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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

what are data colletion method in community diagnodis
loice Reply
50 prefix and surfix
Martha Reply
why arteries deeper than veins?!
Cismaan Reply
arteries colour of blood is deeper than that of vein because its blood contains oxygen which is adhered to haemoglobin(a protein which gives the blood its red color) , while vein contains deoxygenated blood(blood without oxygen)
As we know, vein carries used blood to the heart. when we say used blood, we mean to say, blood that its content(oxygen and other nutrients) has been used up.
Arteries are deeper b'cuz they need to be protected.......If they are ruptured they cannot form clot and repair themselves.... Moreover, the pressure of blood is too high for the artery to form the clot and repair itself....... Hence, Arteries are deeper than veins........
Than u all. Special thanks too AMEL JEELANI.
You're welcome......
Thanks all
describe the location of the macula densa and explain its role in the regulation of renin secretion and in tubuglomerular feedback
mwamba Reply
its located near the vascular pole of the glomurelus also regulate blood pressure and the filtration rate of glomurelus
what are the three methods of data collection used during a community diagnosis
Interviews. Questionnaires and Surveys. Observations.
Describe two early induced responses and what pathogens they affect
olivia Reply
what are pathogens
pathogens are disease-causing agents/organisms
pathogen are the causative of disease
thank you sister
What are organelles
The are little organs found in cells of living things... Eg gogi apparatus
what is anatomy
Linda Reply
is the study of the structures of the body and how they relates to each other
Anatomy is the study of the structures of body parts and how they relates to each other
is the study of the structure of the body and how they relates to each other
what are the difference between Pacinian corpuscle and cutaneous vascular plexus?
thivya Reply
what are membranous epithelial tissues
Naa Reply
they are the lining and covering epithelial tissues which cover body surfaces and line cavities... they're grouped into simple and stratified according to the number of layers and squamous, cuboidal and columnar according to their shape
what is an acina
acina is known to be the basic functional unit of the lungs .(singular:- acinus) this is where the alveoli(the gaseous exchange site) is found...
what happens to the unfertilized egg
the study of tissues is called
Scandy Reply
microscopic or histology anatomy
What specific types of biological macromolecules do living things require and why?
Marieland Reply
what is partial pressure?
Tariq Reply
it is the pressure exerted by mixture of gases...
What is the Important of studying anatomy and philosophy
Michael Reply
because to know the mechanisms of our body
to discover the regional structural of human body based on physically and also biochemically.
how many region do we have in human body
nsofor Reply
head thorax abdomen and many kind of...
what is principal ponatine nucleas
Human body can be divided into different regions on the basis of: 1. Systems: e.g. digestive system, respiratory system, excretory system etc.. 2. Parts: e.g. head, thorax, neck, upper limbs, lower limbs etc..
we have 9 region in d human body
what is systematic anatomy?
nsofor Reply
it is the anatomy or study of a certain body system for example the digestive system. or respiratory system.
It is a group of structure that work together to perform a unique function..

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