It may seem strange that the word "cancer" can cause fear, and yet few really understand its meaning. Perhaps the reason lies in the fear of this. For lack of knowledge creates in our imagination the most negative picture, but the quality of human nature is such that most of us react that way. The ancient Romans gave the Latin name "cancer" (cancer) incurable's growing ulcer-like shape of a crab. Words such as "tumor" or "tumor" used to describe cancer, say little to us (if at all, they say) about what really is a cancer.
They really descriptive: "tumor" means nothing more than a swelling, bloating, a "tumor" - is literally "new disease". A more recent term "oncology", originating from the Greek word "onkos" (swelling), applies to the part of medical science that deals with tumors. "Carcinoma" is derived from the Greek word for "crab", but now the term is restricted to those cancers that affect tissues such as skin and oral mucosa and intestine, and the term "sarcoma" is used to refer to cancer bearing tissues such as bone , fat and connective tissue. A closer analysis of these terms does not help the understanding of cancer.
It should appeal to what we know about the formation of his own body, as one of the most rapidly growing tumors is the fruit of man. A comparison of his cancer might seem unfair and unjust, because the fetus is associated in our imagination with normal development. However, consideration of the rules from this perspective helps us to better understand, what is the difference between cancer. The body of each of us is composed of approximately 15 million cells, while our life is born from a single cell at the moment of conception.
Cell - the basic unit of life, and some living organisms consist of only one cell, but even in this case it is a very complicated structure. Cancer also originates from a single cell, like the first cell of the fetus, it has great potential for growth. Before considering the development of cancer cells, let us trace of our own evolution from a single cell.
Once the egg is fertilized by sperm mother-father, newly formed within the nucleus of the unit cell is a striking genetic material from each parent, known as DNA, which carries an enormous amount of information. This cell starts to divide, forming new cells. They in turn are divided with the formation of new cells that contain the same genetic material with information about the symptoms from each parent. This process continues steadily, hour after hour, and each cell gives rise to a complex hierarchy of cells.
One can imagine that for the formation of at least one of the smallest part of the body of the child requires a completely unique control mechanisms. During the early development of cells that perform different functions, referred to the emerging body to the correct place, where they Organization (distribution) relative to each other and their surrounding cells to form various structures. Different cells, merging with other cells such a type and form tissues such as skin, which can lead as the most obvious examples.
But even in the skin is not the same cell, for example, around the hair, lips, inside the mouth and on the inner surface of the eyelids. Thus, in the flickering century involved the structures and mechanisms that man strives to model using all means at its disposal modern knowledge in the field of electronics, but quite in vain. All this indicates that the growth and development in nature is a controlled and harmonious way, which is not yet able to reproduce artificially. Cancer can arise from individual cells within a tissue. But the most striking, given the number of cells involved, is not the fact of cancer, but that happens rarely.
Mammalian cells are very similar in structure. Each has an outer coating called the cell membrane, and the central core. The space between the nucleus and cell membrane occupied by gelatinous material, or the cytoplasm. Just as the outer clothing of various mammals, including the skin, varies depending on their habitats, for example, polar bears, monkeys, whales and humans, and cell walls have different structures, depending on their localization in the body and functions. The cells of the skin, for example, must constantly be in adhesion with each other without it (that applies to the cells of some other structures), we would literally broke into pieces.
On the other hand, blood cells can not adhere to each other as circulating in the blood vessels. In addition, they perform different functions, so their cell membranes have properties not found in skin cells: in particular, they lack the structure to ensure adherence to each other. In the center of the cell is its "brain" - the kernel. This information comes and goes in the form of signals in different parts of the cell. Inside the nucleus is a very long thread of DNA, which is spirally twisted and folded with the exact fitting to the nucleus.
Just before cell division genes, each of which defines the characteristics of the cells are packed into chromosomes that allow them to move from one of the dividing cells in newly formed daughter cells. The behavior of cells in the literal sense, is controlled from the nucleus. This command may be sent to the construction material of the cell, and here, too, can enter information. When the substance is some form is associated with precisely tailored to the cell membrane receptor in the nucleus receives information. Any chemical can penetrate the cell and cause a similar effect. Such a signal may, for example, stimulate the reproduction of cells. This occurs when the cell is damaged: the chemicals released from damaged cells trigger recovery mechanisms that are active in the surrounding cells, resulting in a damaged area is filled with new formed cells.
The space between the nucleus and cell membrane filled with cytoplasm. It forms the framework of cells, which prevents its spadeniyu, and may in some cases assist her movement. The cells of our bodies have their own education system and storage of energy needed for life. Furthermore, since cells of different tissues perform varying functions in the cytoplasm and cell membrane possesses specific characteristics associated with these functions.
Most body cells are constantly in a state of rest, which in normal conditions changed only if damaged tissues. However, some tissue continuously regenerate itself, such as intestinal tissue, and skin. Others are in constant activity (the cells of the hair sac) or continuously divide to form daughter cells, for example, in the ovaries, testes and bone marrow. The level of activity in different tissues varies, in the tissues of the uterus, it is cyclical, in which the new stage of recovery begins after menstruation. Throughout the body, these processes occur in an orderly manner, but if the order is violated, there may be a well-recognized disease, having nothing to do with cancer. As an example, psoriasis, in which excessive formation of cells occurs in localized areas of skin.
For the development of cancer requires several factors, including disruption of the normal behavior of cells. In contrast to the cells formed during the healing of wounds, when at the conclusion of the process of division stops cancer cells "ignore" the signal to stop dividing. This can be called "automatic" behavior of cells. About involved in this process mechanisms is gradually becoming known more and more.
In some cases, the gene (genetic incorporation of control cell division, addressed to a unique segment of DNA) is included because it is a direct change, or another nearby gene makes the first more active. It may also be lost, a gene that otherwise would have blocked the "active" gene. The latter mechanism is included with some very rare types of cancer such as retinoblastoma, affects eyes of young children, but in general the causes of specific types of cancer are unknown. Identified some risk factors for cancer. Cancer of the scrotum caused by soot contained in the chemicals, so-called carcinogens: they come into direct interaction with the DNA of cells and determine the changes in genetic material, or "mutations".
Very rarely it leads to cancer. There are several chemicals, such as benzene, which may increase the risk of cancer. As another example, naphthalene dyes, the use of which is now strictly controlled, but which are recognized as substances that may lead to the development of bladder cancer. Asbestos is derived from natural minerals, for many years used as a thermal insulator. Asbestos dust can cause cancer of the lining the lungs many years after exposure. Best-known risk factor among the common sources of tobacco smoke carcinogens.
It contains small amounts of a chemical (3,4-bepzopiren), which is on the skin of mice at higher concentrations, they invariably causes cancer of the place. The use of known carcinogens is strictly controlled by law, excluding tobacco smoke. Exposure to ionizing radiation may in some circumstances also cause mutations (changes in genetic material), which lead to increased risk of cancer.
In this regard, the most obvious example is a small but marked increase in the incidence of cancer among persons who survived the bombing during the Second World War. This effect is ultraviolet radiation (especially visible in strong sunlight), if the effects long enough. It is well known that exposure to intense sunlight over many years may lead to increased incidence of certain cancers, including basal cell and squamous cell carcinoma and malignant melanoma.
The role of viruses in cancer development is still uncertain. A simple infection to initiate the cancer process is not enough, because otherwise the cancer would be much more common in younger age groups. To start the mechanism that leads to the emergence of cancer, appears to be a complex interaction between viruses and other factors, such as environmental carcinogens, or genetic defects, but even then the cancer would arise only in rare cases.
It is assumed that Epstein-Barr virus (EBV), found throughout the world, is related to cancer tissue lymph glands (Burkitt's lymphoma), distributed among the population of Africa. One of the consequences of HIV infection is a violation of the immune resistance of the organism, contributing to, apparently, the development of rare tumor of skin and other tissues (Kaposi's sarcoma). It is believed that a relatively common human papillomavirus (HPV) plays a role in the development of cervical cancer.
Undoubtedly, an important role belongs to some environmental factors. Thus, the object of attention are the chemicals contained in the diet. Ongoing research now will help answer some important questions: for example, why among the Japanese is much higher incidence of gastric cancer and significantly lower incidence of colon cancer than in the United States. Meanwhile, among the Japanese, having lived all his life in the United States, this trend is weakening and there is a similar pattern with the Americans, ie they are more likely to suffer from colon cancer than their relatives living in Japan. Similar effects occur over many years, so short-lived changes in diet, apparently, will not cause increase or decrease the risk of colon cancer, and certainly will not affect the development of an already existing disease.
Prior to the development of cancer affected tissue, apparently, some lose stability. Pathology know this state, which in some cases can be called "precancerous." They have to observe cells and tissues taken for biopsy, which are less ordered compared to the norm, and the study of individual cells can be seen abnormalities in the appearance of the nucleus and surrounding cytoplasm. When malignancy cells any significant breaches during quite a long time unnoticed. This is not surprising, since the swelling size of a pea, is formed of many millions of cells.
The proliferation of cells occurs gradually until a very significant site. The speed of this process depends on many factors, while it is possible that some tumors reach a significant size in a few weeks, while others take years. In the case of leukemia, in which a breach occurred hematopoietic tissue in bone marrow, swelling, of course, occur rarely, but they have a tendency to crowd out normal cells, and for that reason, the disease becomes apparent. The main features of solid tumors are mechanical damage due to tumor growth and secondary education, caused the cells originating from the primary tumor and spread to other parts of the body through the bloodstream, lymph, and even through direct spreading. Such secondary education cancer cells are called "metastases.
Metastases and, of course, the primary tumor can grow inside the body of a viable and ultimately cause a violation of its functions. In rare cases, cancer in large quantities are produced by chemical substances, which under normal conditions play an important role in the functioning of the organism, but in high concentrations can cause pathological changes. Certain substances secreted by tumors, leading to the emergence of generalized symptoms such as weakness, anemia, depression, constipation, sweating at night and other very common phenomenon. Effective treatment of cancer will control these problems. With a better understanding of the cancer process and the behavior of cancer cells significantly improved the prognosis for cancer patients.
