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Flashcards in Hemostasis Deck (47)
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1

hemostasis

stopping blood loss in response to vascular injury

2

What is the stages of hemostasis (be straightforward)

vascular constriction --> formation of platelet plug --> formation of blood clot --> fibrous organization

3

When does the formation of the platelet plug occur

primary homeostasis

4

Describe the formation of the platelet plug

platelet aggregation --> vWF connects platelets to endothelium --> exposed collagen allows more aggregation --> fibrinogen connects the platelets together = platelet plug

5

What occurs during secondary homeostasis

formation of the blood clot

6

describe the formation of the blood clot

coagulation cascade = fibrinogen --> fibrin

7

what occurs during fibrous organization

involves fibrinolysis in which the clot is broken up by proteins in the plasma

8

Petechiae

small (1 to 2 mm), round, red or brown lesions resulting from hemorrhage into the skin and are present primarily in areas with high venous pressure, such as the lower extremities

9

Purpura

Extravasation of red blood from cutaneous vessels into skin or mucous ; membranes results in reddish-purple lesions ; NO blanching

10

Vasculitis
Commonly seen in?

inflammation of and damage to blood vessels; most commonly has an infectious or immune-mediated cause.

11

Hematoma

Hemorrhage within a closed space

12

Ecchymosis

bruise; the most common form of hemorrhage in the skin; blanch with pressure

13

Thrombosis

hemostasis in the wrong place; end result is vessel occlusion and tissue ischemia

14

Embolism/thromboembolism

a substance that forms within or enters the vascular system at one site and is carried through the blood stream to another area of the body, where it lodges in a blood vessel and produces its effects (usually infarcts)

15

Infarction

irreversible ischemic or hypoxic damage to cells/tissues resulting in necrosis of the cells/tissue

16

Physical characteristics of platelets

1) form from hematopoietic tissue
2) not a cell; lack a nucleus
3)metabolically active
4) 2-3µM Diameter, 6-8fL
5) Life span= 7-10 days

17

Chemical Characteristics + Role in clotting

Plugs up injury sites by binding to collagen to stop bleeding: releases adhesive glycoprotein and ADP to increase aggregation and size of plug
platelets, damaged blood vessels and plasma promote cascade of 13 plasma proteins to give rise to fibrin to trap RBC, leukocytes and platelets to make blood clot (thrombus)

18

Describe the general mechanisms of blood coagulation

1)conversion of prothrombin to thrombin
2) conversion of fibrinogen to fibrin
3) development of a blood clot = fibrin threads mix in
4) clot retraction
5) lysis of blood clots= plasminogen --> plasmin (fibrinolysin). Fibrinolysin lyses fibrin and helps remove the clot.

19

what leads to activation of prothrombin to thrombin?

Factor Xa

20

What are the common pathways used in the intitation of clotting?

Extrinsic, Intrinsic and Common

21

Explain the Extrinsic Pathway

Extrinsic Pathway (tested by prothrombin time (PT): Injury to a tissue -> release of tissue factor -> activates factor VII ­– activates factor X

22

Explain the Intrinsic Pathway

Intrinsic Pathway (tested by partial thromboplastin time (PTT): Factor XII -> activated factors XI then IX and then VIII (VIIIa) combine to activate factor X

23

Explain the Common Pathway

Common Pathway (both extrinsic and intrinsic)= regulated by antithrombin III (which inactivates excess thrombin)
Factor X ­-> II (prothrombin) -> Thrombin -> I (Fibrinogen) -> Fibrin (which makes a clot and removes excess thrombin regulating the cycle so the clot doesn’t get to big)

24

role of Vitamin K in the formation of blood clotting factors

Vitamin K activates clotting factors II (prothombin), VII, IX, X, C, S. --> Warfarin is an anticoagulant (prevents blood clots)

25

hemophilia

-blood does not clot normally
-an X-linked recessive disorder of factor VIII deficiency or inactivity.
-bruise easily and hemorrhage at points of trauma, most notably in the joints (referred to as hemarthrosis).

Physiology: VIII is deficient and we know factor VIII is part of the intrinsic pathway, PTT is therefore prolonged. The PT and bleeding time, however, will be normal because the extrinsic pathway is still intact and the platelets are still functional.

26

deep vein thrombosis

-occlusion of the venous system (LE)
Causes: blood stasis (most common), hypercoagulability and endothelial damage.
-95% of all PE’s (pulmonary emboli) derive from deep leg vein thrombosis
-increased with pregnancy, cardiac failure, prolonged bed rest, ortho surgery.
-Thombosis accompanied by inflammation is called thrombophlebitis.

27

thrombocytopenia

-decreased number of platelets NOt an abnormality in function
-AIDS, SLE and viral infections, heparin use.

28

pulmonary embolism

blood clot that has traveled to the lungs.
-are derived from DVT’s.

29

disseminated intravascular coagulation

-primarily involves thrombus formation due to activation of the coagulation cascade.
-occurs secondary to another disease.
- if all the clotting factors are used up, excessive bleeding could occur

30

Bleeding time test

A small cut is place don the patient’s forearm, with a BP cuff kept on the arm at 40mm Hg to resist venous flow. Normal bleeding time may be 2-7 minutes. If the bleeding time is prolonged, this usually suggests a defect in platelet function.