C1-inhibitor (C1-inh, C1 esterase inhibitor) is a protease inhibitor belonging to the serpin superfamily. Its main function is the inhibition of the complement system to prevent spontaneous activation. C1-inhibitor is an acute-phase protein that circulates in blood at levels of around 0.25 g/L. The levels rise ~2-fold during inflammation. C1-inhibitor irreversibly binds to and inactivates C1r and C1s proteases in the C1 complex of classical pathway of complement. MASP-1 and MASP-2 proteases in MBL complexes of the lectin pathway are also inactivated. This way, C1-inhibitor prevents the proteolytic cleavage of later complement components C4 and C2 by C1 and MBL. Although named after its complement inhibitory activity, C1-inhibitor also inhibits proteases of the fibrinolytic, clotting, and kinin pathways. Note that C1-inhibitor is the most important physiological inhibitor of plasma kallikrein, fXIa, and fXIIa.


Capillaries are the smallest of a body’s blood vessels (and lymph vessels) that make up the microcirculation. Their endothelial linings are only one cell layer thick. These microvessels, measuring around 5 to 10 micrometres (µm) in diameter, connect arterioles and venules, and they help to enable the exchange ofwater, oxygen, carbon dioxide, and many other nutrients and waste chemical substances between blood and thetissues surrounding them. Lymph capillaries interconnect with larger lymph vessels to drain lymph collected in the microcirculation.

During early embryonic development new capillaries are formed through vasculogenesis, the process of blood vesselformation that occurs through a de novo production of endothelial cells followed by their forming into vascular tubes. The term angiogenesis denotes the formation of new capillaries from pre-existing blood vessels and already present endothelium which divides.


Cardiology (from Greek καρδίᾱ kardiā, “heart” and -λογία -logia, “study”) is a branch of medicine dealing with disorders of the heart be it human or animal. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians who specialize in this field of medicine are called cardiologists, a specialty of internal medicine. Pediatric cardiologists are pediatricians who specialize in cardiology. Physicians who specialize in cardiac surgery are called cardiothoracic surgeons or cardiac surgeons, a specialty of general surgery.

Cardiovascular disease

Cardiovascular disease is a class of diseases that involve the heart, the blood vessels (arteries, capillaries, and veins) or both.

Cardiovascular disease refers to any disease that affects the cardiovascular system, principally cardiac disease, vascular diseases of the brain and kidney, and peripheral arterial disease. The causes of cardiovascular disease are diverse butatherosclerosis and hypertension are the most common. In addition, with aging come a number of physiological and morphological changes that alter cardiovascular function and lead to increased risk of cardiovascular disease, even in healthy asymptomatic individuals.

Cardiovascular diseases are the leading cause of deaths on the globally. According to a World Bank analysis, cardiovascular mortality has been declining in many high-income countries since 1970s. At the same time, cardiovascular deaths and disease have increased at a fast rate in low- and middle-income countries. Although cardiovascular disease usually affects older adults, the antecedents of cardiovascular disease, notably atherosclerosis, begin in early life, making primary prevention efforts necessary from childhood. Consequently, there is increased emphasis on preventing atherosclerosis by modifying risk factors, for example by healthy eating, exercise, and avoidance of smoking tobacco and excessive alcohol intake.


Coagulation (also known as clotting) is the process by which blood changes from a liquid to a gel. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism of coagulation involves activation, adhesion, and aggregation of platelets along with deposition and maturation of fibrin. Disorders of coagulation are disease states which can result in bleeding (hemorrhage or bruising) or obstructive clotting (thrombosis).

Coagulation is highly conserved throughout biology; in all mammals, coagulation involves both a cellular (platelet) and a protein (coagulation factor) component. The system in humans has been the most extensively researched and is the best understood.

Coagulation begins almost instantly after an injury to the blood vessel has damaged the endothelium lining the vessel. Exposure of blood to the space under the endothelium initiates two processes: changes in platelets, and the exposure of subendothilial tissue factor to plasma Factor VII, which ultimately leads to fibrinformation. Platelets immediately form a plug at the site of injury; this is called primary hemostasis. Secondary hemostasis occurs simultaneously: Additionalcoagulation factors or clotting factors beyond Factor VII (listed below) respond in a complex cascade to form fibrin strands, which strengthen the platelet plug.

Coagulation cascade

The coagulation cascade of secondary hemostasis has two initial pathways which lead to fibrin formation. These are the contact activation pathway (also known as the intrinsic pathway), and the tissue factor pathway (also known as the extrinsic pathway) which both lead to the same fundamental reactions that produce fibrin. It was previously thought that the two pathways of coagulation cascade were of equal importance, but it is now known that the primary pathway for the initiation of blood coagulation is the tissue factor pathway. The pathways are a series of reactions, in which a zymogen (inactive enzyme precursor) of a serine protease and its glycoprotein co-factor are activated to become active components that then catalyze the next reaction in the cascade, ultimately resulting in cross-linked fibrin. Coagulation factors are generally indicated by Roman numerals, with a lowercase a appended to indicate an active form.

The coagulation factors are generally serine proteases (enzymes), which act by cleaving downstream proteins. There are some exceptions. For example, FVIII and FV are glycoproteins, and Factor XIII is atransglutaminase. The coagulation factors circulate as inactive zymogens. The coagulation cascade is therefore classically divided into three pathways. The tissue factor and contact activation pathways both activate the “final common pathway” of factor X, thrombin and fibrin


Coagulopathy (also called clotting disorder and bleeding disorder) is a condition in which the blood’s ability to clot (coagulate) is impaired. This condition can cause prolonged or excessive bleeding, which may occur spontaneously or following an injury or medical and dental procedures.


Collagen is the main structural protein of the various connective tissues in animals. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole-body protein content.

Collagen, in the form of elongated fibrils, is mostly found in fibrous tissues such as tendons, ligaments and skin. It is also abundant in corneas, cartilage, bones, blood vessels, the gut, intervertebral discs and the dentin in teeth. In muscle tissue, it serves as a major component of theendomysium. Collagen constitutes one to two percent of muscle tissue, and accounts for 6% of the weight of strong, tendinous muscles. Thefibroblast is the most common cell that creates collagen.

Gelatin, which is used in food and industry, is collagen that has been irreversibly hydrolyzed. Collagen also has many medical uses in treating complications of the bones and skin.

The name collagen comes from the Greek κολλα, kolla meaning “glue” and suffix -γέν, -gen denoting “producing.” This refers to the compound’s early use in the process of boiling the skin and sinews of horses and other animals to obtain glue.

Collagen Binding Assay

The Collagen Binding Assay (vWF:CBA) is a test procedure that measures the binding of vWF to collagen. Collagen binding of vWF is associated with the functionally more important HMW forms of vWF. Therefore, vWF:CBA may correlate more closely with vWF function and bleeding problems than vWF antigen assay (vWF: Ag) which measures total vWF multimers. When used in conjunction with the vWF: Ag assay, vWF:CBA can be used to differentiate between vWD type 1 and type 2 (A and B subtypes) by calculating a ratio of the two assay results (ratio = vWF:CBA/vWFAg).

Common Pathway

A part of the coagulation system where the intrinsic and extrinsic pathways converge to activate factor X. Coagulation factors X, V, II, and fibrinogen are part of this pathway; both the APTT and PT measure the integrity of this system.

Congenital afibrinogenemia

Congenital afibrinogenemia is a rare inherited blood disorder in which the blood does not clot normally due to a lack of or a malfunction involving fibrinogen, a protein necessary for coagulation.

Fibrinogen is also known as Factor I. Its lack is inherited in an autosomic recessive way. It can express itself with excessive bleeding since birth (bleeding from umbilical cord, easy bruising, bleeding after circumcision).

Coronary artery disease

Coronary artery disease (CAD) also known as atherosclerotic heart disease, atherosclerotic cardiovascular disease, coronary heart disease, or ischemic heart disease (IHD), is the most common type of heart disease and cause of heart attacks. The disease is caused by plaque building up along the inner walls of the arteries of the heart, which narrows the lumen of arteries and reduces blood flow to the heart.

While the symptoms and signs of coronary artery disease are noted in the advanced state of disease, most individuals with coronary artery disease show no evidence of disease for decades as the disease progresses before the first onset of symptoms, often a “sudden” heart attack, finally arises. Symptoms of stable ischaemic heart disease include angina(characteristic chest pain on exertion) and decreased exercise tolerance.

Unstable IHD presents itself as chest pain or other symptoms at rest, or rapidly worsening angina. The risk of artery narrowing increases with age, smoking, high blood cholesterol, diabetes, high blood pressure, and is more common in men and those who have close relatives with CAD. Other causes include coronary vasospasm, a spasm of the blood vessels of the heart, it is usually called Prinzmetal’s angina.

Diagnosis of IHD is with an electrocardiogram, blood tests (cardiac markers), cardiac stress testing or a coronary angiogram. Depending on the symptoms and risk, treatment may be with medication, percutaneous coronary intervention(angioplasty) or coronary artery bypass surgery (CABG).

It was as of 2012 the most common cause of death in the world, and a major cause of hospital admissions. There is limited evidence for population screening, but prevention (with a healthy diet and sometimes medication for diabetes, cholesterol and high blood pressure) is used both to prevent IHD and to decrease the risk of complications.


Cytokines (Greek:Cyto from Greek “κύτταρο” kyttaro “cell” + Kines from Greek “κίνηση” kinisi “movement”) are a broad and loose category of small proteins (~5–20kDa) that are important in cell signaling. They are released by cells and affect the behavior of other cells, and sometimes the releasing cell itself. Cytokines includechemokines, interferons, interleukins, lymphokines, tumour necrosis factor but generally not hormones or growth factors (despite some terminologic overlap). Cytokines are produced by a broad range of cells, including immune cells like macrophages, B lymphocytes, T lymphocytes and mast cells, as well as endothelial cells,fibroblasts, and various stromal cells; a given cytokine may be produced by more than one type of cell.

They act through receptors, and are especially important in the immune system; cytokines modulate the balance between humoral and cell-based immune responses, and they regulate the maturation, growth, and responsiveness of particular cell populations. Some cytokines enhance or inhibit the action of other cytokines in complex ways.

They are different from hormones, which are also important cell signaling molecules, in that hormones circulate in much lower concentrations and hormones tend to be made by specific kinds of cells.

They are important in health and disease, specifically in host responses to infection, immune responses, inflammation, trauma, sepsis, cancer, and reproduction.