anatomy 2

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anatomy 2
2011-02-04 01:30:42

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  1. What is hemostasis?
    a sequence of responses that stops bleeding
  2. What are the 3 mechanisms that reduce blood loss in hemostasis?
    1. vascular spasm

    2. platelet plug formation

    3. blood clotting
  3. When hemostasis is successful, what does it prevent?
  4. What is hemorrhage?
    the loss of a large amount of blood from the vessels
  5. Hemostatic mechanisms can prevent hemorrhage from smaller blood vessels, but extensive hemorrhage from larger vessels usually requires what?
    medical intervention
  6. What is vascular spasm?
    When arteries or arterioles are damaged, the circularly arranged smooth muscle in their walls contracts immediately.
  7. How long does vascular spasm reduce blood loss?
    for several minutes to several hours, during which time the other hemostatic mechanisms go into operation
  8. What probably causes vascular spasms?
    damage to the smooth muscle, by substances released from activated platelets, and by reflexes initiated by pain receptors
  9. What clotting factors are in platelets?
    ADP, ATP, Ca2+, and serotonin
  10. What is platelet-derived growth factor?
    A hormone within platelets that can cause proliferation of vascular endothelial cells, vascular smooth muscle fibers, and fibroblasts to help repair damaged blood vessel walls.
  11. What is platelet adhesion?
    Initially, platelets contact and stick to parts of a damaged blood vessel, such as collagen fibers of the connective tissue underlying the damaged endothelial cells
  12. What is platelet release reaction?
    Due to adhesion, the platelets become activated, and their characteristics change dramatically. They extend many projections that enable them to contact and interact with one another, and they begin to liberate the contents of their vesicles.
  13. What is platelet aggregation?
    The release of ADP makes other platelets in the area sticky, and the stickiness of the newly recruited and activated platelets causes them to adhere to the originally activated platelets
  14. what is a platelet plug?
    Eventually, the accumulation and attach-ment of large numbers of platelets form a mass called a platelet plug
  15. When is a platelet plug very effective?
    In preventing blood loss in a small vessel
  16. What is a platelet plug reinforced by?
    fibrin threads formed during clotting
  17. Can a platelet plug stop blood loss completely?
    yes, if the hole in a blood vessel is not too large
  18. what is serum?
    blood plasma minus the clotting proteins
  19. Normally, blood remains in its liquid form as long as it stays within its vessels. But, what happens if it is drawn from the body?
    it thickens and forms a gel...the gel separates from the liquid...the liquid is serum and the gel is called a clot
  20. What does a clot consist of?
    a network of insoluble protein fibers called fibrin in which the formed elements of blood are trapped
  21. What is the process of gel formation where a series of chemical reactions culminate in the formation of fibrin threads?
    clotting or coagulation
  22. If blood clots too easily, the result can be...
  23. What is thrombosis?
    clotting in an undamaged blood vessel
  24. when can hemorrhage occur?
    if the blood takes too long to clot
  25. What are the clotting (coagulation) factors?
    calcium ions

    several inactive enzymes that are synthesized by hepatocytes (liver cells) and released into the bloodstream

    various molecules associated with platelets or released by damaged tissues
  26. How are most clotting factors identified?
    By roman numerals that indicate the order of their discovery
  27. How many stages are in clotting?
  28. What are the 3 stages of clotting?
    1. Two pathways, called the extrinsic pathway and the intrinsic pathway, lead to the formation of prothrombinase. Once prothrombinase is formed, the steps involved in the next two stages of clotting are the same for both the extrinsic and intrinsic pathways, and together these two stages are referred to as the common pathway.

    2.Prothrombinase converts prothrombin (a plasma protein formed by the liver) into the enzyme thrombin

    3.Thrombin converts soluble fibrinogen (another plasma protein formed by the liver) into insoluble fibrin. Fibrin forms the threads of the clot
  29. Is blood clotting a positive or negative feedback?
    positive feedback
  30. What is the outcome of the first stage of blood clotting?
    the formation of prothrombinase
  31. How soon after a trauma does the extrinsic pathway of blood clotting occur?
    within a matter of seconds
  32. Why does extrinsic pathway have its name?
    because a tissue protein called tissue factor (TF), also known as thromboplastin, leaks into the blood from cells outside blood vessels and initiates the formation of prothrombinase
  33. What is thromboplastin?
    a tissue protein called tissue factor (TF) that initiates the formation of prothrombinase
  34. What is TF made of?
    a complex mixture of lipoproteins and phospholipids released from the surfaces of damaged cells
  35. What does TF ultimately activate?
    clotting factor X
  36. What is the intrinsic pathway?
    When the activators are either in direct contact with blood or contained within the blood, outside tissue damage is not needed
  37. Is the intrinsic pathway simpler than the extrensic pathway?
  38. How long does the intrinsic pathway take?
    more slowly than the extrinsic pathway, usually requiring several minutes
  39. What marks the beginning of the common pathway?
    the formation of prothrombinase
  40. What is the 2nd stage of blood clotting?
    pothrombinase and Ca2+ catalyze the conversion of prothrombin to thrombin
  41. What is the 3rd stage of blood clotting?
    thrombin, in the presence of Ca2+, converts fibrinogen, which is soluble, to loose fibrin threads, which are insoluble. thrombin also activates factor XIII (fibrin stabilizing factor), which strengthens and stabilizes the fibrin threads into a sturdy clot
  42. Thrombin has 2 ___ ___ effects
    positive feedback
  43. In the first positive feedback loop of thrombin, which involves factor V, what happens?
    it accelerates the formation of prothrombinase. Prothrombinase in turn accelerates the production of more thrombin, and so on
  44. What happens in the 2nd positive feedback loop of thrombin?
    thrombin activates platelets, which reinforces their aggregation and the release of platelet phospholipids