Science questions for kids | How long can a person go without drinking?

Armas Karmala, 4

By evaluations according to this, a person can go without drinking for about three days. After that, there is not enough water available in the body, as a result of which a person can even die.

However, the time varies depending on the circumstances. If the environment is dry and hot, the loss of fluid in the body is so great that the time is shorter.

However, if a person gets liquid from food, the need to drink is clearly reduced. If the diet is very water-rich, the need to drink can even approach zero.

Humans need water especially to maintain the amount of body fluids and salt content.

If there is not enough water in the body, for example, the blood becomes too dense. It affects the function of the cells, i.e. the building blocks of the body, in such a way that the organs eventually stop working one after the other.

That’s why the body strives to always have enough water available. If there is too little water in the body, the body notices it and signals it with a feeling of thirst.

The body also tries to save water by reducing sweating if necessary and directing the kidneys to produce more concentrated urine. Then water is saved and people have more time to find water to drink.

Mikael Segerstråle

university lecturer of physiology and neuroscience

university of Helsinki

Do all people see colors the same? Is blue the same for everyone?

Mikael Karekallas, 6

Colors arise from light waves of different lengths that reach our eyes from, for example, the objects and organisms around us. Finally, the perception of color is born in our brain. We have started to call those phenomena arising from light waves as colors.

Many surfaces only reflect part of the light due to their structure alone. For example, peacock feathers are actually brown, but they reflect blue and green wavelengths.

In the retina, the sensory part of our eye, there are three types of cone cells, i.e. cells specialized for sensing light.

Some are specialized for long wavelengths that we call red, others for medium wavelengths that we call green, and still others for short wavelengths that we call blue.

However, not everyone sees colors the same way. Seeing colors is an individual, inherited characteristic. Especially in the ability of pin cells specialized for red and green to recognize wavelengths, there is sometimes even so much variation that not all colors can be recognized.

About one in twelve boys and two hundred girls confuses red and green, which can make it difficult to distinguish, for example, red berries from bushes. Almost everyone recognizes blue: only one in twenty thousand confuses blue and yellow.

Also, for example, some diseases and medicines can change color vision. It is indeed very challenging to describe colors in a way that everyone would understand in the same way.

Tero Kivelä

professor of ophthalmology

University of Helsinki and University Hospital

What does the hospital do with an amputated limb or other part removed from a person?

Amos Herrero, 11

Mostly the removed body part is transported to a pathologist working in a hospital.

Based on the additional examination by the pathologist, a more accurate diagnosis is often obtained, on the basis of which additional treatments may be planned after the operation.

The samples he takes are stored in the hospital’s archives, because they may be needed later in the patient’s treatment.

However, the removed part is not always needed for further examinations. This happens quite often, for example, to a limb that has just been amputated.

In this case, the removable parts are packed in a red bag with a sticker indicating the contents.

The bag is then transported to the waste management floor, where it is packed in a sealable barrel and transported to the incineration plant. The bag is burned with barrels for days. Material unsuitable for the pathologist’s samples is also disposed of in the same way.

Paulina Salminen

professor of surgery and abdominal surgery, senior physician

University of Turku and TYKS

Why do some fish have lungs but no other species have gills?

Niilo Vehmanen, 9

Also many species of underwater animals other than fish have gills. This is the case, for example, with clams, octopuses, crayfish and some amphibians such as axolotls.

The structure and location of the gills varies. For example, in crayfish, the gills are sheltered on both sides under the dorsal shield.

Tadpoles, or frog larvae, on the other hand, have gills and then lungs during their development. They initially have small and feather-like gills on the sides of the head, then develop internal gills and finally grow lungs to breathe air.

Gills are a handy organ when living underwater. With them you can breathe underwater, because they enable the body to get oxygen from the water and remove carbon dioxide. Gills consist of thin leaf-like or feather-like structures that provide a large surface area for gas exchange.

Among fish, adult lungfish have rudimentary lungs. Their lungs have evolved from a swim bladder. Lungs help them survive in their habitats in the shallow ponds and estuaries of the southern hemisphere. There, the environment often dries up or the water is oxygen-free.

For animals that live above water, the lungs are a much more functional organ than the gills. The lungs are clearly better at taking oxygen from the air. The gills wouldn’t work well enough.

Teppo Vehanen

docent of fish biology

Natural Resources Center

Send the question, the questioner’s full name and age to [email protected]. The column is provided by Touko Kauppinen.