Normal and Abnormal Coagulation

This lecture covers a lot of material that I also wrote about when I was in Canada, which is nice. What is less nice is that it doesn't have a nice little summary slide at the end. Oh well.

Platelets

See earlier post: Composition of the Blood

Structure and Function of Blood Vessels

See earlier post: Tubes

Clot Formation

Clotting factor cascade: Cell injury
Thromboembolic diseases (e.g. DVT): Vascular disorders
Atherosclerosis: Coronary Artery Disease

And now for all the stuff that I haven't covered yet!

Another bad place to get a clot is in your atrium. This might happen due to atrial fibrillation. A clot in your left atrium can be pushed into the systemic circulation, where it might lodge into one of the arteries supplying the brain, ultimately causing a stroke. In fact, atrial fibrillation is one of the leading causes of stroke.

Platelets can also cause clots. Platelets are activated when they come into contact with the damaged arterial wall. When this happens, they release thromboxane A2 (TxA₂) and adenosine diphosphate (ADP). These bind to receptors on other platelets, resulting in platelet aggregation and adhesion. As mentioned here, synthesis of thromboxane from arachidonic acid can be blocked by aspirin.

Clot Removal

While clots are important to stop us from bleeding to death, it's also important that the process can stop at some point. Otherwise, we'd turn into a giant human clot after getting a tiny little wound. One important factor in stopping this process is antithrombin III, or AT III. AT III can bind to thrombin, inactivating it. Another important substance is plasmin, which can break up a clot (as mentioned here).

Coagulation Deficiencies

As you can probably tell, there are a lot of components involved in forming and breaking up clots. If any of these factors are missing, problems can result. Deficiencies in clotting factors and platelets, and/or problems in platelet function, can all increase the risk of bleeding. Deficiencies in "anticoagulant" factors, such as AT III, can increase the risk of clots.