherent stickiness, and the aforementioned spiny shape serve to compliment each other during this process. Von Willebrands Factor (vWF) is absorbed by surface receptors on both the platelet and exposed subendothelial tissue, thereby linking the platelets to the tissue. Release – This process occurs prior to aggregation. Platelets dump the contents of their granules (ADP, Serotonin, & Calcium), which aids the upcoming aggregation process by acting as a chemical signal. Aggregation – Platelets physically bind to each other, not just to the exposed subendothelial walls and collagen of the breached vessel. Platelet aggregation requires sufficient chemical signal stimulation. Stabilization (technically part of secondary hemostasis as fibrin is a product of secondary hemostasis)– This process strengthens the platelet plug with the addition of interwoven fibrin strands, ultimately producing a fibrin clot. The durable fibrin clot is the ultimate goal of hemostatic processes. | View Page |
| PETINIA Particle-enhanced turbidimetric inhibition immunoassay (PETINIA) is a homogeneous competitive immunoassay.Antibody fragments and drug-latex particles will bind to form aggregates that increase the turbidity of the solution. Free drug from the sample competes for the antibody fragment, thereby decreasing the rate of particle aggregation. The rate of aggregation is inversely proportional to the concentration of drug in the sample. | View Page |
| Albinism Albinism, one of the striking physical characteristics of Chediak-Higashi syndrome, is also thought to be related to the general dysfunction of cells. Albinism has been specifically related to the aggregation of melanosomes, the pigment producing cells in the body. | View Page |