nodes are also the site of maturation for some lymphocytes, a type of white blood cell important to the body’s defense system.
Peyer’s patches are large specialized collections of lymphoid tissue located in the small intestine, particularly in the ileum. They were named after Johann K. Peyer (1653-1712), a Swiss anatomist, and are mentioned in over sixty readings by Cayce. Bacteria, which enter the body through the mouth, eventually penetrate into the wall of the small intestine, where they multiply in the area of the Peyer’s patches. After a week or two, the bacteria enter the bloodstream. The Cayce readings concur with this function, recognizing this area as the place where poisons can be absorbed into the system. (More about this structure in chapter 5.)
Lastly, we have the lymphatic organs: tonsils, thymus, spleen, liver, appendix, and bone marrow. They, too, help the body fight infection, each in its own unique way.
The tonsils are located at the back of the mouth, at either side of the throat. They assist in trapping and destroying microorganisms and keeping infections away from the lungs. During childhood, around ages six or seven, they are the largest in size but gradually shrink throughout one’s life. They are removed usually in cases where recurrent attacks of tonsillitis (inflammation and swelling of the tonsils) may interfere with the child’s breathing, swallowing, or general health, but—aside from these instances—the operation is usually not necessary and only performed as a last resort.
Figure 2
The lymphatic vessels, larger lymphatic trunks, and lymph nodes
In the long unrecognized thymus, a small gland near the heart, the cells of the immune system learn to differentiate self from non-self. When the immune system starts developing in the fetus, stem cells migrate to the thymus. Here they develop into T lymphocytes, white blood cells which help protect against viral infections as well as detect and destroy some cancer cells. (When these T lymphocytes lose their ability to differentiate self from non-self, autoimmune disease may result.) That it plays a critical part in the body’s defense against infection was not well known until the 1960s. Largest in size at puberty, the gland gradually shrinks and eventually atrophies when the person is much older, its lymphatic tissue replaced by fat, perhaps completing most of its essential work early in childhood. Despite this atrophy, however, some T cells continue to proliferate in the thymus throughout one’s lifetime.
About the size of a fist, the spleen, which is the largest mass of lymphatic tissue in the body, is located in the upper left part of the abdominal cavity, just under the rib cage. Its function is to produce, monitor, store, and destroy blood cells. Its spongelike tissue is of two types: white pulp, which is part of the infection-fighting (immune) system and where some lymphocytes are produced, and red pulp, which removes unwanted material from the blood, especially defective red blood cells. Before birth, red blood cells are formed here, and in the normal adult the spleen serves as a reservoir for blood. If it is surgically removed, the body loses some of its ability to produce protective antibodies and to extract unwanted substances from the blood, thus lessening one’s ability to fight infection. However, other organs, especially the liver, will compensate for this loss and take up the infection-fighting job.
One of the largest organs in the body, the liver is also one of the most important. Similar to a chemical processing plant, it performs a variety of vital functions: production of cholesterol and bile; manufacturing of proteins; storage of iron, glycogen, and vitamins; removal of poisons and waste products from the blood; and conversion of waste to urea. It is also a main component of the digestive system, though it lies outside of the digestive tract. Because it filters and destroys bacteria and helps detoxify the body, some texts (for example, The Merck Manual) list it as part of the lymphatic system as well. Located in the upper right section of the abdomen behind the lower ribs, it is dark red in color and one of the most versatile organs in our body.
The appendix, also called vermiform appendix, is a small, finger-shaped, wormlike tube that projects from the ascending colon (on the right side of the abdomen) of the large intestine at its junction with the small intestine. Because it is chiefly lymphatic tissue, an infection anywhere in the body that also produces enlarged lymph nodes can increase its glandular tissue, eventually causing inflammation and infection. Unless the body’s defenses overcome the infection, the appendix may have to be removed before it ruptures, leading to peritonitis, a serious and dangerous condition. Sometimes considered a rather useless structure, it is often routinely removed by surgery because of its potential for this painful and serious inflammation.
Red blood cells, white blood cells, and platelets are produced in the bone marrow, which is the innermost portion of the bone and shaped like a hollow cavity. In response to infection, the bone marrow produces and releases more white blood cells, the body’s major mechanism for fighting infections. When blood cells for some reason show abnormalities, a bone marrow examination is often used to determine the cause. Disorders of bone marrow include diseases in which either too many or too few blood cells are produced.
From this brief overview of the main components of the lymphatic system, we may get a sense of the important role it plays in our body’s overall health and well-being. Just the extent and pervasiveness of this system, affecting a wide range of tissues, organs, and vessels, may give us a clue to the necessity of caring for it and keeping it working in an optimal fashion.
Here follow a few more points regarding the composition of the lymphatic system:
Analogous to the tree trunk, mentioned earlier as a visual description, are two large, main lymphatic vessels: the thoracic duct and the right lymphatic duct (the latter actually comprises three collecting ducts). These structures, located roughly in the center of the thorax, are the principal channels through which lymph passes into the venous blood. (See Fig. 1.) They serve as receivers of the lymph from the whole body: lymph from the body’s upper right quadrant drains into the right lymphatic duct (and then into the right subclavian vein), while lymph from the rest of the body drains into the thoracic duct (and then into the left subclavian vein). (See Fig. 3.) As their names indicate, the subclavian veins are located underneath the right and left clavicles (collar-bones) in the upper chest area. Thus, the important function of lymphatic vessels is now fulfilled: to return “leaked” plasma proteins and fluid, arising from the spaces between the cells and flowing through the lymphatics, and finally deposit them in the bloodstream.
Schematically, the flow of fluid, then, may be represented in this manner (the words in parentheses give the name of the fluid in those vessels): arteries (blood plasma)
