Platelets

Appearance • Irregular shape • Colourless • Sticky • Very very tiny!

What do they do? • Maintain homeostasis •Preventing blood loss

•Homeostasis = ability to maintain a balanced internal environment in response to the environmental changes around them

How? • Adhesion: platelets attach to the rip or tear

in the blood vessel• Activation: platelets change shape, turn on

receptors and secrete chemical messages to other cells

• Aggregation: they connect to each other through receptor bridges

Definitions • Coagulation cascade = combination of

proteins activated by the chemical messages from the platelets. At the end of the coagulation cascade fibrinogens have become fibrin.

• Fibrin = product of fibrinogens which are blood clotting proteins

How? (cont’d)• As the platelet plug forms it activates the

coagulation cascade which uses fibrin deposits to form the clot.

• A “white clot” is made up mostly of platelets, while a “red clot” is made up of mostly fibrin.

• Typically our clots are a mixture of both

Good vs. Bad• What would be an example of a good blood

clot? • A bad one? • What might be the results of a bad blood

clot?

Blood Clots inside the Blood Vessels• Can be caused by: • Cancer, pregnancy, lupus, rheumatoid arthritis, certain medications• Sticky blood

• Damage to the inside of blood vessels • Can lead to: • Heart attack, stroke, embolism

Factors • Smoking• Physical inactivity

Blood clots and Aspirin• What do you think will happen to a blood

clot if you take aspirin? Does it make it make it better or worse?

• https://www.youtube.com/watch?v=--bZUeb83uU