The cell is the simplest element, endowed with life itself, which is organized tissues. It consists of a mass of protoplasm surrounded containing a nucleus.
A cell wall surrounds the cell and separates of their environment. Inside the nucleus is the DNA that contains the information that programs the cell life. Man is composed of millions of cells.
The cell divides and to make their structures are also divided into other exactly the same as above, with the same components and features than the original.
Normal cells grow at a rate limited and remain in their respective areas. Muscle cells are formed and grow in the muscles, not bones, those of the kidneys do not grow in the lungs, etc.
These functions and this growth rate is determined by the DNA. Some cells have less time to live than others, such as intestinal cells have a life span of two weeks while red blood cells live for about three months.
Other cells will live for the lifetime of the person and only divide to replace themselves, this would be the case of bone cells that act when it comes to repair a fracture. The life of each group of cells is different and operate on it to make its DNA is different for each type of cell. Each cell is distinct.
The blood brings oxygen and nutrients necessary for cellular life and lists the products waste produced by the cells and transports them to the filtering and cleansing organs (kidneys, liver, lungs). Lymph is a colorless liquid that is composed mostly by lymphocytes, a type of white blood cells and travels through the body through the lymphatic vessels. The immune system is responsible for defending the body by white blood cells that seek and destroy bacteria and viruses.
leukocytes travel in the blood and lymph and accumulate in areas where infection is to surround and kill the bacteria or virus and, later, migrate through lymphatic vessels to lymph nodes. Lymph nodes are like clusters of grapes located in different parts of the body. Each node receives lymphocytes and this is where they are filtered and destroy bacteria, cell debris and worn themselves.
When an infection occurs, the lymph nodes may swell. If the infection occurs in a tooth, will ignite the neck. If the infection is in one hand, will be increased for those in the armpit. The lymph nodes also can be enlarged when a tumor. normal cell becomes a cancer cell to become due to a change or mutation in DNA. A Sometimes these cells, whose genetic makeup has changed, die or are eliminated in the lymph nodes. But other times, still alive and reproduce. cancer cells look different, either because its form has changed or because nuclei contain larger or smaller.
These cells are unable to perform the functions that correspond to cells belonging to that tissue. usually multiply very quickly, because they lack a mechanism for growth control. often are immature because they are multiplied in a very quick and do not have enough time to fully grow before splitting. In forming a large number of cancer cells, pile, press or to other organs and block them from performing their work. As
not limited to the original space where they form, and spread to other areas, are said to be invasive. tend to migrate to other places, through blood or lymph. The cells that are responsible for defending the body usually destroy them, thus separated, but if they survive may produce new growth in a different place, metastasis, and damage to other organs.
http://www.elmundo.es/elmundosalud/especiales/cancer/basicos.html
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