Teacher Training College 2008 - EDI

"In questions of science,authority of a thousand is not worth the humble reasoning of a single individual"

The cell is the structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. Some organisms, such as most bacteria, are unicellular (consist of a single cell). Other organisms, such as humans, are multicellular. (Humans have an estimated 100 trillion or 1014 cells; a typical cell size is 10 µm; a typical cell mass is 1 nanogram.) The largest known cell is an unfertilized ostrich egg cell.

There are many different cells in the human body. The different cells in the body are generally grouped into tissues that have similar properties. The four main groups of tissues in the body are, muscular, nervous, connective, and epithelial.