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Haemostasis
Describe how blood loss stops (haemostasis)
| Question | Answer |
|---|---|
| What is haemostasis? | A process which causes bleeding to stop, meaning to keep blood within a damaged blood vessel |
| What is haemostasis the first stage of? | Wound healing |
| What does haemostasis involve? | Blood changing from a liquid to a gel |
| What happens when endothelial injury occurs? | The endothelial cells stop secretion of coagulation and aggregation inhibitors and instead secrete Von Willebrand factor which initiate the maintenance of haemostasis after injury |
| What are the 3 major steps to haemostasis? | 1. Vasoconstriction 2. Temporary blockage of a break by a platelet plug 3. Blood coagulation, or formation of a fibrin clot |
| Explain Vascular Spasm | Blood vessels 1st response to injury.The damaged vessels will constrict (vasoconstrict) which reduces the amount of blood flow through the area and limits the amount of blood loss |
| What type of blood vessels is vascular spasm most effective in? | Smaller blood vessels |
| Describe the start of platelet formation | Platelets adhere to damaged endothelium to form platelet plug (primary haemostasis) and then degranulate. They stick together (aggregation) to form a plug that temporarily seals the break in the vessel wall |
| Name 6 things you find inside the blood that are relevant to haemostasis | Clotting factors, platelets, prothrombin, erythrocytes, fibrinogen, Von Willebrand factor |
| What secretes Von Willebrand factor? | endothelial cells |
| What surrounds the blood vessels? | Smooth muscles |
| What constricts the blood vessels during vasospasm/vasoconstriction? | Smooth muscles surrounding the blood vessels |
| During vasospasm/vasoconstriction how do the smooth muscles know when to contract? | Cells around the injured area, particularly the endothelial cells, begin secreting signals telling the smooth muscles to contract, enhancing vasoconstriction. Our nerve reflexes also cause the smooth muscles to contract. Also myogenic spasm. |
| What is myogenic spasm? | Myogenic contraction refers to a contraction initiated by the myocyte cell itself instead of an outside occurrence or stimulus such as nerve innervation. |
| What happens once the platelet plug has been formed by platelets? | The clotting factors begin creating the blood clot |
| What is thromboregulation? | The platelets release chemical messengers such as ADP and serotonin which cause more platelets to stick to the area and release their contents and enhance vascular spasms. This process is called thromboregulation |
| What happens during step 3 of haemostasis, blood coagulation? | Clots form upon the conversion of fibrinogen to fibrin, and its addition to the platelet plug |
| What being released plays an essential part in the clotting process and why? | The release of Prothrombin also plays an essential part in the coagulation process because it allows for the formation of a thrombus (clot) to form |
| What happens as the fibrin mesh begins to form and what does this do? | As the fibrin mesh begins to form the blood is also transformed from a liquid to a gel like substance This final step forces blood cells and platelets to stay trapped in the wounded area |
| What is thromboxane A2 and what does it do? | Thromboxane A2 (TXA2) is a type of thromboxane that is produced by activated platelets and has prothrombotic properties: it stimulates activation of new platelets as well as increases platelet aggregation |
Created by:
Aimee76
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