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

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When you enter the kitchen, you can smell your mother's hot baking cookies.

After staying for some time in the kitchen, you may notice that you cannot

smell the cookies anymore.

The nose has 'olfactory receptors' (smell detectors) in the nasal mucosa on

the roof of the nose. When an odour molecule dissolves in the mucosal fluid,

it stimulates the olfactory receptors which send signals to the brain.

Your brain interprets the type of smell you are experiencing.

Olfactory receptors are so sensitive that as few as eight odour molecules

dissolved in the mucosal fluid can trigger them.

Humans can detect some thousands of smells. But, this is nothing when

compared to the olfactory sensitivity of a dog. Your dog can detect millions of

smells!

The olfactory receptors are 'phasic’ or ‘dynamic’ receptors. This means that

when they continue to detect the same smell continuously, they decrease the

signals which they send to the brain. After a while, they slowly stop sending

signals about that smell to the brain.

This is why we stop smelling the same odor after a while.

When we move away from the source of that smell, the olfactory receptors

slowly regain their sensitivity to the odour for the next time you encounter it.

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Blood and Circulation

Why should we avoid sitting too long?

The human body is designed to be upright and active. We stand on our legs

and move around.

When we stand, the pressure in the blood vessels in the lower body is higher

than that in the blood vessels near our heart. Since the blood can't move

from higher pressure to lower pressure, we need some mechanism that

pushes the blood towards the heart.

Venous system of the leg – Some call it a 'SECOND HEART'.

There is a pumping system in our legs. It is provided by our leg muscles

which squeeze the deep veins between them when we walk or run, and that

causes the blood to be pushed up toward the heart.

Our veins have flaps, called 'valves' that stop the blood flowing backwards

after the muscles relax. These valves close when the muscles relax and that

stops our blood pooling in the lower legs.

When we sit for long hours, this pumping mechanism does not operate and

we feel heaviness in the legs. This can cause blood pooling and damage to

valves. People who sit for long hours should take regular breaks and move

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about for at least a few minutes each time.

Why do you sometimes feel dizzy when you get up?

If you are lying down and get up suddenly, you may feel dizzy or light-

headed for a few seconds. This is called ‘postural’ or ‘orthostatic’

hypotension.

It is caused by low blood pressure. Our blood vessels usually start to tighten

when we get up, to help maintain the supply of oxygen-rich blood to the

brain.

If we get up so suddenly that they do not tighten enough, less blood is

available to our brain and symptoms like mild dizziness or blurred vision may

happen.

This is common. But, if it occurs frequently, even when we get up more

slowly, then we should consult our doctor because it may be a symptom of a

treatable condition such as loss of fluids from the body, fever or heart

problems.

What are the Odd Artery and the Odd Vein in our

bodies?

Put your left hand on a table with palm facing up. Now, put your right index

and middle finger just above the wrist (1 or 11/2 inch above wrist line) a

little left to the center. Press lightly. Do you feel pulsations from an artery?

When your heart beats, it pumps blood in to arteries so whole body is

supplied with oxygen. All body tissues need oxygen to live.

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Circulation of blood:

Point #1: All arteries carry oxygenated blood and are shown in red. All

veins carry deoxygenated blood and are represented by blue.

Point #2: Arteries ALWAYS carry blood from heart to body and body organs.

Veins ALWAYS carry blood from body and body organs to heart.

Point #3: This is a simplified diagram. The arteries and veins in the body are

NOT separated left and right side. In most cases each artery is accompanied

by a related vein. e.g.: The artery which carries blood to the liver is called

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the 'hepatic artery'. It is accompanied by a 'hepatic vein' which carries blood

towards the heart.

Point #4: The direction of the arrows shows the blood flow.

In the image, PA represents the pulmonary artery. It is supposed to carry

oxygenated blood as it is an artery, but it carries de-oxygenated blood to the

lungs to get oxygen from the lungs.

PV means pulmonary vein. It is supposed to carry deoxygenated blood as it

is a vein, but it carries oxygenated blood to the heart.

Circulation: Oxygenated blood goes from left ventricle (LV) to the body and

organs. The body uses oxygen and gives off carbon dioxide into the blood.

This deoxygenated blood flows back to the right atrium (RA) and then to

right ventricle (RV).

It goes from there to the lungs to get rid of the carbon dioxide and get

oxygen.

Then, it travels from the lungs to the left atrium (LA) and to the left ventricle

(LV).

Then, the cycle repeats.

An Artery is a blood vessel that carries blood from the heart to the body

organs. Arteries carry 'oxygenated blood' (blood rich in oxygen). Your tissues need plenty of oxygen.

But, Yes - there is an odd artery!

It is called the 'pulmonary artery'. Though it is an artery and carries blood

from the heart to the lungs, it carries poorly-oxygenated blood.

Once the artery supplies oxygen to tissue, the blood becomes less

oxygenated. The de-oxygenated blood then travels through small vessels,

called venules, in the tissues. The venules slowly merge to become veins

which carry to blood back to the heart.

A Vein is a blood vessel that carries 'de-oxygenated blood' from body tissues

(that used up the oxygen) to the heart. .

What is this odd vein?

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It is called 'Pulmonary vein'. It carries blood from the lungs to the heart but,

unlike other veins, it carries blood that is rich with oxygen.

How does our body stop bleeding from a cut?

If there was no protective mechanism to stop the bleeding, we would bleed

continuously from any cut to our skin. When there is a cut, blood pours out

from the blood vessels under the skin.

Blood clotting near the damaged blood vessel.

There are tiny cells called 'platelets' in the blood. The platelets clump

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together when they are exposed to air in the cut, forming a loose plug.

Some chemical substances from the damaged tissue change a blood protein

called ‘prothrombin' to an enzyme called 'thrombin'. The thrombin, in turn,

changes a protein called 'fibrinogen' to 'fibrin', which forms a strong plug

over the leaking blood cells.

Did you know that you need Vitamin K and calcium for the blood to clot

properly?

Keep your supply of these essentials at proper levels by eating green, leafy

vegetables like spinach and broccoli as well as liver and cereals. For calcium,

drink milk regularly!

Which organs in our body get the most blood?

BLOOD SUPPLY PER MINUTE:

Liver: 1500 ml per minute.

The liver is the organ with the

highest blood flow per minute.

It is around 1500 ml/min. (Ref.

Ganong) The peculiarity of the

blood supply to the liver is that

2/3 of the blood is venous blood

and it is from the digestive tract

(stomach, intestine, colon,

spleen). The remaining 1/3 is arterial blood from the hepatic artery.

The liver participates in important body functions like storage, synthesis,

modifying harmful substances to less harmful ones and cholesterol

metabolism.

BLOOD SUPPLY BY WEIGHT:

Kidney: 420 ml per 100 gm

weight per minute.

If we take the weight of the

organ into consideration, the

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kidney receives more blood than the liver. The kidney is the organ which

filters blood and absorbs vital substances from the filtered fluid and forms

urine. Urine contains nitrogenous waste that needs to be eliminated from the

body.

Whole blood in our body passes through the kidneys once within every 5

minutes to ensure that the blood is clear of nitrogenous wastes.

Why does your heart beat faster when you run?

When you run, your body needs more oxygen and energy, especially the leg

muscles. The heart has to pump faster to satisfy this increased demand.

During running, hormones called epinephrine and norepinephrine are

released from a gland called the 'adrenal gland' in our body. These hormones

increase our heart rate and the strength of its contractions.

When you finish running, the heart rate of a healthy person should return to

normal with just a few minutes of rest.

Why is Blood red in Color?

Our blood contains many cells; red blood cells, white blood cells and

platelets.

The red blood cells are dumb-bell shaped when looked at from the side and

look like discs from the front. There are millions of them in each drop of

blood.

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The red blood cells contain a protein called 'hemoglobin'. This hemoglobin is

a combination of 'Heme', which binds oxygen to it and a 'globin chain' which

is the protein part of the hemoglobin.

Hemoglobin contains elemental iron in the center.

The hemoglobin helps to carry oxygen from your lungs to the your body

tissue and then carry the carbon dioxide back from the tissue to your lungs

so that it can be breathed out.

When blood goes to your lungs and gets oxygen, it becomes bright red. You

will see this bright red blood in arteries. Once the blood gives the oxygen to

the tissues and takes back the carbon dioxide, it becomes dark red or bluish.

You will see this dark red or bluish-red blood in veins.

What do I need to know about Hemoglobin?

The normal hemoglobin content in blood is about 16 grams per deciliter in

men and about 14 grams per deciliter in women.

16 grams is about .56 (a little over half) of an ounce.

14 grams is about .49 (just under half) of an ounce.

A decilitre is about 3.4 (just under three and a half) fluid ounces.

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0.3 grams of old Hemoglobin is destroyed and 0.3 grams of new hemoglobin

is synthesized (produced) every hour.

Each red blood cell has 97% of hemoglobin by dry weight.

Hemoglobin synthesis is very important and it relies on you eating food which

contains iron. Meat, green vegetables and enriched cereals are rich sources

of iron. You should get enough of the right foods every day to ensure the iron

you need for making hemoglobin.

People are likely to get 'anemia' when the level of hemoglobin decreases in

their blood.

Who are the universal donors

and universal recipients?

Doctors test blood types before giving blood from the blood banks to

patients. They do this to prevent any incompatibility reactions in patients

because these may cause death.

There are 4 blood groups:

1) A

2) B

3) AB

4) O

The blood group names are based on the 'antigen' present on the red blood

cell. If a person has an 'A' antigen on their red blood cell surface, he belongs

to the 'A' blood group.

Like the antigen is on the red blood cells, antibodies are present in the liquid

part of the blood (called 'plasma'). These antibodies are different to the

antigens. If a person is in 'A' blood group, he has 'b' antibodies in his plasma.

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During a transfusion, the donor’s antigen on his red cells reacts with the

antibody present in the patient’s plasma. If the donor has blood group A

(which has antigen A) and their blood is given to a person with blood group B

(who has antibody 'a' in their plasma), the red cells of donor and the

antibody of the recipient will stick together and cause an allergic reaction.

The picture shows you that a person with blood group O is a universal donor.

He can give blood to anybody because he has no antigen.

Someone with blood group AB is a Universal Recipient; they can receive

blood from any donor because he has no antibodies to react with the

antigens of the donor’s red cells.

Why do we feel 'pins and needles' are in our arms

and legs?

When you have been sitting on a couch with your both feet up for a long

time, maybe watching TV, you might feel some prickly sensations in your

feet. Or, perhaps you have fallen asleep while sitting at your computer and

your head fell onto your hand and pressed it against the desk. Then, you got

that same feeling in your hands. We call this sensation, ‘pins and needles’.

It results from the blood vessels in your feet or hands being unable to get

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sufficient oxygen because of the abnormal position of your limbs.

Your head pressing against your hand reduces the flow of blood through the

blood vessels there.

When you legs are raised and unmoving for a long period, less blood reaches

your feet and so they get less oxygen for the cells in them.

These positions also cause pressure on nerves in those areas and, when they

cannot transmit their impulses properly, you get the feeling of pins and

needles.

When you take off the pressure on your blood vessels or nerves, that pins

and needles feeling will slowly go away.

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Breathing and Related Topics

Why can't people breathe and swallow at the same

time?

Food travels from the mouth food into the food pipe on its journey to our

stomach.

Air that we breathe in goes from our nose goes into the wind pipe on its way

to our lungs.

Both pipes are next to each other in the neck. But the food won't go into the

wind pipe. Why?

First image: Breathing opens the epiglottis. Air goes into trachea

(wind pipe - brown colored tube)

Second image: Swallowing the food closes the epiglottis and food

goes into esophagus (food pipe - dark pink tube)

In the above picture, you will see the food pipe and the wind pipe next to

each other. And there is a thin membrane called 'epiglottis' which closes the

wind pipe when we swallow the food doesn't enter the wind pipe.

If a person is eating, talking and laughing at the same time, food can get

stuck in the trachea and make the person choke.

So kids, be careful while eating!

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Cells

Are all cells in our body the same?

The cell is the basic building block of the body. A simple cell has some

common features:

A cell membrane

A nucleus

Cytoplasm (the contents of a cell, excluding the nucleus), mitochondria

(the part of the cell which generates energy for cell) and

Endoplasmic reticulum (a network of membranes where proteins are

produced).

All of the cells in all the organs in your body have this basic structure but

there are many different types of cells with special features that help them

do the special task which each particular type of cell does.

Heart muscle: The heart muscle is

made of 'cardiac muscle cells'. Each

cardiac muscle cell has fine lines called

striations in the cytoplasm (the part of the

cell outside of its nucleus).

The cells are connected with each other so

that the heart can smoothly contract as a

single unit.

Neuron: A neuron is a nerve cell. It has

a round cell body with many thin fibres projecting from it called dendrites.

These dendrites receive impulses from the other neurons.

Each neuron also has an elongated thick fiber called an 'axon'. The signal

received from dendrites is passed on to the next cell through the axon.

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Liver cell: A Liver cell is a hexagonal (six-sided) cell with lots of

mitochondria (that part of the cell which generates energy for the cell) and

an endoplasmic reticulum (network of membranes where proteins are

produced).

These liver cells specialize in protein

synthesis, glycogen storage (your Liver

stores glucose as 'Glycogen'. If you miss a

meal, it slowly breaks down glycogen to

glucose and releases it into your blood),

producing bile from simple chemical

compounds (bile synthesis), storage of

Vitamin A and other vital substances, and converting toxic substances to less

toxic and soluble substances so they can be excreted from the body.

Which specialized part of a cell is called the

'Powerhouse”?

Our body is made up of millions of cells. These cells are the same in basic

structure but they differ in certain aspects. Every cell in the body needs

energy for its metabolic activities like respiration, storage, synthesis and

maintaining a normal

internal environment.

Mitochondrion -

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The energy factory of the cell.

The organelle (specialized part of a cell) that produces the energy for a cell is

called a Mitochondrion ('Mitochondria' are more than one Mitochondrion).

They have round or oval bodies, about one micrometer wide and 2 to 4

micrometers long. A micrometer is one millionth of a meter. A meter is about

36.4 inches.

Mitochondria create 'ATP' (Adenosine Tri Phosphate) molecules, which are

used as energy in the cell, from cellular citric acid.

Can the cells in our body talk to each other?

Yes. That’s surprising, isn’t it?

How can a cell talk to other cells?

We have a mouth and words to communicate with each other.

Cells can communicate with each other by means of 'cell signaling':

1. They communicate directly by contact

2. They release some short-lived chemicals which communicate with

neighbouring cells

3. They release some long-lived chemicals which communicate with cells

that are some

distance from the cell

which created the

chemical in the body.

Direct contact:

(Signalling through cell

junctions) See the image

here. Two cells that are next

to each other connect by

means of junctions so

chemicals pass through this

channel and transfer the

message. Example: Cells in

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our heart (heart muscle cells). It helps in contracting heart muscle to pump

the blood.

Short lived chemicals (called Paracrine signalling): Short

lived chemicals just act on a few other cells near them. They are rapidly

destroyed. Example: Cells in the nerve (nerve cells) and brain cells

(neurons). The chemical substance called 'acetylcholine' is released by one

cell and binds to nearby cells to start the desired action.

Long lived chemicals: (Called Endocrine signaling) Some

chemicals are released by cells in one organ. They get into the blood stream,

go to one or more different organs in the body and act there. Example:

Insulin is secreted by the pancreas, and then travels through the blood to the

liver as well as muscle and fat cells in the body. Then, it acts on many tissues

like muscle, liver and fat cells.

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Digestion and Nutrition

Why are some of our teeth shaped differently from

others?

If you have a baby brother or baby sister, look at their teeth. How many do

they have?

A baby’s teeth are called 'deciduous teeth' because they fall out (like leaves

from a deciduous tree) when they get a bit older. Babies usually start getting

these teeth by the age of 5 months. By their third birthday, they will have

about 20 deciduous teeth.

Remember that they are not strongly fixed into the jaw, so they start falling

out from the age of 7.

Once they start falling, new permanent teeth will replace them. Most of the

permanent teeth will appear by the age of 17 years. A person will usually

have a total of 32 teeth.

Incisors: 8 (4 upper and 4

lower)

Canines: 4 (2 upper and 2

lower)

Premolars: 8 (4 upper and

4 lower)

Molars: 12 (6 upper and 6

lower)

Why do the 4 types

of teeth have

different shapes?

We eat different types of

food including fruits, meat, bread and vegetables. They have different

textures and consistency. So, we need different types of teeth to deal with

different types of foods.

Our incisors are chisel-shaped for cutting and biting, like when we eat an

apple or banana.

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Our canines are dagger shaped for grasping and tearing like when we eat

chicken.

Our premolars are broad with a flat or bumpy surface for crushing and

grinding like when we chew meat that was torn apart by our canines.

Our molars are like our premolars; broad with a flat or bumpy surface for

crushing and grinding like when we chew meat that was torn apart by our

canines.

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

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

bones.

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

C.

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

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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 do we have to chew our food properly?

Your parents have said that you must chew your food well, right?

They are absolutely right; you need to chew the food properly before

swallowing it and for proper digestion.

Why?

That’s because chewing your food breaks the food into many smaller pieces

which increases the surface area of the food.

That greater surface area means that, after you swallow it, much more of the

food’s surface can be worked on by your gastric juices and that helps with

better digestion.

Your saliva has an enzyme called 'salivary amylase' which starts digesting the

complex carbohydrates from your food while it is still in your mouth.

There is also another enzyme called 'Lingual lipase'. This helps your body to

start digesting the fat in your mouth itself.

Your saliva also lubricates your food and helps you to swallow it more easily.

When you chew properly, you are helping your digestive system to digest

your favorite food easily! You use less energy processing the food and get

more value from the food you eat!

Why do sportsmen eat bananas

during their strenuous activity?

Banana is a delicious fruit that can be used in many ways. You can eat it

regularly. You might have seen many athletes eating bananas and wondered

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whether they could help you during your school sports?

Bananas are rich in sugars, including

glucose, fructose and sucrose.

Glucose and fructose provide instant

energy. They don't need much effort

to digest as they are just simple

sugars and are quickly absorbed into

your blood stream.

Sucrose is a complex carbohydrate

and needs a little more effort to

digest. It will become available a little later and be an energy source after the

glucose and fructose are exhausted.

Bananas have about 450 mgs of potassium which is very useful during

exercise to replace the potassium you lose when you sweat. Potassium helps

with your blood pressure and smooth operation of your muscles. It also helps

your body to change glucose to glycogen who gives you energy.

Why can't some people eat dairy products?

Dairy products contain a type of sugar called 'Lactose' which is a

'disaccharide'. That means it contains two simple sugar molecules (Galactose

and Glucose) attached to each other.

If someone’s intestine does not have a special enzyme called 'Lactase', they

cannot digest lactose. Lactose cannot be absorbed in its original form. The

lactase, which is produced by intestinal brush border cells, breaks the lactose

into two simple sugars which the body can use.

For people with lactase deficiency, the undigested lactose is fermented by the

bacteria in their intestine. They feel like their abdomen is bloated, they feel

pain and may start to break wind.

Some people have this intolerance since they were babies. Others may get it

when they are adults.

If a person gets gastroenteritis (infection of the intestinal epithelium and

diarrhea), they will have a temporary lactase deficiency because of damage

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to the epithelial covering of their internal organs.

Where do we get our energy if we

skip our breakfast and lunch?

Sometimes we rush to work or school and, because of our busy schedule, we

often miss our breakfast or lunch, or both.

So, where do we get the energy to do our work if we don't eat a regular

meal?

1) Breakdown of stored glycogen: Our liver stores glucose (sugar) in

the form of ' Glycogen'. When our blood glucose levels drop, our liver

starts breaking down the glycogen into glucose and slowly releases it

into the blood. But, these glycogen stores won't last long.

2) Breakdown of stored fat: Next, our liver starts synthesizing

(producing) glucose for our body by the process called

'gluconeogenesis' from fatty acids and glycerol that were stored in our

body’s fat deposits.

3) Ketone bodies: Then, the liver starts producing another major energy

source called 'ketone bodies' from those fatty acids.

If people fast for a long time, their muscle protein starts breaking down to

supply amino acids to the liver for the glucose synthesis. So, it is advisable to

eat your food at the usual times and not skip meals.

Why do you hear growling sounds when you are

hungry?

Those sounds are called 'hunger contractions' or 'hunger pangs'. When your

stomach is empty, it contracts significantly. This produces that noise and

mild discomfort in your stomach area.

These hunger pains occur after 12 to 24 hours of fasting and when your

blood glucose is low.

Once you eat some food, these hunger contractions disappear. Food moves

down to the stomach by 'peristaltic movement'. The hunger sensation is

controlled by our brain (hypothalamus area).

Peristaltic Movement - Peristalsis: Contraction of muscles around the

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digestive tract which gently moves food to the stomach after it has been

eaten and prevents it from going back up to the mouth.

What causes bad breath?

Bad breath from the mouth is

called ' Halitosis' by doctors.

Millions of bacteria live and flourish

in our mouths. Bad breath can

come from diseased gums and

decaying deposits of waste

material in our mouths.

It is more common at night

because we produce less saliva

and our mouths are dry, so the

bad material is not flushed down to

our stomach. That’s why you feel

the need to brush your teeth and rinse your mouth early in the morning.

Did you know that about seventy percent of bad breath comes from the back

part of the tongue? That happens because we cannot get our tongue clean in

that area. So, the bacteria build up there in deposits from postnasal drip and

dead epithelial cells that flake off surfaces in the mouth and stick there. All

these increase the bad odor.

Diseases of the mouth, including gum diseases, are another cause of bad

breath. Food particles that get stuck in between our teeth when we eat food

and decay if we don’t brush and floss make the problem worse.

Here are a few simple steps to reduce possible embarrassment from bad

breath:

1) Brush after eating any food

2) Clean your tongue gently with a tongue cleaner, especially the back

part of the tongue

3) Drink more water, especially in hot weather ,to keep your mouth moist

and wash away any left over particles

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4) Have regular dental check-ups. Dentists are very good these days at

keeping their patients comfortable and pain-free.

Is belching inevitable after eating?

Not every person belches after eating food.

Those who do, have swallowed some air while eating. So, drinking gassy

soda drinks with your food could cause you to belch as well.

Some adults have 'acid reflux disease', where the stomach acids are pushed

into the lower oesophagus (food pipe), and this can cause them to belch.

Air that is collected will be pushed out as a belch.

If you ask your doctor about how to

stop belching, he will say:

1) Eat food slowly and chew

properly.

2) Don't drink gassy liquids with

your food.

3) Avoid swallowing air if you drink

through a straw.

If you belch at the dinner table, just

say 'excuse me!' It is good manners. In some countries, belching after eating

food may be thought of as a sign of satisfaction.

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Skin and Related Topics

Why do we get pimples?

Pimples are small bumps on the face which most people get, especially

during puberty. Most teenagers get them and many become depressed

because of the effect on their appearance.

What causes pimples?

We all have tiny ‘sebaceous’ glands under our skin. They produce an oil-like

substance called 'sebum'. This oil is secreted through thin ducts on to the

skin and keeps the skin smooth.

But, dirt and flaking dead skin cells can block the tiny openings of the ducts

in the sebaceous glands. As more sebum is produced, it builds up in the

glands and pimples develop.

Other factors which affect their development may include fatty food,

genetics, stress, hormones and drugs etc.

Why does our skin wrinkle in our old age?

Our skin is the biggest organ in our body. It is divided into three layers; the

epidermis, dermis and subcutaneous layer.

The dermis has two connective tissue proteins called 'Collagen' and 'Elastin'

which are present around the cells and support them.

Collagen gives tensile strength to the skin which is what allows it to be

stretched or twisted.

Elastin helps your skin to regain its shape after stretching and pulling. It also

supports the cells in the dermis layer of our skin.

With old age, we have less 'Collagen' and 'Elastin' in our skin, so the skin

loses much of its tensile strength and lines and wrinkles increase.

What is the largest organ of the human body?

Our skin is the largest organ of the human body. It is estimated to weigh as

much as sixteen percent of your body weight.

The surface area of an adult’s skin is about two square meters

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(approximately twenty-one and a half square feet).

The thickness of your skin varies with different body parts. It is thinner in

areas like eyelids and the tip of your nose, but thicker in areas like the palms

of your hands and the soles of your feet.

Your skin has many functions:

It protects your body’s internal organs.

It helps to keep many germs and other harmful things from affecting