Lecture #10 Cardiovascular System: The Blood: Platelets and Clotting Flashcards
What are thrombocytes?
Cell fragments that circulate for 5-9 days, then die.
2/3 of mature platelets circulate, 1/3 reside in the spleen
This type of cell refers to clot formation and the clot is called a thrombus also known as?
Throbosis
What is it called when there is a circulating clot?
An embolus
What is caled when a condition so severe that leads to uncontrollable bleeding?
Hemorrhage
What is Thrombocytopoiesis?
Myelooid stem cells produce megakaryocytes with a diameter of ~160um
What is Thrombopoietin (TPO)?
Causes fragments to slough off the megakaryocyte
How many fragments, or platelets enter the circulation?
2,000-3,000 & the platelet diameter ~2-4um and ~1 um thick.
What is hemostasis?
It’s a series of reactions designed to stop bleeding
What are the three phases of hemostasis that occur in rapid succession?
First–Vascular spasm i.e., immediate vasoconstriction in response to injury
Second–platelet plug formation
Third–coagulation (blood clotting)
What is phase 1 of vascular spasm?
Only occurs in blood vessels that have a smooth muscle—spasm reduces vessel diameter which results in pressing of endothelial surfaces together.
Does phase 1 of the vascular stop blood flow or continue blood flow?
Stops blood flow almost instantly.
Where does phase 1 take place?
Effective only in very small vessels (meta) arterioles, precapillary sphnicters
What is the function of phase 2 platelet plug formation?
Platelets normally do not stick to each other or to the endothelial lining of blood vessels
What happens to platelets when their is damage to the blood vessels?
In order for the platelets to stick, they become exposed to collagen fibers and they become activated, which is allowing them to stick to one another.
After the platelets are exposed to collagen fiber what transformation happens to the activated platelets?
Platelets liberate thromboxane A2, serotonin, and ADP which attract & activate still more platelets
What are the functions of ADP, Thromboxane A2, and serotonin?
ADP makes platelets stick, while thromoboxane A2 and serotonin cause vasoconstriction. Which results in a formation of platelet plug.
What happens in Phase 3 Coagulation?
It is a complex process, where it involves 13 clotting factors which is a set of reactions in which blood is transformed from a liquid to a gel.
Does phase 3 coagulation involve intrinsic, extrinsic pathways, or both?
Both pathways are activated–the activation of the intrinsic pathway takes more time than for the extrinsic pathway
What are the final steps that constitute the common pathway which must be completed for effective clotting?
Once Prothrombinase is formed it is converted to thrombin.
What are the two main functions of thrombin?
Converts fibrogen (soluble) into a fibrin (insoluble stable threads) mesh
Activates factor XIII which stabilizes the fibrin network
During the formation of clotting factors, Prothrombin, fibrinogen, and factors ________are synthesized in the liver.
Factors V, VII, IX, and X
What is the purpose of Vitamin K?
Vitamin K is needed for the synthesis of factors II,VII,IX, and X—deficiency of K can lead to failure of blood clotting.
If an individual is lacking factor VIII they are?
Hemophiliacs
Why must clots be dissolved?
So that they do enter the circulation as an embolus (a blood clot transported by the bloodstream)
A dissolution of a clot is known as?
Fibrinolysis
When a clot is formed, an inactive plasma enzyme called _______ is incorporated onto the clot.
Plasminogen
Both body tissues and blood contain substances that can activate plasminogen to ______ or fibrinolysin, an active plasma enzyme.
Plasmin
Among these substances are ____activated factor XII, and _______ activator, which is synthesized in endothelial cells of most tissues and liberated into the blood.
Thrombin, Tissue Plasminogen
Once _____ is formed, it can dissolve the clot by digesting fibrin threads and inactivating substances such as fibrinogen, prothrombin, and factors V and XII.
Plasmin
