Blood

"Blood is a constantly circulating fluid providing the body with nutrition, oxygen, and waste removal. Blood is mostly liquid, with numerous cells and proteins suspended in it, making blood ""thicker"" than pure water. The average person has about 5 liters (more than a gallon) of blood.
A liquid called plasma makes up about half of the content of blood. Plasma contains proteins that help blood to clot, transport substances through the blood, and perform other functions. Blood plasma also contains glucose and other dissolved nutrients.
About half of blood volume is composed of blood cells:
• Red blood cells, which carry oxygen to the tissues.
• White blood cells, which fight infections.
• Platelets, smaller cells that help blood to clot.
Blood is conducted through blood vessels (arteries and veins). Blood is prevented from clotting in the blood vessels by their smoothness, and the finely tuned balance of clotting factors."

Polycythemia vera

"Polycythemia vera is a bone marrow disease that leads to an abnormal increase in the number of blood cells. It may also result in the overproduction of white blood cells and platelets. Polycythemia vera is a disorder of the bone marrow. It mainly causes too much production of red blood cells, although the numbers of white blood cells and platelets are also increased.
It is a rare disease that occurs more often in men than women, and is rare in patients under age 40. It is usually associated with a gene mutation called JAK2V617F. The cause of this mutation is unknown. Symtomps: 1. Breathing difficulty when lying down
2. Dizziness
3. Excessive bleeding
4. Fullness in the left upper abdomen (due to enlarged spleen)
5. Headache
6. Itchiness, especially after a warm bath
7. Red coloring, especially of the face
8. Shortness of breath
9. Symptoms of phlebitis"