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Extrinsic pathway

The quicker responding and more direct extrinsic pathway    (also known as the tissue factor    pathway) begins when damage occurs to the surrounding tissues, such as in a traumatic injury. Upon contact with blood plasma, the damaged extravascular cells, which are extrinsic to the bloodstream, release factor III (thromboplastin). Sequentially, Ca 2+ then factor VII (proconvertin), which is activated by factor III, are added, forming an enzyme complex. This enzyme complex leads to activation of factor X (Stuart–Prower factor), which activates the common pathway discussed below. The events in the extrinsic pathway are completed in a matter of seconds.

Intrinsic pathway

The intrinsic pathway    (also known as the contact activation pathway) is longer and more complex. In this case, the factors involved are intrinsic to (present within) the bloodstream. The pathway can be prompted by damage to the tissues, resulting from internal factors such as arterial disease; however, it is most often initiated when factor XII (Hageman factor) comes into contact with foreign materials, such as when a blood sample is put into a glass test tube. Within the body, factor XII is typically activated when it encounters negatively charged molecules, such as inorganic polymers and phosphate produced earlier in the series of intrinsic pathway reactions. Factor XII sets off a series of reactions that in turn activates factor XI (antihemolytic factor C or plasma thromboplastin antecedent) then factor IX (antihemolytic factor B or plasma thromboplasmin). In the meantime, chemicals released by the platelets increase the rate of these activation reactions. Finally, factor VIII (antihemolytic factor A) from the platelets and endothelial cells combines with factor IX (antihemolytic factor B or plasma thromboplasmin) to form an enzyme complex that activates factor X (Stuart–Prower factor or thrombokinase), leading to the common pathway. The events in the intrinsic pathway are completed in a few minutes.

Common pathway

Both the intrinsic and extrinsic pathways lead to the common pathway    , in which fibrin is produced to seal off the vessel. Once factor X has been activated by either the intrinsic or extrinsic pathway, the enzyme prothrombinase converts factor II, the inactive enzyme prothrombin, into the active enzyme thrombin    . (Note that if the enzyme thrombin were not normally in an inactive form, clots would form spontaneously, a condition not consistent with life.) Then, thrombin converts factor I, the insoluble fibrinogen, into the soluble fibrin protein strands. Factor XIII then stabilizes the fibrin clot.

Fibrinolysis

The stabilized clot is acted upon by contractile proteins within the platelets. As these proteins contract, they pull on the fibrin threads, bringing the edges of the clot more tightly together, somewhat as we do when tightening loose shoelaces (see [link] a ). This process also wrings out of the clot a small amount of fluid called serum    , which is blood plasma without its clotting factors.

Questions & Answers

Functions of the thoracic cage
Fereh Reply
protect all the organs and tissues from any impact or injury
Javier
why sickle cell carrier people don't get malaria
Boakye Reply
What is the amniotic fluid
bollywood Reply
structure of heart and it's function (10 mark )
Priyanka Reply
What is the best book on physiology?
cesar Reply
describe varicocele
malulu
what do you mean by peritoneum
Siba Reply
It is thick covering surrounding the abdomen
Awais
r8
how to become good in Anatomy and physiology
malulu
hi
Milkah
hlo
Wani
What are is the last solution to abdomen pain in pregnant women
Umoru
no it is in kidney
Tantray
Kk
Umoru
structure of heart and it's function
Priyanka
Serous membrane lining the cavity of the abdomen
bollywood
it is four lobs structure and it is triangular in shaped. it 's function pumping the blood
ABDULLAH
explain root of lungs
ABDULLAH
Glomerular pressure -capsule pressure -colloid osmosis pressure
malulu Reply
how to describe mechanism of micturition
malulu
spleen is important?
AKASH Reply
helpful in destruction of rbc
It is imp in storing blood and destruction of microbes and harmful particles
Awais
ty sir
AKASH
K
Umoru
what are the sources of glucose in the body
malulu
describe mechanism of micturition
malulu
Pancreatic hormones with function
mami Reply
Insulin, which helps to regulate our blood sugar levels.
Bb
glucagon which is antagonistic to insulin increase the blood glucose level,. Somatostatin help to regulate the levels of both insulin and glucagon
Ashish
thnks for helping
nimco
thanks
Narendra
what is a lymph node.?
AKASH
lymph nodes are small kidney shaped organs of the lymphatic system.
Trishauna
there are several hundred lymph nodes found mostly throughout the thorax and abdomen of the body with the highest concentrations in the auxiliary (armpit) and inguinal groin regions.
Trishauna
what is life
Yar Reply
life is the existence of an individual human being animal or plant
Furmose
how I join this
Ahmed
meaning
Furmose
to day I am new person and I can't participate questions so to morow I shall participate question sopleas excuse me
Ahmed
I had a debate earlier about nutrition and it didn't get a clear answer on that,can one tell me what the definition of nutrition.?
kelvin
the nutrition is nourish person is feeling an nutrition
Ahmed
I think nutrition is the process of taking food and using it for growth, metabolism and repair.
Methila
life is full of happy and sorrow
Sanamacha
life is achievement
Nandini
life is the nothing but god gave us 1 body. and we all service k in this body. The things which we do for the Survivation for this body I felt that this is called as the life
AKASH
Yes God gave us life but not god who gave us the life. Hope u understood what i meant by God n not god who gave life..... ?
laku
What's the question?
Sherman Reply
once you lose pigmentation can you ever get it back
Shannon Reply
s
Nandini
females are lesser prone to acne
Ritika Reply
why please expain
Janvi
described the skin
Yayra Reply
skin is outer covery of human body and it is largest organ of human body. it do three fauntion protection regulation and sensation of human body that is men fauntion of human skin it has seven part.
ABDULLAH
how thick is the epidermis?
Sovilace
the integumentary system is the largest system of the body 16% of body weight and 1.5 to 2m² in area
Trishauna
function of the endocrine system
Hamo Reply
produces hormones that plays specific functions
has endocrine gland calld as ductless gland so as produces hormones

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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