1. What is the composition of blood?• Red blood cells (contain haemoglobin)

– Contain iron, which gives the red colour– Transports oxygen around the body

• White blood cells (many different types)– Fight disease, destroys foreign matter

• Platelets– Broken up blood cells– Forms clots to prevent excessive bleeding

when cut

• Plasma (55% of blood)– 90% water, but also waste (specifically

bicarbonate – dissolved CO2) and nutrients

2. How is blood carried?

Order of the blood vessels

The blood vessels

• Blood is carried from the heart via the aorta (primary artery) which splits in to:

• Arteries• Arterioles• Capillaries• In the various organs and tissues capillaries

exchange oxygen for carbon dioxide and nutrients for waste then return to the heart via:

• Venules• Veins• Superior & inferior vena cava (primary veins)

Arteries & arterioles

Capillaries• Oxygen in delivered to the cells of our

body via capillaries

Veins & Venules

Note the one-way valve

Peristalsis in veins & venules

• Blood leaves the heart via arteries and return via veins

• Almost all arteries carry oxygenated blood (exception: pulmonary artery)

• Almost all veins carry deoxygenated blood (exception: pulmonary vein)

Blood types – the ABO system• There are 4 blood types – A, B, AB & O• Each type of blood contains its own antigen• Each blood type has antibodies against the other

antigens

Blood type

A B AB O

Antigen A B AB -

Antibody B A - AB

Percentages of each blood type in the Australian population

Blood types – the ABO system• Antibodies are part of our defence system

and will clot and destroy its target antigen

• When blood is donated, it contains its own antigens but carries no antibodies

• If you have no antibodies, then you can receive any type of blood

• If your blood contains no antigens it can be given to anyone

Blood types – the Rhesus system

• The other main blood type is Rhesus (Rh), for this you can only be positive or negative.

• Rh+ carries the Rh antigen

• Rh- people produce the Rh antibody

Putting it all together

• So, we have a total of 8 blood types to consider when giving someone a transfusion:

• A+, A-, B+, B-, AB+, AB-, O+, O-

• Maintains body temperature by delivering heat from the liver to other parts of the body.

AB+ AB- A+ A- B+ B- O+ O-

AB+

AB-

A+

A-

B+

B-

O+

O-

AB+ AB- A+ A- B+ B- O+ O-

AB+

AB-

A+

A-

B+

B-

O+

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XX

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