Question

the extrinsic mechanism for activation of clotting comes from the __________. a blood b damaged tissue c external environment d central nervous system

Explanation:

The extrinsic pathway of blood - clotting is initiated by tissue factor (TF), also known as thromboplastin. Tissue factor is a protein found in the membranes of cells in damaged tissue. When there is tissue injury, tissue factor is exposed to the blood. It then combines with factor VII (a blood - clotting factor in the blood) to form a complex that activates factor X, which is a key step in the clotting cascade.

• Option A: The intrinsic pathway of clotting is initiated within the blood (by factors such as contact with collagen from damaged blood vessels). The extrinsic pathway is not initiated from within the blood itself.
• Option C: The external environment is not directly involved in the activation of the extrinsic clotting mechanism. The process is a biological response within the body, not a response to the external environment.
• Option D: The central nervous system has no direct role in the activation of the extrinsic clotting mechanism. The clotting mechanism is a part of the hematological (blood - related) system.

Answer:

B. damaged tissue