<unk>  is a complex process by which blood forms solid clots. It is an important part of hemostasis (the cessation of blood loss from a damaged vessel) whereby a damaged blood vessel wall is covered by a platelet- and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel. Disorders of<unk>  can lead to an increased risk of bleeding and/or clotting and embolism.<unk>  is highly conserved throughout biology; in all mammals,<unk>  involves both a cellular (platelet) and a protein<unk>  factor) component. The system in humans has been the most extensively researched and therefore is the best understood.<unk>  is initiated almost instantly after an injury to the blood vessel damages the endothelium (lining of the vessel). Platelets immediately form a hemostatic plug at the site of injury; this is called primary hemostasis. Secondary hemostasis occurs simultaneously—proteins in the blood plasma, called<unk>  factors, respond in a complex cascade to form fibrin strands which strengthen the platelet plug.
Coagulation
Hemostasis
Oxygenation
Thermoregulation
Gastrointestinal physiology
Blood flow
Photosynthesis
Dynamical system