ks4 what is blood (boardworks)

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KS4 Biology

What is Blood?


Contents

What is Blood?

What is blood made of?

Plasma

White blood cells

Red blood cells

Platelets

Summary activities


Blood and the circulatory system

The circulatory system is made up of the heart, blood and blood vessels.

What exactly is blood and what does it do?

Blood is the fluid that flows in the circulatory system and carries substances around the body.


How much blood?

How many litres of blood are there in the circulatory system of an average adult?

5.5 litres 5.5 litres



Blood is made up of a liquid called plasma and blood cells that float in this plasma.

If a test tube of blood is left to stand for a while what happens to it?

The blood cells sink to the bottom of the test tube and separate from the plasma which is a clear yellow liquid.

The liquid in blood is yellow! So why does blood look red?

blood cells(45% ofvolume)

plasma (55% ofvolume)


Different types of blood cells

Blood plasma carries three types of blood cells. They have different shapes and carry out different functions.

red blood cell

white blood cell

platelet


What’s in a drop of blood?


Contents

What is Blood?


Plasma

White blood cells

Red blood cells

Platelets

Summary activities


Blood flows around the body transporting substances from one place to another.

Plasma is the blood fluid that surrounds blood cells and carries them along as it flows through the blood vessels.

Plasma is mostly water and contains other substances that are dissolved in it.

What useful and waste substances are dissolved in and transported by plasma?

What does plasma do?


What is dissolved in plasma?

Plasma is mostly water with other substances dissolved in it.

Useful substances dissolved in plasma are digested food.

This must be transported to where it is needed in the body.

Waste substances dissolved in plasma are carbon dioxide and urea.

These must be transported to where they can be removed from the body.


Plasma: transporting digested food

The digestive system breaks long insoluble molecules of food into small soluble molecules that the body can use.

Where does soluble digested food enter the blood?

Soluble digested food diffuses from the small intestine into the bloodstream and dissolves in the plasma.

The digested food is then carried to the body’s cells and used in various chemical reactions.

digested food in blood plasma


Carbon dioxide is produced by respiration in the body’s cells.

This waste product is poisonous to the body and so must be removed as quickly as possible. How does this happen?

Plasma: transporting carbon dioxide

carbon dioxide in blood plasma

Carbon dioxide diffuses from body cells into the blood where it dissolves in plasma.

Carbon dioxide then carried from the cells to the lungs.How is this waste product finally removed from the body?


Urea is another waste substance that is transported by the blood. It is made in the liver.

Urea is toxic to the body and must be removed as quicklyas possible.

Plasma: transporting urea

urea in blood plasma

Urea enters the blood in the liver and dissolves in plasma.It is then carried from the liver to the kidneys.

The kidneys filter blood and remove urea from plasma. This waste product is then removed from the body in urine.


Dissolved substances in plasma


What does plasma do?


Contents

What is Blood?


Plasma

White blood cells

Red blood cells

Platelets

Summary activities


Red blood cells are the most common type of blood cell.

What do red blood cells do?

The job of red blood cells is to transport oxygen from the lungs to the body’s cells, where is used in respiration.

The body contains millions and millions of red blood cells.Why does it need so many?

oxygen


Features of a red blood cell

A red blood cell has several features that help it do its job:

Disc-shaped, witha dent on each side, creates a

large surface area for gas exchange.

A large surface area compared to volume, so oxygen is always close to

the surface.

It has no nucleus, so there is more

space for haemoglobin and so more oxygen.

It contains haemoglobin,

a special pigmentthat combines with oxygen.


Another important feature of a red blood cell is its size.

How does this help the release of oxygen?

The size of a red blood cell forces it to slow down as it passes through a capillary. The surface of the red blood cell is exposed to the surface of the capillary and so gas exchange will definitely happen.

Another feature of red blood cell

The diameter of a red blood cell is slightly bigger than the average diameter of a capillary.


Features of a red blood cell – activity


haemoglobinhaemoglobin

Red blood cells and haemoglobin

Haemoglobin is the special pigment in red blood cells.

At the lungs, oxygen diffuses into red blood cells and combines with haemoglobin to form oxyhaemoglobin.

This is how red blood cells are able to bind to oxygen and carry it in the blood.

Oxyhaemoglobin makes red blood cells appear bright red.

oxygenoxygen

++ oxyhaemoglobinoxyhaemoglobin


++oxygenoxygen

haemoglobinhaemoglobin

Red blood cells and haemoglobin

Red blood cells loaded with oxyhaemoglobin carry oxygen from the lungs to the body’s cells.

Here, oxyhaemoglobin changes back to haemoglobin and oxygen is released.

Oxygen is then able to diffuse into the body’s cells.

Why do red blood cells appear a dull red colour when oxygen is released?

oxyhaemoglobinoxyhaemoglobin


Journey of a red blood cell

Oxygen enters the body when air is inhaled into the lungs.

How does this oxygen enter the blood?

Oxygen diffuses from the alveoli on the surface of the lungs into the bloodstream.

The oxygen then diffuses into the red blood cells where it meets haemoglobin.

(not to scale)

oxygen +haemoglobin

oxygen +haemoglobin




In the red blood cells at the lungs, oxygen combines with haemoglobin to form oxyhaemoglobin.

This oxygen-rich blood travels fromthe lungs, through the circulatory system, to body cells.

How does oxygen get from red blood cells into the body’s cells?

oxygen +haemoglobin

oxygen +haemoglobin

(not to scale)




When red blood cells reach the body’s cells,oxyhaemoglobin changes back to haemoglobin and oxygen is released.

Oxygen then diffuses from the red blood cells across the lining of the capillary and into the body’s cells.

What happens next to the red blood cells?

oxygen +haemoglobin

oxygen +haemoglobin


(not to scale)

haemoglobinhaemoglobin+ oxygen + oxygen



haemoglobinhaemoglobin+ oxygen + oxygen


Red blood cells that have released oxygen to the body’s cells have to get back to the lungs.

So this oxygen-poor blood travels from the body’s cells through the circulatory system.

At the lungs, the red blood cells can pick up more oxygen and start another journey around the body.

oxygen +haemoglobin

oxygen +haemoglobin


(not to scale)



Red blood cells in an alvelous


Red blood cells in a capillary bed


How do red blood cells carry oxygen?


Contents

What is Blood?


Plasma

White blood cells

Red blood cells

Platelets

Summary activities


What do white blood cells do?

White blood cells are the largest type of blood cell.

They have a large nucleus and can change their shape.

White blood cells protect the body from disease by fighting invading microbes that can cause infection.

White blood cells can squeeze through the walls of capillaries. How does this help them fight against microbes?


Different types of white blood cells

Different types of white blood cells protect the bodyin different ways:

Some white blood cells fight against infection by surrounding invading microbes and then digesting them!

Other white blood cells produce antibodies or antitoxins to fight against infection.


White blood cell count

unwellwhite blood cell number is high

healthywhite blood cell

count is low

Doctors can check the number of white blood cells in a person’s blood to find out if they are healthy or fighting off an infection.

Why is the white blood cell count higher when a person is fighting off an infection?


Contents

What is Blood?


Plasma

White blood cells

Platelets

Red blood cells

Summary activities


Platelets are the third type of blood cell.

They are important for blood clotting.

What do platelets do?

Platelets are cell fragments that have broken off from other larger cells.

They are much smaller than red and white blood cells and do not have a nucleus.

platelet


Platelets and blood clotting

Platelets help to make tiny fibres that form a net at the site of a cut.

11 The clot dries and forms a scab which protects the cutwhile new skin grows.

33

Red blood cells are trapped in this net forming a blood clot.

22Why is it important not to pick a scab?


Contents

What is Blood?


Plasma

White blood cells

Red blood cells

Platelets

Summary activities


What do blood cells do?


Which type of blood cell?


Multiple-choice quiz

ks4 what is blood (boardworks)

Documents

blood flows

blood fluid

blood vessels

blood plasmaurea

drop of blood

litres of blood

millions of red blood

job of red blood cells