4.1: Introduction to Cell Division

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Rosanna Hartline
West Hills College Lemoore

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Introduction to Cell Division

Cells divide sometimes. This means that one cell splits into two cells. Humans would not exist without cell division. Every human starts life as one single cell, the result of egg and sperm fusing during fertilization. Then, as the human develops, a

One cell is shown with an arrow next to it representing the process of cell division. On the other end of the arrow are two cells nearly completely separated from each other, ending the cell division process.

series of cell divisions occurs to make an embryo. One cell becomes two cells, two cells divide to produce four cells, four cells divide to produce eight cells, eight cells divide to produce sixteen cells, and so on. By the time a human is a fully grown adult, the human is composed of trillions of cells! Cell division does not end when a human is an adult since cell division is necessary to repair injuries and to replace old and worn out cells. Cells divide in humans for a variety of reasons including:

embryonic development
growth (infant --> child --> adolescent --> young adult --> adult)
regeneration of dead and worn out cells
repair of injuries (e.g. broken bone, broken skin, etc.)
cell differentiation (cells change from stem cells to specific cell types)
abnormal cell division (benign tumors; cancers)

Another reason cells divide is to produce gametes, specialized sex cells that produce offspring (egg/ovum and sperm/spermatozoa). Although production of gametes requires cell division, the process of producing gametes is distinctly different from the type of cell division discussed in this chapter. See Chapter 21: Reproductive Systems to learn about cell division for gamete production (meiosis).

Attributions

"Mitotic Prophase" by LadyofHats is in the Public Domain
"Mitotic Cytokinesis" by LadyofHats is in the Public Domain