adherence, platelets stick to vessel injury

aggregation, platelets stick to each other

204 micrometers

oval/disc shape

two zones; hyalomere and granulomere

size is relatively the same as resting platelet

large number of pseudopods develop

granular components are expelled during activation

alpha granules

delta granules, aka dense bodies

each contains different substances that play roles in coagulation and inflammatory response

platelet dervied growth factor

endothelial growth factor

fibronectin

plasminogen

thrombospondin

ADP

ATP

serotonin

calcium & magnesium ions

occurs due to agonists

agonist binds to membrane receptor

binding causes G-protein activation

shape change and release of granules occurs

directly binds to collagen

plays a role in adherence

directly binds to vonWillebrands factor

plays a role in adherence

binds to fibrinogen and vonWillebrands factor

plays a role in aggregation

start off as two separate glycoproteins

G-protein complex activates phopholipase A2

phospholipase A2 leads to breakdown of phosphatidyllinositol to arachidonic acid

thromboxane A2 is produced

thromboxane A2 causes cAMP decrease

calcium is released from dense tubular systems

initial phase of primary hemostasis

vessel damage exposes collagen

collagen is the agonist

vWF binds directly to collagen and forms a coating

platelets bind to vWF via GP Ib/IX

glycoprotein

forms bridge between exposed collagen and glycoprotein receptor on platelet surface

stabilizes initial platelet adhesion

secondary phase of primary platelet plug formation

facilitated primarily by GP IIb/IIIa which doesn't form until after activation