154 Questions
Where are platelets formed in the body?
Bone marrow
What is the normal concentration of platelets in the blood?
150,000 - 450,000/ μL
What is the half-life of platelets in the blood?
8 to 12 days
Which organelle is NOT found within platelets?
Nucleus
What is the main function of the coat of glycoproteins on platelets' membrane?
Repulses adherence to injured areas of the vessel wall
Which enzyme system is NOT found within platelets?
ATP synthase
What is the function of serum in blood clotting?
It is blood plasma minus its fibrinogen and most of the other clotting factors
What is the role of activated platelets in blood clot contraction?
Activating platelet thrombosthenin, actin, and myosin molecules
Which factor is responsible for catalyzing the cross-linkage in blood clotting?
Factor XIII (fibrin-stabilizing factor)
What is the rate-limiting factor in causing blood coagulation?
Formation of prothrombin activator
Which pathway has fewer steps and occurs rapidly in blood coagulation?
Extrinsic pathway
Where does the intrinsic pathway for blood coagulation begin?
Within the blood itself
What is the role of vitamin K in blood clotting?
Is required by the liver for normal activation of prothrombin
Which enzyme acts on fibrinogen to form fibrin in blood coagulation?
Thrombin
What is the function of fibrin-stabilizing factor in blood clotting?
(I) Activated XIII Loose fibrin threads STRENGTHENED FIBRIN THREADS 3
Why does little fibrinogen normally leak from the blood vessels into the interstitial fluids?
Because of its large molecular size
How do the intrinsic and extrinsic mechanisms usually operate when a blood vessel ruptures during tissue injury?
The extrinsic mechanism stops blood in the injured vessel while the intrinsic mechanism clots blood that escaped into the tissue before the vessel was sealed off.
What limits the explosive nature of the extrinsic pathway in blood coagulation?
The amount of tissue factor released from traumatized tissues and by the quantities of Factors X, VII, and V in the blood.
What is the main factor responsible for the prevention of blood coagulation while it is circulating in the blood vessels?
The smoothness of the endothelial cell surface
What happens when the endothelial wall is damaged?
Factor XII and platelets are activated, setting off the intrinsic pathway of clotting
Which substance is among the most important anticoagulants in the blood, responsible for removing thrombin?
Fibrin fibers formed during the process of clotting
What is the main function of Heparin in the blood?
Prevents contact activation of platelets and Factor XII
What can cause thromboembolism according to the text?
Release of tissue thromboplastin into the blood from traumatized tissue
What are the causes of thromboembolic conditions mentioned in the text?
Roughened vessel surfaces associated with atherosclerosis
What is a characteristic feature of DIC (Disseminated Intravascular Coagulation)?
Bleeding due to removal of clotting factors by widespread clotting
'Thromboembolic' conditions generally refer to:
Conditions involving widespread clotting and embolism formation
What does antithrombin III mainly combine with in order to prevent clot formation?
Thrombin adsorbed to fibrin fibers
What happens when a vessel is ruptured according to Slide 40?
Procoagulants from area of tissue damage become activated, overriding anticoagulants
What is responsible for inhibiting platelet aggregation and initiation of blood clotting, according to Slide 40?
Intact endothelial cells producing prostacyclin and nitric oxide (NO)
What is the role of aspirin in hemostasis?
Inhibiting the formation of a platelet plug
What prevents further blood loss by adhering to damaged surfaces of blood vessels?
Fibrin fibers
Which event results from a series of chemical reactions and culminates in the formation of fibrin threads?
Blood clotting (coagulation)
What is the first event in hemostasis?
Vascular constriction
What is the primary function of the aggregated platelet plug in hemostasis?
Physically sealing the break in the vessel
What role does von Willebrand factor (vWF) play in platelet plug formation?
Adhesion of platelets to the subendothelial matrix
What is the significance of thromboxane A2 in platelet plug formation?
Inducing profound vasoconstriction
How does aspirin work to prevent blood loss?
By irreversibly inhibiting the enzyme cyclooxygenase (COX-1)
What is the primary function of hemostasis?
Prevention of blood loss
What is the role of tissue factor in the extrinsic pathway of blood clotting?
Formation of prothrombin activator
What is the function of activated factor X in the intrinsic pathway of blood coagulation?
Activates factor IX
What is the primary deficiency in hemophilia A?
Factor VIII
What is the role of thrombin in blood coagulation?
Converts fibrinogen into fibrin
Why do we use Ethylenediaminetetraacetic acid (EDTA) tube to collect blood for CBC?
Chelates calcium ions required for blood clotting
What is the final step before dissolution of a blood clot?
Release of tissue plasminogen activator
What is the main function of fibrous organization in hemostasis?
Repair the injured vessel wall
Which pathway requires the activation of factor XII and release of platelet phospholipids?
(b) Intrinsic pathway
What role does activated factor V play in blood clotting?
Formation of prothrombin activator
What is the significance of hemophilia A and hemophilia B being X-linked disorders?
They predominantly affect males.
What is the primary role of plasmin in blood coagulation?
Dissolution of remaining unnecessary blood clots
What is the main function of thrombosthenin in platelets?
ATP production
Which organelle is NOT found within platelets?
Nucleus
What is the normal concentration of platelets in the blood?
200,000 - 450,000/ μL
What is the main role of the coat of glycoproteins on platelet membranes?
Repulse adherence to injured areas of the vessel wall
What is responsible for inhibiting platelet aggregation and initiation of blood clotting, according to the text?
Vascular endothelial cells
What limits the explosive nature of the extrinsic pathway in blood coagulation?
Factor VII
What is the primary role of thromboxane A2 in platelet plug formation?
Activating platelet aggregation
What is the primary function of Heparin in the blood?
Inhibiting blood coagulation
What is the significance of hemophilia A and hemophilia B being X-linked disorders?
They are more common in males than in females
What happens when the endothelial wall is damaged?
von Willebrand factor adheres to the exposed collagen
What is the main factor responsible for the prevention of blood coagulation while it is circulating in the blood vessels?
Antithrombin III in plasma
What is the role of tissue factor in the extrinsic pathway of blood clotting?
Initiating blood coagulation cascade
What is responsible for inhibiting platelet aggregation and initiation of blood clotting, according to Slide 40?
Aspirin
What is the function of activated factor X in the intrinsic pathway of blood coagulation?
Catalyzing conversion of prothrombin to thrombin
'Thromboembolic' conditions generally refer to:
'Blockage of a blood vessel'
Why do we use Ethylenediaminetetraacetic acid (EDTA) tube to collect blood for CBC?
To prevent coagulation of blood during storage and transportation
What is the primary function of fibrous organization in hemostasis?
Preventing further blood loss by adhering to damaged surfaces of blood vessels
What role does activated factor V play in blood clotting?
Accelerating the formation of fibrin fibers
Which of the following statements about blood coagulation is true?
The extrinsic pathway requires damaged platelets to initiate the formation of prothrombinase
What is the role of thrombin in blood coagulation?
Thrombin strengthens the fibrin meshwork by forming covalent bonds between fibrin monomer molecules
What is the primary function of hemostasis?
To stop bleeding and maintain blood within a damaged blood vessel
What is the main function of the aggregated platelet plug in hemostasis?
To adhere to damaged surfaces of blood vessels and prevent further blood loss
What is responsible for inhibiting platelet aggregation and initiation of blood clotting, according to Slide 40?
Antithrombin III
Why does little fibrinogen normally leak from the blood vessels into the interstitial fluids?
Because fibrinogen is formed in the liver and remains primarily in the plasma
What is the significance of thromboxane A2 in platelet plug formation?
It promotes platelet aggregation and vasoconstriction at the site of injury
What can cause thromboembolism according to the text?
Increased permeability of capillaries during pathological conditions
What is responsible for removing thrombin from the clot, thus preventing further clot growth?
Plasmin
How does Ethylenediaminetetraacetic acid (EDTA) work in collecting blood for CBC?
It chelates calcium ions necessary for blood coagulation
What is the primary function of Heparin in the blood?
To prevent further clot growth by inhibiting thrombin activity
What is the role of thrombomodulin in blood coagulation?
Binds with thrombin and activates plasma protein C
What can cause thromboembolism according to the text?
Roughened vessel surfaces associated with atherosclerosis
What is the primary function of heparin in blood coagulation?
Inhibits thrombin and activated factors X, XI, IX, and XII
What is the main function of the coat of glycocalyx on the endothelial cell surface?
Inhibits platelet aggregation and initiation of blood clotting
What is the primary role of antithrombin III in preventing clot formation?
Inhibits activated factors V and VIII
Where do platelets originate in the body?
Bone marrow
What is the function of soluble oxalate and citrate ion outside the body?
Decreases ionic calcium level to block blood coagulation
What is the significance of thromboxane A2 in platelet plug formation?
Inhibits platelet aggregation and initiation of blood clotting depending on slide 40
What is responsible for inhibiting platelet aggregation and initiation of blood clotting, according to Slide 40?
A layer of glycocalyx on the endothelium
What is the main factor responsible for preventing blood coagulation while it is circulating in the blood vessels?
A layer of glycocalyx on the endothelium
Which pathway requires activation of factor XII and release of platelet phospholipids?
Intrinsic pathway
What is the primary role of thrombin in blood coagulation?
Converting fibrinogen into fibrin
What is the main function of fibrous organization in hemostasis?
Forming connective tissue all through the clot
Which substance is among the most important anticoagulants in the blood, responsible for removing thrombin?
Plasmin
What does 'Thromboembolic' conditions generally refer to?
Blood clots that obstruct blood vessels
What is the main function of the aggregated platelet plug in hemostasis?
Stopping bleeding until the vessel can be repaired
What is responsible for inhibiting platelet aggregation and initiation of blood clotting, according to the text?
Heparin
What is the role of tissue factor in the extrinsic pathway of blood clotting?
Formation of prothrombin activator
What is the first event in hemostasis?
Vascular constriction
What is the function of activated factor X in the intrinsic pathway of blood coagulation?
Combining with tissue phospholipids to form prothrombin activator
What is responsible for inhibiting platelet aggregation and initiation of blood clotting, according to Slide 40?
Antithrombin III
What limits the explosive nature of the extrinsic pathway in blood coagulation?
Blood trauma
Platelets have a half-life in the blood of 5 to 7 days.
False
Platelets contain nuclei.
False
Platelets contain enzyme systems that synthesize insulin.
False
The coat of glycoproteins on platelet membranes causes adherence to normal endothelium only.
False
Platelets are eliminated from the circulation mainly by the liver.
False
Platelets contain large amounts of phospholipids that inhibit multiple stages in the blood-clotting process.
False
The edges of the broken blood vessel are pulled together by the retraction of the clot, contributing further to hemostasis.
True
Serum is blood plasma minus its fibrinogen and most of the other clotting factors.
True
Platelets contribute directly to clot contraction by activating platelet thrombosthenin, actin, and myosin molecules.
True
Most of the proteins involved in blood-clotting are inactive forms of proteolytic enzymes.
True
Prothrombin activator is usually considered to be the rate-limiting factor in causing blood coagulation.
True
Fibrin-stabilizing factor, also known as factor XIII, catalyzes the cross-linkage of fibrin to form a stable clot.
True
The intrinsic and extrinsic mechanisms usually operate simultaneously in response to tissue injury.
True
Clots are typically fully formed in 3 to 6 minutes.
True
The extrinsic pathway for blood coagulation requires fewer steps than the intrinsic pathway and occurs rapidly.
True
Thrombin is an enzyme with weak proteolytic capabilities and acts on fibrinogen to form fibrin monomer.
True
Fibrin monomer has the automatic capability to polymerize with other fibrin monomer molecules to form fibrin fibers.
True
Fibrinogen, a high-molecular-weight protein found in plasma, does not normally leak from blood vessels into interstitial fluids due to its large molecular size.
True
Blood clotting depends on the balance between procoagulants and anticoagulants.
True
Prostacyclin and nitric oxide (NO) promote platelet aggregation and initiation of blood clotting.
False
Heparin is normally found at a high concentration in the blood.
False
Siliconized containers prevent contact activation of platelets and Factor XII.
True
Thrombus refers to freely flowing clots in the blood vessels.
False
Roughened endothelial surfaces of blood vessels are unlikely to initiate the clotting process.
False
DIC (Disseminated Intravascular Coagulation) often results from the presence of large amounts of traumatized tissue releasing tissue factor into the blood.
True
T-PA (tissue plasminogen activator) is used when blood must be passed through a heart-lung machine or artificial kidney machine.
False
Prothrombin time (PT) measures the integrity of the intrinsic pathway of blood coagulation.
False
Activated thromboplastin time (aPTT) measures the integrity of the intrinsic pathway of blood coagulation.
True
Activated factor X inhibits thrombin in the intrinsic pathway of blood coagulation.
False
Thromboembolic conditions may be triggered by imbalances in the clotting–anticlotting systems.
True
The intrinsic pathway is much slower to proceed, usually requiring 1 to 6 minutes to cause clotting.
True
Tissue factor is composed especially of phospholipids from the membranes of the tissue plus a lipoprotein complex that functions mainly as a proteolytic enzyme.
True
The activated Factor X combines immediately with tissue phospholipids and Factor V to form the complex called prothrombin activator.
True
Activated factor V greatly accelerates the protease activity of the prothrombin activator complex.
True
The common sites of bleeding in newborns include the central nervous system, and sites of medical interventions such as circumcision, heel sticks, and venipunctures.
True
Hemophilia A and B are X-linked disorders that predominantly affect males.
True
Patients with more severe hemophilia are less likely to have spontaneous bleeding.
False
Thrombin has positive feedback effects: it accelerates the formation of prothrombinase, activates platelets, and acts in a positive-feedback fashion to facilitate its own formation.
True
In the absence of calcium ions, blood clotting by either pathway does not occur.
True
Fibrous organization or dissolution of the blood clot is an event of hemostasis.
True
A clot is meant to be a permanent solution to vessel injury.
False
Plasminogen when activated becomes a substance called plasmin (or fibrinolysin) which removes the remaining unnecessary blood clot.
True
The formation of a platelet plug is one of the events of hemostasis.
True
Thrombocytopenia can lead to increased bleeding time.
True
A break must be present in the vessel wall for bleeding to take place from a vessel.
True
Platelets do not adhere to the smooth endothelial lining of blood vessels under normal conditions.
True
Aspirin works by irreversibly inhibiting the enzyme cyclooxygenase (COX-1) which is required to make the precursors of thromboxane within platelets.
True
The clot begins to develop in 15 to 20 seconds if the trauma to the vascular wall is severe.
False
The aggregated platelet plug releases several powerful vasodilators that induce profound constriction.
False
Clot retraction occurs within a few hours after a clot is formed.
False
Platelets begin to contract and usually express most of the fluid from the clot within 20 to 60 minutes.
True
Fibrin fibers prevent further blood loss by adhering to damaged surfaces of blood vessels.
True
Hemostasis includes fibrous organization or dissolution of the blood clot as one of its events.
True
Fibrin threads are formed as a result of a series of chemical reactions culminating in clotting.
True
Test your knowledge on the role of clot retraction in contributing to hemostasis and the process of blood clot contraction. Explore concepts such as blood plasma, platelet activation, and the intrinsic and extrinsic pathways of hemostasis.
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