Skip main navigation

What is bleeding?

Overview of the types of bleeding
Cut hand with blood coming from wound
© University of Glasgow, 2017

What causes bleeding?

Bleeding occurs when an injury causes a break in the skin and damage to blood vessels.

Most of the time when we cut ourselves, we bleed and the body forms a clot to stop it. In severe bleeds when a large vessel is damaged, the bleeding can flow too quickly for a clot to form. If the bleeding is not controlled then the casualty may lose too much blood and go into shock – a state in which there is not enough blood in the body to supply all of your organs with enough oxygen, shock can quickly prove fatal.

Source of Bleeding

The three sources of bleeding are:

Arterial Arterial blood is oxygenated and carried away from the heart. A bleeding artery tends to produce profuse bright red blood that spurts out in time with the casualty’s heartbeat.

Venous Venous blood is deoxygenated and is carried back towards the heart. A bleeding vein tends to produce dark red blood that pours out of the wound and doesn’t pulsate.

Capillary Capillaries are small blood vessels just under the skin. They are damaged in even the least severe wounds and do not tend to produce enough bleeding to be of concern. When capillaries burst underneath the skin, bruising develops.

© University of Glasgow, 2017
This article is from the free online

Basic First Aid: How to Be an Everyday Hero

Created by
FutureLearn - Learning For Life

Our purpose is to transform access to education.

We offer a diverse selection of courses from leading universities and cultural institutions from around the world. These are delivered one step at a time, and are accessible on mobile, tablet and desktop, so you can fit learning around your life.

We believe learning should be an enjoyable, social experience, so our courses offer the opportunity to discuss what you’re learning with others as you go, helping you make fresh discoveries and form new ideas.
You can unlock new opportunities with unlimited access to hundreds of online short courses for a year by subscribing to our Unlimited package. Build your knowledge with top universities and organisations.

Learn more about how FutureLearn is transforming access to education