Name: Animated Introduction to Cancer Biology (Full Documentary)
Uploaded: 2014-04-16T18:54:20.000Z
Duration: 12 min 8 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

The human body is a complex and wondrous living machine

Basic passive voice

like any machine our bodies are composed of smaller parts that work together

the various tasks that are performed each day

such as breathing eating and digesting food

and the movement of our blood are performed by specialized structures

organs. Examples of organs include the lungs

All of these organs and other body parts like our skin and muscles

are made of smaller living units called cells.

of how many cells work together to perform a specialized task

the cells in our lungs work together to allow us to take in oxygen from the air

and get rid of waste products such as carbon dioxide.

our lungs are composed of many millions of cells

that begins when one of the cells in an organ or tissue

becomes damaged or altered in a way that causes it to break free

from the normal controls that allow our cells to work together in harmony.

can cause the same kinds of problems in a body

that a defective part would cause in any other type of machine.

A normal cell will divide only when it receives a chemical signal telling it to

these signals are interpreted in the nucleus

and the cells reproduce their genetic information and divide into two

through a process called my mitosis. Cancer cells do not obey this rule

and will divide even if they do not receive appropriate signals

in addition to the signals that normal cells receive telling them to divide

they are also told when to stop dividing. This prevents too many cells from being

is a highly ordered process. This is a critical issue

in cancer because cancer cells do not obey

or require normal signals for division. This can lead to the formation of a

that piles up and may form a tumor. Also different from normal cells

is the ability of cancer cells to continue dividing indefinitely

is that no matter what their job is in the body they all have the same general

or brain are all similar in their overall appearance

even though their jobs are quite different. just as the organs that the former made

cells themselves are composed of smaller parts that help them perform their jobs.

these smaller structures are called organelles.

Of particular importance in cancer is the organelle known

as the nucleus. The nucleus can be thought of as the brains of a cell

it contains the information that acts as the blueprint for

each and every one of us just as a manual would contain instructions to

Specifically this information is contained within the chromosomes

individual units have information are called genes.

At a chemical level genes are made of deoxyribonucleic acid

or DNA. All of our cells contain the same set of information

It is only how the information is used that makes them different.

For example cells in the lungs use different bits of the blueprint to do

changes to the DNA cause some of the genes to fail to perform

or to do their job in a way that causes problems for the affected

In short all cancers are thought to result from changes to DNA

that alter critical genes and change the behavior of the affected cells.

If a change occurs to the nucleotide sequence

it is like having the letters of a word changed.

An alteration in a gene is called the mutation

How do all these changes occur? There are actually a number of different things

Examples include chemicals that can be swallowed or inhaled

Such as those found in chewing tobacco and cigarette smoke

and radiation from the Sun or artificial sources like

a tanning bed Sometimes mutations occur without

any known external cause They just happen.

Certain genes make products that lead cells to reproduce

This would be equivalent to the gasoline system in cars

The genes that are responsible for making cells divide

are known as Proto-Oncogenes. Changes in these normal genes

lead to the production of Oncogenes The result may be cells that divide in

absence of proper signals It is the equivalent

of a gas pedal that is stuck in the on position

Genes whose products function as the equivalent of cellular breaks

also exist  As a group these genes are known as tumor suppressors

Humans have two copies of each gene one inherited from each parent

If a single copy of a tumor suppressor is damaged

the other copy is usually able to stop the cell from behaving abnormally

This would be like losing either the front

or rear brakes of a car.  The car may be damaged

but would still be able to stop and but if the second set of brakes is damaged

the car would not be able to stop. Just as the cell would not be able to stop

if both copies of the tumor suppressor genes are damaged