The internal jugular vein collects blood from the brain, the outside of the face and the neck. It runs down the inside of the neck outside the internal and common carotid arteries and unites with the subclavian vein to form the innominate vein.
The external jugular vein collects most of the blood from the outside of the skull and the deep parts of the face. It lies outside the sternocleidomastoid muscle, passes down the neck and joins the subclavian vein.
The jugular veins are particularly prominent during congestive heart failure. When the patient is sitting or in a semirecumbent position, the height of the jugular veins and their pulsations provides an estimate of the central venous pressure and gives important information about whether the heart is keeping up with the demands on it or is failing.
The word "jugular" refers to the throat or neck. It derives from the Latin "jugulum" meaning throat or collarbone and the Latin "jugum" meaning yoke. To go for the jugular is to attack a vital part that is particularly vulnerable.