The Blood Clotting Mechanism. Vascular Spasm The smooth muscle in blood vessel walls contracts immediately the blood vessel is broken. This response reduces blood loss for some time, while the other hemostatic mechanisms become active.
What causes vascular spasm?
vascular spasm. Immediately after a blood vessel is cut, the vessel wall contracts, this reduces blood flow from the ruptured vessel. The contraction results from: Nervous reflexes initiated by pain. Local myogenic contraction of the blood vessels. Humoral factors from the traumatized tissues and platelets.
How long does a local vascular spasm last?
This local vascular spasm can last for many minutes or even hours during which the process of platelet plugging and blood coagulation can take place. When the receptors on the platelet membrane come in contact with damaged endothelium or collagen fibers in the vascular wall, the platelets immediately change their shape.
How do platelets mediate the vasoconstriction of blood vessels?
Platelets mediate much of the vasoconstriction by releasing the vasoconstrictor substances, thromboxane A2 & serotonin, Also, thrombin that is generated in the coagulation cascade, triggers the endothelium to release the powerful vasoconstrictor, endothelin-1.
How does calcium affect blood clotting?
In the body, the calcium ion concentration rarely falls low enough to impair blood clotting. But, reducing the calcium ion concentration in a blood sample prevents it from clotting. After 20-60 minutes of clot formation, the clot begins to contract and expresses most of the fluid from the clot.
What role does a vascular spasm play in the clotting process?
Blood clotting involves three steps. First, vascular spasm slows the flow of blood. Next, a platelet plug forms to temporarily seal small openings in the vessel. Coagulation then enables the repair of the vessel wall once the leakage of blood has stopped.
What is one role of vascular spasm in clotting quizlet?
What is one role of vascular spasm in blood clotting? Vascular spasms reduce blood flow to a damaged site.
What happens during vascular spasm?
When a vessel is severed or punctured, or when the wall of a vessel is damaged, vascular spasm occurs. In vascular spasm, the smooth muscle in the walls of the vessel contracts dramatically. This smooth muscle has both circular layers; larger vessels also have longitudinal layers.
What is the function of a vascular spasm quizlet?
Vascular spasm is when smooth muscle contracts, causing vasoconstriction. The benefit is that it slows blood down.
What is vascular spasm quizlet?
Vascular spasm (vasoconstriction) Immediate but temporary constriction of blood. vessel (Vasoconstriction) Damage to blood vessels activate the nervous system reflexes that cause vascular spasms.
Do platelets release factors that influence vascular spasm and coagulation?
Activated platelets release factors to stimulate further platelet activation, perpetuating plug formation in a positive feedback loop, while other factors stimulate the coagulation cascade and maintain vasoconstriction.
What is vascular spasm in hemostasis?
Vascular spasm is the first response as the blood vessels constrict to allow less blood to be lost. In the second step, platelet plug formation, platelets stick together to form a temporary seal to cover the break in the vessel wall. The third and last step is called coagulation or blood clotting.
How do vascular spasms contribute to the process of hemostasis?
What do vascular spasms contribute to the process of hemostasis? Vascular spasms decrease blood vessel diameter to limit blood loss. Medications known as anticoagulants interfere with: the coagulation cascade.
What is the functional consequence of vascular spasms during hemostasis quizlet?
What is the functional consequence of vascular spasms during hemostasis? Vascular spasms decrease blood vessel diameter to limit blood loss.
What is the role of fibrinogen in clotting?
Fibrinogen (clotting factor I) is synthesized in the liver and plays a critical role in the hemostatic process. Fibrinogen promotes platelet aggregation by stimulating platelet clumping. Soluble fibrinogen also converts to insoluble fibrin, which is cross-linked to form a mesh-like network.
What effect does vasoconstriction have on the process of hemostasis?
Primary hemostasis is characterized by vasoconstriction, which is the initial phase for stopping the blood flow10. Vascular spasm occurs whenever there is an injury or damage to the blood vessels. This will trigger a vasoconstriction, which could eventually stop the blood flow.
Why does blood rarely remain clotted inside blood vessels?
- Heparin is the anticoagulant that is a highly sulfated form of heparan sulfate. It is mainly made by connective tissue mast cells as a large heparin proteoglycan. It is having an anticoagulant property due to which the blood does not clot in the blood vessels.
How long does a vascular spasm last?
This local vascular spasm can last for many minutes or even hours during which the process of platelet plugging and blood coagulation can take place.
How long does it take for a clot to form after a vascular injury?
The clot begins to develop a few seconds after the vascular injury. Coagulation factors are essential to coagulation. They are mostly plasma proteins (inactive proteolytic enzymes) synthesized by the liver. However, some are not protein (e.g. calcium ions) and some are released by the platelets.
What happens to blood vessels after a cut?
Immediately after a blood vessel is cut, the vessel wall contracts, this reduces blood flow from the ruptured vessel. The contraction results from: 1 Nervous reflexes initiated by pain. 2 Local myogenic contraction of the blood vessels. 3 Humoral factors from the traumatized tissues and platelets. Platelets mediate much of the vasoconstriction by releasing the vasoconstrictor substances, thromboxane A2 & serotonin, Also, thrombin that is generated in the coagulation cascade, triggers the endothelium to release the powerful vasoconstrictor, endothelin-1.
What happens when the platelets in the vascular wall are damaged?
When the receptors on the platelet membrane come in contact with damaged endothelium or collagen fibers in the vascular wall, the platelets immediately change their shape. They become sticky and develop finger-like processes so that they stick to the collagen fibers, a process called platelet adhesion.
What is hemostasis in a vessel?
Hemostasis means the prevention of blood loss or the stoppage of bleeding. When the vessel is ruptured, hemostasis is achieved by several mechanisms. Platelets are necessary for clot retraction to occur. Resting platelets are smooth and discoid shaped. Activated platelets are swollen, sticky with finger-like processes, and secretory.
What is the difference between activated and resting platelets?
Resting platelets are smooth and discoid shaped. Activated platelets are swollen, sticky with finger-like processes, and secretory. Activation of the platelet contractile proteins can cause a strong concentration of the platelets attached to the fibrin.
Which pathway converts prothrombin into thrombin?
The final common pathway. Prothrombin activators (Factor Xa from the extrinsic or intrinsic pathway, factor Va, Ca+2, and phospholipids) convert prothrombin (factor II, one of the plasma proteins) into thrombin.