Coagulation system

Platelets or thrombocytes () are a part of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping to form a blood clot. Platelets have no cell nucleus; they are fragments of cytoplasm from megakaryocytes which reside in bone marrow or lung tissue, and then enter the circulation. Platelets are found only in mammals, whereas in other vertebrates (e.g. birds, amphibians), thrombocytes circulate as intact mononuclear cells.

Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel forming a blood clot. The process involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin. Coagulation results in hemostasis, the cessation of blood loss from a damaged vessel, allowing repair.

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. Hemostasis involves three major steps: vasoconstriction temporary blockage of a hole in a damaged blood vessel by a platelet plug blood coagulation (formation of fibrin clots)

Fibrinogen (coagulation factor I) is a glycoprotein complex, produced in the liver, that circulates in the blood of all vertebrates. During tissue and vascular injury, it is converted enzymatically by thrombin to fibrin and then to a fibrin-based blood clot. Fibrin clots function primarily to occlude blood vessels to stop bleeding. Fibrin also binds and reduces the activity of thrombin. This activity, sometimes referred to as antithrombin I, limits clotting. Fibrin also mediates blood platelet and endothelial cell spreading, tissue fibroblast proliferation, capillary tube formation, and angiog

thumb|right|Composition of a fresh thrombus at microscopy, [[HE stain, showing nuclear debris in a background of fibrin and red blood cells.]] thumb|right|Micrograph showing fibrin (dark pink amorphous material) in a blocked [[vein surrounded by extravasated red blood cells (right of image). An artery (left of image) and the amnion (far left of image) is also seen. Placenta in a case of fetal thrombotic vasculopathy. H&E stain.]]

thumb|360px|alt=Schematic diagram of the blood coagulation and protein C pathways. In the blood coagulation pathway, thrombin acts to convert factor XI to XIa, VIII to VIIIa V to Va, fibrinogen to fibrin. In addition, thrombin promotes platelet activation and aggregation via activation of protease-activated receptors on the cell membrane of the platelet. Thrombin also cross over into the protein C pathway by converting protein C into APC. APC in turn converts factor V into Vi, and VIIIa into VIIIi. Finally APC activates PAR-1 and EPCR.|Role of thrombin in the blood coagulation cascade

mammalian protein found in Homo sapiens

Antithrombin (AT) is a small glycoprotein that inactivates several enzymes of the coagulation system. It is a 464-amino-acid protein produced by the liver. It contains three disulfide bonds and a total of four possible glycosylation sites. α-Antithrombin is the dominant form of antithrombin found in blood plasma and has an oligosaccharide occupying each of its four glycosylation sites. A single glycosylation site remains consistently un-occupied in the minor form of antithrombin, β-antithrombin. Its activity is increased manyfold by the anticoagulant drug heparin, which enhances the binding of

mammalian protein found in Homo sapiens

mammalian protein found in Homo sapiens

mammalian protein found in Homo sapiens

mammalian protein found in Homo sapiens

mammalian protein found in Homo sapiens

mammalian protein found in Homo sapiens

mammalian protein found in Homo sapiens

mammalian protein found in Homo sapiens

mammalian protein found in Homo sapiens

class of enzymes

mammalian protein found in Homo sapiens

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Thrombomodulin (TM), CD141 or BDCA-3 is an integral membrane protein expressed on the surface of endothelial cells and serves as a cofactor for thrombin. It reduces blood coagulation by converting thrombin to an anticoagulant enzyme from a procoagulant enzyme. Thrombomodulin is also expressed on human mesothelial cell, monocyte and a dendritic cell subset.

chemical compound

mammalian protein found in Homo sapiens

Thromboplastin (TPL) is derived from cell membranes and is a mixture of both phospholipids and tissue factor, neither of which are enzymes. Thromboplastin acts on and accelerates the activity of Factor Xa, also known as thrombokinase, aiding blood coagulation through catalyzing the conversion of prothrombin to thrombin. Thromboplastin is found in brain, lung, and other tissues and especially in blood platelets.

The prothrombinase enzyme complex consists of factor Xa (a serine protease) and factor Va (a protein cofactor). The complex assembles on negatively charged phospholipid membranes in the presence of calcium ions. The prothrombinase complex catalyzes the conversion of prothrombin (factor II), an inactive zymogen, to thrombin (factor IIa), an active serine protease. The activation of thrombin is a critical reaction in the coagulation cascade, which functions to regulate hemostasis in the body. To produce thrombin, the prothrombinase complex cleaves two peptide bonds in prothrombin, one after Arg2

Emicizumab, sold under the brand name Hemlibra, is a humanized bispecific monoclonal antibody for the treatment of haemophilia A, developed by Genentech and Chugai (both organizations are subsidiaries of Hoffmann-La Roche). Emicizumab is a bispecific factor IXa- and factor X-directed antibody.

type of immunoglobulin

protein-coding gene in the species Homo sapiens

medical diagnostic method

fragments formed by the action of plasmin on fibrin or fibrinogen

Thromboelastography (TEG) is a method of testing the efficiency of blood coagulation. It is a test mainly used in surgery and anesthesiology, although increasingly used in resuscitations in emergency departments, intensive care units, and labor and delivery suites. More common tests of blood coagulation include prothrombin time (PT) and partial thromboplastin time (aPTT) which measure coagulation factor function, but TEG also can assess platelet function, clot strength, and fibrinolysis which these other tests cannot.

InterPro Family

protein family