Where do tears come from and why do we cry?

Where do tears come from and why do we cry?

This question comes in from the very lovely, and very curious, Kayla, aged six, who can sometimes be found over at My little babóg blog. Kayla would like to know…

Where do tears come from?



Where do tears come from?

Tears are made by little glands above our eyes, called tear glands, or lacrimal glands. There is one gland above each eye; each produce tears that travel to the eye through tiny pipes, called ducts. There are a number of these tear (lacrimal) ducts behind our upper eye lids.

Our tear ducts are constantly producing tears, to keep our eyes clean and moist, but we don’t usually even notice. When we blink we wipe the tear fluid over our eyes, keeping them moist. This fluid is then drained off from the eyes through more ducts. It is only when we start producing a lot more tears that we start to notice them. The ducts that drain the fluid away cannot cope with all the extra tears and they start to run down our cheeks.

What are tears made of?

Tears are basically made of slightly salty water. They also contain enzymes that kill bacteria and vitamins and minerals. Some tears contain proteins, called hormones, that can change how we feel.

Why do we cry?

Scientists are still working this one out. We do know that we cry different kinds of tears in response to different things. Science defines crying as the process of producing tears in response to an emotion – be it sadness, fear, anger or happiness. When we produce tears to clear something out of our eye or to moisten the eye… Then we call this lacrimation.

So how does it all work? Well, the emotional crying seems to be triggered as a response to activity in a part of the brain called the hypothalamus. This part of the brain responds to our different emotions and can produce chemicals, called neurotransmitter, that will travel to specific parts of the body and induce a response. In the case of crying, the neurotransmitter produced is called acetylcholine and it triggers tear production in the lacrimal gland.

The reason why our brain responds in this way to emotions can vary. Babies, for example, cry to communicate with us… Telling us the are tired, hungry or in pain. This makes sense as they do not have many other forms of communication available to them. But why do we still cry here we are all grown up? It may be that crying creates other responses in our bodies, our heart rate changes, our breathing alters and other chemicals are released into the body. Crying can make us feel better.

Crying also allows us to show people how we feel! We may have evolved our crying mechanism to let people know what we are feeling, or to get sympathy or support.

Sometimes we cry when we see others hurt or sad and this created empathy, something that allows us build strong bonds and create supportive communities.

What different types of tears are there?

As I said above, we have three types of tears and they are…

Basal tears – these are the ones we produce to keep our eyes moist;

Reflex tears – we produce these in response to something else, usually something that is irritating our eye… From a small piece of dirt to a strong chemical, such as the vapour off a cut onion.

Emotional tears – these are the ones that get switched on by our emotions, even if we try to suppress them! These tears make us human!

Mystery creature revealed – the scorpion fly

Mystery creature revealed – the scorpion fly

This week’s Mystery Creature was certainly a bizzare looking insect; it looked like a hybrid of a fly and a scorpion, which is why it is aptly named as the scorpion fly. Scorpion flies come under the order Mecoptera, of which there are many families. This scorpion fly is a common scorpion fly (the Panorpidae family).

Well done to Sandra M. who rightly identified this week’s Mystery Creature!


P. Communis; Image credit: Mikkel Houmøller (Lostmonkey); Image source: wiki commons

There are nearly 600 species of scorpion fly worldwide.

The scorpion fly (sometimes called a scorpion wasp because of colouring) has some very distinctive features. Firstly, that scorpion-like tail, found only in males, which is not actually a tail at all, but the genitals of the insect! These scorpion-like tails also have notal organs to help hold a mate. The females body just tapers into a straight point, with no dramatically curving appendages!

The scorpion fly also has a very long face, forming a beak-like projection, with mouth parts (mandibula) at the end.

Both the male and female have patterned wings, with a delicate appearance. They are poor fliers and prefer short flights. The spend much of their time crawling among vegetation.

Although this is a foreboding looking insect, it poses no threat to humans. It usually feeds on other dead insects, rotting fruit and nectar.

The eggs of the scorpion fly are laid in the soil and the larvae live underground. They are scavenger feeders too and have a caterpillar appearance during their early stages of development.

Romance comes in an unusual form, the males will typically woo the female with a gift, which may be a piece of a dead insect or a drop of saliva!

They like to live in damp, shaded areas such as lightly wooded spaces, hedgerows or uncultivated patches of land. They are often spotted in nettle patches.

Scorpion flies are considered living fossils as their fossil records date back 250 million years.

Mystery creature – can you name this insect?

Mystery creature – can you name this insect?

Nature is truly amazing, isn’t it? Just looking at the diversity of creatures on this planet confirms that. This week’s mystery creature is a very bizarre looking insect, and an excellent example of just how creative mother nature really is.

Can you name it?


Image credit: Sebastian Wallroth;

Here is a clue: say what you see and you will probably work out the name of this insect! As always you can leave your comments, questions or guesses below. Remember to check back at the end of the week to find out for sure.

Update: Want to find out what it is? Here is the post that reveals what this insect is and some interesting facts about it!

Mystery Creature revealed – the binturong

Mystery Creature revealed – the binturong

How did you do with this week’s mystery creature? A cute but unusual looking animal, don’t you think? Some say it has a face like a cat and a body like a bear which is why it is commonly called the bearcat, but its proper name is the Binturong (Arctictis binturong).


Image credit: Pomax

The Binturong belongs to the viverridae family, making it a cousin to civets, genets, fossas and mongooses. These shy animals live in dense rainforests of Southeast Asia and tend to live solitary lives. They can grow to more than a metre in length; their strong, thick tails are about as long as their bodies. The females tend to be larger than the males, about 20% larger, and are the dominant sex of the species.

Binturong spend much of their time in the dense canopies up in the trees. Their thick tails are prehensile, and they use them like a monkey, to help them grip and hold branches when they move around. The top of their tails even have a short leather patch, to help with gripping.

Binturong move about the trees slowly and carefully, they are too large and heavy to jump from tree to tree and must instead climb down to the forest floor. Most of their time is spent in the trees, they even sleep up there.  They are mainly nocturnal animals, sleeping for most of the day and emerging at dusk to feed.  Although they eat some meat – such as birds and small mammals and insects, most of their diet consists of fruit and plants. They are good swimmers and will also feed on fish.

As with other members of the viverridae family, they have scent glands under their tails. To humans binturong smell like buttered popcorn and recent studies have identified the same compound, 2-acetyl-1-pyrroline(2-AP), to be found in both binturong urine and popcorn.

Binturong have a wide variety of vocal sounds; depending on its mood and what it wants to communicate it can make sounds like purrs, chuckles, growls, grunts  and hisses.

They walk like bears and humans, flat on both feet with an ambling appearance. Unlike bears and humans, they can turn their ankles 180 degrees, allowing their semi-retractable claws to grip the bark of trees, no matter what direction the animal is facing.

It is thought that females can delay implantation of their fertilised egg. This means that they can time the birth of their young to the most favourable season.

Due to their fruit rich diet, binturong play an important part in seed distribution within the tropical rain forests they inhabit. They are particularly important to strangled fig plants as their digestive systems contains rare enzymes, capable of breaking down the fig seed’s tough outer coating, allowing the seeds to be dispersed in the binturongs droppings.

Binturong have no known predators other than humans but are classes as vulnerable, with a population decline of more than 30% over the past 30 years.


Remember to check back tomorrow for a new mystery creature; I found the binturong a cute, and fascinating animal,  especially the fact that it smells like popcorn, what did you think?


Do bugs fart?

Do bugs fart?

Do bugs Fart?

That was a recent question from my three children, shouted in through an open door as they rummaged around in the garden. The answer is… yes they do! Most insects have micro-organisms (bacteria etc) that live in their digestive systems (just as we do); they do no harm and they help the bug by breaking down (digesting) their food. When this food is broken down gases are released, such as nitrogen, hydrogen, methane, carbon dioxide, oxygen and hydrogen sulphide. These gases have to go somewhere, and that usually means they get passed through the gut and out the insects anus!

Some bugs do more than just pass a bit of wind; check out these three extreme farting bugs… the Bombardier beetle, the Beaded lacewing larvae and termites…



Image credits: Bombardier Beetle: Cotinis; Beaded Lacewing: Cotinis; Termites: Scott Bauer

Remember to keep sending in your questions!

The things that say ‘me’

The things that say ‘me’

I have kept a very ‘sciencey’ focus to my blogs for the last while; it was a deliberate and conscious move in a slow transitional way. However, some of my very favourite posts here are the personal ones and sometimes I do miss writing them. And then I read this lovely post by Awfully Chipper (objects of me), about all the little things that project her character and likes, that will trigger memories of ‘mom’ in her childrens’ minds. As I read, all my own little personal images popped into my head and I decided to join in.

So here you are, a personal post with not a bit of science in sight: The things that say ‘me’…


My daughter recently said to me…  “You look lovely today mum, even though you are not wearing stripes”. That says it all really. I was surprised initially by her comment, but one look in my clothes drawer reveals my love of all things stripy.



Red and spotty

Red and spotty

This item is new, but still very ‘me’. After a recent phone change, I asked my husband to buy me a cover. I told him which type I wanted, but as for the colour and pattern, I suggested he ‘surprise me!’ (Every husbands nightmare.) The man did good though. I was delighted when he returned home with this red, spotty cover. Along with my love of stripes, I also have a hankering for things that are red, or spotty… or both! This was emphasised when someone pointed out how coordinated I was one day… my scarf matched my phone! (I hadn’t even noticed.)



Speaking of scarves… I love them. I wear them most days of the year. Warm ones in Winter, lighter ones in Summer… but nearly always with a scarf.




I love, love, love elephants, such beautiful animals; For me, their sense of community and ‘love’ for their babies adds to their appeal; I began to collect little elephant trinkets many years ago. These little collections suddenly reached a critical mass, as other people noticed and suddenly it was ‘elephants’ for every birthday/Christmas/gift thereafter. I found myself with a house brimming with elephant paraphernalia, and the appeal waned. Over the years, my elephant stocks have dwindled to a small number of much-loved objects. My sister, who happens to have the best talent in the world for buying gifts, still manages to give me elephant themed gifts. They are subtle, they are beautiful, and I love them. These are some of my favourites.




Apparently a lot of food items popped up on this list when I asked my children for suggestions. They spoke of the dishes I make that they like the most, but pizza seemed to make it to the top of the list. No surprise really, as I have been making it every Friday night for more years that I care to remember.



Mammy’s smell

Don’t worry, this is not as bad as it may sound. I’m very sensitive to smells and it seems some of my children are too. My boys can literally tell if someone has visited the house while they were at school. My youngest says he loves the ‘smell of mammy’, sometimes he likes to curl up with one of my scarves because it smells of me. I remember that as a child too, the lovely comfort and safety in the smell of my mum and dad. If I wear an usual perfume he will comment that I don’t smell of me, and he doesn’t tend to like it much!




This was the nicest one of all. When I asked my daughter for a suggestion she said “when people respect me it makes me think of you, Mum“. What a heart melter! For that comment, I even let her drink out of my favourite mug – wouldn’t you?



They are my objects, an unusual mix when I look back on them. What would be on your list? If you want to read more, or join in, check out the lovely linky over at Awfully Chipper.

Mystery Creature of the week

Mystery Creature of the week

This week starts with a wet and humid day, not unlike the climate that this creature may experience… do you know what it is?

Mystery creature June132016

Image credit:Tassilo Rau

Remember, ask questions if you want some clues and be sure to check back at the end of the week to find out what the creature is and some very interesting facts about it.

If you want to know what this creature is, check out the ‘reveal’ post here.

Mystery creature revealed – the epaulette shark

Mystery creature revealed – the epaulette shark

We had lots of junior scientists having a guess at this week’s Mystery creature, how did you do? Most guessed it was a shark, but to be exact…

It was an epaulette shark (Hemiscyllium ocellatum)

These small sharks are quite amazing and unique among their species; for one thing, they can walk on land!


Image credit: Jim Capaldi; Image source:Wiki commons

Usually less than one metre in length, these sharks are part of the carpet shark family. They are found in shallow coral reefs and waters off the coast of Australia. Although food can be plentiful in such waters, they have to contend with extreme tides and rapidly changing water levels. When the tide goes out, its larger cousins must retreat into deeper waters, but the smaller epaulette remains behind, left without competition to enjoy the bounty.

However, it is not as ideal as it sounds. Eventually, the water levels recede to dangerous levels. The epaulette shark can no longer swim and runs the risk of being stranded out of water, which would ultimately lead to its death. However, the clever little shark had adapted in two major ways, to overcomes this threat.

The shark requires water as a source of oxygen – to breathe. When the water levels reduce the shark survives by slowing its heart rate and organ use, thereby reducing its body’s demands for oxygen. In this way, it can survive 60 times longer without oxygen than humans can.

The epaulette has one other adaptation to allow it to survive when the tide is out, it can walk to the water! Using its fins as basic legs, it can crawl to a nearby rock pool with enough water to breathe and food to eat, until the tide returns.

Another example of practical and amazing adaptations in Nature. If you have any more examples you’d like to share just leave them in the comments below.

What would happen if the Earth’s gravity suddenly disappeared?

What would happen if the Earth’s gravity suddenly disappeared?

What would happen if the Earth’s gravity suddenly disappeared?

This was a recent question from my 10-year-old son… it certainly got some interesting discussions going around the kitchen table. When I opened up the question on my Facebook page I got more input from Cathal (5) and Ciarán (7) (from the Bumbles of Rice blog); they reckon that if you were indoors you would float upwards, or feel like you were being pulled up…  and bump your head!  A very good point boys; In fact, the bump on the head would be the least of your worries!

Before I go any further though, it is important to say that this cannot actually happen, we can’t just turn off gravity, so when we discuss what would happen if we did, we are talking more science fiction than science; it is good to keep that in mind!



As Cathal and Ciarán said, you would no longer have a force keeping you on the ground . The Earth would keep spinning, as it does, but you would no longer move with it, you would move in a straight line, upwards. In fact, rather than feeling like you are floating away from the Earth, you would probably feel like the Earth is dropping away from you!


Anything not stuck down in some way would move in the same direction you would. Anything inside a building would get stopped by the ceiling, anything outside would float off into space, pretty quickly.


Not only would solid objects float off into space but our air, our atmosphere would too; which means that unless you had an oxygen tank to hand you’d have no air to breathe.


Liquids would leave the Earth’s surface too, so all the water on our planet, in lakes, rivers and seas would start to float off. A first, water  would probably start floating off in large blobs, but as the atmosphere of the  Earth disappears then the heat of the sun would penetrate to the Earth’s surface even more than it does now and water would probably start to boil off, into steam that would float off into space.


So initially we said that if you were inside a building you would find yourself up at the ceiling; If you had an oxygen tank then you might be OK for a while. But you would start to feel those temperatures rise pretty quickly. The Earth would start to feel an incredible pressure which would ultimately mean that the buildings attached to its surface would start to break up and float away. Then rocks and clumps of earth would break off and float up too.


Eventually, the whole Earth would break apart and float away into space, but we would be long gone by then.

So while the notion of floating around in zero gravity might, at first, seems appealing, when we look at the idea a little more closely we realise it is not a very nice concept at all. Fear not, as I said at the beginning… this cannot happen, it is just an imagining of what would happen if it did.

While scientists cannot really predict what would happen if we suddenly lost gravity on Earth, they can tell us the short term effect that lack of gravity (or weightlessness) has on our bodies… by observing what happens to astronauts while in space.


Image source: pixabay.com
  • Initially astronauts lose their sense of orientation, they find it hard to tell up from down. This disorientation can also make them feel sick for a while.
  • Another issue they report is feeling like their arms and legs are disconnected from their body!
  • The change in pressure can affect their vision a little, this may be due to the altered pressure on the eye ball, brain and spinal fluid (some astronauts report more long term problems when they return to Earth; recent studies have found a genetic link to this problem, but the exact mechanism is still unclear).

They usually get used to these issues pretty quickly but there are greater health effects the longer they stay in space.

  • Due to the lack of weight on their bodies, their muscles and bones begin to weaken; this is why astronauts spend so much time in space exercising!
  • An astronaut will actually get taller in space; without the pressure of gravity on their bodies, they can stretch about an inch or more. Of course, once they return to Earth they soon return to their usual height.
  • Astronauts immune systems can become weak in space too (the number of white blood cells that help to fight infection can reduce) and healing can be slowed down.

Now that we have learned a little about gravity and the lack of it, here is a fun experiment; try out this gravity defying trick with a glass of water and amaze your friends and family!



  • A glass
  • A small piece of stiff paper or cardboard (large enough to cover the mouth of the glass)
  • A basin
  • Some water
  • (Adult supervision)
  • Fill the glass to the very top with water.
  • Place the piece of paper over the mouth of the glass, making sure there are no air bubbles underneath.
  • While holding the glass in one hand, and keeping the paper in place with the other, quickly turn the glass upside-down, over the basin (or ask an adult to do this for you).
  • Once the glass is inverted remove your the hand that is holding the paper in place.
  • The paper should stay in place and the water should stay in the glass.
  • Watch all the amazed faces of your family and friends as they observe your gravity defying feat!


While this appears to be an experiment about defying gravity, it is actually all down to air pressure. The lack of air in the glass produces a difference in air pressure on either side of the paper. The air pressure on the underside of the paper is greater than the pressure on the water side, pushing the air up and keeping the paper in place.

I hope this experiment works for you without anyone getting wet feet! Be sure to let me know if you try it!