The human body is one of the most amazing machines in the world. It is made up of thousands of parts all working together. Each group of parts is called a system. You could not live with only some of the systems, you need them all to stay alive. So many people are suffering and dying because of their lack of knowledge about how the body responds to attacks within its systems.
brain looks like a mass of gray jelly and is very soft. The human brain is quite
large but wrinkled which makes it compact. The brain is the body's control center.
It is involved with what we do, what we think, as well as what we feel and
remember. The brain has three main sections: the cerebrum, the cerebellum, and
the brain stem. The cerebrum fills the entire upper part of the skull, about
nine-tenths of a personís entire brain. The cerebrum is divided into four parts called
lobes. This is the ďthinking brainĒ in which language, memory, sensations, and
decision-making are located.
THE EYE The eye is an important part of the body. The eye tells you when danger is near. The colored part of the eye is called the iris. The retina at the back of your eye is made from millions of light cells called rods and cones, which send signals to the brain along the optic nerve (optic means for eyes). If you didnít have a retina you would not be able to see. Your eye works in both darkness and light. The black part of the eye is called the pupil. The pupil opens up when it is dark, and closes when it is light. The eye is filled with jelly and fluid. There is a lens called a cornea at the front of the eye, and another lens behind the cornea.
THE HEART The human heart is a muscle about the size of your fist. Its job is to pump blood around the body at the rate of 10 liters a minute. The heart beats around 3 billion times in an average person's lifetime. Your heart beats more than 100,000 times every day and about 42 million times every year. The heart rests for a moment between heartbeats. The total amount of time the heart rests in one day adds up to more than 5 hours. An adults heart will pump about 10,000 quarts or 2,500 gallons of blood each day.
THE LUNGS The lungs supply the body with oxygen by inhaling air. Without oxygen most body cells would only live for a few minutes. Cells use oxygen to break down food into energy, carbon dioxide, gas, and water. This is called respiration. When you inhale in air, it is drawn in through the nose and mouth and travels down a large tube called the windpipe. The windpipe divides into two bronchi, one going to each lung. Air passes through these and then through a series of smaller and smaller blood vessels. Oxygen from the air seeps through the walls of the alveoli into blood. The oxygen is picked up by red blood cells and carried around the body. If your diaphragm contracts too quickly, you inhale in air too quickly and hiccup.
The digestive system helps our body break down the food we eat so that it
can be absorbed into the bloodstream and into the different parts of our body.
you swallow your food, the food goes down through the
esophagus into the stomach. Here it churns around for up to four hours while it
is broken down into chyme, a soupy liquid. It is then gradually squeezed out of
the stomach through a long coiled tube called the small intestine. Here
the parts of food that you need are absorbed into the blood and the remainder
passes on into the large intestine. About 24 hours after swallowing, the
remaining waste, called feces, is pushed out of the body.
THE KIDNEYS The kidneys look like purplish-brown beans and are about the size of an adultís fist. If the kidneys fail to function, water and waste build up in the body, eventually causing death. Two healthy kidneys contain a total of about 50 gallons (190 liters) of blood. Pressure forces the blood through the small blood vessels into the kidney. The poisons are filtered out, and they become urine. The rest of the blood is recirculated back into the blood stream.
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