11 Striking Facts About the Jugular

The human body is an amazing thing. For each one of us, it's the most intimate object we know. And yet most of us don't know enough about it: its features, functions, quirks, and mysteries. Our series The Body explores human anatomy, part by part. Think of it as a mini digital encyclopedia with a dose of wow.

Jugular veins are popular in horror flicks for their gushing at the mouths of vampires, werewolves, and knife-wielding assassins. While that's unlikely to happen to most of us, this crucial vein does give up copious blood. Jugular veins are big—much larger than the veins you typically offer to your doctor for a blood test and those you find spidering off the side of your legs. Jugular veins are also key players in the circulation and drainage systems to the brain, face, and neck. To learn more, Mental Floss spoke with William W. Ashley, a cerebral-vascular neurosurgeon at Sandra and Malcolm Berman Brain & Spine Institute at LifeBridge Health Hospital, in Baltimore, Maryland. Here are 11 things you might not have known about this crucial body part.

1. IT'S A REAL BRAIN DRAIN.

"The jugular vein is an important body part because it drains deoxygenated blood from the head and the neck," Ashley tells Mental Floss. "Most important is to drain the brain. If you block the jugular veins, the pressure in the brain goes up."

2. YOU ACTUALLY HAVE FOUR JUGULAR VEINS.

There's an internal and an external jugular vein on each side of the neck. The internal jugular vein (really a pair of veins) largely drains the cerebral veins—those coming from the brain—while the external jugular vein (also a pair) drains those structures more on the surface of the head, such as the scalp, sinuses, and other portions of the face. The left vein is usually smaller than the one on the right, but both possess valves that help transport blood. At two points in the vein it looks wider, and these parts are called the superior bulb and the inferior bulb.

3. THESE ARE THE VEINS THAT STAND OUT ON EITHER SIDE OF YOUR NECK.

Your jugular veins run alongside the thyroid gland down to just above your collarbone, and close to your trachea, or windpipe. When you're picking up a heavy box, or clenching your jaw, your jugular veins might bulge slightly. "They respond to changes in pressure, so you can see them get big and small," Ashley says.

4. SOME PEOPLE HAVE MORE THAN THEIR SHARE OF THESE VEINS …

According to the Indian Journal of Plastic Surgery, during a surgery to treat a 65-year-old woman's cancer of the tongue, surgeons discovered a surprise: She had two right internal jugular veins, "a rare congenital abnormality," the authors write. While unusual, it didn't appear to cause any other health problems.

5. … WHILE OTHERS MAKE DO WITH FEWER.

Ashley had a patient with the opposite issue: "I've seen an absence of one [right vein] where everything drained on the left side. We found it incidentally. If she injured her one jugular vein, she'd be in bad shape. We were doing an angiogram to see if she had a brain aneurism." Her dearth of jugulars hadn't caused any health problems, however, he said, because "the body had adopted a different pattern [of drainage]."

6. A BULGING JUGULAR VEIN CAN BE A CAUSE FOR ALARM.

A bulging or "distended" jugular vein can be a sign of emergency. Unless you're The Hulk, that distended vein is a sign that the jugular is carrying more blood than the heart has the ability to pump back out. The conditions that can cause this include tension pneumothorax—where air has leaked from the lungs into the chest cavity and can't get back out without being released by a needle—or cardiac tamponade, a condition where fluid leaks from the heart into the pericardium, the sac that surrounds the heart. In this case, pericardiocentesis is required—drawing the fluid out through a needle. Lastly, constrictive pericarditis, an infection of the pericardium, can also cause this condition, which may require surgery and antibiotics to treat.

7. IN RARE CASES, IVF IS LINKED TO DANGEROUS INTERNAL JUGULAR VEIN BLOOD CLOTS.

A blood clot in the internal jugular veins (IJV), known as a thrombosis, is a very serious condition that can prove fatal if not caught and treated quickly. Clots in the IJV are rare compared to those that occur in legs and lungs, but they can happen. Most commonly they are the result of an infection or a tumor. In a very small number of cases, in vitro fertilization (IVF) treatments, in which a woman receives hormones and drugs to stimulate ovulation to increase chances of pregnancy, can cause a thrombosis of the IJV. This seems to be related to ovarian hyper stimulation syndrome (which can occur in an IVF cycle), where swelling and inflammation of the ovaries also causes blood leaving the ovaries to become hypercoagulated, or extra thick. This thickened blood can then form a clot in the IJV. Any thrombosis is treated with anticoagulation medicines, and if infection is present, antibiotics.

8. THESE VEINS DON'T DO WELL UNDER PRESSURE …

"One interesting thing about them is that they can cause a variety of brain problems, such as elevated pressure in the brain," says Ashley. One is a condition known as Eagle syndrome, which he calls "pretty cool" (as only a cerebral-vascular neurosurgeon could). In this syndrome, "a congenital bony prominence at the base of skull pushes on the jugular vein and causes the brain to swell up and become engorged with blood," Ashley describes. As the pressure builds in the brain, it has to be surgically released or it will cause serious damage. "We can do that by putting in a shunt [in the brain] to drain off fluid," he says. Occasionally, doctors can also surgically remove the piece of the bone that's causing the problem.

9. … OR WITH TRAUMA, WHICH IS THE MOST COMMON CAUSE OF CONSTRICTION.

Other than congenital issues—those you're born with—the most common causes of constriction in the jugular veins are from traumas, such as car accidents and other traumatic brain or neck injuries. "Blood clots and trauma can constrict the jugular vein," Ashley says, as can "congenital narrowing of the vein."

10. WE CAN NOW TREAT JUGULAR-DERIVED BRAIN PRESSURE BETTER.

In the past five to 10 years, surgeons have begun to use stents, metal tubes inserted directly into the vein, to open it up. "A shunt is a tube that goes into the brain that helps drain off spinal pressure. The stent goes into the vein, that's a little more elegant a solution," Ashley says.

11. AS EVERY HORROR MOVIE SUGGESTS, BE CAREFUL WITH SHARP OBJECTS AROUND YOUR JUGULAR.

If your jugular is punctured, Ashley warns, "you can rapidly lose blood." A needle is less likely to cause problems than a knife, but blood is likely to flow out of your jugular "more rapidly than out of a vein in wrist or arm," making a puncture a serious problem.