Sunday, March 21, 2010

Apple #446: Jugular

A jaguar in the jungle may attack the jugular.

  • There are actually 4 jugular veins. They carry blood from the head, brain, face, and neck down to the heart.
  • The word, by the way, comes from the Latin word jugul, which means throat.  That word itself comes from another Latin word jugum, which means yoke.  Thinking of the jugulars as veins that descend along and yoke your throat is a pretty good way to describe them.
  • They are named posterior and anterior, meaning that one is toward the back of your head (posterior) and the other is closer to the front (anterior).
  • They are also called external and internal.  That's supposed to indicate that the blood they collect comes from places closer to the external part of the head (skin of the face or neck, for example). But of course it doesn't all get divided up so neatly as the names might suggest.
  • It's easiest to describe them with a diagram.

This diagram shows all the veins in the head and neck.  I've labeled four -- the jugular veins.
(Diagram from Gray's Anatomy with my labels added)

  • The posterior external jugular collects blood from the back part of the skull and neck.  It's pretty small.  It comes down the back of the neck and connects with another jugular about mid-way down the neck.
  • The external jugular is what the posterior external jugular connects up with.  It's larger than the posterior external jugular, and it collects blood from deep under the face and comes down the side of the neck.
  • The anterior jugular descends below the jaw and comes down into the neck near the voice box.  In this diagram, the anterior jugular is pretty small, but it varies widely in size from person to person. Also, some people have two of these, a right and a left, while other people may have only one.
  • The internal jugular is the biggest and fattest of the four.  It also sits the deepest in the neck.  When people say "the jugular" this is usually the one they mean.  This collects blood from the brain and the outer parts of the face and from the neck.  It runs alongside the carotid artery, which is where you can feel the pulse in your neck.  Everyone has two of these, a left one and a right one.  The left one is usually smaller than the right.
  • The larger, right internal jugular usually measures around 1.4 centimeters (the left is around 1.2 cm).  1.4 cm is about the width of my index finger.  I'm looking at my index finger and imagining that to be a vein full of blood.  That's my internal jugular vein.
  • You would think that veins with this much essential fluid in them would be well-protected.  But relatively speaking, they are not.  Even the internal jugular is quite close to the surface, and it isn't hidden under lots of muscle or under bone.  So it is pretty vulnerable.
  • If it does get damaged (bitten into by a jaguar, torn open, shot, etc.), you can suffer lots of blood loss really fast, go into shock, and die.  This is a pretty accurate description, by the way, of what happens at the end of  Don't Look Now, which I coincidentally watched last night.
  • This is also why the phrase "going for the jugular" means that someone is being particularly vicious, intending to kill, so to speak.
  • You can't feel the pulse in the jugular.  The pulse you can feel most of the time at the base of your neck is the carotid artery.  But someone else can see your pulse in the jugular if you stand at an angle to the observer and turn your head about 45 degrees.

This man's jugular is visible, as indicated by the arrow.  This is usually an indicator of hypertension and some level of heart failure on the right side of the heart.  You do not want to be able to see this.
(Photo from Wikimedia Commons)

    • A doctor or a nurse may ask you to tilt or move your head in order to see your jugular.  The jugular will move as you move, while the carotid artery does not.  
    • They may do these and other tests to check the blood pressure in the jugular.  If they're doing this, chances are they're trying to get a sense of whether or not there's some sort of cardiovascular problem going on, something that could affect the atrium of the heart or the blood pressure in your veins.
    • If a person is experiencing congestive heart failure (a heart attack, basically), the pressure in the atrium will push back up the jugular, and you'll be able to see the jugular vein standing out and the pulse visible in it.  Really, this is not something you want to see because if you can, it means bad things are happening.
    • Sometimes medical professionals will put a catheter into the internal jugular vein. ER doctors might have to do this, or doctors in an ICU. They might need to use this vein because the patient's arms are too swollen or damaged or are otherwise problematic to introduce necessary fluids. So they'll have to use the internal jugular.  But they have to be really really careful about inserting the needle with the tube attached because if they miss the jugular, they can hit the carotid artery and then they'll really have a gusher. Or they could puncture the vagus nerve and, boop, everything will go haywire in the patient's head and neck.  Comforting, isn't it?

    The moral of the story: don't mess around with the jugular.  The end.

      Sources
      Dictionary.com, jugular
      MedicineNet.com, Definition of jugular vein
      Gray's Anatomy of the Human Body, The Veins of the Neck
      Academic Dictionaries and Encyclopedias, Internal Jugular Vein
      R.K. Batra, Unusual Complication of Internal Jugular Vein Cannulation, Indian J Chest Dis Allied Sci, 2002: 44: 137-139. 
      Khatri, Vijay P. et al., "The Internal Jugular Vein Maintains its Regional Anatomy and Patency After Carotid Endarterectomy: A Prospective Study," Annals of Surgery, 2001 Feb; 233(2): 282-286.

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