Definition and Process of Hemostasis
- Hemostasis is the process to prevent and stop bleeding in biology.
- It is the first stage of wound healing.
- Hemostasis involves coagulation, which changes blood from a liquid to a gel.
- Intact blood vessels prevent blood clotting with certain molecules and inhibit platelet aggregation.
- When blood vessel endothelium is damaged, von Willebrand factor is secreted to initiate hemostasis.
Steps of Hemostasis Mechanism
- Vascular spasm is the first response of blood vessels to injury, reducing blood flow and promoting vasoconstriction.
- Platelet plug formation occurs when platelets adhere to damaged endothelium and release granules.
- Coagulation or blood clotting reinforces the platelet plug with fibrin threads.
- Platelets play a major role in primary hemostasis by creating the platelet plug.
- Hemostasis is maintained through vascular spasm, platelet plug formation, and clot formation.
Platelets in Hemostasis
- Platelets adhere to the sub-endothelium surface of a damaged blood vessel.
- Platelets release cytoplasmic granules containing serotonin, ADP, and thromboxane A2.
- ADP attracts more platelets to the affected area.
- Serotonin acts as a vasoconstrictor.
- Thromboxane A2 assists in platelet aggregation, vasoconstriction, and degranulation.
Clot Formation in Hemostasis
- Once the platelet plug is formed, coagulation cascade is activated.
- Coagulation cascade leads to the formation of fibrin from inactive fibrinogen plasma protein.
- Fibrin mesh is produced around the platelet plug, creating a secondary hemostasis plug.
- Red and white blood cells can be trapped in the clot, making it harder.
- Blood clot formation is essential for wound healing but can cause health problems if detached.
Types of Hemostasis
- Hemostasis can be achieved through natural means or with assistance during surgery or medical treatment.
- Chemical, mechanical, or physical agents can be used for hemostasis.
- The type of hemostasis used depends on the situation.
- Developmental hemostasis refers to differences in the haemostatic system between children and adults.
- In emergency medicine, hemostatic agents are primary tools for smaller bleeding injuries.
In biology, hemostasis or haemostasis is a process to prevent and stop bleeding, meaning to keep blood within a damaged blood vessel (the opposite of hemostasis is hemorrhage). It is the first stage of wound healing. This involves coagulation, which changes blood from a liquid to a gel. Intact blood vessels are central to moderating blood's tendency to form clots. The endothelial cells of intact vessels prevent blood clotting with a heparin-like molecule and thrombomodulin, and prevent platelet aggregation with nitric oxide and prostacyclin. When endothelium of a blood vessel is damaged, the endothelial cells stop secretion of coagulation and aggregation inhibitors and instead secrete von Willebrand factor, which initiate the maintenance of hemostasis after injury. Hemostasis involves three major steps:
These processes seal the injury or hole until tissues are healed.
hemo- + stasis. From Ancient Greek αἱμόστασις (haimóstasis, “styptic drug”).
