31-03-2012, 12:09 PM
HUMAN BODY SYSTEMS
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INTRODUCTION
Who are we?
We can learn the answer to this question by
observing, hypothesizing, experimenting, and
analysing. We are complex living beings in a
complex, contradictory, ever-changing world. We
know that we do not understand everything about
ourselves, but by using this scientific method
we can keep learning more and more.
Without our bodies we are nothing. A person
cannot exist without a body. In this book you
can see pictures of some basic structures of the
human body. You can also begin to see the
interconnections between the different parts of
the body in order to understand how the body
functions.
We should warn you that there are two serious
misconceptions that you may get from this book.
One misconception is that any part of the human
body exists in a static state. Actually everything
in the body is in a constant state of movement
and change. It is constantly being broken down
and rebuilt. Every thing is in the process of
becoming something else. Actually, we are not
made of things, but of processes. Thus, on the
left-hand pages, we have briefly discussed some
of the processes and functions of the structures
seen on the right-hand pages.
SKELETAL SYSTEM
Our skeleton consists of all our bones, teeth,
cartilage, and joints. Some bones protect our
internal organs. Some bones provide a
framework for the body (just as the spokes of an
umbrella provide a framework). Some bones
contain red marrow that produces blood cells and
yellow marrow that also stores fat.
MUSCULAR SYSTEM
There are three kinds of muscles:
Skeletal muscle
These muscles are
attached to bones. They are
also called ‘voluntary
muscles’ because we can
consciously contract them.
Smooth muscle
These are found in the walls
of the digestive tract, urinary
bladder, arteries, and other
internal organs. They are
‘involuntary muscles’ because we
do not consciously control them.
Cardiac muscle
These are the muscles
of the heart.Their contraction
is involuntary and continues
in a coordinated rhythm as
long as we live.
DIGESTIVE SYSTEM
Every cell in our body does work. Work requires
energy, which is supplied by the food we eat. Food
also supplies the small molecules that are the building
blocks for cell maintainance, growth, and function.
RESPIRATORY SYSTEM
Through respiration we exchange gases with our
environment. Our cells require a continuous
supply of oxygen (O2) in order to obtain energy
from food molecules. Cells would also die if they
were not able to get rid of the carbon dioxide
(CO2) they produce.
The 3 Processes of Gas Exchange:
1. In our lungs, O2 passes from the air into our
blood, and CO2 passes from our blood into the
air. Some water vapour is also released into the
air.
2. Our circulatory system transports O2 and CO2
to and from all the parts of our body. Haemoglobin
molecules in our red blood cells transport O2.
3. Cells take up O2 and release CO2