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This figure details the steps in the clotting of blood. Each step is shown along with a detailed text box describing the steps on the left. On the right, a signaling pathway shows the different chemical signals involved in the clotting process.
(a) An injury to a blood vessel initiates the process of hemostasis. Blood clotting involves three steps. First, vascular spasm constricts the flow of blood. Next, a platelet plug forms to temporarily seal small openings in the vessel. Coagulation then enables the repair of the vessel wall once the leakage of blood has stopped. (b) The synthesis of fibrin in blood clots involves either an intrinsic pathway or an extrinsic pathway, both of which lead to a common pathway. (credit a: Kevin MacKenzie)

Clotting factors involved in coagulation

In the coagulation cascade, chemicals called clotting factors    (or coagulation factors) prompt reactions that activate still more coagulation factors. The process is complex, but is initiated along two basic pathways:

  • The extrinsic pathway, which normally is triggered by trauma.
  • The intrinsic pathway, which begins in the bloodstream and is triggered by internal damage to the wall of the vessel.

Both of these merge into a third pathway, referred to as the common pathway (see [link] b ). All three pathways are dependent upon the 12 known clotting factors, including Ca 2+ and vitamin K ( [link] ). Clotting factors are secreted primarily by the liver and the platelets. The liver requires the fat-soluble vitamin K to produce many of them. Vitamin K (along with biotin and folate) is somewhat unusual among vitamins in that it is not only consumed in the diet but is also synthesized by bacteria residing in the large intestine. The calcium ion, considered factor IV, is derived from the diet and from the breakdown of bone. Some recent evidence indicates that activation of various clotting factors occurs on specific receptor sites on the surfaces of platelets.

The 12 clotting factors are numbered I through XIII according to the order of their discovery. Factor VI was once believed to be a distinct clotting factor, but is now thought to be identical to factor V. Rather than renumber the other factors, factor VI was allowed to remain as a placeholder and also a reminder that knowledge changes over time.

*Vitamin K required.
Clotting Factors
Factor number Name Type of molecule Source Pathway(s)
I Fibrinogen Plasma protein Liver Common; converted into fibrin
II Prothrombin Plasma protein Liver* Common; converted into thrombin
III Tissue thromboplastin or tissue factor Lipoprotein mixture Damaged cells and platelets Extrinsic
IV Calcium ions Inorganic ions in plasma Diet, platelets, bone matrix Entire process
V Proaccelerin Plasma protein Liver, platelets Extrinsic and intrinsic
VI Not used Not used Not used Not used
VII Proconvertin Plasma protein Liver * Extrinsic
VIII Antihemolytic factor A Plasma protein factor Platelets and endothelial cells Intrinsic; deficiency results in hemophilia A
IX Antihemolytic factor B (plasma thromboplastin component) Plasma protein Liver* Intrinsic; deficiency results in hemophilia B
X Stuart–Prower factor (thrombokinase) Protein Liver* Extrinsic and intrinsic
XI Antihemolytic factor C (plasma thromboplastin antecedent) Plasma protein Liver Intrinsic; deficiency results in hemophilia C
XII Hageman factor Plasma protein Liver Intrinsic; initiates clotting in vitro also activates plasmin
XIII Fibrin-stabilizing factor Plasma protein Liver, platelets Stabilizes fibrin; slows fibrinolysis

Questions & Answers

yellow marrow has been identified as
Raychelle Reply
Which of the following accurately describe external resipration
Gwendolyn Reply
from the heart to the lungs
I think it's not outside organ of respiratory all respiratory organ are inside of human body
diffusion of CO2 and oxygen at a pulmonary capillary surrounding an alveolar sac.
In other words, from the external environment to the lungs (alveoli) then to the pulmonary capillary then to the heart. So this is a stage of inhalation. inhale = external respiration.
What kind of discussion
horyaal Reply
what is the function of the placenta
Nchimunya Reply
The placenta acts to provide oxygen and nutrientsto the fetus, whilst removing carbon dioxide and other waste products.
Also it's the barrier through which the mother is connected to the fetus.
I want to discuss... atherosclerosis.., everything about it, about to treatment n prevention at age 50 +
Please participate in discussion
ok let's discuss now
first define the word artherosclerosis
a disease of the arteries characterized by the deposition of fatty material on their inner walls.
hardening of the arteries, due to fats..
Q = which type of fat utilized for this.., I.e LDL, HDL, TG, VLDL...?
Atherosclerosis is a condition of deposition of plaque inside the artries
Plaque include such as fat, chalestrol, calcium etc
Thank you kumar...., is there any way that we can protect these plaques without any medicines., I. e exercises n food stuffs
go to the gym
what is chylomicrons?
how can plaque buildup in The angina or vessels ?
Atherosclerosis is a condition of deposition of plaque inside the artries
atherosclerosis can also be caused by tortuousness of arteries with old age as contributing factor.
You tube Prof Fink...he is an amazing lecturer and does a brilliant job on arteriosclerosis
what are cell
Chigozie Reply
The basic structural and functional unit of any living thing. Each cell is a small container of chemicals and water wrapped in a membrane. 
cell is the structural and functional basic unit of life
So every living thing was Created From a Cell
from a fusion of two cells , the sperm and the egg
What is the only bone that doesn't have any articulation?
that magical fusion of cells
why body immune system attack and destroy the body own cell during type 1 diabetes?
Sanamacha Reply
It's an autoimmune disease... targeting the pancreas
what are the three genetic defects of pregnancy?
Belinda Reply
structure of fallopian tubes
Akash Reply
what z the role played by the transport system
zinitha Reply
how fats are digested in the human body
Nabukwasi Reply
Fat digestion begins in the stomach but some argue in that it starts in the mouth. Reason is because the sublingual gland secretes an enzyme called lingual lipase. However, this enzyme is not activated until it comes into contact with gastric fluids (HCl). In the stomach, HCl breaks down the lipid..
due to body heat
into smaller molecules. Going from a triglyceride and a fatty acid to a monoglyceride and a a fatty acid no longer bound to one another. This is known as lipolysis.
After lipolysis in the stomach from gastric and lingual lipase, an acidic chyme is produced after stomach churning the bolus. The chyme exits the stomach at the pyloric sphincter and enters the first section of the small intestine known as the duodenum.
in the duodenum. An alkaline mucus from goblet cells neutralizes the acidic chyme to prevent acid burns. After that, the pancreas and gallbladder secrete a number of enzymes to continue lipolysis. Bile from the gallbladder enters the duodenum via common bile duct. The acinar cells in the pancreas...
secretes pancreatic lipase after enteroendocrine cells in the duodenum secrete a stimulator hormone called CCK. Cck stimulates bile synthesis and secretion as well as pancreatic lipase.
Bile emuslifies the lipid, allowing the lipases to continue lipolysis
this breakdown continues until it reaches the jejunum of the small intestines. At this point, the lipid has been broken down small enough to absorbed into the blood stream. So villi in the jejunum, absorb the contents.
ileum, the last small intestine region, absorbs anything that wasn't absorbed previously. Like minerals, vitamins, bile salts, water soluble material. Villi here complete that task. Fatty acid and glycerol however, are absorbed by lacteals. small lymph vessels. And are transported to the liver.
That concludes lipid digestion. Anything else that remains is deficated after it travels through the large intestines.
parents with blood group AB & 0,,,what will b the blood group of their offspring
what are the different branches of anatomy
hopefully that helped.
which ion is low of blood level?
Ezra Reply
what is coagulation?
feng Reply
liquid turning to solid... blood clots.
coagulation : liquid blood into blood clots caused with a coagulant.
when the blood turn from liquid form to solid
it said to coagulate by the action of active plasma protein called *fibrin*
I.e liquid inform of blood when to solid
it is the process by which blood becomes more viscous or becomes thick
cloting of blood cells
clot of blood
the process of forming semi solid lumps in a liquid
conversion of blood to solid state
semi solid., rather than solid form
what is pivot functioned
to less thefriction
how to calculate the micrograph
Ampong Reply
it can be used to knw the disease condition
Akbar Reply
which gland secret tears
lacrimal glands
explain the blood supply to the brain
Brenda Reply
There are two paired arteries which are responsible for the blood supply to the brain; the vertebral arteries, and the internal carotid arteries. These arteries arise in the neck, and ascend to the cranium.
two arteries main vertebral arteries & internal carotid artery

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