Hematology Flashcards
Upon injury to a vessel, platelets form ……..
a temporary plug
What are the steps in platelet plug formation??
- Adhesion
- Aggregation
- Platelet swelling and release of reaction
See P. 511 for details
What happens to the platelets upon adhering to the cut surface??
swelling, with the formation of spiny processes protruding from their surfaces to enhance platelets adhesion
Platelets release several products when adhering to the injury site. What are they??
- ADP: induces platelet aggregation
- Ca: increases degree of aggregation and strengthen the plug
- Vasoactive amines: epinephrine, serotonine, all which promotes local vasoconstriction
- Thromboplastin: initiates formation of permanent plug
- PF 3: involved in platelet plug formation
* Adenosine is different than ADP. It is a potent vasodilator
Damaged cells release two initiator for clotting, …. & …..
tissue phospholipids & tissue thromboplastin (factor III)
Von Willbrand factor is ……
synthesized by megakaryocytes. Bound to Factor VIII while inactive in the circulation. Important for platelet adhesion
Factor VIII is synthesized by ……. & …… . High levels may cause ……
vessels endothelium & liver
DVT or pulmonary embolism
Factor II (thrombin) converts …….. to ……
soluble fibrinogen (factor I) to insoluble fibrin
- It is produced from prothrombin by the action of factor X & V
- Factor II synthesis is inhibited by warfarin
The most common type of coagulation disorders is …..
Von willbrand disease (deficiency of VWF)
* Followed by hemophilia A (F VIII deficiency), B (christmas disease, F IX deficiency), and C (F XI deficiency)
Prothrombin time measures ….., normal range is …..
the common and the extrinsic pathways of coagulation
- Normal is 12-15 seconds
- Value depends on F VII & presence of vitamin K, factor X
- Also called PT/INR, where INR is international normalized ratio
Partial thromboplastin time (PTT) measures ….., normal range …..
intrinsic and common pathways of coagulation
- Normal range is 27-37 seconds
- Called partial due to absence of F III from the pathway
- Prolonged with heparin use
Extrinsic pathway requires ….. & ….. to be activated
F III (thromboplastin, tissue factor) & tissue phospholipids
Virchow’s triad is
the factors that causes DVT
- Hypercoagulability
- Stasis
- Injured vessel endothelium
Explain the extrinsic pathway
- Trauma to tissues produces tissue factor (F III)
- F III + Ca activates F VII
- F VIIa activates F X
Explain the intrinsic pathway
- F XII (hageman) is activated upon contact with collagen
- F XIIa activates F XI
- F XIa activates F IX (christmas)
- F IXa + F VIII + platelet phospholipids activate F X
Explain the common pathway
- F Xa + F Va + tissue phopholipids + Ca form the prothrombin activator
- Prothrombin forms thrombin
- Thrombin forms fibrin from firbrinogen
- F XIII (fibrin stabilizing factor) is also activated by thrombin
- F XIIIa forms covalent bonds between fibrin to form a 3 dimensional clot
Fluid oozing out of clot is …..
serum (has not F I or clotting factors)
- Albumin is available in serum
- Serotonin level is high in serum due to platelet break down from the extraction process.
The final stage of hemostasis is …..
dissolution of the fibrin clot by plasmin. This is after the fibroblast start repairing the injury site
Raynaud’s phenomenon is …….
an exaggeration of vasomotor response to cold or emotional stimuli (hyperactive sympathetic system). Can be idiopathic (primary) and secondary (caused by a factor)
Bleeding time is used to …..
assess platelet function. Affected by asprin, VWD, thrombocytopenia
* normal value is 2-5 min
In VWD, bleeding time and PTT are …..
increased
* Prothrombin time & platelet count are normal
In nephrotic syndrome, hypercoagulability occurs. Why?
because more anticoagulant protein are lost than coagulation activators
Lines of Zahn are characteristic of …..
thrombus in the heart and the aorta
DIC is diagnosed by …..
the presence of fibrin split products in the blood, low platelets and prolonged PT & PTT
