Where is the Spleen?
A normal Spleen is about 12 cm long, 7 cm wide, and 250 cm3. It lies obliquely in the upper left part of the abdominal cavity sitting directly under the diaphragm behind the stomach and protected behind the 9th 10th and 11th ribs. It is shaped like a largish fist and its longest axis runs parallel to the 10th rib. When it is normal in size and position, the Spleen is generally unable to be felt by a doctor during examination.
What does the Spleen normally do?
It is an organ rich in blood vessels, it is soft and purplish in colour. The role of the Spleen is rather like that of the Human Resources Department in a large company.
1. Staff management -
Staff quality surveillance
The Spleens main function is to recognise and dispose of red blood cells that are past their "use by date" or not working properly. Blood flows into the Spleen where the red blood cells go through a sort of quality control test. They must pass through a maze of narrow passages and some just dont make the grade. Damaged, fragile or abnormally shaped red blood cells will be detected and destroyed by the Spleen. However, the Spleen is a an ergonomic organ and as such useful bit-parts of the cells such as iron are stored and recycled in new red blood cells.
Casual staff management
The Spleen can store blood to be made available in times of need. Some animals have a muscular capsule around their Spleen. This can contract to squirt extra blood into the system if needed. Unfortunately we do not have this facility. However, the blood vessels in human Spleens are capable of expanding and narrowing in response to bodily needs. This means that when vessels are expanded the organ can actually hold up to may be a cup or so of reserve blood. If the body requires some extra blood short term say if trauma causes blood loss the Spleen can respond by releasing it back into the system.
Permanent staff recruitment
During early development in the uterus the Spleen is an important centre for production of red blood cells however usually as birth approaches this organ loses its ability to make the cells which becomes the job of bone marrow after birth. The Spleen does however continue, throughout life, to produce white blood cells as part of the immune system.
While one department of the Spleen is looking after red cell management there is another part which is looking after body security. The Spleen plays an important role in the bodys defence mechanism the immune system. When an invader is detected in the blood stream the Spleen, along with the lymph nodes, jumps to action and produces an army of defender cells which are made to a blue print specific for that invader. These are released into the blood stream like homing missiles to attack and kill the invading germ.
What can go wrong with the Spleen?
While the Spleen is nicely protected by the ribs a blow to the upper left abdomen which hooks under the ribcage like a foot ball boot, or a squeezing injury, such as an ill-fitting seat belt in a motor vehicle accident can cause the Spleen to rupture. Like a plastic bag full of beads in water, once burst it is hard to stop its demise. Because the Spleen has such a rich network of blood vessels rupture can result in death through blood loss. Any serious injury to the left upper abdomen needs proper assessment quickly.
There are many conditions which result in splenic enlargement
1. Infections :
Acute enlargement can occur during some serious infectious diseases when the spleen is called to arms to produce defender cells. Examples are Malaria, Infectious Mononucleosis (Glandular fever),Typhoid. It is particularly important remember that when the Spleen is enlarged and no longer protected by the rib cage it is most vulnerable to trauma this is why young people with glandular fever are strongly advised not to play sport until the organ has recovered to its normal size .
2. Disorders of Immune regulation:
Rheumatoid arthritis and Systemic Lupus Erythematosis are examples of auto-immune disorders. The immune system has created attacker cells, which mistake normal body cells for invaders. The body believes it is under massive attack and so mobilises all immune resources as it would in a bacterial infection. As a consequence sometimes in these disorders the spleen enlarges too. As a side effect of the splenic enlargement this may also lead to the "over" filtering of red cells too and so anaemia can be associated with these conditions.
3. Disorders of blood flow :
If the heart is not coping with its load there is back flow of blood down the vein system to the liver. This can cause a build up of traffic such as when a main road to the city is congested back down the system. The spleen is capable of "taking up the slack " and so it bears the brunt to problems with back log in blood flow in the heart and liver.
4. Infiltrative diseases :
Cancers of the immune system such as Hodgkins Disease and those of blood cells such as the leukaemias can also cause the Spleen to enlarge as a centre of abnormal immune cell production which is why it may be suggested that these patients have their spleen surgically removed.
5. Blood disorders :
Disorders of blood cell production, like Sickle Cell anaemia or Thalassaemia may mean that there are more abnormally shaped red blood cells in the system. The spleen may need to enlarge to cope with the increases surveillance work required .
6. Unknown causes:
Sometimes the spleen enlarges, well because it can ! Medical scientists are still trying to understand this often forgotten organ.