How does our Digestive System Work? + more videos | #aumsum #kids #science

AumSum was enjoying a big meal of fruits and bread when he suddenly wondered,

"How does our digestive system work?"

His curiosity sparked, he shrank and slipped inside his own mouth.

All around him, teeth were grinding food into smaller pieces.

Streams of saliva splashed down, making the food soft and mushy.

AumSum tried to keep his balance but slipped and slid down the throat.

>> >> Powerful muscles pushed him forward like waves,

carrying him through a long tunnel called the esophagus.

Suddenly, he was dropped into a huge chamber, the stomach.

The walls around him moved like giant muscles,

squeezing and squashing the food again and again.

From the walls oozed strong digestive juices filled with acid and enzymes.

The juices bubbled and frothed,

turning chunks of food into a thick soupy liquid called chyme.

Then, the stomach squeezed the mixture into narrow winding tubes, the small intestine.

Here, tiny finger-like shapes called villi covered the walls.

AumSum watched in amazement as nutrients seeped through the villi into the blood.

But, the powerful squeezing of the intestines tossed him back and forth.

Next, he was carried into the large intestine.

Here, water was absorbed, leaving the rest thicker and drier.

AumSum tumbled along with the waste as strong muscles pushed everything forward.

At last, AumSum was pushed out, landing safely outside the body.

He smiled proudly.

How do these make honey?

No idea.

To make honey, the worker honeybee sucks nectar from flowers

and stores it in its honey stomach.

Once the worker bee returns to the hive,

it vomits the nectar into a processor honeybee's mouth.

Ew.

In the processor bee's mouth and stomach,

an enzyme called invertase is added to the nectar.

Invertase breaks some nectar into simple sugars like glucose and fructose.

Huh?

Then it vomits the partially converted nectar into another processor bee's mouth,

who also adds more invertase, helping break down more nectar.

>> >> This process goes on until most of the nectar is converted into simple sugars.

Then the mixture of simple sugars is stored in the honeycomb.

At this point, the mixture is still watery.

Hence, the bees flap their wings,

which evaporates water and thickens the mixture to eventually form honey.

Why can't dogs eat chocolates?

Cuz I would love to have all the chocolates for myself.

All right.

Now listen.

Chocolates and other cocoa products contain a toxic component called theobromine.

Oh.

The darker the chocolate, the more theobromine, and the more it is harmful.

But I eat chocolates, and I'm completely fine.

Our body quickly metabolizes the theobromine.

Thus, it is not quite harmful for us.

However, dogs process theobromine much more slowly.

So, it stays in their bodies for a longer time, resulting in vomiting, diarrhea,

etc.

Moreover, if large quantities of chocolate are ingested by the dog,

the effects can be much more severe.

The heart rate of the dog might be twice its normal rate,

increasing the blood flow.

This can prove to be lethal to the dog.

How are pearls formed?

It's a top secret.

I can't reveal it.

All right, I'll tell you.

Pearls are the result of a biological process within living sea creatures like an

oyster as it protects itself from foreign substances.

Wow.

The oyster looks beautiful.

Indeed, an oyster has two shells.

Inside the shells there is an organ called mantle.

Mantle covers and protects all the internal organs of the oyster.

Whenever any foreign substance like a grain of sand

or parasite makes its way into the oyster

and gets stuck in between the shell

and mantle.

The mantle's a natural reaction is to cover

that foreign substance to protect the oyster's internal organs.

For this, the mantle secretes a mineral called nacre around the foreign substance in

layers.

Over time, layer upon layer of nacre leads to the formation of a pearl.

Oh.

>> Why are flamingos pink?

Wait, I'll explain.

A baby flamingo is not pink.

It is actually born with gray feathers.

So does it spray paint itself with pink color?

>> No.

Flamingos get their pink

or orange color from their food

which is mainly algae

and shrimps.

These organisms contain carotenoids.

Carotenoids are reddish-orange colored pigments.

When a flamingo eats algae and shrimps, its liver extracts the colored pigments.

The pigments are then absorbed by fats.

These fats start depositing in the flamingo's growing feathers

which eventually cause the flamingo to turn pink

or orange.

Now, an interesting fact is

that we also eat fruits

that contain carotenoids such

as carrots,

apricots, mangoes, etc.

But we do not eat enough of these fruits for them to affect our

skin color.

What is a tsunami?

I don't know.

Tsunami is a series of giant waves.

In Japanese, tsunami means harbor wave.

And in Chinese?

Oh, just listen.

A wave is created when energy passes through water.

Moving air or wind provides energy to water forming regular waves.

Hmm.

Oh.

>> While on the ocean floor, when a tectonic plate suddenly slides beneath the other,

the resulting earthquake releases a tremendous amount of energy.

This energy spreads outward from the point of earthquake triggering waves

that can form tsunami.

Initially, these waves are small in size, but they travel at great speeds.

>> Oh.

However, when the waves approach the shore,

the rising seabed obstructs the energy of waves.

This slows down the speed of waves,

but the energy flux must remain constant leading to an increase in the height

of waves,

thus resulting in tsunami.

Why do we shiver when we feel cold?

Cuz our body is on vibrate mode.

Oh, no.

We shiver because our body tries to keep us warm.

Our core body temperature is about 37° C or 98.6° F.

Oh.

A part of our brain called hypothalamus controls and maintains the core body temperature.

Will it also maintain my physique?

Oh, please listen.

Usually during cold months, the temperature is quite low.

Hence, if we have not worn any warm clothes, we feel cold.

Our body temperature starts to decrease.

This decrease in temperature is instantly detected by our hypothalamus.

Thus, it sends signals to our muscles to contract

and relax rapidly making us shiver.

This rapid contraction and relaxation of our muscles generates heat.

This heat warms our body, thus helping us maintain our core body temperature.

What is color blindness?

A color festival.

No.

Color blindness or color deficiency is a vision problem.

Now, our eyes have light-sensitive cells called rods and cones.

Can I put ice cream on these cones?

Oh.

You are just unbelievable.

Rods are responsible for black and white vision.

They do not detect color, whereas >> >> cones detect color.

There are three types of cones.

One cone perceives red light, another perceives green, and the third perceives blue.

>> >> Together, these cones help us to see the whole spectrum of colors.

Now, in some cases,

when one or more types of cones do not work properly,

it causes color blindness.

People with such deficiency have a difficulty in distinguishing between certain colors or shades.

For example, in red-green color blindness, the apple tree may appear like this.

Topic: Pins and Needles.

Why do limbs fall asleep?

Cuz they're tired.

It basically happens because of nerves.

Through nerves, our brain communicates with our limbs.

Wow.

Nerves are so amazing.

Yep.

However, when we cross our legs or sleep on an arm for very long,

we apply pressure causing the nerve pathways and its surrounding arteries to squeeze.

Hence, the nerves do not work properly

and the arteries cannot supply required nutrients to the nerves.

As a result, the signals sent by our brain do not reach the limb.

Thus, we cannot move it.

So, we say that our limb has fallen asleep.

Also, in some situations, some of these squeezed nerves stop sending signals,

while some fire hyperactively.

This gives us the sensation of pins and needles.

Topic: Vaccines.

How do vaccines work?

Huh?

By giving extreme pain?

Not at all.

Vaccines train our body to fight against the dangerous disease-causing pathogens.

Oh, really?

Do they have a training academy?

Oh, you are just unbelievable.

Huh?

>> Vaccines often contain weakened or dead pathogens.

When they are injected into our body, they just trigger the immune response,

but do not cause fully fledged diseases.

Our immune cells recognize these pathogens as foreign invaders, and thus produce antibodies.

These antibodies kill the pathogens.

Also, the immune cells record the information about the pathogens

and the way they were killed.

Hence, in case in the future, a similar strong pathogen enters our body,

our immune cells remember and easily identify that pathogen.

They produce the required antibodies to fight it back.

Thus, we remain healthy.

Topic: Earthquakes.

>> >> What causes earthquakes?

I, me, and myself.

Yeah, yeah, you show-off.

An earthquake is violent shaking of the Earth's crust.

The Earth's crust is a hard outer covering made up of many pieces called

tectonic plates.

These plates are always moving.

However, the motion is very slow.

In a year, they move only 2 to 5 cm.

My hair grows faster than their movements.

Huh?

>> Absolutely.

Mostly, when these tectonic plates move,

they brush against each other without causing great damage.

However, sometimes they get stuck and cannot easily slide against each other,

but the plates still keep pushing, thus creating pressure.

Eventually, the pressure builds up

so much that one of the plates suddenly moves above the other

or they may crash into each other,

causing the crust to shake violently.

>> Huh?

Thus, creating an earthquake.

Oh.

Topic, rain.

Huh?

>> >> Why does rain smell?

Maybe it applies a special perfume.

Nah.

Rain is just water and water doesn't have any smell.

Yeah, dude.

So, what's that smell?

Huh?

>> smell which frequently accompanies the first rain after a dry weather is scientifically

called petrichor.

It basically comes from plants and bacteria called actinomycetes, which live in the soil.

Now, during a long dry spell,

the plants release oils into the soil to block other seeds from germinating,

thus reducing competition for water.

Oh.

Whereas, the actinomycetes produce a chemical called geosmin.

Now, when rain hits the ground, it brings up the oils and geosmin,

which then mix with air.

The combination of this geosmin along with the plant oils form the smell

which we receive after the rain.

Topic, tooth decay.

What causes cavities?

A black sketch pen.

Nah.

Huh?

Our mouth contains billions of bacteria which live on our teeth, tongue, etc.

Most of these bacteria are usually harmless.

>> Oh.

Just like me, right?

Yeah, yeah.

Now, listen.

A tooth consists of enamel, dentin, and pulp.

>> Huh?

Enamel is mostly made up of minerals.

Dentin is a layer underlying the enamel, whereas pulp has blood vessels and nerves.

Oh.

>> Now, when we eat foods containing sugars,

some of these bacteria feed on the sugars producing acid.

This acid starts to dissolve the minerals of the tooth enamel, causing tooth decay.

Usually, our saliva restores these minerals, thus preventing further decay.

Huh?

But if we continuously eat sugary foods, then our saliva cannot keep up,

causing the bacteria to pass into the dentin and then eventually into the pulp,

thus creating cavities.

>> >> Topic, paper cuts.

Why do paper cuts hurt so much?

It is because paper hates us.

No.

Huh?

>> We use our fingers and hands to sense our surroundings.

Hence, they have more number of nociceptors than any other parts of our body.

Nociceptors are pain receptors that respond to change in pressure, temperature, etc.

Now, the edges of the paper are not smooth, but are rough or jagged.

Oh, they are like a saw.

Absolutely.

Hence, sometimes when we rub our hands or especially fingertips against the edges,

it cuts them like a saw, activating the nociceptors.

Now, as there are more nociceptors on our hands, we feel more pain.

In addition to this,

the paper cut might also have fragments of paper containing chemicals

which may irritate the skin

and thus increase the pain.

Topic, pneumonia.

What causes pneumonia?

The letter P.

Nah.

Pneumonia is a lung infection caused by microorganisms,

which generally leads to difficulty in breathing.

Normally, we inhale oxygen-rich air, which reaches our alveoli.

>> >> Alveoli are surrounded by blood capillaries.

Oh.

Here, the oxygen through the walls of alveoli diffuses into our blood.

However, sometimes we also inhale harmful microorganisms.

Mostly, the cilia and mucus in our respiratory tract trap these microorganisms,

which are then expelled while coughing.

But sometimes, the microorganisms don't get trapped and reach the alveoli.

There, they start to multiply, causing lung infection.

That is, pneumonia.

Oh, no.

Now, what do we do?

Now, to protect ourselves, the immune cells start attacking the microorganisms,

causing inflammation and accumulation of fluid in the alveoli.

As a result, the inhaled oxygen cannot get easily diffused into blood,

thus causing difficulty in breathing.

Topic, dandruff.

Oh.

Why do we get dandruff?

Tearing of pages.

Nah.

Dandruff is a condition in

which our scalp sheds skin cells in the form of white flakes.

A yeast called Malassezia globosa is one of the mostly accepted reasons for causing

dandruff.

Wow.

What a classy name it has.

Indeed.

Malassezia globosa is naturally present on our scalp.

Huh?

It feeds on sebum and releases oleic acid.

Now, some people are sensitive to this oleic acid.

>> >> When it penetrates the upper layers of their skin, it causes inflammation.

Hence, in response to this inflammation,

their skin sheds a large number of skin cells at a higher rate.

These cells then join together forming white flakes, thus causing dandruff.

Topic, joints.

Why do knuckles pop?

So that when we get bored, we can pop them for time pass.

Nah.

>> Huh?

A knuckle is a joint in the finger where two bones come together

or connect.

This joint is filled with a fluid called synovial fluid.

Synovial fluid is a viscous fluid containing dissolved gases like oxygen and carbon dioxide.

When bones move, the synovial fluid prevents them from grinding against each other.

Wow, it's so amazing.

Indeed.

When we stretch or bend our finger, the space between the two bones increases.

This causes the synovial fluid to stretch, thus creating low pressure in it.

Now, as gases are less soluble at low pressure,

the dissolved gases in the synovial fluid undissolve,

resulting in the formation of a bubble, which we hear as the pop sound.

Topic, anaerobic respiration.

What is the cause of muscle cramps?

Excess sleep.

No.

Respiration is a process in which the cells of our body produce energy.

Normally, our cells respire aerobically.

In this process, the glucose, with the help of oxygen,

is completely broken down to produce energy, water, and carbon dioxide.

Is this energy then used for all our activities?

Indeed.

However, during heavy exercise,

our body cannot deliver enough oxygen to the cells of our muscles.

Hence, in such situations,

anaerobic respiration helps us to produce some energy temporarily and thus continue our work.

In anaerobic respiration, the glucose is partially broken down in the absence of oxygen

to produce comparatively less amount of energy

and a waste product called lactic acid.

Now, one of the most prominent reasons for the muscle cramps is the accumulation

of this lactic acid.

>> >> Topic, sinkholes.

What causes sinkholes?

Maybe water.

This time you are absolutely correct.

>> Yippee!

A sinkhole is a depression

or cavity in the ground

which is caused by water erosion.

Water erosion is a naturally occurring process in

which water wears off soil

and rocks.

Wow, water is so powerful.

Indeed.

Now listen, the upper layers of the soil comprise of sand, clay, etc.

While the bottom-most layer called bedrock has rocks.

>> Oh.

Generally, sinkholes form in places where the bedrock layer has rocks made up of

limestone or dolomite.

>> Huh?

When rain falls, it seeps into the soil reaching the bedrock.

Over time, the water dissolves these rocks and thus erodes them forming hollow cavities.

As these cavities get bigger, the ceiling of the cavity, that is,

the upper layers of soil cannot hold the weight.

Hence, they collapse forming sinkholes.

Topic, human nose.

Why do we get nosebleeds?

I don't know.

All right, I'll explain.

The medical term for a nosebleed is epistaxis.

The most common epistaxis is anterior epistaxis where bleeding happens from the front part

of our nostrils.

Each of our nostrils has a massive blood vessels called Kiesselbach's plexus

which is very close to the skin surface.

Now, usually the mucus moisturizes the skin in our nose thus protecting the blood

vessels in it.

Wow, mucus is so useful.

Yes, >> >> it is.

However, during winter, the air is dry.

Hence, when we inhale this dry air, it draws moisture from the mucus,

which in turn leads to the drying of skin in our nose.

Mhm.

Now, some people's skin is very sensitive.

If it dries, the skin and blood vessels in it get easily damaged,

causing an anterior epistaxis or nosebleed.

Oh.

Mhm.

Topic, cheese.

Huh?

Why does Swiss cheese have holes?

Oh.

>> Those are not holes.

They are eyes of the cheese.

No.

Huh?

Cheese is made from milk.

Milk contains a sugar called lactose,

which is very important in the formation of cheese.

>> Oh.

Huh?

Now, while making Swiss cheese, bacteria like S. thermophilus, Lactobacillus, and P.

Shermanii are added to milk.

What?

Bacteria are added to milk?

Absolutely.

However, they are good bacteria.

Out of these bacteria,

the S. thermophilus and Lactobacillus first convert the lactose into lactic acid, producing curd.

Then, after undergoing certain processes, when the curd is kept fermenting, the P.

Shermanii bacteria consumes the lactic acid and releases carbon dioxide gas.

Being trapped, the carbon dioxide gas forms bubbles.

Oh.

>> Eventually, Huh?

when we cut the cheese, the bubbles pop,

resulting in holes in the Swiss cheese.

Topic, chapped lips.

What causes chapped lips?

Making weird faces Oh, no.

Our lips are very sensitive.

This is because the outermost layer of our skin called stratum corneum is much

thinner on our lips than on any other body parts.

As it is thinner, the blood vessels inside them are more prominent.

Making our lips appear reddish or pinkish.

Besides this, the skin on our lips doesn't have oil

and sweat glands which secrete substances to moisturize the lips.

Hence, our lips have very less moisture.

Now, usually during cold months, as the air has less moisture,

the moisture from our lips evaporates, causing them to get dry and chapped.

So, to provide moisture, we can lick our lips and apply saliva.

No.

Saliva draws more moisture and heat from our lips and evaporates,

thus leaving our lips more drier than before and thus making the condition worse.

Topic, bad breath.

Why do we get bad breath?

It's not bad breath, it's perfume.

Oh, gross.

Bad breath is generally caused by bacteria that live in our mouth.

These bacteria feed on the food particles which get stuck in our teeth, gums,

and tongue.

They break down the food particles into simpler forms,

releasing foul-smelling compounds such as hydrogen sulfide, methanethiol, and cadaverine.

These gases form your bad breath.

But why is morning breath so bad?

Usually during the day,

saliva carries the food particles and bacteria from the mouth into our stomach,

thus controlling the bad breath.

However, when we sleep, we produce less saliva, making our mouth dry.

This increases the growth of bacteria,

thus increasing the breakdown of food and producing bad breath in the morning.

Topic, human eyes.

What are eye boogers?

They are similar to burgers.

Oh, gross.

No.

Eye boogers generally contain oil, dust, germs, etc.

They are formed from the tear film on our eyes.

Does the film have any action scenes?

Oh, no.

The tear film mainly consists of three layers.

Oh.

>> Mucin layer, aqueous layer, and lipid or oily layer.

Together, these layers moisturize our eyes.

They also trap dust and germs, which are removed while blinking.

When we blink, the eyelid closes and if there is any dust or germ,

it gets discarded along with some tear film through the tear duct into the

nasal cavity.

Oh.

>> But while sleeping, since we don't blink, the tear film, dust,

and germs get collected in the inner corners of our eyes

and start to dry out,

forming eye boogers. topic human eyes.

What are eye floaters?

Huh?

They are worms.

No.

Eye floaters are tiny spots

or thread-like strands that drift in our field of vision.

When we move our eyes and try to look at them directly,

they seem to dart away.

Yeah, dude.

I think they try to hide.

Nah.

Huh?

Oh.

When light from an object enters into our eyes,

it passes through the vitreous humor to form an image on the retina.

Vitreous humor is a clear gel-like substance.

It is 99% water and 1% collagen fibers.

These collagen fibers are spread evenly throughout the vitreous humor,

but sometimes these fibers tend to come together forming clumps or strands.

When we look at a clear sky

or a blank page

and the clumps or strands are very close to the retina,

they cast a strong shadow on the retina,

making them easily detectable in the clear background and thus forming eye floaters.

>> >> Topic, motion sickness.

Why do we get car sickness?

Because some cars are haunted.

Nah.

Huh?

According to a prevailing theory,

car sickness occurs because of mismatched or conflicting sensory signals.

In a moving car, our eyes see that the car seats are not moving,

thus informing our brain that we are stationary.

However, the inner ear, which detects motion,

notices the turns and bumps in the road

and tells our brain

that we are moving,

thus creating a sensory mismatch and making us carsick.

But why do we vomit?

During human evolution, when there were no vehicles,

only the intake of foods containing neurotoxins made our brain receive conflicting signals.

Now, the only way to remove these neurotoxins was to vomit.

Hence, in the present time, when our brain receives such a mismatched signals,

it thinks that there is some neurotoxin in our stomach, thus it induces vomiting.

What is a cataract?

It may be a cat's nickname.

No.

Hey, a cataract is an eye disease.

How does it form?

Wait, I'll explain.

Each of our eyes consists of a transparent lens.

Is it similar to my camera lens?

Absolutely.

Our eye lens is made up of water and protein.

They are arranged in such a way

that keeps the lens clear

and lets light pass through it.

Hence, a sharp image is formed on the retina.

However, as we age, the protein begins to clump together, making the lens cloudy.

>> Oh.

This clouding of our eyes' natural lens is called a cataract.

In such situations, when light from an object enters our eye,

the clumped protein blocks or scatters the light.

As a result, a blurred image is formed on the retina,

thus making it hard to see.

Hmm.

What is earwax?

It is a wax used to make candles.

Oh, gross.

Not at all.

Earwax is used to lubricate and protect our ear canal, middle ear,

and inner ear.

Oh, but how does it form?

Huh?

>> Our ear canal consists of special glands.

They produce an oily and waxy substance called cerumen.

Cerumen moisturizes our ears.

It traps dust and dead skin cells, keeping our ears clean.

Hmm.

Besides this, cerumen also has antibacterial properties.

When harmful microbes try to enter deeper into our ears,

the cerumen traps and kills the microbes.

These dead microbes, dust, oil, and dead skin cells together form the earwax.

Oh.

Huh?

Why do we stretch in the morning?

>> >> So that we can sleep for 2 more hours.

>> >> Nah.

Wait, I'll explain.

When we wake up in the morning,

we yawn and stretch our arms and legs.

>> This coordinated yawning and stretching is referred to as pandiculation.

I thought it is referred to as calculation.

>> >> Oh, just listen.

>> When we are asleep, we don't perform any activities.

>> >> Hence, our heart rate becomes slow when the blood flow is decreased.

Also, as many people lie in the same position for long hours,

their muscles become stiff and tight.

Hmm.

>> Thus, a good stretch in the morning awakens our body.

It brings our heart rate back to normal,

improving the blood flow to various body parts.

>> >> Stretching also loosens and realigns our stiff muscles,

making them more flexible and ready for the day ahead.

>> >> Why do animals' eyes glow in the dark?

Cuz they have hidden torches.

Nah.

Wait, I'll explain.

Our eyes have a layer called retina, which is made up of photoreceptors.

When light enters our eyes, it hits the photoreceptors.

Photoreceptors detect light, thus making it possible to see.

Hmm.

However, the light which doesn't hit the photoreceptors remains undetected.

Aw, poor undetected light.

Now, nocturnal animals like owls need to see better during the night.

Hence, their eyes have another layer below the retina called tapetum lucidum.

Now, when light doesn't hit the photoreceptors, it reaches the tapetum lucidum.

This layer acts like a mirror.

It reflects light back onto the photoreceptors,

thus giving them a second chance to detect light.

Some of this reflected light also comes out of the animal's eyes,

thus making it seem that its eyes are glow.

Why do we have seasons?

Because of season fairies.

No.

It is mainly because of our Earth's axis.

Our Earth's axis is tilted at an angle of about 23.5°.

Hence, as the Earth revolves around the Sun,

sometimes the Northern Hemisphere points towards the Sun, while sometimes the Southern Hemisphere.

This causes seasons.

Oh, man.

It is too complicated.

All right.

Let us observe the Northern Hemisphere to learn more about seasons.

When the Northern hemisphere points towards the sun,

the sun rays directly strike the northern hemisphere.

Thus, the temperatures are high, resulting in summer season in that region.

However, when the northern hemisphere points away from the sun,

the sun rays fall slanting on it.

Thus, the temperatures are low, resulting in winter season.

But, when the northern hemisphere is neither tilted towards nor away from the sun,

the temperatures are moderate, resulting in spring and autumn season.

>> >> Why does sunlight make you sneeze?

Cuz sun teases our nose.

No.

Wait, I'll explain.

Sneezing caused by sunlight or bright light is called photic sneezing.

According to a prevailing theory,

it happens because of a thick nerve bundle called the trigeminal nerve.

The trigeminal nerve detects

or senses irritants in our nose

and thus triggers sneezing to expel them out.

The trigeminal nerve lies quite close to the optic nerve,

which sends visual information from our eyes to the brain.

Now, in some people, this optic nerve is oversensitive.

Just like me, right?

Oh, just listen.

When bright light suddenly stimulates the optic nerve,

the optic nerve mistakenly transmits some signals to the nearby trigeminal nerve.

Hence, the trigeminal nerve misinterprets the signal

as an irritant in the nose

and thus triggers sneezing.

What is frostbite?

An ice candy.

No.

Our core body temperature is about 37°C or 98.6°F.

To maintain this temperature, our blood transports warmth to all our body.

But prolonged exposure to cold temperatures can decrease our core body temperature.

Oh, no.

Now what to do?

Now our brain constricts the blood vessels of our limbs.

Diverting blood to the vital organs to maintain their core temperature.

As our limbs don't get sufficient warmth, they start to freeze, giving us frostbite.

Frostbite progresses in three stages.

First is frostnip, in which the surface of our skin freezes.

During the second stage, called superficial frostbite, often ice crystals form in the skin.

During the third stage, that is deep frostbite, the underlying tissues, blood vessels, bones,

etc. freeze and may get permanently damaged.

What is fracking?

A dance form.

Deep inside the earth, there is a layer of shale rocks.

These rocks contain fossil fuels like oil and gas in their pores.

To extract these fuels, a technique called fracking or hydraulic fracturing is used.

In fracking, a vertical well is drilled into the layer of shale rocks.

Then the drill is turned by 90° and drilling continues horizontally.

When the targeted distance is reached, the fracking well is encased.

Then a perforating gun is inserted into the well.

When the perforating gun reaches the required distance, the rocks are perforated.

Then the perforating gun is removed

and a fracking fluid is pumped into the well.

This fluid builds pressure in the perforations, creating cracks in the rocks,

thus releasing the fossil fuels.

These fuels and the fracking fluid are then drawn to the surface.

Oh.

>> What causes brain freeze?

An empty wallet.

Nah.

Brain freeze or ice cream headache is a short-term headache.

Scientifically, it is called sphenopalatine ganglioneuralgia.

Oh man, what a complicated name.

Indeed.

In the back of our throat, there are two main arteries.

They are internal carotid artery and anterior cerebral artery.

They supply blood to the entire brain.

Oh.

>> Now, when we have cold foods,

such as an ice cream or cold beverage rapidly,

the temperature in our throat drops suddenly.

This causes the two arteries

which are supplying blood to the brain to contract quickly.

Oh.

As there is a sudden change in the blood flow,

it results in a type of headache called a brain freeze.

It is the brain's way of telling us to slow down

and have that ice cream

or cold beverage slowly.

>> >> Topic: Human hair.

Oh.

>> Why do we get goosebumps?

To burst balloons.

Nope.

Goosebumps served a purpose for our ancestors who had a lot of hair on

their body.

When our ancestors felt cold, their adrenal glands produced adrenaline.

Oh.

>> Adrenaline caused the arrector pili muscles, which are attached to the hair follicles,

to contract, creating shallow depressions on the skin surface

and making the hair stand straight up,

thus causing goosebumps.

The straightened hair trapped more air,

which prevented their body heat from escaping and hence kept them warm.

Oh.

Also, when our ancestors felt afraid of any animal,

The adrenaline made their hair stand up,

making them look bigger and thus scared their attacker.

Yeah, dude.

It scares me, too.

Oh.

Now, as this characteristic of goosebumps is inherited by us,

we also get them during strong emotions or when it is cold.

Why is the ocean blue?

Cuz ocean water reflects blue color of the sky.

Hmm.

You are right, but not completely.

The main reason for oceans to be blue is the way water molecules absorb

and scatter the colors of sunlight.

Sunlight has seven visible colors.

They are red, orange, yellow, green, blue, indigo, and violet.

Yeah, I saw them in a rainbow.

Now, when sunlight falls on the ocean, it passes deep into the water.

Here, red, orange, yellow,

and green colors of sunlight are absorbed more strongly by water molecules, while blue,

indigo, and violet colors are not absorbed much.

Instead, they are scattered, making the ocean appear blue to us.

However, as the blue shades penetrate deeper into the ocean,

eventually they also get absorbed.

Hence, at greater depths, the ocean is completely dark.

What is vocal fry?

It may be similar to a french fry.

Not at all.

Vocal fry is a creaky or raspy voice seldom used in speech.

I thought it is used by leech.

>> >> Oh, gross.

Just throw that away and listen.

Oh.

>> When we speak, air from our lungs passes through the vocal folds,

making them vibrate.

>> >> These vibrations make the air in our mouth and nose to vibrate,

thus producing sound or voice.

Generally, human voice can be divided into three ranges or registers.

They are falsetto, modal, and fry.

Most people speak and sing in the modal range.

But sometimes, when we speak in fry range, our vocal folds slam shut.

However, longitudinally, they are not stretched tightly.

Air from the lungs bubbles out through this loosely closed folds,

thus creating that creaky voice called fry.

How can we smell things?

Dude, I don't have a nose, so how will I know?

At the back of our nose, there's a tissue called olfactory epithelium.

It is covered with mucus.

This tissue has specialized neurons called olfactory receptor neurons.

There are about 40 million olfactory receptor neurons.

These neurons are chemoreceptors, that is, neurons which detect chemicals.

Wow, they have a cool name.

Now, when any substance releases its smell or odor, the odor consists of chemicals.

When we breathe in, these chemicals enter our nose.

When they reach the olfactory epithelium, the chemicals get stuck in the mucus,

causing them to activate the neurons.

As a result, these activated neurons send signals through the olfactory tract to the

brain,

informing it about the smell.

Why do mosquitoes bite only some people?

Cuz they are lazy.

Nah.

There are a number of reasons why some people are more prone to mosquito

bites.

One of them is body odor.

Millions of bacteria which live on our skin produce various gases.

These gases form our body odor.

>> Oh.

Some of these body odors attract the mosquitoes.

So, this is the reason why mosquitoes prefer me?

Huh?

Besides this, a popular research found

that mosquitoes tend to bite people with type O blood nearly twice

as often as those with type A.

Exercising can also entice mosquitoes.

This is because when we exercise, we release more carbon dioxide, heat, and sweat.

Mosquitoes can detect this carbon dioxide and heat.

They can also sense the various substances in our sweat, such as lactic acid.

Thus, making us more likely to get bitten.

Oh.

Huh?

Why does hot air balloon float?

Cuz it has invisible wings.

No.

It is because of density.

Density is the measure of mass present per unit volume.

Lesser the density, lighter will be the object.

Now, density varies with temperature.

Oh, dude.

It is so complicated.

All right.

I'll explain.

When a hot air balloon is on ground,

the air inside and outside the balloon is of same temperature and density.

However, when we turn on the burner of the balloon,

the air inside the balloon starts getting hot.

The molecules of air move faster and spread apart, taking up more space.

Hence, the air inside the balloon becomes less dense than the air outside.

As less dense air is lighter,

the hot air balloon rises and thus begins to float.

What happens if a plane is struck by lightning?

It will start glowing like a disco ball.

No.

Lightning is a massive flow of charge

which carries thousands of volts of electric current.

Thus, it is extremely fatal for living beings

and can damage anything

that comes in its way.

Yeah, dude.

It is really terrifying.

Now, many times airplanes get caught in a heavy lightning storm.

However, airplanes are designed to handle the lightning strikes.

The outer skin of most planes is primarily made of aluminum.

Aluminum is a good conductor of electricity.

When lightning hits the airplane,

>> >> the electric current travels through the outer skin of the plane.

It does not pass into the plane.

Eventually, it exits off through another extremity such as tail.

Thus, the airplane and the passengers within remain protected.

Hey.

Why can't we tickle ourselves?

>> >> Cuz we are lazy.

No.

Oh.

>> Areas that are more prone to getting tickled are our vulnerable areas like neck,

stomach, and armpits.

Yeah, dude.

You are right.

Some researchers suggest that laughing on getting tickled by others could be a defense

mechanism.

It has evolved over the years when touched suddenly in vulnerable areas.

>> >> This laughter could either be a way to laugh out of a

tense situation or to show submission to the person tickling you to stop further

tickles.

Now, when we tickle ourselves,

our brain is programmed in such a way

that it predicts and recognizes our own movements.

It knows where our hands can reach.

There's no element of surprise or threat, even if touched in vulnerable areas.

Hence, we can't tickle ourselves.

Why is fluoride added to water?

To make water taste like soft drink.

Nah.

According to a prevailing study,

when fluoride is added to public water supplies at an average concentration of about

one part per million

or slightly below,

it prevents tooth decay.

Oh.

But how?

Huh?

Enamel is the hard outer covering of our tooth.

It is primarily made up of hydroxyapatite.

Hydroxyapatite is a compound of calcium, phosphorus, and hydroxide.

Now, when bacteria in our mouth feed on food particles, they produce acid.

This acid dissolves the hydroxyapatite, >> >> leaving behind a residue of calcium and phosphate ions.

This results in a tooth decay.

Now, when we drink water containing fluoride,

the fluoride binds with calcium and phosphate ions, forming fluorapatite.

As fluorapatite is less susceptible to acid attacks,

it helps to stop the tooth decay process.

>> >> What causes body odor?

Duh, obviously sweat.

No.

Huh?

Sweat is odorless.

Oh.

What?

But how is that possible?

Our skin contains two types of sweat glands, >> >> eccrine glands and apocrine glands.

Eccrine glands are present all over our body.

They produce sweat, which is mostly water.

Whereas apocrine glands are concentrated in regions such as ear canals, armpits, etc.

They produce thicker sweat, which has proteins.

Can I eat these proteins and become a bodybuilder?

Oh, gross.

Just listen.

We know that millions of bacteria are normally found all over our skin.

When apocrine glands produce sweat,

the bacteria on our skin break down the proteins in that sweat,

releasing unpleasant smell, which we call as body odor.

Mhm.

Why does water go stale overnight?

Cuz you left it alone overnight.

Nah.

>> Huh?

In water purification plants, chlorine is added to water.

Chlorine kills microorganisms in water, thus keeping it clean and safe to drink.

This chlorine gives our drinking water a slightly different taste.

>> Mhm.

However, if we keep the water open for a long time or overnight,

the chlorine will dissipate into air.

>> Oh.

As a result, the taste of water alters.

Huh?

>> Also, water is a universal solvent.

It can dissolve almost anything.

Hence, if we keep water open for quite a long time,

the atmospheric carbon dioxide gets dissolved in it.

This results in the formation of mild carbonic acid.

What?

Acid is formed in water?

Indeed.

However, it is not harmful.

Huh?

>> The presence of carbonic acid slightly lowers the pH of water,

making it slightly acidic and thus unpleasant to taste.

What makes tattoos permanent?

Glue sticks.

The immune response.

No.

Our skin has three layers: epidermis, dermis, and hypodermis.

Epidermis sheds thousands of skin cells every day.

Hence, when we get a tattoo, the tattoo needles,

which are coated with colored pigment, are inserted through the epidermis into the dermis,

thus preventing the tattoo pigment from getting shed away.

However, it is mainly our body's immune response which makes tattoos permanent.

What?

But how?

The tattoo needles create wounds in the skin, activating the immune response.

Immune cells, like macrophages,

reach the wounded site

and start to eat the small particles of colored pigment

and clean the area.

Bigger pigment particles that cannot be eaten by macrophages are absorbed by fibroblasts present

in the dermis.

These fibroblasts, along with some macrophages, remain at the site, making the tattoo permanent.

Hmm.

Where does the fat go when you lose weight?

>> Uh-huh.

Santa Claus takes it away.

Nah.

Our food contains nutrients like carbohydrates, fats, and proteins.

When we eat food, these nutrients give us energy and help us to grow.

Hmm.

However, when we eat excess amount of these nutrients,

our body stores them as triglycerides in fat or adipose cells for later use.

This ultimately results in weight gain.

Now, according to a prevailing research, when we try to lose weight,

we actually break down these triglycerides in the presence of oxygen,

converting them into carbon dioxide, water, and energy.

What?

My fat turns into carbon dioxide, water, and energy?

Yep.

We exhale the carbon dioxide gas.

Water is given out in the form of urine, sweat, or tears.

Whereas, we use the energy to perform various activities.

Why do we get sunburn?

Cuz sun is jealous of my skin.

No.

Huh?

Sunburn is a term for red and inflamed skin.

Hey!

It is caused by ultraviolet radiation present in sunlight.

Sunlight consists of three types of ultraviolet radiation: UVA, UVB, and UVC.

Oh.

>> Does it contain UVC as well?

Oh, just listen.

Huh?

Our skin is made up of cells.

These cells have DNA.

When we are in the hot sun for very long,

the UVB radiation enters into our skin cells and starts to damage the DNA.

Huh?

>> DNA damage can lead to cancer.

Thus, to reduce the risk of cancer, the damaged skin cells kill themselves.

This programmed cell death is called apoptosis.

Apoptosis activates the immune response.

As a result, the blood flow increases to that area to heal the skin.

This leads to red and inflamed skin which we call as sunburn.

Hmm.

How do fireflies glow?

>> >> Using a magic wand.

Nah.

Huh?

Fireflies glow because they produce light by a biochemical reaction.

Oh.

In the lower abdomen of fireflies,

there's a chemical called luciferin and an enzyme called luciferase.

When oxygen enters into their lower abdomen through tracheal tubes,

it basically reacts with luciferin in the presence of luciferase.

This reaction produces light.

This production and emission of light by living organism is called bioluminescence.

Bioluminescence is a cold light.

Hmm.

This means the light produced generates very less heat,

thus preventing the fireflies abdomen from getting overheated.

Yeah, dude, it's not hot.

However, one more interesting fact is

that not only adult fireflies

but also their eggs

and larvae are bioluminescent.

Wow.

They look so stunning.

Huh?

Huh?

Why can we see our breath in the cold?

So that we can make weird shapes.

No.

Oh.

>> Our lungs help us to exchange gases.

They are always moist and warm.

Now, when we breathe,

we inhale oxygen-rich air and exhale carbon dioxide-rich air.

However, as the lungs are warm and moist,

the exhaled air is warm

and has more moisture in the form of water vapor.

Really?

In cold months, when this warm

and moist exhaled air comes in contact with the cool air,

the moisture in the exhaled air condenses to form tiny water droplets.

Thus, we can see these tiny water droplets

as cloud or fog in our breath.

Why does helium make you sound funny?

Cuz helium converts you into a joker.

Nah.

Huh?

Air mainly consists of gases such as nitrogen and oxygen.

It is present in our surroundings, lungs, mouth, nose, etc.

>> Oh.

When we speak, air from our lungs passes through the vocal folds,

making them vibrate.

These vibrations make the air in our mouth

and nose to vibrate back

and forth,

producing sound.

The speed of sound in air is about 340 m/s.

My running speed is 500 m/s.

Oh, please listen.

Oh.

Helium is lighter than nitrogen and oxygen.

Huh?

>> >> Being lighter, sound travels faster in helium as compared to air.

Hence, when we inhale helium and try to speak, the sound produced travels faster,

thus producing that funny voice.

Hello.

Why does our voice sound different when recorded?

Huh?

Our inner ear detects sound vibrations,

informing our brain about the voice or sound and thus helping us hear.

But, did you know that when we speak,

we hear our own voice in two different ways?

What?

In two different ways?

Indeed.

The first way is through our outer ear.

Our voice travels to the outer ear creating vibrations in the eardrum.

These vibrations eventually reach the inner ear.

While the second way is through our flesh and skull bones.

However, they are better at transmitting deeper lower frequency sounds

as compared to shriller higher frequency sounds.

As a result, the combination of sounds obtained from the two ways makes our

voice appear deeper.

Now, when we hear our recorded voice,

we only hear the voice which has traveled through our outer ear.

Hence, our voice sounds different when recorded.

Why does airplane food taste bad?

I don't know.

Wait, I'll explain.

Our ability to perceive taste is affected by a few factors such as humidity,

air pressure, etc.

In an airplane, the humidity is less as compared to that on the ground.

This makes the air in the airplane quite dry.

Also, to maintain the air pressure inside and outside the airplane,

the air pressure inside it is decreased.

Decreased air pressure and dry air dries our nose and mouth.

Dry nose cannot properly smell odors.

Yeah, dude.

I'm not able to smell the burger.

Now, >> >> smell of food helps us to understand the flavor

and ingredients of the food.

Thus, the food which we cannot smell properly appears unappealing.

Also, dry mouth reduces the sensitivity of our taste buds.

As a result, we cannot perceive the taste of food properly.

Oh.

Why do mosquito bites itch?

Cuz mosquitoes don't brush before biting.

Nah.

A mosquito doesn't actually bite.

What?

It doesn't bite?

Nope.

>> Huh?

A mosquito sucks our blood through a straw-like structure called proboscis.

A proboscis is made up of six parts.

>> Oh.

>> Out of the six parts,

four parts are used to pierce into our skin

and blood vessels and hold the tissues apart.

Through the fifth part called hypopharynx, the mosquito drops its saliva containing an anticoagulant.

Anticoagulant prevents the blood from clotting

so that the sixth part of proboscis called labrum can easily suck up the

blood.

Hmm.

>> Now, our immune system recognizes the anticoagulant as an invader.

Hence, it releases histamine.

Histamine dilates the blood vessels

so that blood along with immune cells can come to attack the invaders

and heal the affected area.

This histamine causes the itchy feeling.

Why do dogs wag their tails?

Cuz they are happy.

A dog's wagging tail doesn't always mean that it is happy or excited.

So, what does it mean?

Popular research and studies over the years suggest

that the tail position

and wagging direction represent different feelings

or moods of dogs.

When the tail is hung down in its natural position,

it means that the dog is calm and is not worried.

If the tail is curled in between its legs,

it indicates that the dog is scared or anxious.

When the tail is straight up,

it indicates that the dog is curious

or wants to show other smaller dogs

that it is bigger

and dominant.

Moreover, if the tail wags towards the right,

the dog is expressing positive emotions such as joy, excitement, etc.

However, if it wags towards left, it conveys negative emotions such as anxiety, stress,

etc.

How do dolphins sleep?

By covering their face with fins.

No.

>> Huh?

Like humans, dolphins are mammals.

They breathe through lungs.

Hence, dolphins need to come up to the surface of water at regular intervals

to breathe.

Also, dolphins have to protect themselves from dangerous predators.

Hence, they always need to be alert.

Just like security guards, right?

Oh, just listen.

Each eye of a dolphin is directly connected to the opposite hemisphere of the

brain.

Now, while sleeping, a dolphin shuts down one hemisphere and the opposite eye.

In the meantime, the other active hemisphere keeps track of internal bodily functions like

breathing and the open eye looks out for predators.

After two to four hours, the dolphin swaps the sleeping task.

It awakens the closed eye

and resting hemisphere and shuts down the active hemisphere

and the open eye.

This type of sleep is called unihemispheric slow-wave sleep.