- Blood looks red, but up close it is cells floating in a pale yellow, watery liquid called plasma.
- Plasma is mainly water and carries dissolved materials such as food molecules, hormones and waste products from cells. Plasma helps to pass heat around the body.
- There are 3 types of cell that float in plasma;
- Red Blood Cells - to transport oxygen
- White Blood Cells - to fight infection
- Platelets - clot blood at an injury site
Red Blood Cells
- They contain a protein called haemoglobin.
- Haemoglobin binds oxygen as it passes through the lungs. oxygen is released into bodily tissues as blood flows around the body.
- Red blood cells have no nucleus which means there is more room for oxygen.
- The flat surface area means that oxygen can diffuse in anout quicker. The shape also means that they can squeeze through capillaries (capillaries are only one cell wide).
White Blood Cells
- White blood cells protect the body by fighting infection (sometimes known as nurse cells).
- To destroy infections they produce antibodies and then engulf and digest the microorganism in a process called phagocytosis.
- Platelets are fragments of cells made up from the cytoplasm of larger cells.
- When you cut yourself, platelets stick to the outside of he cut and clot your blood, preventing you from losing to much blood.
- If you suffer a big loss of blood then you will need a blood transfusion.
- Bags of blood have an anticoagulent in them to stop them from clotting up in the bag.
- It is important that the bags have the blood type clearly printed on the front to prevent problems.
The blood types
- All cells have antigens on the outside of them, this is how White blood cells can detects them and produce the appropriate antibody to stick to the antigen.
- Red blood cells have two different types of antigens, A and B. Depending on which antigens your red blood cells have, you can determine your blood type.
Blood Type Antigens Antibodies
A A anti-B
B B anti-A
AB A and B none
O neither anti-A and anti-B
- It important when transferring blood that the recipient and the donor are the same blood type.
- If they are not blood clots happen and this is fatal because it cannot circulate, leading to a stroke as blood can no longer get to the heart muscles.
- People with the blood group AB can safely be given a transfusion of any blood type due to the lack of antibodies (universal recipient).
- People with the blood group O can be given to anyone due to the lack of antigens (universal donors)
How blood groups are inherited
- Like many of your features, your blood group is determined by a single gene.
- Allele IA - red blood cells have A antigens (Codominant)
- Allele IB - red blood cells have B antigens (Codominant)
- Allele IO - red blood cells have neither antigen A nor antigen B (Recessive)
- To predict a child's blood type you use a genetic cross diagram.