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Human body Building blocks

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					Human body

Building blocks
Every part of your body is made of
tiny building blocks called cells, which
fit together like bricks in a wall. Cells
are so small that hundreds could fit
on the point of a pin.
                      The nucleus                     DNA is
                      controls the rest              stored in
                      of the cell.                    the cell
The inside of                                        nucleus.
a cell is packed
with a kind of
living jelly called




                                                                          NA
cytoplasm.                                                                                The skin on your
                                                                           D              fingertips is made
                                                                                              of lots of small
                                                                                                         ridges.



                                                                                 Inside a cell
                                                                                 In the middle of a cell
                                                                                 is its control centre – the
                                                                                 nucleus. The nucleus sends
                                                                                 instructions to the rest of
                                                                                 the cell, telling the cell
                                                                                 what chemicals to make.

                                                                 Before a cell divides,
                                                                 the nucleus splits to
                                                                 make two nuclei.

The outer skin, or
membrane, stops
things leaking out.             Tiny generators
                                provide cells with
                                power.

                                 Making new cells
               A cell makes new cells by dividing.
               The two new cells are half the size,
              but they soon grow back. Millions of                                                                 The new cells pull apart
                                                                                                                    and separate, but they
            your cells die every second, but millions                                                                    usually stay close
                      of others divide to replace them.                                                                        neighbours.
8
                                 How many cells are there in the human body?
                                                                                             Building blocks
How big are cells?                                                       than 2000 de
                                                                    More              ad
Cells are too small to see with the                                                                ski
                                                                                                      nc
naked eye, but scientists can                                                                           ell
                                                                                                                 sf
photograph them through




                                                                                                                   ell
powerful microscopes.




                                                                                                                       o ff
The cells on your skin




                                                                                                                            y   ou
are about a hundredth




                                                                                                                                   whil
of a millimetre wide.




                                                                                                                                       e you read this sen tenc
                                                                                                                                                               e.
                                                                                                                The cells on
                                                                                                              the surface of
                                                                                                        your skin are tough
                                               A microscope can                                   and flat. They overlap to
                                            zoom in to see the                                   form layer of armour that
                                         tiny, flaky cells on the                            protects the softer cells below.
                                     ridges of
                                 a person’s fingerprint.




                                                                                             Cells make tissue
                                                                                             Your body contains
                                                                                             hundreds of different
                                                                                             types of cells that do
                                                                                             different jobs. Cells of
    Fat cells are     Many blood cells           Nerve cells are thin    Bone cells make
   bubble shaped.    are red. They carry          and wiry. They         your bones hard.    the same type usually
   They store fat    oxygen around the             carry electrical      They live in tiny   group together to form
  under your skin.          body.                      signals.           holes in bones.
                                                                                             tissue. Fat, muscle,
                                                                                             bone, and nerves are
                                                                                             types of tissue. Blood
                                                                                             is a liquid tissue.

                                                About 100 trillion.                                                                         9

				
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posted:10/10/2012
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