Platelets and plasma
Platelets are small cell fragments without a nucleus: 150000–400000 in every mm3, living 5–7 days.
How a cut stops bleeding
Vessel damaged
→
Platelets release thromboplastin
→
Fibrin threads form
→
Clot
The fibrin threads trap blood cells and seal the wound.
Plasma
Plasma is about 90% water. Dissolved in it are:
- Digested food: glucose, amino acids, fatty acids
- Plasma proteins, including those for clotting and the antibodies
- Salts, hormones and vitamins
- Waste: urea and carbon dioxide