Vascular Response and Coagulation Process Quiz
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Questions and Answers

What is primarily responsible for the vasoconstriction in smaller vessels after trauma?

  • Sympathetic nervous system stimulation
  • Direct damage to the vascular wall
  • Thromboxane A2 released by platelets (correct)
  • Local autacoid factors from injured cells

Which substance is NOT involved in the processes initiating vascular constriction?

  • Adenosine triphosphate (ATP) (correct)
  • Thromboxane A2
  • Prostaglandins
  • Nerve impulses

What role do glycoproteins on the platelet membrane play?

  • Facilitate adherence to injured vessel walls (correct)
  • Inhibit the aggregation of platelets
  • Enhance platelet secretion of thromboxane A2
  • Prevent adherence to injured vascular areas

What happens as the severity of vascular trauma increases?

<p>The degree of vascular spasm increases (B)</p> Signup and view all the answers

Which enzyme system is involved in the synthesis of local hormones affecting vascular reactions?

<p>Prostaglandin synthesis system (C)</p> Signup and view all the answers

What is the consequence of local myogenic spasm?

<p>Increased resistance in blood vessel lumen (B)</p> Signup and view all the answers

How long can vascular spasms last after an injury?

<p>Minutes to hours (C)</p> Signup and view all the answers

What role does activated Factor V play in the clotting process?

<p>It accelerates the proteolytic action of thrombin. (B)</p> Signup and view all the answers

What initiates the extrinsic pathway of coagulation?

<p>Release of tissue factor from traumatized tissue. (D)</p> Signup and view all the answers

Which statement correctly describes tissue factor?

<p>It contains both phospholipids and a lipoprotein complex. (A)</p> Signup and view all the answers

What is the role of platelet phospholipids in the clotting process?

<p>They serve as a vehicle that accelerates prothrombin activation. (B)</p> Signup and view all the answers

How does thrombin affect the clotting process once it begins?

<p>It has a positive feedback effect through Factor V. (D)</p> Signup and view all the answers

What role does ADP and thromboxane play in the platelet activation process?

<p>They activate nearby platelets to adhere to each other. (B)</p> Signup and view all the answers

What occurs within 3 to 6 minutes after a blood vessel ruptures?

<p>A platelet plug begins to form. (D)</p> Signup and view all the answers

What is the primary composition of the tight plug formed during blood coagulation?

<p>Fibrin threads and activated platelets. (C)</p> Signup and view all the answers

How do platelets contribute to the closure of small vascular ruptures?

<p>By fusing with endothelial cells to create a barrier. (D)</p> Signup and view all the answers

What happens to the clot after 20 minutes to an hour following its formation?

<p>The clot retracts, further closing the vessel. (B)</p> Signup and view all the answers

Which of the following factors is synonymous with fibrinogen?

<p>Factor I (B)</p> Signup and view all the answers

What occurs to the vessel if the platelet plug successfully forms?

<p>It effectively blocks blood loss. (A)</p> Signup and view all the answers

Which factor is referred to as tissue factor or tissue thromboplastin?

<p>Factor III (A)</p> Signup and view all the answers

What nature does the platelet plug initially have when it is formed?

<p>A loose structure that can adapt. (B)</p> Signup and view all the answers

What initiates the blood clotting process after vascular trauma?

<p>Activator substances from the vascular wall and platelets (B)</p> Signup and view all the answers

Which factor is known as the Stuart factor?

<p>Factor X (B)</p> Signup and view all the answers

What is the time frame for clot formation in a severe trauma case?

<p>15 to 20 seconds (D)</p> Signup and view all the answers

Factor IX is also known by which of the following names?

<p>Christmas factor (C)</p> Signup and view all the answers

What are the hemorrhagic areas in individuals with impaired clotting factors primarily caused by?

<p>Low levels of antihemophilic globulin (A)</p> Signup and view all the answers

Which factor is referred to as the Hageman factor?

<p>Factor XII (A)</p> Signup and view all the answers

Which factor is associated with fibrin stabilization?

<p>Factor XIII (A)</p> Signup and view all the answers

The term 'plasma thromboplastin component' refers to which clotting factor?

<p>Factor IX (A)</p> Signup and view all the answers

What is the role of prekallikrein in hemostasis?

<p>It activates Factor XII (C)</p> Signup and view all the answers

What happens to a person with an inhibited hemostatic mechanism?

<p>They develop numerous small hemorrhagic areas (D)</p> Signup and view all the answers

What role does thrombin play in the conversion of fibrinogen to fibrin?

<p>It removes four low-molecular-weight peptides from fibrinogen. (C)</p> Signup and view all the answers

Which ions are essential for the acceleration of platelet contraction during clotting?

<p>Calcium ions released from intracellular stores. (B)</p> Signup and view all the answers

What characterizes the early stages of polymerization of fibrin monomer molecules?

<p>Fibrin monomer molecules are held together by weak noncovalent hydrogen bonding. (B)</p> Signup and view all the answers

How does the formation of the blood clot initiate positive feedback?

<p>By releasing thrombin into the surrounding blood. (B)</p> Signup and view all the answers

What happens to the fibrin reticulum as time progresses after clot formation?

<p>It strengthens during the following minutes. (B)</p> Signup and view all the answers

What is the primary mechanism by which thrombin contributes to hemostasis?

<p>By facilitating the conversion of fibrinogen to fibrin. (D)</p> Signup and view all the answers

What occurs to the edges of the broken blood vessel during clot retraction?

<p>They are pulled together, aiding in hemostasis. (A)</p> Signup and view all the answers

Why are the initial fibrin fibers described as weak and easily broken apart?

<p>They are held together by weak noncovalent bonds. (C)</p> Signup and view all the answers

What is the significance of calcium ions being released from platelet organelles?

<p>They help in the contraction of the clot. (A)</p> Signup and view all the answers

What describes the role of actin and myosin in platelets during clot formation?

<p>They facilitate strong contractions for clot retraction. (B)</p> Signup and view all the answers

What is the consequence of a deficiency in Factor VIII during the activation of Factor X?

<p>Impaired conversion of prothrombin to thrombin (A)</p> Signup and view all the answers

Which component is essential for the activation of Factor IX?

<p>Activated Factor VIII (C)</p> Signup and view all the answers

In which condition is the availability of platelet phospholipids particularly critical?

<p>After vascular trauma (B)</p> Signup and view all the answers

Which factor is referred to as the antihemophilic factor?

<p>Factor VIII (D)</p> Signup and view all the answers

What role do activated Factor IX and Factor VIII play together?

<p>They activate Factor X (D)</p> Signup and view all the answers

What impact does short supply of platelets and Factor VIII have on coagulation?

<p>Deficiency in Factor X activation (D)</p> Signup and view all the answers

What is the primary source of the factor 3 (or thromboplastin) needed for clotting?

<p>Traumatized platelets (D)</p> Signup and view all the answers

What is the main advantage of using citrate anticoagulants over oxalate anticoagulants?

<p>Citrate is non-toxic when injected in moderate amounts. (B)</p> Signup and view all the answers

What is the role of the citrate ion when used as an anticoagulant?

<p>It forms a compound with calcium that prevents coagulation. (C)</p> Signup and view all the answers

Which of the following substances could be used to decrease blood coagulation outside the body?

<p>Sodium citrate (B)</p> Signup and view all the answers

In what context is heparin primarily used?

<p>In surgical procedures involving heart-lung machines. (C)</p> Signup and view all the answers

What effectively happens when a soluble oxalate compound is mixed with blood?

<p>It precipitates calcium oxalate and decreases ionic calcium. (C)</p> Signup and view all the answers

What condition is characterized by the appearance of small, purplish blotches on the skin due to low platelet levels?

<p>Thrombocytopenic purpura (D)</p> Signup and view all the answers

How long prior to surgery should vitamin K be administered to a deficient patient to ensure adequate clotting factors are produced?

<p>4 to 8 hours (C)</p> Signup and view all the answers

What is the primary deficiency in most cases of classic hemophilia?

<p>Factor VIII (A)</p> Signup and view all the answers

What typically characterizes bleeding episodes in individuals with thrombocytopenia?

<p>Failure of the blood to retract (A)</p> Signup and view all the answers

In relation to normal platelet levels, how low does the platelet count need to drop to potentially cause lethal bleeding?

<p>Below 50,000/µl (A)</p> Signup and view all the answers

What genetic factor contributes to the transmission of hemophilia?

<p>Sex-linked inheritance via the female chromosome (D)</p> Signup and view all the answers

What causes the bleeding tendency in 15 percent of hemophilia cases not caused by Factor VIII deficiency?

<p>Deficiency of Factor IX (A)</p> Signup and view all the answers

What is the primary role of platelets during clot retraction?

<p>To aid in the mesh formation of the clot (A)</p> Signup and view all the answers

What might be indicated if a person's blood exhibits a failure to retract?

<p>Potential thrombocytopenia (C)</p> Signup and view all the answers

What is the primary role of tissue plasminogen activator (t-PA) in hemostasis?

<p>Converts plasminogen to plasmin to dissolve clots (A)</p> Signup and view all the answers

Which condition is primarily necessary for heparin to exhibit significant anticoagulant effects?

<p>Presence of anti-thrombin III (A)</p> Signup and view all the answers

How does heparin increase the effectiveness of antithrombin III?

<p>By enhancing its capacity to bind thrombin (D)</p> Signup and view all the answers

What is the main function of the plasmin system in the vasculature?

<p>Remove small clots from peripheral blood vessels (B)</p> Signup and view all the answers

What is the effect of excessive heparin on thrombin levels in the blood?

<p>Removes free thrombin rapidly (D)</p> Signup and view all the answers

What consequence does a deficiency in clotting factors have on bleeding tendencies?

<p>Results in excessive bleeding conditions (C)</p> Signup and view all the answers

What characterizes the nature of the heparin molecule?

<p>It is a conjugated polysaccharide with negative charge (D)</p> Signup and view all the answers

What change occurs approximately 12 to 20 minutes after a clot forms?

<p>The clot begins to dissolve gradually (A)</p> Signup and view all the answers

Which aspect of heparin's action is particularly emphasized in its clinical use?

<p>It prevents intravascular clotting effectively (B)</p> Signup and view all the answers

What percentage of normal coagulant activity is achieved in the blood by 24 hours after administering warfarin?

<p>20% (B)</p> Signup and view all the answers

What method is most widely used for determining blood clotting time?

<p>Collecting blood in a chemically clean test tube (D)</p> Signup and view all the answers

Which factor is primarily affected by the use of siliconized containers for blood collection?

<p>Factor XII (B)</p> Signup and view all the answers

What is the standard time frame for bleeding to last when a finger is pierced?

<p>1 to 6 minutes (B)</p> Signup and view all the answers

What is one reason why blood in siliconized containers may not clot for an extended period?

<p>Prevention of platelet contact activation (D)</p> Signup and view all the answers

After discontinuation of coumarin therapy, when does normal coagulation usually return?

<p>1 to 3 days (A)</p> Signup and view all the answers

What can notably prolong bleeding time?

<p>Lack of any one clotting factor (A)</p> Signup and view all the answers

What is the normal clotting time for blood collected in a chemically clean glass test tube?

<p>6 to 10 minutes (B)</p> Signup and view all the answers

What substance can be used to prevent coagulation of blood both inside and outside the body?

<p>Heparin (D)</p> Signup and view all the answers

What can contribute to variability in clotting time measurements?

<p>Method of clotting time measurement (A)</p> Signup and view all the answers

Flashcards

Vasoconstriction

The immediate response to blood vessel damage is a narrowing of the blood vessel called vasoconstriction. This is achieved by the smooth muscle cells in the vessel wall constricting, reducing blood flow through the damaged area.

Causes of Vasoconstriction

Vasoconstriction can be triggered by a variety of mechanisms, including direct damage to the blood vessel wall, the release of chemicals like thromboxane A2 from platelets, and nerve impulses. This coordinated response helps control bleeding and minimize blood loss.

Platelets and Vasoconstriction

Platelets are small cell fragments in the blood that play a vital role in blood clotting. They contain substances like thromboxane A2 that help in vasoconstriction, but their primary function is to stick together and form a plug at the site of injury.

Platelet Adhesion

Platelets have a surface coating that prevents them from sticking to healthy blood vessel walls. However, when a blood vessel is injured, this coating changes, allowing platelets to adhere to the damaged area and begin the clotting process.

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Temporary Platelet Plug

The initial plug formed by platelets is a temporary fix. It is crucial in stopping immediate blood loss, but is not a permanent solution. The next step in the healing process is the formation of a more stable blood clot.

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Platelet Plug Formation

The formation of a platelet plug is a complex process involving multiple steps. It begins with platelet activation, followed by platelet adhesion to the damaged site, and culminates in the formation of a plug that temporarily seals the wound.

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Thromboxane A2 and Platelet Plug

A key step in the formation of the platelet plug is the release of thromboxane A2, a strong vasoconstrictor, from the platelets. This constricts blood vessels further, reducing blood flow to the damaged area and promoting clot formation.

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Blood Coagulation

The process of blood clotting, which involves a complex cascade of events leading to the formation of a blood clot, also known as a thrombus.

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Clot Formation Timing

The first step in blood clotting, usually taking 15 to 20 seconds for severe trauma and 1 to 2 minutes for minor trauma.

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Clotting Activators

Substances from the damaged blood vessel, platelets, and blood proteins that trigger the clotting process.

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Platelet Plug

A temporary plug formed by platelets at the site of a blood vessel injury, preventing blood loss.

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Platelet Adhesion Factors

Adhesive molecules released by platelets during activation, enabling them to stick to each other and the vessel wall.

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Platelet Stickiness

The ability of platelets to stick to each other and the injured vessel wall.

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Platelet Aggregation

The process by which activated platelets attract and recruit more platelets to the injury site, forming a larger plug.

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Fibrin Formation

The process of converting fibrinogen, a soluble protein, into fibrin, an insoluble protein network that reinforces the platelet plug.

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Platelet-Plugging Mechanism

The mechanism that repairs minor blood vessel ruptures by a quick and efficient process of platelet aggregation and fibrin formation.

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Clotting Factors

A group of proteins involved in blood coagulation, numbered from I to XIII, each playing a specific role in the process.

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Tissue Factor

A clotting factor also known as Factor III, released from damaged tissues, which initiates the coagulation cascade.

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Clot Retraction

The process by which the platelet plug contracts, pulling the edges of the injured vessel closer together, further reducing blood loss.

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What is the first step in the extrinsic pathway of coagulation?

The extrinsic pathway for initiating coagulation starts with tissue injury, leading to the release of tissue factor (TF) from damaged tissue. This factor activates Factor VII, forming a complex that activates Factor X. This activation is further enhanced by the presence of calcium ions and phospholipids.

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What is the first step in the intrinsic pathway of coagulation?

The intrinsic pathway begins with an injury inside the blood vessel, leading to the exposure of collagen. This exposure activates Factor XII, then Factor XI. Factor IX, along with Factor VIIIa, forms a complex that activates Factor X. This is also accelerated by the presence of calcium ions and phospholipids.

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What is the role of Factor X (Xa) in the coagulation cascade?

Factor X, when activated (Xa), is a key component of the prothrombin activator complex. This complex, along with Factor V and platelet phospholipids, works to convert prothrombin into active thrombin. Thrombin is the central enzyme driving the coagulation cascade.

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What is the main function of thrombin?

Thrombin has a significant role in the coagulation cascade. It activates Factor V, accelerating the formation of itself. It also converts fibrinogen into fibrin, which forms the meshwork of a clot. Additionally, it activates platelets and reinforces the platelet plug.

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What is the main purpose of the clotting cascade?

The clotting cascade is a series of enzymatic reactions that amplify the clotting process. These reactions are triggered by both intrinsic and extrinsic pathways. The two pathways converge, culminating in the generation of thrombin, which ultimately leads to the formation of a stable fibrin clot.

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Thrombin

A protein enzyme that initiates blood clotting by converting fibrinogen into fibrin, forming a meshwork that traps blood cells.

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Fibrinogen

A soluble protein found in blood plasma that, when activated by thrombin, forms the fibrous meshwork of a blood clot.

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Fibrin

Insoluble protein fibers that form the main structure of a blood clot.

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Fibrin Polymerization

The process by which fibrinogen molecules join end-to-end to form long fibrous strands.

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Noncovalent Hydrogen Bonds

Weak chemical bonds that initially hold fibrin monomers together. These bonds are easily broken, resulting in a weak clot.

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Fibrin Cross-Linking

The process by which fibrin fibers become cross-linked, creating a strong and stable clot.

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Calcium Ion Release

The release of calcium ions from intracellular stores, which activates the contraction of platelets and accelerates clot retraction.

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Positive Feedback of Clot Formation

The process in which a developing blood clot triggers the release of more clotting factors, amplifying the clotting response.

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Activation of Factor IX

Activated Factor XI, a clotting factor, acts on Factor IX, another clotting factor, to activate it. This process requires calcium ions (Ca++) and occurs during the intrinsic pathway of blood coagulation.

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Activation of Factor X

Activated Factor IX (IXa), in conjunction with activated Factor VIII (VIIIa), platelet phospholipids, and factor 3, activates Factor X. This step is crucial for blood clotting and is deficient in hemophilia. Note the role of Factor VIII (missing in hemophilia) and platelets as essential components of this process.

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Extrinsic Pathway of Coagulation

The extrinsic pathway initiates blood clotting when tissue injury occurs. Damaged tissue releases tissue factor (TF), which activates Factor VII, forming a complex activating Factor X. This activation is enhanced by the presence of calcium ions (Ca++) and phospholipids.

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Intrinsic Pathway of Coagulation

The intrinsic pathway initiates blood coagulation when there is injury inside the blood vessel. This process begins with the exposure of collagen, activating Factor XII, then Factor XI. Factor IX, along with Factor VIIIa, further activates Factor X. The presence of calcium ions and phospholipids accelerates this process.

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Role of Factor X (Xa)

Activated Factor X (Xa) is a key component of the prothrombin activator complex. This complex works with Factor V and platelet phospholipids to convert prothrombin into active thrombin. This step is central to blood clotting.

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Conversion of Prothrombin to Thrombin

Prothrombin, a protein, is activated by the prothrombin activator complex to form thrombin. This enzyme is crucial for the final stages of blood clotting.

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Functions of Thrombin

Thrombin plays a central role in coagulation. It activates Factor V, accelerating its own formation. It converts fibrinogen into fibrin, forming the clot's meshwork, and activates platelets to reinforce the platelet plug.

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Tissue Plasminogen Activator (t-PA)

A powerful activator released by injured tissues and endothelium that, after a few days, converts plasminogen to plasmin, which in turn removes unnecessary clots.

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Heparin

An anticoagulant that inactivates thrombin and removes clots from blood vessels, especially smaller ones.

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Antithrombin III

A protein that binds to heparin and greatly increases its anticoagulant effect by enhancing its ability to remove thrombin from the blood.

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Fibrinolysis

The process that dissolves clots by breaking down fibrin, allowing blood flow to resume.

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Plasmin

A protein that, when activated, breaks down fibrin, removing blood clots.

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Cause of Excessive Bleeding

A deficiency of any one of the clotting factors can lead to excessive bleeding.

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Bleeding Tendency

The condition where a lack of proper clotting factors leads to excessive bleeding.

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Hemophilia

A bleeding disorder primarily affecting males, often caused by a deficiency in Factor VIII (hemophilia A) or Factor IX (hemophilia B).

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Hemophilia A

A type of hemophilia caused by a deficiency in Factor VIII, accounting for 85% of cases.

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Hemophilia B

A type of hemophilia caused by a deficiency in Factor IX, accounting for 15% of cases.

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Thrombocytopenia

A condition where the blood fails to clot properly due to a low platelet count, resulting in excessive bleeding.

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Thrombocytopenic purpura

The purplish blotches on the skin of a person with thrombocytopenia, caused by bleeding under the skin.

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Idiopathic thrombocytopenia

A type of thrombocytopenia with an unknown cause.

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Antibodies against platelets

Antibodies that mistakenly target platelets, leading to their destruction and thrombocytopenia.

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Normal platelet count

The normal range of platelets in the blood, essential for clotting and wound healing.

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Lethal platelet count

A critical platelet count below which bleeding becomes life-threatening.

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Anticoagulant

A substance that reduces the concentration of calcium ions in the blood, preventing coagulation.

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Citrate

A common anticoagulant that combines with calcium in the blood to form an un-ionized compound, preventing coagulation.

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Prothrombin Time (PT)

A measurement of the time it takes for blood to clot, indicating the concentration of prothrombin, a clotting factor.

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International Normalized Ratio (INR)

A test that measures the clotting ability of blood, used to monitor patients on anticoagulants.

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Oxalate

A compound that, when mixed with blood, causes precipitation of calcium oxalate, preventing coagulation.

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Clotting Time

A measure of how long it takes for blood to clot outside the body. Using a glass test tube, blood is tipped back and forth until clotting occurs.

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Warfarin

A medication that reduces the production of clotting factors in the liver, leading to a decrease in blood clotting ability. It is commonly used to prevent blood clots.

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Bleeding Time

A test that measures how long it takes for a small wound to stop bleeding.

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Intrinsic Pathway

The intrinsic pathway starts when blood contacts a foreign surface, like collagen, causing the release of clotting factors that trigger the coagulation cascade.

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Extrinsic Pathway

The extrinsic pathway starts when tissue is injured, releasing tissue factor, which activates the coagulation cascade, starting a chain reaction of clotting.

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Study Notes

Hemostasis and Blood Coagulation

  • Hemostasis is the prevention of blood loss.
  • Several mechanisms achieve hemostasis:
    • Vascular constriction
    • Platelet plug formation
    • Blood clot formation
    • Fibrous tissue growth

Vascular Constriction

  • Vessel wall smooth muscle contracts reducing blood flow.
  • Mechanisms include:
    • Local myogenic spasm
    • Local autacoid factors from traumatized tissue and platelets
    • Nervous reflexes (pain and sensory impulses)
  • Platelets play a role in smaller vessels, releasing thromboxane A.
  • Spasm duration varies with vessel trauma (from minutes to hours).

Platelet Plug Formation

  • Platelets are minute discs (1-4 micrometers).
  • Formed in bone marrow from megakaryocytes.
  • Normal concentration: 150,000-300,000 per microliter.
  • Platelets have cellular characteristics despite lacking a nucleus
  • Contain:
    • Actin and myosin (contractile proteins)
    • Thrombosthenin (contractile protein)
    • Endoplasmic and Golgi residuals (enzymes and Ca storage)
    • Mitochondria and ATP/ADP enzyme systems
    • Prostaglandin synthesizing enzymes
    • Fibrin-stabilizing factor
    • Growth factor for vascular cells
  • Platelet membrane has glycoproteins aiding adherence to collagen, and von Willebrand factor.

Platelet Plug Mechanism

  • Contact with damaged vascular surfaces (especially collagen) activates platelets drastically.
  • Platelets swell, form pseudopods, contract, release factors.
  • Adhere to collagen, von Willebrand factor.
    • ADP and thromboxane A2 activate nearby platelets causing aggregation.
  • Loose plug forms, which is strengthened by blood coagulation.
    • Platelets entrapped in the clot continue to release procoagulant substances.

Importance of Platelet Plugging

  • Crucial for closing tiny vessel ruptures (thousands occur daily).
  • Essential for preventing internal bleeding even in normal individuals

Blood Coagulation in Ruptured Vessels

  • Blood clot forms within 15-20 seconds (severe trauma), 1-2 minutes (mild trauma).
  • Clot forms from substances from traumatized vascular wall, platelets, and blood proteins.
  • Clotting factors listed in Table 36-1
    • Clotting times vary based on trauma and testing methodology.

Blood Clot Organization

  • Fibroblasts invade the clot forming connective tissue.
  • Clot dissolves if not needed, through enzymatic action (e.g. plasmin).
  • Clot retraction occurs, compressing the clot and expressing serum.

Blood Coagulation Mechanism

  • Complex cascade of chemical reactions involving more than a dozen blood coagulation factors.
  • Prothrombin activator converts prothrombin to thrombin.
  • Thrombin converts fibrinogen to fibrin fibers that entrap blood cells and platelets.

Prothrombin Activation

  • Prothrombin activator formed from extrinsic and intrinsic pathways, stimulated by tissue trauma or blood trauma/collagen exposure.
    • Extrinsic pathway initiated by tissue trauma.
    • Intrinsic pathway triggered by blood trauma or exposure to collagen.
  • Both pathways involve multiple factors (listed in Table 36-1).
  • Positive feedback loops amplify clot formation, accelerating the process.

Blood Clot Prevention

  • Endothelial surfaces (smoothness, glycocalyx, molecules that repel and inactivate) in normal vascular systems prevent clot formation.
  • Anticoagulants (e.g. heparin, antithrombin III) remove thrombin and other clotting factors and regulate blood clotting factors (e.g. activating protein C which downregulates activated factors V and VIII).

Clot Dissolution

  • Plasminogen, a trapped plasma protein, converts to active plasmin (fibrinolysin).
  • Plasmin digests fibrin, other clotting factors and byproducts to resolve the clot

Anticoagulants for Clinical Use

  • Heparin (intravenous), coumarins (e.g. warfarin) delay coagulation.
  • Warfarin inhibits vitamin K-dependent clotting factors.

Excessive Bleeding Conditions

  • Deficiency of a clotting factor (e.g., vitamin K deficiency, hemophilia, thrombocytopenia) causes excessive bleeding.
  • Vitamin K needed for clotting factor production by liver.

Blood Coagulation Tests

  • Bleeding time (time to stop bleeding from small wound).
  • Clotting time (time for blood to clot in a test tube).
  • Prothrombin time (measures prothrombin concentration using factors and calcium).
  • International Normalized Ratio (INR) standardizes prothrombin time measurements for better comparison and management of anticoagulant therapy.

Thromboembolic Conditions

  • A thrombus is an abnormal clot in a blood vessel, often developing in an area with slow blood flow.
  • Thrombi originating from large arteries or the left side of the heart can block peripheral arteries.
  • Thrombi from the venous system/right side of the heart can block pulmonary arteries.
  • Clots develop from conditions like roughened surfaces, slow blood flow, and prolonged inactivity.

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Chapter 36: Hemostasis and Blood Coagulation PDF

Description

Test your knowledge on the mechanisms of vasoconstriction and coagulation following vascular trauma. This quiz covers the roles of various substances and enzymes in the clotting process and the time frame of platelet activation. Challenge yourself to understand the intricate details of vascular reactions during injury.

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