101 Facts About the Human Body by Radhika Venkata - HTML preview

PLEASE NOTE: This is an HTML preview only and some elements such as links or page numbers may be incorrect.
Download the book in PDF, ePub, Kindle for a complete version.

- 80 -


"101 Facts About the Human Body" by Radhika Venkata

Page 81 of 107

Health and Related Topics

Is sun light enough for your daily dose of Vitamin


Many doctors advise their patients to get at least five to ten minutes of

sunlight if they are light skinned, and thirty to sixty minutes if they are dark

skinned people, every day.

Sunlight stimulates the Vitamin D synthesis in the skin and most people may

get enough vitamin D from this source with that amount of exposure.

But, people are afraid of getting skin cancers through exposure to the ultra-

violet rays from the sun.

Vitamin D is very essential for strong bone development. New research says

that Vitamin D helps to prevent cancer. It is sometimes called the 'sunshine


People from cold areas like Alaska and northern Canada, who see less

sunshine, probably won't get enough vitamin D because of less exposure to

the sun.

Exposure to the sun without sun screen for 30 minutes can synthesize

approximately 10,000 to 20,000 IU of vitamin D in the skin. This is more

than adequate when compared to the daily requirement.

But, you should always use an appropriate sunscreen preparation when you

are in the sun.

Each person needs 400 to 600 IU (International Unit) of vitamin D through

their diet per day and 800 or more IU/day if sun exposure is inadequate.

Some people that cannot get their Vitamin D requirement from the sun, use

vitamin D supplements like cod liver oil or vitamin tablets.

You should consult your doctor or pharmacist for advice about what might be

the most appropriate ways for you to ensure that you get the Vitamin D

which your body requires.

Should you take water soluble vitamins every day?

Your body needs vitamins every day for body metabolism, cell growth and

cell repair. You just need them in minute quantities, but they have an


Copyright 2009 All rights reserved

- 81 -


"101 Facts About the Human Body" by Radhika Venkata

Page 82 of 107

essential role in your body's health.

Vitamin A is needed for good vision

Vitamin B helps respiration, building red blood cells and normal activity

of your nervous system

Vitamin C can assist the healing of damaged tissues

Vitamin D is believed important for maintaining the strength of your


Vitamins are divided into two groups:

Fat soluble vitamins: These include the vitamins A, D, E and K. They are

soluble in fats, so they need a complex mechanism for absorption in the

small intestine. Once they are absorbed into the body, they can be stored in

the body organs like your liver. A healthy human body can use fat-soluble

vitamins it has stored for a few days if fresh supplies are limited, so a daily

supply is not essential.

Water soluble vitamins: These include the Vitamin B-Complex; includes

Thiamine(B1), Riboflavin(B2), Niacin(B3), Pantothenic acid(B5),

Pyridoxine(B6), Biotin(B7), Folic acid(B9) and Cobalamin(B12), and Vitamin


These are soluble in water, so they are easily absorbed in the small intestine.

They cannot be stored in the body; you need to get a supply of these

vitamins every day.

So kids, ask your mother to give you green vegetables, liver, meat and citrus

fruits for a good supply of the B-complex group of vitamins and vitamin C.

You can get fat-soluble vitamins from carrots, eggs, dairy products, liver and

green vegetables.

Consuming too much of some vitamins, maybe in the form of supplements,

can be risky so always check with your doctor before adding supplements to

your diet to ensure that you really need them.

Why is cigarette smoking bad?

Cigarettes contain substances, including nicotine, tar and carbon monoxide


Copyright 2009 All rights reserved

- 82 -


"101 Facts About the Human Body" by Radhika Venkata

Page 83 of 107

that will damage our health.

Nicotine is an addictive compound which causes damage to the cilia in the

respiratory tract. These cilia and the mucus in that area are vital for trapping

dust particles and germs so they don’t get to our lungs.

People that have damaged cilia get frequent lung infections.

Nicotine raises our blood pressure and also increases our risk of getting

osteoporosis which causes our bones to become brittle and fracture very


Tar damages the lung tissue and is a cause of lung cancer.

Carbon monoxide binds with the haemoglobin in our blood and reduces the

amount of oxygen which it can carry. So, smokers can become short of

breath from only a small level of activity and find more strenuous exercise

much more demanding.

Is sneezing a good thing?

Yes, it is. When the mucosa in your nose gets irritated by strong smell, pollen

or dust etc., you sneeze to get rid of whatever irritating things landed on the

nasal mucosa.

This is a simple protective mechanism to get rid of foreign bodies from there.

How we sneeze: When our nasal mucosa gets irritated, it sends signals to

the brain stem through the sensory nerves of your Trigeminal nerve.

The brain stem tells the muscles of the face, chest and diaphragm to


First, you inhale deeply, and then push the air out with force through your

nose. This pushes the irritating substance from the nasal mucosa.

You might expel air at a speed up to 160 miles per hour from your nose

when you sneeze. Your body may vibrate and your eyes close while you are

sneezing to reduce any bad effects of that rush of air.

But remember to always cover your nose when you sneeze! People who have

a cold, fever or a viral infection push germs into other people’s faces when

they sneeze.


Copyright 2009 All rights reserved

- 83 -



"101 Facts About the Human Body" by Radhika Venkata

Page 84 of 107

Covering your nose is safer, and it’s also good manners!

Are Hiccups dangerous?

There is a big, flat muscle called the 'diaphragm' below the lungs and heart

which separates the chest from the abdomen.

The diaphragm is very important in our breathing. It contracts to increase

the space in the thorax (chest) and reduces the pressure in the thorax so

that air is sucked into the lungs. This is called 'inspiration'.

When the diaphragm relaxes, it pushes itself upwards so the space in the

thoracic cavity decreases and the air in the lungs is pushed out. This is called


If the diaphragm is irritated by a full stomach or for any other reason, it

contracts suddenly and air rushes into the lungs. While this ‘inspiration’ is

happening, the epiglottis (an elastic flap of cartilage that acts as a lid over

our windpipe when we are swallowing) closes suddenly.

The expelled air strikes the epiglottis surface and produces the 'Hic' sound in

our hiccups.


Copyright 2009 All rights reserved

- 84 -



"101 Facts About the Human Body" by Radhika Venkata

Page 85 of 107

These hiccups usually go away in a few minutes. If they are still there for,

say, more than 48 hours, get further advice from your doctor.

Why do you get Vaccinations (shots) from your


Vaccinations are injections against common diseases that people can get.

Different vaccinations will protect us against particular diseases.

When we get an infection, our body fights against it and gets rid of it by

producing a protein substance in our blood (called an 'antibody') that fights

against the germ protein (an antigen).

If we are infected by the same type of germ later on, our body remembers it

from the earlier infection and stops further spread. (See the question; ‘How

germs are killed in our body? ')

But, this does not happen with some infections which are more dangerous.

So, scientists produce antibodies in laboratories against these germs that can

be safely injected into us before we have that first attack.

Cool, huh?

You should be thankful to Dr. Edward Jenner, the British physician who

discovered a vaccine against 'smallpox', which was once a deadly disease.

Why is Cancer compared to a


What is cancer? Cancer is when a normal cell

changes to an abnormal cell and grows in the

body to be a mass of cells.

Why is cancer is compared to a crab? Because

of the way that a crab moves.

When you go to the beach, look for a crab

under the rocks. You will see that it moves

sideways because of the way that its leg joints

are arranged and its tough exoskeleton.

When a crab moves fast, it looks like it is


Copyright 2009 All rights reserved

- 85 -



"101 Facts About the Human Body" by Radhika Venkata

Page 86 of 107

moving in all directions at once!

That is like the way that cancer

moves (spreads) through someone’s

body; in all directions.

Also, 'carcinos' means crab in Greek

and carcinos is a type of cancer.


Copyright 2009 All rights reserved

- 86 -


"101 Facts About the Human Body" by Radhika Venkata

Page 87 of 107

Men, Women and Related Topics

Why are men affected by baldness more than women?

Usually, men will show signs of baldness after the age of 30. Their hair line

slowly recedes as they lose some hair. There are both genetic and hormonal

reasons which play a role in male pattern baldness.

Men have hormones called 'androgens', including 'dihydrotestosterone'.

Dihydrotestosterone is responsible for male-type baldness.

There will be thinning of a woman’s hair as she ages but it will not be like

typical male pattern baldness.

Do men have a uterus (the sac that holds a

developing baby)?

Yes, all males have a rudimentary uterus called the 'prostatic utricle' near the

prostate, but it is really just a small sac that is not any use.

When the fetus develops normally in the mother's belly, its organs develop

slowly as the fetus approaches full term.

In a female baby, the uterus and the fallopian tubes develop from a tube-like

structure called the 'paramesonephric duct'.

With male babies, most of this duct disappears because of the hormonal

influence. But, both ends of the paramesonephric duct remain as small,

useless sac-like structures.


Copyright 2009 All rights reserved

- 87 -



"101 Facts About the Human Body" by Radhika Venkata

Page 88 of 107

Paramesonephric duct - Part of it is like the uterus in a woman.

The end part of the duct will become a non-working, small sac-like structure

attached to the prostate and called the 'prostatic utricle'. It is only

rudimentary and equivalent to the uterus in a female.

The beginning part of the paramesonephric duct becomes another small sac-

like structure attached to the testes.

What determines the sex of a person?

A baby is conceived after the fertilization of an ovum from the mother by a

sperm from the father. When the sperm fertilizes the ovum, a zygote

(fertilized cell with two sets of chromosomes) is formed. This zygote gets

chromosomes from both the ovum and the sperm.

All ova only have X chromosomes, but sperm can have either X or Y

chromosomes. A baby always gets one X from the mother. The baby's sex

depends on whether the sperm which fertilizes the ovum has X chromosomes

(so it will become a female) or Y chromosomes (so it will become a male).


Copyright 2009 All rights reserved

- 88 -




"101 Facts About the Human Body" by Radhika Venkata

Page 89 of 107

Why are children’s and women’s voices

softer than males?

Our voice is produced by the 'larynx' which

is part of the trachea (wind pipe). It has

two thin membranes called 'Vocal cords'.

These vocal cords are protected by the

cartilages that form the 'Adam's apple' in

the neck.

When the air from the lungs is pushed

against the closed vocal cords, they

vibrate in a rhythmic manner to produce

the sound. This sound is converted to

actual words and speech by our pharynx,

larynx and the oral cavity (space behind our lips).

The vocal cords are controlled by the laryngeal muscles which open, close

and alter the length of the vocal cords which affects the loudness and pitch of

the sound produced.

Children and women have thinner and shorter vocal cords which vibrate more

when compared to the thick and long vocal cords of men. The more

vibrations; the sweeter the voice. After puberty, a boy's voice changes as his


Copyright 2009 All rights reserved

- 89 -



"101 Facts About the Human Body" by Radhika Venkata

Page 90 of 107

vocal cords become thicker and longer.

Can some diseases affect only boys and men?

Yes, there are some diseases that can only be seen in the male population.

When a baby is born, it gets genes from both parents. The sex of the baby is

determined by the 'Y chromosome' from the father.

In the picture, the mother has two sex chromosomes (X and X). The father

has two sex chromosomes (X and Y).

The mother produces ovum that carry only X chromosomes.

The father produces sperm that may carry either X chromosomes or Y


If an ovum (all X chromosomes) combines with an 'X' sperm, the baby will be

a girl.

If an ovum combines with a 'Y' sperm, the baby will be a boy.

So far, so good!

But there can be problem if the X chromosome that the boy gets has a

disease carrying gene. There is no other X gene in boys (like girls), so they

will be affected by that particular disease.


Copyright 2009 All rights reserved

- 90 -



"101 Facts About the Human Body" by Radhika Venkata

Page 91 of 107

In our example, let’s say that the mother is a carrier of the gene for the

disease hemophilia (Hemophilia is a bleeding disorder where the affected

person bleeds longer time after an injury when compared to a normal

person) on one of her X chromosomes. If she conceives a boy, there is an

approximately fifty percent chance of him getting that carrier gene and the



Copyright 2009 All rights reserved

- 91 -


"101 Facts About the Human Body" by Radhika Venkata

Page 92 of 107

Our Brain and Related Topics

Why does the brain use a larger

area for hands than our whole trunk?

When you read the question, ' Which part of the brain determines your

personality? ', you see that sensations from the whole body are received by

our parietal lobe by the 'sensory cortex' and all of our body movements are

controlled by the frontal lobe through our 'motor cortex'.

The most important feature of the 'motor cortex' is that the muscles which

make fine movements are represented by a larger area in the cortex than the

rest of the body. The whole face is represented by almost half of the motor

area. The whole trunk is represented by a much smaller area because the

muscles of the trunk only perform crude movements, unlike the face.

Our thumb and face muscles are represented by larger area than the muscles

of the trunk or the arm.

This representation is called 'motor homunculus'.


Copyright 2009 All rights reserved

- 92 -



"101 Facts About the Human Body" by Radhika Venkata

Page 93 of 107

Why cannot our brain feel pain?

Though the brain is the main center for the sensation of the pain from

different parts of the body, the brain itself doesn't have any pain receptors.

If somebody pricks you with a pin on your hand, you will feel pain. You feel

pain when you get a belly ache. Pain receptors in all other parts of the body

send signals to the brain so we feel the pain.

But, if a neurosurgeon (brain surgeon) opens up the skull and cuts the brain,

we don't feel any pain because the brain doesn't have any nerve receptors to

‘feel’ the pain.

So, why do we get headaches?

A headache comes from the blood vessels, nerves and meninges (meninges


Copyright 2009 All rights reserved

- 93 -



"101 Facts About the Human Body" by Radhika Venkata

Page 94 of 107

are the brain coverings) surrounding the brain, not from the brain itself.

These have many pain receptors.

Why can't we move our ears towards a sound like

animals do?

The outer part of the human ear gets sound waves and directs them into our

ear canal.

Animals can move their ears backwards and even upward to collect sound

waves but we can’t.

This picture shows the

three main external

ear muscles in

humans. You can see

that they are

rudimentary (not well

developed). Some

people have a little

more control of these

muscles and can

wiggle their ears a

little bit to the front

and back

independently without

any scalp or forehead


Which part of our Brain determines our personality?

People are very different in their emotions, personality and social behavior;

the so-called 'higher intellectual functions' or 'cognitive functions'.

The front part of the brain is called the 'frontal lobe'. Our frontal lobe controls

cognitive functions like:




Copyright 2009 All rights reserved

- 94 -



"101 Facts About the Human Body" by Radhika Venkata

Page 95 of 107

Social Behavior



Problem solving


Motor movements: All your body movements are controlled by the frontal

lobe through the 'motor cortex/motor area'.

Functional areas of brain: Imaginary Blue lines are drawn to show

frontal, parietal, occipital and temporal lobes separately.


Copyright 2009 All rights reserved

- 95 -


"101 Facts About the Human Body" by Radhika Venkata

Page 96 of 107

Other parts of brain and how they affect you :

Cerebrum: Consists of the frontal lobe, parietal lobe, occipital lobe

and temporal lobe.

Frontal lobe: Its functions are listed above.

Parietal lobe: Sensations from your body by 'sensory cortex/sensory


Occipital lobe: Vision

Temporal lobe: Hearing

Cerebellum: Controls body balance and co-ordination

Medulla: Controls involuntary actions like your heartbeat, blood

pressure and breathing etc.


Copyright 2009 All rights reserved

- 96 -



"101 Facts About the Human Body" by Radhika Venkata

Page 97 of 107

Other Questions

Is the right side of our body bigger than the left


Most people’s bodies are not exactly symmetrical (both sides exactly the

same). The right side of the body is often a little bigger than the left.

Scientists think that the reason for this difference is more usage of the right


To test this, ask for permission

from your parent to make prints

of your hands on a piece of

paper. They may like to help

you with the experiment.

Take a large sheet of white

paper and put it onto an area

which won’t be harmed if any of

the color gets on it. Rub some removable paint on to the palms of your hands

and then press them on to a large sheet of paper.

Now you can check if you have one hand slightly bigger than the other.

Why are our fingers not equal in size?

Look at your fingers. All five of them are:

different lengths

different shapes

This helps us to do many different tasks like:

Picking up a small needle from the floor

squeezing a grape or

holding and playing a musical instrument.

These tasks would be much harder or even impossible if our fingers were all

the same.

Our thumb is a very powerful finger with a movement called 'opposition'.

Your thumb would not be as useful if it was the same as your other fingers.


Copyright 2009 All rights reserved

- 97 -



"101 Facts About the Human Body" by Radhika Venkata

Page 98 of 107

Why do some people have flat feet?

If you have a baby sister or baby brother, look at the soles of their feet. They

look flat. Now, sit down, then lift your feet and look at your own soles.

They have a little gap (arch) on the instep where the surface of your foot

doesn’t touch the ground.

Your baby sister or baby brother has flat feet.

Compare the arch of the bony skeleton in normal and flat feet.

Take a large sheet of white paper, wet the sole of your foot and the baby’s

foot. Take prints on the paper. Compare both of them and see how much of

each foot’s bottom surface comes in contact with the paper.

Don’t worry, most babies have flat feet but, once they start walking, the

bony arch develops in their feet.

What happens if the flat foot persists?

About twenty percent of all adults have flat feet to some degree because

their arches have not fully developed. These people may feel pain every time

they walk.

It is important that they visit their doctor so that they find out what help is

available for their condition.

Why do we stop growing at a certain age?

When a baby is born, it is about twenty inches long. By the age of eighteen


Copyright 2009 All rights reserved

- 98 -



"101 Facts About the Human Body" by Radhika Venkata

Page 99 of 107

to twenty years, he or she may be three times as tall or even bigger. Most

young people grow about two inches taller each year from when they are

three years of age.

What affects your growth?

A. Well balanced nutrition - You need enough protein and vitamins from

what you eat.

B. Genes - the genetic material that we inherit from our parents.

C. Hormones - Three main hormones affect our growth – the ‘growth

hormone', 'thyroid hormones' and 'sex hormones'.

Growth hormones are produced by the 'pituitary gland which is at the bottom

of your brain.

1) Thyroid hormones are from the 'thyroid gland' which is in your neck.

2) Sex hormones (androgens and estrogens) from the 'ovaries’ in a

woman or the ‘testes' in a male.

These hormones help us to grow until puberty. This is called ‘linear growth’.

After puberty, the 'growth plates' of your long bones fuse and no longer

respond to these hormones. So, we stop growing after the growth plates are


Copyright 2009 All rights reserved

- 99 -



"101 Facts About the Human Body" by Radhika Venkata

Page 100 of 107


Why do we feel sleepy after a meal?

We don't feel like studying after a good meal and a delicious desert! Why is


After a meal, your blood sugar level will increase. This turns off some special

neurons in the brain called 'orexin neurons' which help to keep you awake.

As their functioning is reduced, we start to feel sleepy after a heavy meal.

(Reference article: Published in June 1, 2006, Neuron. “Denis Burdakov of the University of Manchester and his colleagues pinpointed that glucose

inhibits neurons which are key to regulating wakefulness”.)

Other researchers have other explanations about this. Some are:

1) Increased blood sugar levels cause the release of the insulin from our

pancreas. The insulin causes tryptophan (an aminoacid in protein) to

enter our brain cells. Tryptophan produces 'serotonin', a chemical

transmitter in brain that causes sleep.

2) After a heavy meal, the blood circulation to our brain slows and more

is diverted to our intestines. This causes a slowing of our brain


Why do your grandparents have gray hair?

Hair has two parts; the shaft and the root. A

layer of cells, called the 'hair follicle', surround

the root. Hair follicles have matrix cells from

which the root grows and melanocytes which

have melanin in them. The melanocytes

transfer melanin into the matrix cells and in

turn grow as hair. Our hair color depends on

the amount of melanin in this area. As people

grow older, the number of melanocytes in the

hair follicle reduce, so there is less melanin.

This causes colored hair to become gray.


Copyright 2009 All rights reserved

- 100 -



"101 Facts About the Human Body" by Radhika Venkata

Page 101 of 107

Do we need our belly button?

We all have a little depression on our lower belly which we call our 'navel' or

'belly button'.

Do you know what it is and why it is there?

While a baby is growing in its

mother's belly, it cannot breathe

or eat by itself. The mother sends

all the nutrients and oxygen which

her baby needs to the baby

through a tube-like connection

called the 'umbilical cord' which

connects the mother's placenta

and her baby's belly.

When the baby is born, it no

longer needs this cord. So, the

obstetrician carefully cuts the

umbilical cord near the baby's

belly and leaves a small stump.

This slowly dries up and falls off

the baby's belly. The place where

the tube from the mother had

been connected forms the

depression which we grow up

calling our belly button.

Does the human body generate electricity?

Yes, the human body does produce electricity. But, it’s not the same as the

electricity that you know is in the electrical wires around your home.

The charge that is carried in the body (especially in nerve cells) is in the form

of 'action potential'.

This is how an electric impulse is produced in a nerve cell:


Copyright 2009 All rights reserved

- 101 -


"101 Facts About the Human Body" by Radhika Venkata

Page 102 of 107

Usually the nerve cell is slightly negative inside and slightly positive outside.

When an impulse is needed (maybe to send a signal to a muscle to contract

or to send a signal to a nearby neuron), a small channel opens up in the


This channel lets the sodium and potassium ions move in and out of the cell,

which changes the charge inside and outside the cell, and an electric impulse

is generated. The electric impulse opens up more channels further down the

membrane and changes the electric charge there. So a message is passed

down the membrane as an electrical impulse.

This continuous movement of electric impulses in our nerve cell is very

important for our body to work properly.

Why do people shiver in cold weather?

Humans are warm blooded creatures which means that we can usually keep

our body temperature at about 98.6 F. (F is short for Fahrenheit) with a

variation of about one degree either way. If we don't maintain our body

temperature in this range, we feel uncomfortable and may become ill.

When we feel cold, signals from our skin go to the hypothalamus, which is a

part of the brain that controls shivering. Muscles of the body start shivering

which produces some heat and that, in turn, raises our body temperature.

Muscles will become tired after shivering to produce heat for some time. So,

you need to move to a warmer area or take other action that will warm you

up as soon as possible.

Which of our five fingers is most important?

Humans have 5 fingers on each hand:

1) Thumb

2) Index finger

3) Middle finger

4) Ring finger

5) Little finger


Copyright 2009 All rights reserved

- 102 -




"101 Facts About the Human Body" by Radhika Venkata

Page 103 of 107

When we count our fingers, we start with the thumb and count across to the

little finger. So, the thumb is 1, the index finger is 2, the middle finger is 3

and so on.

Now, pretend for a second that you don't have a


1) Try to hold a pen and write on a piece of

paper ...

2) Try to hold a piece of fruit and eat it ...

3) Try to comb your hair ... all without using your thumb.

You will find it very difficult to do all these tasks. Right?

The thumb is a very important finger because it has a

function called 'opposition’; the movement by which your

thumb can touch the pads of the other four fingers. This

powerful movement of the thumb is a vital part of many

actions that your hand does.

This opposition movement is also seen in some animals like

apes, gorillas and chimpanzees that also need to hold and pick fruits.

Why are some Twins not identical?

Most people think that twins are supposed to be identical in all aspects, but

that is not true. The degree of similarity between twins depends on the type

of fertilization between the ovum and the sperm.

The usual type of baby develops when one ovum from the mother and one

sperm from the father forms a 'Zygote' which develops into a baby.

But, the story is different with twins.

Twins are of TWO types:

1. Monozygotic twins

2. Dizygotic twins.


Copyright 2009 All rights reserved

- 103 -



"101 Facts About the Human Body" by Radhika Venkata

Page 104 of 107

Monozygotic twins (identical twins):

Here one zygote is formed in the normal way, but the zygote divides into two

halves. These two halves

develop into two babies.

Here the twins are of the

same sex and look similar

in features.

Dizygotic twins

(fraternal twins):

Here two zygotes are

formed from two ova and

two sperms separately.

Each zygote develops into

a different baby. Here

there is no division of

zygote. Each zygote grows into a baby. These twins may be the same or

different sexes and may not resemble each other because they are from

completely different zygotes.

Does our body have Living tissue with NO Blood


All the living tissue in our body needs blood supply to survive. Tissue gets its

nutrition and oxygen from blood and carbon dioxide diffuses back into the

blood. Simply put, the tissues will die without a blood supply.

But, not the cornea. It is a very thin and transparent membrane in the front

and center of the eye. It covers the pupil. If there are blood vessels are in

the cornea, it becomes hazy and white and we cannot see. To maintain the

essential transparency, the cornea has no blood vessels.

Though the cornea doesn't have a single blood vessel, it is rich in nerves. So

any small scratch on the cornea is much more painful than you might expect

from the size of the lesion.

The cornea is still a living tissue, so it needs nutrition and oxygen. It gets


Copyright 2009 All rights reserved

- 104 -


"101 Facts About the Human Body" by Radhika Venkata

Page 105 of 107

them from aqueous humor (fluid that is in contact with the cornea in the eye)

and lacrimal fluid (tears).

The cornea is very important for focusing the object you are looking at on the

retina. It works along with the lens to focus the object.

Why is it easy to wake people in early mornings?

While a person is sleeping, he sleeps in a rhythm. There are two types of

sleep which repeat one after another until the person wakes up.

1) Non-Rapid Eye Movement sleep (NREM Sleep): This is deep sleep

and people are hard to awaken during it. Their heart rate is slow, their

body temperature decreases, there are no eye movements and muscle

tone is high.

2) Rapid Eye Movement Sleep (REM Sleep): This is light sleep and

people in this state are easy to awaken. Their heart rate and

respiration rate increase. There are rapid eye movements and their

muscles are relaxed. In this stage, their brain is active and the body is


So, why is a person is easy to wake up in the morning?

Usually sleep starts with the NREM stage, then a REM stage follows. This

cycle repeats about five times during one night. As early morning

approaches, the duration of the REM stages increase and they are more likely

to be in this state in the morning rather than the NREM state. So, it is usually

easy to wake up a person in the morning.


Copyright 2009 All rights reserved

- 105 -


"101 Facts About the Human Body" by Radhika Venkata

Page 106 of 107

A Few Words from the Author

I wrote this book as a simple and interesting, but accurate publication about

various aspects of the human body, using my answers to many medical

questions from my two kids, in a way that is understandable for everyone.

I want this book to help you and other parents answer their children's

questions on medical matters in a way that helps them to be comfortable

with their own bodies and encourages them to look after their health.

I made every effort to put colorful pictorial illustrations to explain the medical

content. I shall consider this work very rewarding if every reader finds it

useful and also helpful in teaching their kids a few fun facts about human


My other ebooks are 'Your Diet and Cancer' (pdf format) and 'Absolute

Beginners Guide to CGI' (Windows only), which can both be obtained from

the eBookwholesaler Member that supplied this book to you.

My sincere thanks to Tom Hua, the Owner of ebookwholesaler, for accepting

my work, '101 Facts About the Human Body - Simply Explained and

Illustrated!', for publication and John Williams for helping me in editing and

compiling the content of my ebook.

I would like to thank my family and kids for encouraging me to write this


Also, I want to thank you, my readers, for buying my book and making the

effort to help your children understand and look after themselves.

Dr Radhika Venkata



Copyright 2009 All rights reserved

- 106 -


"101 Facts About the Human Body" by Radhika Venkata

Page 107 of 107

Another eBookWholesaler Publication


Copyright 2009 All rights reserved

- 107 -