Assuming that you are not a space alien of some sort, the clear fluid that you saw was lymph.
Apparently when you cut yourself you did not puncture any sort of blood vessel, so you had a rare
opportunity to actually see your lymph!
One of the amazing things about lymph is that we all have it but we generally know nothing about it. Yet
your entire body is soaked in lymph and there is a whole lymph vessel system that is just as
complex as your blood vessels!
We all know that we have a heart, arteries, veins, blood vessels and ultimately capillaries. Blood
carries many different things to the cells, including:
Capillaries flow past cells but do not actually connect to them. What happens is that the clear, watery
blood plasma - containing the oxygen, proteins, glucose and white blood cells - "leaks" out through
the capillary walls and flows between all the cells. The pores in the capillaries are
too small to let red blood cells through, however - that is why lymph is clear rather than red.
All of the cells in your body are therefore
bathed in lymph, and they receive their nutrients and oxygen from the lymph.
- Oxygen (blood also picks up carbon dioxide so it can be exhaled)
- White blood cells (to find and eliminate bacteria, viruses and other foreign materials)
Somehow all of this lymph has to end up somewhere, so it is recirculated. The lymph capillaries
and vessels pick up the lymph fluid and start pumping it away from the cells. Lymph vessels
do not have an active pump like the heart. Instead, lymph vessels have one-way valves and muscle motion
pumps the lymph. You have just as many lymph vessels and capillaries as you have blood vessels
Lymph in the lymph vessels eventually reaches a lymph node - there are about 100 nodes scattered
throughout the body. Lymph nodes filter the lymph and also
contain large numbers of white blood cells (a big part of the immune
system) which remove foreign cells and debris from the lymph. When you get certain infections, the
lymph nodes swell with billions of white blood cells working to clear the foreign cells
causing the infection. The filtered lymph then flows back into the blood stream at certain points.
One thing this explains is how a shot at the doctor's office works. The fluid of the shot is injected into
the lymph - not the blood stream. But eventually it makes it to the bloodstream through the lymph system!
Here are several interesting links: