“Our
Amazing “White Bloodstream”
By
J.D. RATCLIFF
It is one of the world’s rivers of mystery—sluggish, largely unmapped,
many miles long. A remote Amazon
tributary? No, the lymphatic system of
your body.
The lymphatic system has puzzled physiologists since
early Greek times. Only now is the
‘white bloodstream’ beginning to yield up its secrets—thanks to new tools and
laboratory techniques. One thing
becomes increasingly clear: our healths, even our lives, depend on how well
this complex system functions.
In contrast to the bloodstreams, which follows a
swift-flowing closed circuit from arteries to capillaries to veins and then
back to arteries, the lymphatic system flows slowly in a single direction. Its initial rivulets—microscopic in
dimension—originates in intercellular spaces.
Fluid gathered here passes through ever-enlarging ducts until it reaches
the lower neck region, where it empties into veins leading to the heart.
Much of the mystery surrounding the lymphatic system
traces to the fact that most of its ducts are so fragile that they are
invisible—the smallest have walls of only one-cell thickness. And the fluid they carry is ordinarily
almost clear as water. Moreover, at the
touch of a probe, all bug the largest lymphatic vessels collapse, as they’d at
death. Exploring such a gossamer stream
has called for supreme ingenuity which cast shadows on X-ray films, second,
radioactive isotopes, which leave a track of telltale radiation.
Explorations via these and other techniques reveal
fascinating insights into the ‘geography’ of the body. In many respects the body is like a vast
swamp. Its trillions of fluid bathed
cells live an aquatic life. The lymphatic
network, it can now be seen, provides an all-important drainage system. To nourish cells, blood capillaries constantly
leak minerals, fats, vitamins and sugars, along with fluids and blood
proteins. Much excess fluid, together
with cellular wastes, passes back through capillary walls to be carried away
bye veins. But not all. If the lymphatic system did not carry a
large portion of their remaining seepages back to the bloodstream, we would all
‘bleed’ to death internally in a matter of hours.
Loss of blood proteins through capillary walls would
be particularly disastrous. Dr.
H.S.Mayerson, of Tulane Medical School, tagged blood proteins with radioactive
iodine, then measured the rate at which they passed into lymph vessels. Calculations indicated that half of our
blood protein is lost every 24 hours!
But for the prompt retrieval of the protein by the lymphatic system this
constant loss would spell catastrophe.
The route of return is reasonably well known. A gathering system of minute lymph capillaries collects
fluid—how, no one knows—and passes it along until it finally reaches the right
lymphatic duct or the thoracic duct.
The later is the largest vessel in the lymphatic system;
soda-straw-size, it passes some 16 inches upward through the center of the
body, finally emptying into the bloodstream.
What propels this great lymphatic system? Reptiles and fish have lymph
‘hearts’—pulsating tubes—to move fluid along.
Man does not. Apparently—this is
one of the lymphatic system’s mysteries—lymph is propelled mainly by muscular
contractions from breathing, walking, of internal pulsations. As muscles tighten, lymph vessels are
squeezed, and fluid is pushed along.
Backflow if prevented by flap valves located at regular intervals in the
larger lymphatic.
The lymphatic network has other jobs besides
drainage and maintenance of fluid balance.
Spaced along the channels are hundreds of nodes—bean-shaped masses of
tissue that range from pinhead size up to an inch long. They serve as filters, removing dangerous
impurities much as an oil filter does in a car. These lymph nodes are so numerous that, if one fails, another a
few inches farther along is likely to do the job. This filter system traps almost anything that is potentially
harmful—dead red-blood cells, chemicals, even excess tattoo dye. Lymph modes in the lung areas of city
dwellers are often dark form soot filtered out of murky city air.
Suppose you cut your finger or step on a nail. Inevitably, bacteria are carried into the
body. They could be lethal but for the
lymph nodes that strain them out, then destroy them. Generally, these filters are so efficient that the lymph they
finally deliver to the bloodstream is clean and safe.
Still, they can be overwhelmed. The most dramatic examples are offered by
that terror of a disease, bubonic plague.
Here the lymph nodes struggle valiantly to filter out and destroy the
invading organisms, but it is a losing battle.
On a less dramatic scale, we have all seen evidence
of lymph-node difficulties. It may seem
odd, for example that an infected finger causes pain and swelling in the
armpit; of that an infected toe similarly affects the groin. But concentrations of lymph nodes are
located in these areas, and discomfort there announces that a battle royal
against bacterial invaders is under way.
While lymphatic filtering action is one of the
body’s greatest protective mechanisms, it can also lead to trouble. Striving to trap anything that would be
harmful in the bloodstream, the lymph nodes trap cells shed by cancers. These cancer seeds often sprout and grow
there; indeed, this appears to be one of the chief routes of cancer
spread. This is why surgeons always pay
particular attention to the lymphatic system near a primary cancer. In breast removal, for example, the greatest
care is exercised to remove lymphatic and lymph nodes in all surroundings
areas, particularly the armpit.
Transport is one of the lymphatic system’s big
jobs. Mounting evidence indicates that
this is probably the route by which some of the critically important hormones
are distributed through the body.
Another of the system’s intriguing activities is the handling of dietary
fats. Proteins and carbohydrates are
absorbed directly into the bloodstream along the digestive tract. Most fats are not directly absorbed—and with
good reason: in heavy concentration, fats are injurious to red-blood
cells. The lymphatic system solves this
problem by absorbing fats from the intestine and dribbling them into the
bloodstream in amounts that can be safely handled.
The lymphatic system also produces antibodies, which
destroy invading bacteria, and it manufactures at least one fourth of the
infection-fighting white cells that circulate in the blood stream. Whenever infections develop, the lymphatic
system goes into frantic activity, producing white cells by the tens of
thousands and rushing them to the scene of trouble.
Usually, the lymphatic system performs so
efficiently that we are hardly aware of its existence. Still, from time to time it does announce
its presence. On long plane rides and
in theaters, women sometimes kick of their shoes. Reason: when the feet are inactive, fluid stops flowing and
collects; feet5 swell. During surgery,
lymph channels are inevitably severed, where upon fluid collects in
intercellular spaces, swelling follows in the surgical area and persists until
new lymph channels sprout. Children
after suffer from ‘swollen glands,’ particularly in the neck area. This means that lymph nodes “glands” are
inflamed.
At times, too, the system lacks the reserve capacity
to handle jobs thrust upon it. In the
lungs, for example, blood vessels may ooze fluid faster than the lymphatics can
carry it away. This can happen in
pneumonia, in certain type of heart disease or when irritating chemicals damage
lung tissue. Unless the lymphatic
system can meet the challenge, the victim may drown in his own juices.
The lymphatic system has its own special disease
problems. It is the chief target of
lymphatic leukemia, and of Hodgkin’s disease—a cancer like illness marked by
enlargement of nodes. Until lately,
medical texts said that the latter disease was always fatal. Recent advances offer some hope of changing
the picture, however. High-voltage
radiations appear to destroy the lymph system.
In one recently reported series of cases, where treatment was begun
early, two thirds of those treated in this manner were alive at the end of five
years—the usual yardstick of cancer cure.
Other studies suggest a link between lymphatic
difficulties and deposition of fat in artery walls—which can lead to blockage
of heart arteries and to death.
Similarly, there may be a link between lymphatic disorders and serious
malfunction of the kidney.
Thus, this great river of mystery may well hold the
key to dozens of disease riddles. As it
is given-increasing research attention, discoveries of vital importance to all
of us will inevitably be made along its banks.
