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A thrombus (plural thrombi), colloquially called a blood clot, is the final product of the
blood coagulation Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...
step in
hemostasis 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, whi ...
. There are two components to a thrombus: aggregated
platelets Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby ini ...
and
red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...
s that form a plug, and a mesh of cross-linked
fibrin Fibrin (also called Factor Ia) is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerize. The polymerized fibrin, together with platele ...
protein. The substance making up a thrombus is sometimes called cruor. A thrombus is a healthy response to
injury An injury is any physiological damage to living tissue caused by immediate physical stress. An injury can occur intentionally or unintentionally and may be caused by blunt trauma, penetrating trauma, burning, toxic exposure, asphyxiation, o ...
intended to stop and prevent further bleeding, but can be harmful in
thrombosis Thrombosis (from Ancient Greek "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thro ...
, when a clot obstructs blood flow through healthy
blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...
s in the
circulatory system The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
. In the microcirculation consisting of the very small and smallest blood vessels the capillaries, tiny thrombi known as microclots can obstruct the flow of blood in the capillaries. This can cause a number of problems particularly affecting the
alveoli Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit. Uses in anatomy and zoology * Pulmonary alveolus, an air sac in the lungs ** Alveolar cell or pneumocyte ** Alveolar duct ** Alveolar macrophage * ...
in the
lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
s of the
respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
resulting from reduced oxygen supply. Microclots have been found to be a characteristic feature in severe cases of
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was COVID-19 pandemic in Hubei, identified in Wuhan, China, in December ...
, and in long COVID. Mural thrombi are thrombi that adhere to the wall of a large
blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...
or heart chamber. They are most commonly found in the aorta, the largest
artery An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...
in the body, more often in the descending aorta, and less often in the
aortic arch The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins a ...
or
abdominal aorta In human anatomy, the abdominal aorta is the largest artery in the abdominal cavity. As part of the aorta, it is a direct continuation of the descending aorta (of the thorax). Structure The abdominal aorta begins at the level of the thoracic d ...
. They can restrict blood flow but usually do not block it entirely. They appear grey-red with alternating light and dark lines (known as
lines of Zahn Lines of Zahn are a characteristic of thrombi. They have layers, with lighter layers of platelets and fibrin, and darker layers of red blood cells. They are more present on thrombi formed with faster blood flow, more so on thrombi from the heart ...
) which represent bands of white blood cells and red blood cells (darker) entrapped in layers of fibrin.


Classification

Thrombi are classified into two major groups depending on their location and the relative amount of platelets and red blood cells (RBCs). The two major groups are: # Arterial or white thrombi (characterized by predominance of platelets) # Venous or red thrombi (characterized by predominance of red blood cells).


Microclots

In the microcirculation consisting of the very small and smallest blood vessels the capillaries, tiny thrombi known as microclots can obstruct the flow of blood in the capillaries. This can cause a number of problems particularly affecting the
alveoli Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit. Uses in anatomy and zoology * Pulmonary alveolus, an air sac in the lungs ** Alveolar cell or pneumocyte ** Alveolar duct ** Alveolar macrophage * ...
in the
lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
s of the
respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
resulting from reduced oxygen supply. Microclots have been found to be a characteristic feature in severe cases of
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was COVID-19 pandemic in Hubei, identified in Wuhan, China, in December ...
, and in long COVID.


Mural thrombi

Mural thrombi are thrombi that adhere to the wall of a large
blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...
or heart chamber. They are most commonly found in the aorta, the largest
artery An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...
in the body, more often in the descending aorta, and less often in the
aortic arch The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins a ...
or
abdominal aorta In human anatomy, the abdominal aorta is the largest artery in the abdominal cavity. As part of the aorta, it is a direct continuation of the descending aorta (of the thorax). Structure The abdominal aorta begins at the level of the thoracic d ...
. They can restrict blood flow but usually do not block it entirely. Mural thrombi are not usually found in vessels already damaged by atherosclerosis. A mural thrombus can affect any heart chamber. When found in the left ventricle it is often a result of a heart attack complication. The thrombus in this case can separate from the chamber, be carried through arteries and block a blood vessel. They appear grey-red with alternating light and dark lines (known as
lines of Zahn Lines of Zahn are a characteristic of thrombi. They have layers, with lighter layers of platelets and fibrin, and darker layers of red blood cells. They are more present on thrombi formed with faster blood flow, more so on thrombi from the heart ...
) which represent bands of white blood cells and red blood cells (darker) entrapped in layers of
fibrin Fibrin (also called Factor Ia) is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerize. The polymerized fibrin, together with platele ...
.


Cause

Virchow's triad Virchow's triad or the triad of Virchow () describes the three broad categories of factors that are thought to contribute to thrombosis. *Hypercoagulability *Hemodynamic changes (stasis, turbulence) *Endothelial injury/dysfunction It is named a ...
describes the pathogenesis of thrombus formation: # Endothelial injury: Injury to the
endothelium The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
(interior surface of blood vessel), causing platelet activation and aggregation; #* Common causes include:
trauma Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic inju ...
,
smoking Smoking is a practice in which a substance is burned and the resulting smoke is typically breathed in to be tasted and absorbed into the bloodstream. Most commonly, the substance used is the dried leaves of the tobacco plant, which have bee ...
,
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
, atheroma. #
Hemodynamic Hemodynamics or haemodynamics are the dynamics of blood flow. The circulatory system is controlled by homeostatic mechanisms of autoregulation, just as hydraulic circuits are controlled by control systems. The hemodynamic response continuously mo ...
changes (stasis, turbulence): Blood stasis promotes greater contact between platelets/coagulative factors with vascular endothelium. If rapid blood circulation (e.g., because of
tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal (su ...
) occurs within vessels that have endothelial injuries, that creates disordered flow (turbulence) that can lead to the formation of thrombosis; #* Common causes of stasis include anything that leads to prolonged immobility and reduced blood flow such as:
trauma Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic inju ...
/ broken bones and extended air travel. # Hypercoagulability (also called
thrombophilia Thrombophilia (sometimes called hypercoagulability or a prothrombotic state) is an abnormality of blood coagulation that increases the risk of thrombosis (blood clots in blood vessels). Such abnormalities can be identified in 50% of people who ...
; any disorder of the blood that predisposes to thrombosis); #* Common causes include: cancer (
leukaemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ' ...
), factor V mutation (
Leiden Leiden (; in English and archaic Dutch also Leyden) is a city and municipality in the province of South Holland, Netherlands. The municipality of Leiden has a population of 119,713, but the city forms one densely connected agglomeration wit ...
) - prevents Factor V inactivation leading to increased coagulability.
Disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems moving parts o ...
(DIC) involves widespread microthrombi formation throughout the majority of the blood vessels. This is due to excessive consumption of coagulation factors and subsequent activation of fibrinolysis using all of the body's available
platelets Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby ini ...
and clotting factors. The result is hemorrhaging and ischemic necrosis of tissue/organs. Causes are septicaemia, acute
leukaemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ' ...
,
shock Shock may refer to: Common uses Collective noun *Shock, a historic commercial term for a group of 60, see English numerals#Special names * Stook, or shock of grain, stacked sheaves Healthcare * Shock (circulatory), circulatory medical emerge ...
, snake bites,
fat emboli Fat embolism syndrome occurs when fat enters the blood stream (fat embolism) and results in symptoms. Symptoms generally begin within a day. This may include a petechial rash, decreased level of consciousness, and shortness of breath. Other sympto ...
from broken bones, or other severe traumas. DIC may also be seen in pregnant females. Treatment involves the use of
fresh frozen plasma Fresh frozen plasma (FFP) is a blood product made from the liquid portion of whole blood. It is used to treat conditions in which there are low blood clotting factors (INR > 1.5) or low levels of other blood proteins. It may also be used as the re ...
to restore the level of clotting factors in the blood, as well as platelets and heparin to prevent further thrombi formation.


Pathophysiology

A thrombus occurs when the hemostatic process, which normally occurs in response to injury, becomes activated in an uninjured or slightly injured vessel. A thrombus in a large blood vessel will decrease blood flow through that vessel (termed a mural thrombus). In a small blood vessel, blood flow may be completely cut off (termed an occlusive thrombus), resulting in death of tissue supplied by that vessel. If a thrombus dislodges and becomes free-floating, it is considered an embolus. If an embolus becomes trapped within a blood vessel, it blocks blood flow and is termed as an embolism. Embolisms, depending on their specific location, can cause more significant effects like strokes, heart attacks, or even death. Some of the conditions which increase the risk of blood clots developing include atrial fibrillation (a form of
cardiac arrhythmia Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults ...
), heart valve replacement, a recent
heart attack A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may tr ...
(also known as a
myocardial infarction A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may ...
), extended periods of inactivity (see
deep venous thrombosis Deep vein thrombosis (DVT) is a type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis. A minority of DVTs occur in the arms. Symptoms can include pain, swelling, redness, and enla ...
), and genetic or disease-related deficiencies in the blood's clotting abilities.


Formation

Platelet activation occurs through injuries that damage the
endothelium The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
of the blood vessels, exposing the enzyme called factor VII, a protein normally circulating within the vessels, to the
tissue factor Tissue factor, also called platelet tissue factor, factor III, or CD142, is a protein encoded by the ''F3'' gene, present in subendothelial tissue and leukocytes. Its role in the clotting process is the initiation of thrombin formation from the ...
, which is a protein encoded by the F3 gene. The platelet activation can potentially cause a cascade, eventually leading to the formation of the thrombus. This process is regulated through
thromboregulation Thromboregulation is the series of mechanisms in how a primary clot is regulated. These mechanisms include, competitive inhibition or negative feedback. It includes primary hemostasis, which is the process of how blood platelets adhere to the endoth ...
. File:Fetal thrombotic vasculopathy - very high mag.jpg,
Micrograph A micrograph or photomicrograph is a photograph or digital image taken through a microscope or similar device to show a magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken on a mic ...
showing a thrombus (center of image) within a blood vessel of the
placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mater ...
.
H&E stain Hematoxylin and eosin stain ( or haematoxylin and eosin stain or hematoxylin-eosin stain; often abbreviated as H&E stain or HE stain) is one of the principal tissue stains used in histology. It is the most widely used stain in medical diagnos ...
. File:Blausen 0088 BloodClot.png, Illustration depicting thrombus formation over arterial plaque. File:Composition of a fresh thrombus.jpg, Composition of a fresh thrombus at microscopy, showing nuclear debris in a background of
fibrin Fibrin (also called Factor Ia) is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerize. The polymerized fibrin, together with platele ...
and
red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...
s.


Prevention

Anticoagulant Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...
s are drugs used to prevent the formation of blood clots, reducing the risk of
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
,
heart attack A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may tr ...
and pulmonary embolism.
Heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Since heparins depend on the activity of antithrombin, they are considered anticoagulants. Specifically it is also used in the treatm ...
and
warfarin Warfarin, sold under the brand name Coumadin among others, is a medication that is used as an anticoagulant (blood thinner). It is commonly used to prevent blood clots such as deep vein thrombosis and pulmonary embolism, and to prevent strok ...
are used to inhibit the formation and growth of existing thrombi, with the former used for acute anticoagulation while the latter is used for long-term anticoagulation. The mechanism of action of heparin and warfarin are different as they work on different pathways of the
coagulation cascade Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...
. Heparin works by binding to and activating the enzyme inhibitor
antithrombin III Antithrombin (AT) is a small glycoprotein that inactivates several enzymes of the coagulation system. It is a 432-amino-acid protein produced by the liver. It contains three disulfide bonds and a total of four possible glycosylation sites. α-Ant ...
, an enzyme that acts by inactivating thrombin and factor Xa. In contrast, warfarin works by inhibiting
vitamin K epoxide reductase Vitamin K epoxide reductase (VKOR) is an enzyme () that reduces vitamin K after it has been oxidised in the carboxylation of glutamic acid residues in blood coagulation enzymes. VKOR is a member of a large family of predicted enzymes that are pre ...
, an enzyme needed to synthesize vitamin K dependent clotting factors II, VII, IX, and X. Bleeding time with heparin and warfarin therapy can be measured with the partial thromboplastin time (PTT) and prothrombin time (PT), respectively.


Treatment

Once clots have formed, other drugs can be used to promote thrombolysis or clot breakdown. Streptokinase, an enzyme produced by streptococcal bacteria, is one of the oldest thrombolytic drugs. This drug can be administered intravenously to dissolve blood clots in
coronary vessels Coronary () may, as shorthand in English, be used to mean: * Coronary circulation, the system of arteries and veins in mammals ** Coronary artery disease ** Coronary occlusion ** A myocardial infarction, a heart attack As adjective * Referring t ...
. However, streptokinase causes systemic fibrinolytic state and can lead to bleeding problems. Tissue plasminogen activator (tPA) is a different enzyme that promotes the degradation of fibrin in clots but not free fibrinogen. This drug is made by transgenic bacteria and converts plasminogen into the clot-dissolving enzyme, plasmin. Recent research indicates that tPA could have toxic effects in the central nervous system. In cases of severe stroke, tPA can cross the
blood–brain barrier The blood–brain barrier (BBB) is a highly selective semipermeable membrane, semipermeable border of endothelium, endothelial cells that prevents solutes in the circulating blood from ''non-selectively'' crossing into the extracellular fluid of ...
and enter interstitial fluid, where it then increases excitotoxicity, potentially affecting permeability of the blood–brain barrier, and causing cerebral hemorrhage. There are also some anticoagulants that come from animals that work by dissolving
fibrin Fibrin (also called Factor Ia) is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerize. The polymerized fibrin, together with platele ...
. For example, ''
Haementeria ghilianii ''Haementeria ghilianii'', the giant Amazon leech, is one of the world's largest species of leeches. It can grow to 450 mm (17.7 in) in length and 100 mm (3.9 in) in width. As adults, these leeches are a greyish-brown colour, ...
'', an
Amazon Amazon most often refers to: * Amazons, a tribe of female warriors in Greek mythology * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon River, in South America * Amazon (company), an American multinational technology c ...
leech Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bodie ...
, produces an enzyme called hementin from its salivary glands.


Prognosis

Thrombus formation can have one of four outcomes: propagation, embolization, dissolution, and organization and recanalization. # Propagation of a thrombus occurs towards the direction of the heart and involves the accumulation of additional platelets and fibrin. This means that it is anterograde in veins or retrograde in arteries. # Embolization occurs when the thrombus breaks free from the vascular wall and becomes mobile, thereby traveling to other sites in the vasculature. A venous embolus (mostly from deep vein thrombosis in the lower limbs) will travel through the systemic circulation, reach the right side of the heart, and travel through the pulmonary artery, resulting in a pulmonary embolism. Arterial thrombosis resulting from hypertension or atherosclerosis can become mobile and the resulting emboli can occlude any artery or arteriole downstream of the thrombus formation. This means that cerebral stroke, myocardial infarction, or any other organ can be affected. # Dissolution occurs when the fibrinolytic mechanisms break up the thrombus and blood flow is restored to the vessel. This may be aided by fibrinolytic drugs such as Tissue Plasminogen Activator (tPA) in instances of coronary artery occlusion. The best response to fibrinolytic drugs is within a couple of hours, before the fibrin meshwork of the thrombus has been fully developed. # Organization and recanalization involves the ingrowth of
smooth muscle Smooth muscle is an involuntary non-striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit mus ...
cells,
fibroblast A fibroblast is a type of cell (biology), biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework (Stroma (tissue), stroma) for animal Tissue (biology), tissues, and plays a critical role in wound ...
s and
endothelium The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
into the
fibrin Fibrin (also called Factor Ia) is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerize. The polymerized fibrin, together with platele ...
-rich thrombus. If recanalization proceeds it provides capillary-sized channels through the thrombus for continuity of blood flow through the entire thrombus but may not restore sufficient blood flow for the metabolic needs of the downstream tissue.


See also

*
Thrombogenicity Thrombogenicity refers to the tendency of a material in contact with the blood to produce a thrombus, or clot. It not only refers to fixed thrombi but also to emboli, thrombi which have become detached and travel through the bloodstream. Thrombo ...
(the tendency to clot) *
National Blood Clot Alliance {{More footnotes, date=June 2019 The National Blood Clot Alliance or NBCA for short, formerly known as the National Alliance for Thrombosis and Thrombophilia (NATT), is a United States nationwide not-for-profit alliance of patients and medical profe ...
*
Hemorrhoid Hemorrhoids (or haemorrhoids), also known as piles, are vascular structures in the anal canal. In their normal state, they are cushions that help with stool control. They become a disease when swollen or inflamed; the unqualified term ''hemo ...


References


External links


Muscle Relaxing Drugs Can Reduce Lethal Blood Clots


{{Authority control Hematology Ischemia es:Trombosis it:Trombosi