It is crucial that animals with a cardiovascular system can slow (and ultimately prevent) blood loss from injury or damage to body tissues. In addition, the skin (and accompanying secretions from sebaceous glands) is a highly effective barrier to pathogens such as bacteria, viruses and fungi. The repair of skin is vital to the prevention of contraction of infectious diseases. The faster the organism can ‘plug the leak’, the less blood loss will occur and the chance of infection will be reduced. In this podcast, I will explain how the blood clotting cascade is initiated, and describe the interactions between the different molecules involved in the process. I'll look in detail at some of the genetic conditions linked to problems with the blood clotting cascade mechanism and will explore how some venomous animals use blood clotting biochemistry to their advantage. (With thanks to our sponsor 'Curriculum Press' for providing content for this podcast)