Term
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Definition
| It is the process aimed at closing a leak in the vascular system to prevent blood loss. |
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Term
| What are the steps of hemostasis? |
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Definition
Vasoconstriction
Platelet Plug
Coagulation |
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Term
| Arrange the steps of hemostasis in order of how fast they occur, from fastest to slowest. |
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Definition
Vasoconstriction (immediate)
Platelet Plug (seconds)
Coagulation (minutes) |
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Term
| About how long does it take for an average wound to heal? |
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Definition
|
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Term
| How before clot retraction occurs? |
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Definition
|
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Term
| Vasoconstriction is initiated by which nervous system? |
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Definition
| Sympathetic Nervous System |
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Term
| What kind of muscle cells carry out vasoconstriction? |
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Definition
| Vascular Smooth Muscle Cells |
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Term
| What happens after vasoconstriction occurs? |
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Definition
Endothelial cells of opp sides may stick together.
Endothelial cells contract, exposing the basal lamina
Provides TIME for platelet and coagulation phase.
REDUCES BLD LOSS, though not efficiently. |
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Term
| What does vasoconstriction correlate to? |
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Definition
| Damage. The greater the damage, the greater the duration of vasoconstriction. |
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Term
| Is platelet plug formation controlled by negative or positive feedback? |
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Definition
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Term
| Describe the process of platelet plug formation. |
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Definition
DAMAGE to the ENDOthelial wall exposes COLLAGEN
platelets STICK
platelets SECRETE contents
more platelets STICK
in a +VE FEEDBACK CASCADE |
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Term
| What are the main functions of platelet plug formation? |
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Definition
CLOSURE of leak by formation of temporary patch.
Release of CHEMICAL MEDIATORS to regulate blood clotting.
CONTRACTION of blood clot. |
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Term
| What are the dimensions of platelets? |
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Definition
|
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Term
| How long do platelets survive? |
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Definition
|
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Term
| What hormone are platelets regulated by? |
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Definition
|
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Term
| What are platelets fragments of? |
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Definition
|
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Term
| How much platelets do you have in your blood? |
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Definition
|
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Term
| Are platelets nucleated in humans? |
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Definition
|
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Term
| What organelles and substances to platelets contain? |
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Definition
Contractile proteins (Actin + Myosin)
Mitochondria
ER
GA
Enzyme systems for the synthesis of Prostaglandins
Growth Factors (PDGF [Platelet-derived Growth Factor] + VEGF [Vascular Endothelial Growth Factor])
Factor XIII (Fibrin Stabilizing Factor) |
|
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Term
| Why do platelets have mitochondria? |
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Definition
| For the synthesis of ADP which is a source of energy for movement. |
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Term
| Why do platelets have ER and GA? |
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Definition
ER is a Ca2+ store for movement.
ER + GA are needed together for the synthesis of enzymes. |
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Term
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Definition
It is the formation of platelets.
It begins with the stimulation of precursor cells megakaryoblasts
and is controlled by the hormone thrombopoietin. |
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Term
| According to the notes, what cell eventually breaks down into platelets and what are the intermediate cells? |
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Definition
Hemocytoblast
> Megakaryoblast
> Promegakaryocyte
> Megakaryocyte
> Platelets |
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Term
| Describe the process of platelet activation. |
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Definition
Non-activated platelets do not adhere to normal endothelial cells: ‘repulsive’ glycoproteins on platelet surface. NO and prostaglandin.
Platelets meet collagen > platelets become ACTIVATED
> ‘sticky’ > adhere to the exposed collagen.
> extend filopodia
Actin + myosin contract > forces out the contents of platelet granules.
Degranulated platelets secrete:
-Serotonin and thromboxane A (enhance vascular spasms).
-ADP (enhances platelet aggregation and secretion).
-Platelet factor 3 (PF3, activates blood coagulation).
-Calcium (essential for blood coagulation).
-Factor XIII (FSF) covalently crosslinks fibrin monomers.
-PDGF (promotes growth of fibroblasts).
-VEGF (promotes growth of vascular endothelial cells).
Platelet activation alone is sufficient to seal tiny leaks, which are very frequent.
For bigger ruptures platelets form a temporary batch. |
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Term
| What is the percentage of fibrinogen in blood proteins? |
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Definition
|
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Term
| Describe the coagulation cascade. |
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Definition
Fibrinogen --Thrombin cleaves--> Fibrin
Fibrin polymerizes --> Fibrin Fibers (Within seconds. Fibrin fibers form the structural basis of a clot.)
Fibrin causes plasma to become a gel-like trap.
Fibrin Stabilizing Factor (Factor XIII) --Thrombin activates--> Factor XIII cross-links fibrin (within minutes) --> Strengthens + Stabilizes the clot. |
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Term
| Where do most clotting factors come from? |
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Definition
|
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Term
| Which vitamin do some clotting factors require? |
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Definition
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Term
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Definition
Enhances it's OWN generation (cos it's a +ve feedback loop thing)
FACTOR XIII activation (which stabilized the fibrin mesh)
PLATELET activation
release of PF3 frm platelets (which activates the intrinsic pathway)
release of TISSUE FACTOR (which activates the extrinsic pathway)
Thrombin is ay KEY REGULATOR OF HEMOSTASIS. |
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Term
|
Definition
| Stabilization of clot by squeezing serum from the fibrin strands, leading to the further closure of the leak. |
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Term
| Describe the repair of damaged blood vessels. |
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Definition
PDGF stimulates vascular smooth muscle cells to build new vessel wall.
VEGF stimulates endothelial cells to multiply and restore the endothelial lining. |
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Term
| When does the clot retract? |
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Definition
|
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Term
| When does the clot dissolve or get invaded by fibroblasts? |
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Definition
|
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Term
| Clot retraction is mediated by...? |
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Definition
|
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Term
| When is healing of a damaged blood vessel completed? |
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Definition
|
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Term
| When is a damaged blood clot considered healed? |
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Definition
| When fibrous tissue replaces the blood clot. |
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Term
| What is an important concept behind the regulation of blood clotting? |
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Definition
| Balance b/n pro- and anti-coagulants. |
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Term
| Name 2 procoagulants and the process they are involved in. |
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Definition
Tissue factor (involved in the Extrinsic Pathway)
Collagen (involved in the Intrinsic Pathway + formation of the Platelet Plug) |
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Term
| What is the characteristic of a procoagulant that is involved in the intrinsic pathway? |
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Definition
|
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Term
| What are the 2 kinds of anticoagulants? |
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Definition
|
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Term
| Name the artificial anticoagulants. |
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Definition
Chelators (Citrate, EDTA)
Vitamin K antagonists (Warfarin, Coumarin) |
|
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Term
| Name the endogenous anticoagulants. |
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Definition
Smooth endothelial surface
Antithrombin III
Heparin
Thrombomodulin
Tissue Plasminogen Activator |
|
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Term
| Aside from procoagulants and anticoagulants, what other substances regulate blood clotting? |
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Definition
Prostacyclin (a prostoglandin produced by intact endothelial cells. inhibits platelet activation and limits the spread of blood clotting.)
Serotonin (at high conc, it inhibits ADP activity) |
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Term
| How does the formation of a blood clot regulate blood clotting? |
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Definition
| A blood clot limits the spread of thrombin and other procoagulants. |
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Term
| Brief summary of blood clotting regulation? |
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Definition
Prostacyclin
Serotinin
Presence of blood clot
Procoagulants
Anticoagulants |
|
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Term
| What is the most important anticoagulant? |
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Definition
| A smooth vessel surface. This is assisted by the endothelial cell layer being covered by glycosaminoglycans, a polysaccharide. |
|
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Term
| Tell me about antithrombin III. |
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Definition
It is a COMPETITIVE INHIBITOR. It binds to the active sites of activated Factor II (thrombin), VII, IX, X, XI, XII (2, 7, 9, 10, 11, 12) > inactivates them
Affinity of antithrombin III to these molecules enhanced by heparin (by ~1000x) |
|
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Term
| What is heparin used for clinically? |
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Definition
| Used to prevent thrombosis. |
|
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Term
|
Definition
A glycosaminoglycan.
Consists of a polymerised glucose backbone with 1 of 5 different types of groups attached to each glucose. |
|
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Term
| What is protamine sulfate used for and how does it work? |
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Definition
It is used in emergencies to counteract heparin overdose and to stop bleeding.
This is because protamine sulfate is +vely charged and binds to -vely-charged heparin, does neutralizing heparin's activity. |
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Term
| Which 2 substances inhibit the intrinsic and common pathway? |
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Definition
Antithrombin
Thrombomodulin |
|
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Term
| Where is thrombomodulin made? |
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Definition
|
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Term
| What does thrombomodulin do? |
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Definition
| It binds to thrombin > thrombomodulin/thrombin complex > activates PROTEIN C (a serine protease) > cleaves + inactivates Factors Va and Vllla |
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Term
| What does TFPI stand for? |
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Definition
| Tissue Factor Pathway Inhibitor |
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Term
| How does TFPI inhibit the extrinsic pathway? |
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Definition
| TFPI binds + inhibits Factor Xa > TFPI-Xa complex > inhibits VllA-TF complex > inhibits extrinsic pathway |
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Term
| So.. what does fibrin do to thrombin? |
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Definition
| Fibrin binds and sequesters up to 90% of thrombin. |
|
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Term
|
Definition
| an abnormal condition in which a clot (thrombus) develops within a blood vessel. |
|
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Term
| How does aspirin prevent thrombosis? |
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Definition
| It has ANTI-THROMBOTIC activities > blocks platelet activities |
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Term
|
Definition
| The dissolution of clots. |
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Term
|
Definition
Plasma protein
Protease precursor made by the liver. |
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