of lymphatic capillaries are distributed widely throughout the body. Yet some tissues lack lymphatic capillaries; these include avascular tissues (such as cartilage, the epidermis, the cornea of the eye), the central nervous system (the brain and spinal cord), splenic pulp, and bone marrow. In the small intestine, specialized lymphatic capillaries are called lacteals (lact, meaning “milky”). Located in the villi, they serve an important function in the absorption of fats and other nutrients, carrying dietary lipids (fats) into lymphatic vessels and ultimately into the blood. The presence of these lipids causes the lymph draining the small intestine to appear creamy white; such lymph is referred to as chyle (“juice”). In other areas, of course, lymph is a clear and pale fluid.
Comparison of the lymphatic vessels to the blood circulation is helpful in understanding some of the similarities between the two systems. Another similarity has to do with transport. The same factors that assist venous flow also affect lymph flow. These include breathing movements and muscle and joint “pumps”; in addition to aiding the return of venous blood back to the heart, they maintain lymph flow as well. The so-called respiration pump involves, of course, breathing in and breathing out (inhalation and exhalation). Pressure changes occur in this process, and this helps to move the lymph along. For example, when we take a deep breath (diaphragmatic breathing), lymph flows upward from the abdominal region, where the pressure is higher, toward the thoracic region, where it is lower. When we breathe out (exhalation), the pressure is reversed, yet the one-way valves in the vessels prevent the backflow of lymph. Through the contraction of smooth muscles in the walls of the lymphatic vessel, lymph is moved from one segment of the vessel to the next. Research has shown that thoracic duct lymph is literally “pumped” into the venous system during inspiration. The rate of flow is proportional to the depth of inspiration.
Also serving as lymph pumps are muscles and joints. When skeletal muscles, for example, contract, a “milking action” is created. This frequent intermittent pressure is put on the lymphatics to push the lymph forward. Most often this occurs during exercise and with general bodily movements. The contraction of muscles in both lymphatic vessels and veins force lymph eventually toward the subclavian veins (at the collar-bones). Compared to the blood vascular system, however, the pressure moving through the vessels is very low. Squeezing the fluid along this one-way system will ultimately drain it into the venous system. So the flow of lymph from tissue spaces to the large lymphatic ducts to the subclavian veins is maintained primarily by the contraction of joints and skeletal muscles and by breathing movements. During exercise, however, lymph flow may increase as much as ten- to fifteen-fold.
Other pressure-generating factors that can compress the lymphatics also contribute to the effectiveness of the “lymphatic pump.” These include arterial pulsations (pulse waves), postural changes, and passive compression of the body’s soft tissues (manual lymph drainage therapy).
Even though there is no central pump, lymph vessels themselves assist in transporting and pushing lymph. They do this through a self-activated pumping motion found in the lymphangions, the section in the lymphatic vessel between two valves. The interaction between these valves and the musculature of the vessel wall makes the contractions that propel the lymph forward. Because of this function, these little angions are called “lymph hearts,” which pulsate with an average frequency of ten per minute. In an X-ray, these vessels look like a string of pearls, with the string part representing the valves and the pearls the filled lymphangions. The ring-shaped muscles in the angions contain numerous nerve endings with connections to the autonomic nervous system; they are also influenced by the central nervous system. This is another way, along with the pumping motion, that the lymphangion functions like a “little heart.” In conclusion, lymph drainage comes about as a result of the rhythmic, alternating dilations (expansion) and contractions of these “pearled” segments known as lymphangions.
CONCLUSION
After this rather technical introduction, a few concluding ideas to help summarize the concepts presented are needed here. Offering an overview of any bodily function that one can easily comprehend and grasp is difficult with any system, not only because of its overall complexity but because the understanding of the functioning of our body is a work in progress. Discoveries continue to be made, explorations continue to be done, revising former conceptions and rethinking old formulas.
The lymphatic system has several functions:
1.To drain interstitial fluid; this is the fluid that arises in between the cells; the lymphatic vessels help drain the tissue spaces from excess fluid
2.To transport dietary lipids (fats); these and other substances, such as proteins, are carried by lymphatic vessels and returned by them to the blood
3.To protect against invasion; lymphatic tissue carries out immune responses by targeting particular invaders or abnormal cells (such as bacteria, viruses, cancer cells, and so on) and responding to them in specific ways; in effect, destroying them and eliminating them from the body
Since blood and lymph are part of the circulatory system, comparisons between them may help in understanding more fully their role and function. Some differences include the following:
1.The lymphatic system does not form a complete and closed circuit like the blood.
2.The circulatory system has a muscular pumping organ—the heart; the lymphatic system does not.
3.Lymphatic capillaries structurally have larger diameters than blood capillaries and thinner walls than veins; also pressure is lower than in the blood vascular system.
4.The lymphatic network, unlike the blood, has “interruptions” by way of lymph nodes, stations which slow the movement of lymph temporarily in order to purify and filter the fluid.
Similarities between the two systems include the following:
1.Veins and lymphatic capillaries both have valves which move the fluid through the vessels; lymphatic vessels, however, have more valves.
2.Each forms increasingly larger structures, beginning with tiny capillaries and progressing to larger tubes and channels.
3.Respiration and joint/muscular movements affect transport for both.
4.Both are pervasive and widely distributed throughout the body.
These similarities and differences may assist in a better understanding of how the lymph operates in the physical body as well as the nature of its importance in our overall health and balance.
With the conclusion of this presentation, we will begin in the next chapter to study in greater detail the functioning of the lymphatic system as seen through the readings of Cayce. What were some of the indications, first of all, that pointed to improper lymph flow in the body? How were these conditions described? What were the circumstances surrounding this dilemma? Recognition of the overall pervasiveness of the lymph will be one of the results from this examination.
CHAPTER THREE
Approaching a Balance: Conditions Related to Lymph
In our desire and willingness to learn more about our physical body’s wonderful activity, we discover that we also need to learn a new language to accompany the description of its functioning. We enter a fabulous world, ranging from microscopic
