Hémostase

The hémostase indicates a process in which the bleeding is stopped at the majority of the animals with closed circulatory apparatus.

The hémostase in physiology

The hémostase refers to the physiological process during which the bleeding is stopped. It is also a process allowing the maintenance of blood fluidity.

When a Blood-vessel is wounded, various stages proceed for to dam up the surge of Blood.

  • the Vasoconstriction is an immediate answer to the lesion of a vessel. That corresponds to the " constriction" (contraction) by the blood-vessel, the vascular spasm decreases the diameter of the vessel and slows down the bleeding. The vasoconstriction lasts 15 to 60 seconds and causes to slow down blood circulation on the level of the torn vessel and to make it possible the following reactions to be fully effective.

  • the primary hémostase occurs, which implies that the plates or Thrombocyte S (one of the illustrated elements of blood) bind to the Collagène in the exposed walls vascular to form a viscous cluster, the plate Clou of Hayem in the seconds which follow the traumatism.
  • the secondary hémostase or coagulation occurs. The preparatory phase of coagulation is started by the contact of a plasmatic protein, the Facteur XII or Facteur Hageman with fabrics. Coagulation implies a complex cascade of factors of coagulation, which emerges at the end of the day in the transformation of the Fibrinogène, a protein of blood, in Fibrine polymerized, which creates a clot. This process lasts 3 to 6 minutes after rupture of the vessel.
  • the clot attracts and stimulates the growth of Fibroblaste S and cells of Smooth muscle within the vascular wall, and starts the process of repair which will result finally in dissolution from the clot (fibrinolyse).

Disorders of the hémostase

One can coarsely subdivide the disorders of the hémostase in:
  • turbid plate, like the Purpura idiopathic thrombocytopenic,
  • turbid of coagulation, like the Hemophilia S.

Hémostase by mechanical way

August 1st One also calls hémostase the process of manual blocking of a blood-vessel Surgery gold Dissection, to prevent bleeding from that vessel. -->

See too

Internal bonds

External bonds

  • Blood, blood concealments and coagulation

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