Apple #423: Spleen

I've been hearing people mention the spleen a lot lately. On The Young & the Restless, Chance got recently knifed in the spleen (if you want to see video of this, I've posted them at the end of this entry). Then somebody made a joke during a football game about a player getting his spleen knocked out of him, and I forget now where else I heard it, but it was too many occurrences to ignore. Especially since, how often do you hear people talk about their spleen? Time to do an Apple on it, thinks I.

• The reason you don't hear about the spleen very often is that, even among medical folks, the spleen gets kind of overlooked.

• Spleens can rupture pretty easily during traumas -- sports injuries, car accidents, bizarre knifings in coffee shops. The spleen's default state is to be packed with blood. So when it gets punctured, it bleeds like crazy. So most trauma surgeons just take the whole thing out rather than try to fix it.

• People seemed to survive the splenectomies just fine, so doctors thought, eh. It's a spleen. You can live without it so it must not be that big a deal.

• They're finding out now that the spleen is more important than they'd realized.

• The spleen normally holds an enormous number of a special kind of immune cell called monocytes. Monocytes are the largest of white blood cells and they help to fight infection. They can gang together to form uber-infection-fighters called macrophages. Macrophages are especially good at helping to mend heart tissue. In fact, they remove dead heart tissue, build newer and more stable scar tissue, and stimulate the production of new blood vessels.
  

• If you get suffer some sort of traumatic and serious injury or a heart attack , the spleen opens the floodgates and shoots millions of those monocytes & macrophages to the site of injury.

• One study back in the 1970s found that WWII veterans who had been de-spleened were more likely to die of cardiovascular disease than those who had not. Researchers weren't sure why this would be the case, but the fact that the spleen makes all those monocytes is probably what kept the veterans with spleens better protected against heart disease.
  

• Besides helping to protect against heart injury, the spleen also does a lot of filtration.
  

• Blood circulates through the spleen, not through a series of capillaries which is how blood usually travels through organs, but it gets poured into little pools called sinusoids. To get back out of the sinusoids, the blood has to squeeze out through the cell walls that line the sinusoids.

• The squeezing filters out bad stuff like blood-borne parasites. Since older and more brittle red blood cells won't bend to fit through the cell walls, those older blood cells get filtered out, too. However, the iron and other goodies in the old red blood cells do make it through the sinusoid walls, so it becomes available for younger and healthier blood cells to pick it up. Pretty cool, eh?

Cross-section of the spleen. The red pulp is where the sinusoids are, and this is where the blood filtration takes place. The white pulp is where the lymph is.
(Diagram from Web Books)

• The spleen also works as part of your lymphatic system. Lymph is a clear fluid which contains proteins, sugars, salts, and urea -- good and bad stuff both.
  

• Lymph is constantly being produced by your body, and it circulates throughout your body in your blood vessels. It's like a liquid balancing act. It keeps liquids from building up too much in one place but from getting depleted elsewhere. Also as it circulates, it collects stuff your body doesn't need and carries good things your body does need to help repair it. It's like a two-way cleaning system.

• Something has to clean the bad stuff out of the lymph, and the spleen is one of the things that does that. It also adds monocytes to the lymph and sends it back out again.

• So where is this miraculous little doo-dad and what does it look like?
  

• Normally, it's about the size of your fist. Its shape looks like a fist too, but more of a relaxed fist, not clenched.
  

• This makes it about the same size as your heart, but it's a lightweight by comparison. The spleen only weighs about 4 or 5 ounces, while your heart can weigh between 7 and 15 ounces.

• It's purple because of all the blood hanging out and getting filtered through it.
  

• It lives under your rib cage in the upper left part of your abdomen toward your back.

People often show the spleen as sitting behind your stomach, but it doesn't have any interaction with your stomach or digestive system.
(Diagram of spleen from Why Does My Spleen Hurt?)

• Besides getting ruptured, a spleen can also get enlarged, for any number of reasons. Especially bad infections can do it, liver disease, inflammatory diseases like rheumatoid arthritis, and some forms of cancer. Because it's so tucked away, doctors sometimes can't tell if it's enlarged just by feel and they may want to do some sort of scan.

• If the spleen is enlarged, it's likely the doctor will recommend removing the spleen. I'm not sure why this is except that they don't seem to understand enough about how the spleen works to know how to repair it. Rather than risk an enlargement getting worse and causing more problems, they'll want to take it out.

• These days they can do remove the spleen laparoscopically, which means they will only make small holes in the abdomen, slide their instruments and a camera in through the holes so they can see what they're doing, snip the spleen free and put it in a special little bag, and draw it out through the largest hole.

• One of the things they do when removing a spleen is look around for more of them. 15% of people have additional, smaller spleens. You would think this would be an indication that a spleen is pretty important, since your body is making extra ones. But if you're having your spleen removed, chances are, the doctor is going to take out the little extra ones too, if you have any.

• This brings me back to the prevailing notion that spleens are of secondary importance in the body. This opinion about the spleen may date all the way back to medieval medicine.

• People used to think there were four humours, or fluids, floating around in your body. They were blood, phlegm, black bile, and yellow bile. If you had too much of one of the four, your personality would be so influenced by the nature of that particular humour.

• Too much blood and you were sanguine, or optimistic and happy. Too much phlegm and you were phlegmatic or listless. Too much yellow bile, also called choler, and you would be angry and hot tempered. Too much black bile and and you would be melancholy.

• Galen, a Roman physician living in 200 A.D., decided that black bile came from the spleen. He saw the spleen as working in a support role to the liver, a much larger organ, and that it helped purify things for the liver. So, not that big a deal in its own right, but important only for what it could do for the liver.
  

• The whole black bile = melancholy thing wasn't dispelled by Galen's theory about the spleen, but was in fact expanded on. People then started to say, if you were melancholy or depressed, that meant not only that you had too much black bile but that your spleen was working too hard, or you had too much spleen.

• Despite many medical advances, the whole idea of the humours persisted for a long time and even persists in our language today. We still call people bilious or sanguine, though we have other ideas now for why they're feeling truculent or happy. But we have also seemed to hold onto the notion that the spleen is a secondary and therefore dispensible organ.

• Finally, there's a rather famous poem written by Charles Baudelaire, a Parisian poet who lived from 1821 - 1867. During that time, people were very big on the whole humours theory.

• He wasn't exactly a happy man, but was in fact rather brooding and melancholy. One of his better-known poems is called, simply, Spleen.

Spleen

When the low, heavy sky weighs like a lid
On the groaning spirit, victim of long ennui,
And from the all-encircling horizon
Spreads over us a day gloomier than the night;

When the earth is changed into a humid dungeon,
In which Hope like a bat
Goes beating the walls with her timid wings
And knocking her head against the rotten ceiling;

When the rain stretching out its endless train
Imitates the bars of a vast prison
And a silent horde of loathsome spiders
Comes to spin their webs in the depths of our brains,

All at once the bells leap with rage
And hurl a frightful roar at heaven,
Even as wandering spirits with no country
Burst into a stubborn, whimpering cry.

— And without drums or music, long hearses
Pass by slowly in my soul; Hope, vanquished,
Weeps, and atrocious, despotic Anguish
On my bowed skull plants her black flag.

(translation by William Aggeler, The Flowers of Evil, 1954)

• Not exactly the cheery, is it? But I think the spleen is actually quite cheery. It's your own personal hospital, rushing ambulances to the site of injury. It's purple. It cleans your blood. It helps fix damaged heart tissue. It's a little fist of life! Hooray for the spleen!
  

Chance getting knifed in the spleen. Or somewhere. Starts at 8:47.

Sources
Natalie Angier, The New York Times, Finally the Spleen Gets Some Respect, August 3, 2009
Mayo Clinic, Englarged spleen (splenomegaly)
Teens Health, Spleen and Lymphatic System
Cynthia Graber, Scientific American, Spleen Gives Heart a Leg Up, August 4, 2009
Web Books Publishing, Human Physiology, Lymphatic System
WebMD, Enlarged Spleen
SAGES, Patient Information for Laparoscopic Spleen Removal, March 2004
Stanford, A History of the Liver, Spleen, and Gall Bladder
Wise Geek, What are the Four Humours?