This is related to my first question,I did ask the doctor and he would not give me an answer!!?

Question

Thats why I'm asking if anyone is famaliar with the funtions of the thymus gland!!

Answer 1

The Location And Functions of The Thymus Gland

Serveral authors have made interesting comments regarding the thymus:

"THYMUS GLAND…Lying beneath the sternum (breastbone) and above the treachea (windpipe) and heart is the two-lobed thymus gland; each lobe is made up of LYMPHATIC tissue. The thymus gland plays a significant part in the establishment of the immune system from the 12th week of gestation until PUBERTY, after which it begins to shrink gradually." (Stoppard, M.D., page 84)

"thymus...a ductless, glandlike body, of undetermined function, situated in the upper thorax near the throat: it is most prominent at puberty, after which it disappears or becomes vestigial: the thymus of an animal, when used as food, is called sweetbread..." (Webster's Dictionary, page 1,906)

"There is still considerable ignorance about exactly how the thymus does its job, but it is now known that it is essential for the proper running of the lymphatic system, and that it has really carried out its major function during the first few years of life." (Weston, M.D., pages 98-99)

"Thymus gland. An imperfectly understood gland, the thymus is believed to produce thymosin, which promotes the development of antibodies, especially T lymphocytes, or T cells. The thymus stops working after puberty." (Time-Life, page 75)

"The thymus is found in the upper part of the chest, where it lies just behind the breastbone. In a young adult it is a few centimeters long and weighs about 15 gm. (one-half ounce). However, this simple statement conceals the most remarkable thing about the thymus, and that is the way that, quite unlike any other organ, it is at its largest at about the time of puberty when it may weigh up to 45 gm (one and one-half ounces). In a baby, the thymus is really very large compared to the rest of the body, and it may extend quite a long way down the chest behind the breastbone. It grows quite quickly until about the age of seven; after this the thymus continues to grow, but much more slowly until puberty. After the age of puberty the thymus starts to shrink in size--a process called involution--until in an elderly person there may be no more thymus tissue present apart from a bit of fat and connective tissue." (Weston, M.D., pages 98-99)

"Hormones secreted by the bilobed thymus stimulate the production of white blood cells" (Thomas, M.D., page 239)

"There seems to be little doubt that in the early years of life the thymus is concerned with programming the way in which the body resists infection, and in particular, it seems that the thymus is responsible for making sure that the system does not turn its activities against the body's own tissues." (Weston, M.D., page 99)

"The thymus, a member of the lymphatic system, is located in the anterior/superior mediastinum (just above and in front of the heart). It is known to play a critical role in the seeding of the lymphatic organs (lymph nodes, diffuse lymphatic tissue, etc.) with potential "T" lymphocytes, which secrete a substance that attacks the protein of certain tumor cells, foreign cells, and micro-organisms (cellular immunity). There is evidence that the thymus produces a hormone (thymosin) that enhances the development of "T" lymphocytes. Activity of the thymus wanes significantly after puberty; it ultimately atrophies to be replaced with fibrous tissue." (Kapit and Elson, Anatomist, page or plate 106)

"Thymus hormones travel through the bloodstream and continue to exert their influence over the departed T cells. Thus, the thymus can be considered to be a true endocrine gland-- carried to another part of the body where it will have its effect. We know that the thymus continues to secrete hormones and to 'train' and export T cells until late in life. After puberty it diminishes in size because it is no longer concerned with growth. Any further shrinkage is due to stress and other factors to be discussed in this book." (Diamond, M.D., page 10)

"In embryonic and early life the thymus gland is vitally concerned with growth, as has been demonstrated by the fact that administration of thymus extract dramatically increases growth rate in laboratory animals. More importantly, it is the 'school and factory' for lymphocytes--the white blood cells responsible Under the influence of thymus hormones, these cells mature, then leave the thymus and settle in the lymph nodes and the spleen, where they give rise to other generations of lymphocytes called T cells (T for thymus-derived). Thymus hormones travel through departed T cells. Thus, the thymus can be considered to be a true endocrine gland--that is, an organ that secretes a hormone into the bloodstream to be carried to another part of the body where it will have its effect." (Diamond, M.D., page 10)

"In the fetus and newborn animal, the thymus gland is a large organ lying in the upper mediastinum beneath the sternum. In the very young fetus it is composed primarily of epithelioid cells, but it has a reticular structure that entraps stem cells circulating in the blood. For reasons not understood, these trapped stem cells are then stimulated to proliferate extremely rapidly, and the cells that are formed are the first lymphocytes to appear in the fetus. These lymphocytes migrate into the blood and thence throughout the body, seeding the lymph nodes and other lymphoid tissue. The seeded cells then become either plasmablasts, the progenitors of the plasma cells, or lymphoblasts, the progenitors of the small lymphocytes formed in the lymphoid tissue. Thus, the thymus plays an important role in the original genesis of the entire lymphoid system of the body." (Guyton, M.D., page 122)

"Failure of the Immune System to Develop in the Absence of the Thymus Gland. If the thymus gland is removed early in fetal life, the lymphoid tissue of the entire body fails to become seeded with lymphocytes, and consequently, essentially no immune system develops. Even if the thymus is removed shortly before birth of the baby or within the first few days after birth, the immune system is still greatly impaired. Furthermore, the lymphocytic type of immunity seems to be much more impaired than the humoral type, indicating that plasmablast seeding of the lymphoid tissue occurs earlier than lymphoblast seeding. However, if the thymus gland is removed from an animal a few weeks to a few months after birth, very little harm is done to the immune system, because by that time enough seeding of the lymphoid tissue has occurred for the immune system to function throughout life. One exception to this occurs as follows: If the person is subsequently exposed to some effect, such as a nuclear bomb blast, that destroys most of his immune system, he will have difficulty reseeding his lymphoid tissue without the availability of a thymus gland. Here again, lymphocytic immunity is affected much more severely than is humoral immunity." (Guyton, M.D., page 122)

"Possibility of a Thymic Hormone. Even though the thymus gland is absolutely necessary for the early seeding of lymphoid tissue with lymphoblasts and plasmablasts, once this seeding process has occurred, one might expect that the lymphoblasts and plasmablasts could proliferate within the lymphoid tissue without further intervention from the thymus gland. Yet, even so, removal of the thymus gland still stops or greatly impedes further growth of the lymphoid tissue. If the thymus gland is then re-implanted can get out of the thymus gland, the lymphoid tissue throughout the body immediately resumes its growth. Therefore, it is believed that some hormonal substance released by the thymus gland diffuses throughout the body to activate the growth of the lymphoid tissue. This substance is called simply the thymic hormone. Thus far all attempts to extract from the thymus gland a specific substance that will perform all the functions of the so-called thymic hormone have failed. Nevertheless, there is still reason to believe that such a hormone might exist and that eventually it will be extracted."

Answer 2

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Answer 3

a great medical site with all you could want to know and more. www.medlineplus.gov