Biology - Body Fluids and Circulation Question with Solution | TestHub

Menstrual blood does not clot due to the presence of fibrinolysin.

Fibrinolysin (also known as plasmin) is an enzyme that breaks down fibrin, which is the main protein network involved in blood clotting. This prevents the menstrual blood from coagulating as it is shed from the uterus.

Thromboplastin and prothrombin are factors that promote blood coagulation, while zona lysin is an enzyme released by the acrosome of sperm to penetrate the zona pellucida of the ovum.

Answer: fibrinolysin