And that creates a watertight seal that prevents the movement of blood out of that blood vessel and that ultimately prevents the medical condition we call shock. It prevents the person from going into shock. Now, let's begin by taking a look at the following illustration. So in this lecture, we're actually going to discuss what the blood clotting cascade is and what the proteins are that are involved in this cascade. So let's begin by imagining that we're inside a blood vessel. So this is the endothelial endothelium of one side and this is the endothelium of the other side.