our topic today is platelet plug formation hemostasis or the cessation of bleeding is critical for survival hemostasis can be divided into three steps vascular spasm platelet plug formation and blood clot formation this video discusses the development of the platelet plug which is a plug made of platelets sticking to one another to stop blood flow here's a normal blood vessel damage to the vessel wall begins the formation of the platelet plug playlist begin to attach to the underlying collagen in the damaged area which in turn activates the platelets activated platelets have undergone a physical change in
shape and are also able to attach to one another forming a plug which helps stop bleeding let's take a closer look now at the individual steps by which platelets become activated as mentioned platelet plug formation begins when a blood vessel suffers damage a protein known as von Willebrand factor abbreviated vwf is secreted by endothelial cells and binds to expose collagen in the vessel wall circulating platelets have vwf receptors also known as gp1 B receptors vwf forms a bridge to connect the platelets to the collagen when the playlist bind to the vwf the playlists' become activated
and change shape to increase their surface area activation the playlist also causes the platelets to express active fibrinogen receptors also called gp2 b3a receptors the anchored activated platelets begin to secrete a variety of chemical compounds from granules called alpha and dense granules alpha granules release additional von Willebrand factor which assists with further platelet adherence and activation alpha granules also release platelet derived growth factor abbreviated PDGF which facilitates long-term wound healing after tissue damage dense granules release adenosine diphosphate abbreviated ADP additionally thromboxane abbreviated TX a2 is made inside the platelet using several enzymes including cyclooxygenase and
thromboxane synthase and is released from the playlist cytoplasm ADP and thromboxane bind to their respective receptors p2 by 12 and TP TP receptors on additional circulating platelets this binding causes additional platelets to become activated circulating fibrinogen produced by the liver bind to the fibrinogen receptors on platelets the bound fibrinogen allows platelets to adhere to one another via brenigan serves as a linking molecule between the platelets that Express fibrinogen receptors this makes plateless stick to one another platelets sticking together form a plug the spans across the opening in a damaged vessel to stop blood flow this
is called platelet aggregation platelets are rich in the proteins actin and myosin these proteins allow for contraction and the formation of a more compact platelet plug which is important in the healing process pause the video now to review the summary of platelet plug formation now for some questions to test your understanding pause the video and think of your answers if you answered the following you are correct thanks for watching
