First Children's Encyclopedia by Dorling Kindersley - page 104

How many cells are there in the human body?
Human body
102
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.
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
your cells die every second, but millions
of others divide to replace them.
The skin on your
fingertips is made
of lots of small
ridges.
Building blocks
The nucleus
controls the rest
of the cell.
Tiny generators
provide cells with
power.
The outer skin, or
membrane, stops
things leaking out.
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.
The new cells pull apart
and separate, but they
usually stay close
neighbours.
Before a cell divides,
the nucleus splits to
make two nuclei.
DNA is
stored in
the cell
nucleus.
D
N
A
The inside of
a cell is packed
with a kind of
living jelly called
cytoplasm.
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