What makes cells multiply

But some cells, such as skin cells or blood cells are dividing all the time. When cells become damaged or die the body makes new cells to replace them. This process is called cell division. One cell doubles by dividing into two. Two cells become four and so on. The diagram below shows cells dividing. Stem cells provide a pool of dividing cells that the body uses to restock damaged or old cells. They have the potential to develop into different cell types in the body.

When a stem cell multiplies, the resulting cells may remain as stem cells. But under the right conditions, they become a type of cell with a more specialised function.

For example a muscle cell, red blood cell or brain cell. Stem cells occur in the body in various places and stages during our lifetime. In the embryo, they give rise to all the different tissues and organs of the body. In adults each type of stem cell is usually only able to develop into a few specific types of cell.

For example, adult stem cells in the bone marrow, known as haematopoietic stem cells, usually only give rise to different types of blood cell. Scientists now believe that stem cells might play a role in the development of cancer. They think that some tumours develop from faulty stem cells. This has led to the idea of cancer stem cells, which scientists have now identified in a range of cancer types. The types include bowel, breast and prostate cancer as well as leukaemia.

A special case of this is the monthly replacement of the cells lining the uterus in pre-menopausal women. Wound healing requires that cells in the area of the damage multiply to replace those lost. Viral diseases such as hepatitis may also cause damage to organs that then need to replace lost cells. Replacement of the cells that make up blood. Red blood cells carry oxygen to tissues. White blood cells such as B and T lymphocytes are part of the body's immune system and help to ward off infections.

Most of these cells have very short lifespans and must be constantly replaced. The precursors of these cells are located in bone marrow. These precursors, or stem cells, must reproduce at a very high rate to maintain adequate amounts of the blood cells. In order for this to happen, the following must occur: The genetic material, the DNA in chromosomes, must be faithfully copied. This occurs via a process known as replication. The organelles, such as mitochondria , must be distributed so that each daughter cell receives an adequate amount to function.

The cytoplasm of the cell must be physically separated into two different cells. Sections included on this page: Normal Cell Division Cancer Cell Division Cell Division Summary Normal Cell Division There are several safeguards built into the cell division process to assure that cells do not divide unless they have completed the replication process correctly and that the environmental conditions in which the cells exist are favorable for cell division.

Among others, there are systems to determine the following: Is the DNA fully replicated? Is the DNA damaged? Are there enough nutrients to support cell growth? By the time you are an adult, you will have trillions of cells. That number depends on the size of the person, but biologists put that number around 37 trillion cells.

Yes, that is trillion with a "T. In cell division, the cell that is dividing is called the "parent" cell. The parent cell divides into two "daughter" cells. The process then repeats in what is called the cell cycle.

Cells regulate their division by communicating with each other using chemical signals from special proteins called cyclins.

These signals act like switches to tell cells when to start dividing and later when to stop dividing. It is important for cells to divide so you can grow and so your cuts heal. It is also important for cells to stop dividing at the right time. If a cell can not stop dividing when it is supposed to stop, this can lead to a disease called cancer. Some cells, like skin cells, are constantly dividing. We need to continuously make new skin cells to replace the skin cells we lose. Did you know we lose 30, to 40, dead skin cells every minute?

That means we lose around 50 million cells every day. This is a lot of skin cells to replace, making cell division in skin cells is so important.

Other cells, like nerve and brain cells, divide much less often. Depending on the type of cell, there are two ways cells divide—mitosis and meiosis. Each of these methods of cell division has special characteristics. One of the key differences in mitosis is a single cell divides into two cells that are replicas of each other and have the same number of chromosomes. This type of cell division is good for basic growth, repair, and maintenance.

In meiosis a cell divides into four cells that have half the number of chromosomes. Reducing the number of chromosomes by half is important for sexual reproduction and provides for genetic diversity. Mitosis is how somatic — or non-reproductive cells — divide. Somatic cells make up most of your body's tissues and organs, including skin, muscles, lungs, gut, and hair cells.

Reproductive cells like eggs are not somatic cells. In mitosis, the important thing to remember is that the daughter cells each have the same chromosomes and DNA as the parent cell.

The daughter cells from mitosis are called diploid cells. Diploid cells have two complete sets of chromosomes. Since the daughter cells have exact copies of their parent cell's DNA, no genetic diversity is created through mitosis in normal healthy cells.

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