Humans, like all other vertebrates, in the course of evolution have developed a sophisticated closed blood circulatory system. Basically a pump, the heart powers this fluid transport system and helps to ensure that flow is maintained in this high-pressure system according to the need of tissues.

The upside of such a highly regulated system is its incredible flexibility and versatility in transporting materials to and from every area of the body, such as nutrients, oxygen, water, hormones, removal of spent metabolic materials, CO2, and so on. The downside of such a circulatory system is the critical dependence of the body’s survival on the uninterrupted function of this transport system – and the need for the body to maintain mechanisms to protect the system against injury and to provide emergency repair strategies.

Leakage of blood from the circulatory system (haemorrhage) after injury must be stopped and blood must be kept inside a damaged blood vessel (haemostasis) in order to keep a body alive. Blood carries its own emergency supplies for such situations. All the biochemical components allowing for emergency response and initial repair to stop bleeding, circulate in an inactive form with the blood flow all the time, but are ready to be activated instantaneously. Despite escalating body responses to bleeding, there are narrow limits to the extent of injury and blood loss a body can deal with on its own.

Obviously, there are multiple close relationships between the general themes of ‘bleeding’ and ‘surgery’, oral & maxillofacial surgery is no exception. On the one hand, emergency surgical interventions are often needed to stop bleeding after trauma and to repair damage to tissues, including blood vessels. On the other hand, surgical interventions necessarily cause damage to blood vessels and bleeding. Any conditions that change the normal blood clotting behaviour (either resulting from disease or from various medications) have an impact on the risk of surgical interventions and/or recovery, as well as chances of success or failure of surgical treatments.

With this close relationship in mind, next we briefly explore the normal body response to injury and bleeding, before discussing what can (and does) go wrong with bleeding and blood flow, and what can be done to remedy such bleeding and blood-flow problems.

Next section: Bleeding