Transport of nutrients and water

Water and nutrients are important to keep living things alive and healthy.

Animals, including humans, get these from what they eat and drink, but how do the water and nutrients get transported around their body?

That is the job of the circulatory system.

The circulatory system transports water and nutrients around the body.

How the circulatory system transports water and nutrients

When nutrients and water are taken in through the mouth, they travel down to the stomach.

When they are digested, they into the bloodstream where they are then circulated around the body to where they are needed.

Not all animals have the same circulatory system. Watch this video to learn more.

• Capillaries are the smallest blood vessels in the human circulatory system. They transfer blood from the arteries to the veins.

• Insects take in oxygen through an opening in their exoskeleton called a spiracle.

• The heart uses different sides to pump both oxygenated and deoxygenated blood around the body.

• Molluscs such as snails and slugs have blue blood, not red like humans.

• Some amphibians like frogs and newts which breathe through lungs, also have gills at different stages in their development, to help them breathe underwater.

• If all of an adult's blood vessels were laid in a line, they would stretch to almost 100,000 miles in length.

• There is evidence that the ancient Egyptians were studying the human circulatory system as early as the 16th century BC.

• Veins contain valves which prevent the backflow of blood.

Did you know?

Most marine fish maintain their water balance by drinking large amounts of seawater.

A fish's kidney retains the water and expels (gets rid of) the excess salt.

The bodies of sharks and rays contain high levels of salt similar to the water in which they live.

Mammals, including humans, have a circulatory system that is made of:

• A heart that pumps blood around the body.

• Blood which contains important substances such as nutrients.

• Blood vessels which carry the blood.

• Veins which take blood back to the heart once it has taken oxygen to the rest of the body.

• Arteries which take blood and oxygen away from the heart and spread it around the body.

• Blood with oxygen is called oxygenated blood.

• Blood without oxygen is called deoxygenated blood.

A mammal's circulatory system looks like this:

As blood goes through the heart twice on every complete circuit of the body, we call this a double circulatory system.

This needs to be very efficient because mammals require lots of energy to live.

As blood stays within the blood vessels mammals have a closed system.

Fish have gills instead of lungs. Oxygen in water moves into their blood via their gills.

As with mammals, water and nutrients are transported around the body by their blood.

A fish's circulatory system has the same three parts as a mammal, but they are in a different order. Blood flows around their circulatory system in this order:

A fish's blood goes through the heart only once every complete circuit. This is called a single circulatory system.

Fish have a closed system, just like mammals, which means that their blood stays in blood vessels.

Insects have a different system to mammals and fish. They don't have lungs or gills to pick up oxygen. Instead they take in oxygen through openings in their exoskeleton called spiracles, which connect with tiny tracheal tubes that run into their bodies.

Insects don't have a closed system of blood vessels so their blood moves freely around their organs. This is called an open circulatory system.

Arteries – Arteries take the blood with oxygen away from the heart and spread it around the body.

Blood vessels – Tubes that carry blood around the body.

Circulatory system – The circulatory system transports water and nutrients around the body. Not all animals have the same system.

Closed system – When blood stays within the blood vessels.

Deoxygenated blood – Blood without oxygen.

Double circulatory system – A system where blood travels through the heart twice every loop.

Gills – The organ that allows fish to breath underwater, it's the equivalent of a mammal’s lungs.

Heart – The organ that pumps blood around the body.

Mammals – Warm-blooded vertebrates with fur or hair on their skin.

Open circulatory system – A system with blood that moves freely around organs. Insects have this type of circulatory system.

Oxygenated blood – Blood mixed with oxygen.

Nutrients – Substances found in food that help an organism to stay alive and healthy.

Single circulatory system – Blood goes through the heart only once every loop in a single circulatory system.

Veins – A type of blood vessel that takes deoxygenated blood from the tissues back to the heart.

Can you decide which is the odd one out?

Give reasons for your answer. You may want to draw diagrams to your reasons.