I decided to eventually tackle this topic for two reasons. Firstly, it is important to know something about it in medicine, since it underlies multiple diverse states as wound healing, bleeding tendencies, disseminated intravascular coagulation, deep vein thromboses, etc. - and all of their treatments. Secondly, it's hard to find a decent summary. The subject is overloaded with technicalities and jargon, with the big picture seldom highlighted. I hope I've been able to remedy some of these problems. Inevitably, however, simplifying such a detailed (not to say rapidly expanding) topic has problems of its own, and so if you feel I've left anything important out, or that I've been inaccurate here or there, I'm happy to revise these summaries if needs be.
The core posts for this section are on haemostasis - part 1 and part 2. A post on the body's innate thrombolytic systems will have to be forthcoming at some later point, I'm afraid.
With this knowledge under the belt, we can head off to more distant (and probably interesting!) waters. I've done a post on heparin's mechanism of action, and I've also written a bit on D-dimers, that often-ordered but seldom-understood test.
Adequate coagulation factor function is impossible without vitamin K, and so I've written a bit about it here. The same post explains very briefly how the other major pharmacological anticoagulant, warfarin, works.
Lastly, slow blood flow - the third member of Virchow's triad - is commonly cited as a reason for blood to coagulate. But why should slow blood flow have this effect? This post quotes one answer.