Thrombocytes Flashcards
(30 cards)
basics of thrombocytes.
- they are not cells, but fragments of megakaryocytes.
2. normal thrombocytes counts is 90k-270k Μl or μL.
what is normal thrombocyte count?
90k-270k Μl or μL
thrombocytopoiesis
production of thrombocytes from megakaryocytes in the bone marrow.
simplified thrombocytopoiesis.
- pluripotent stem cells.
- committed stem cells
- CFU-mega
- Megakaryoblast
- basophil megakaryocyte
- Granular megakaryocyte
- mature megakaryocyte
- thrombocytes
hormone responsible for thrombocytopoiesis
thrombopoietin
role of thrombopoietin.
- regulate thrombocytes production, increase number and rate of mature of megakaryocytes.
thrombocytopenia
is a disorder in which the body produces few thrombocytes.
thrombocytosis
is the disorder in which the body produce too many thrombocytes.
main parts of thrombocytes.
- surface connecting tubules
- dense tubules
- mitochondria
- glycogen
- dense granules
- alpha granules
- microtubules
- coat
main roles of thrombocytes.
- role in the immunity
- role in clot formation and retraction.
- role in transport and storage function.
- role in the repair of injured blood vessels
- role in hemostasis: vasoconstriction and platelet plug formation in vessel repair.
how thrombocytes involve in the storage and transport function?
Thrombocytes store and transport chemicals used in the clot formation processes. Eg: histamine etc.
how thrombocytes are involved in immunity?
Platelets sense invading pathogens through their receptors, which results in platelet activation. Activated platelets release antimicrobial proteins and molecules that regulate the host’s response to infection.
how do thrombocyte vasoconstricts local vessels?
Platelets release cytoplasmic granules which contain serotonin and other chemicals which increase the effect of vasoconstriction.
what is clot retraction?
Clot retraction is the “shrinking” of a blood clot over a number of days.
what is vascular spasm
is a sudden, brief tightening of the muscle cells inside the walls of a blood vessel.
what is hemostasis
refers to stoppage of bleeding
what chemicals that released by thrombocytes when the get in contact with collagens.
- adenosine diphosphate (ADP), which helps additional platelets to adhere to the injury site, reinforcing and expanding the platelet plug.
- serotonin, which maintains vasoconstriction
- prostaglandins and phospholipids, phospholipid through different reactions give rise to thromboxane A2 ( together with ADP they contribute to aggregation ).
what are the steps of hemostasis?
- vascular spasm: is constriction of vessels after damage to reduce blood loss.
- aggregation: thrombocytes sticks together resulting in formation of plug.
- coagulation/ clotting: formation of clot that is final repair of damaged vessel.
what is the function of thromboxane and ADP in the hemostasis?
They contribute to aggregation.
Mention 4 main clotting factors and there origin.
- fibrinogen/ I originate from liver.
- prothrombin/ II originate from liver.
- thromboplastin/ III originated from liver.
- calcium ions/ IV originate from diet and bone matrix.
how many clotting factors that contribute to coagulation?
12 factors. I to XIII
extrinsic pathways of coagulation.
- Damage in perivascular tissues cause the release of thromboplastin
- tissue factor / thromboplastin/ III.
- - III acted on by Ca ions, VII to give TF/VIIa complex - TF/VIIa complex
- - TF/VIIa complex act on X - x acted on by TF/VIIa give Xa
- Xa acted on by Ca ions, PF3, and V to give prothrombin activator.
- prothrombin activator act on prothrombin to give thrombin
- thrombin act on both fibrinogen to give fibrin and XIII to give XIIIa.
- fibrin acted on by XIIIa to give cross-linked fibrin polymer.
intrinsic pathways of coagulation.
- vessel endothelium ruptures, exposing collagen.
- thrombocytes cling on collagen and provide a site for mobilization of factors
- thrombocytes mobilize XII to give XIIa
- XIIa act on XI to give XIa
- XIa act on IX
- IX acted on by VIIa( extrinsic), XIa, and Ca ion to give IXa
- IXa acted on by PF3, and VIII to give IXa/VIII complex
- IXa/VIII complex act on X to give Xa
- Xa acted on Ca ions, PF3, and V to give prothrombin activator and Va.
- prothrombin activator act on prothrombin to give thrombin
- thrombin act on fibrinogen and XIII to give fibrin and XIIIa.
- fibrin acted on XIIIa to give cross-linked fibrin polymer.
two ways how, homestasis manage clotting.
- swift removal of clotting factors.
2. inhibition of activated clotting factors.
