Blood transports vital substances like oxygen and nutrients throughout the body. It is composed of plasma and three main cell types - red blood cells, white blood cells, and platelets. Red blood cells are produced in the bone marrow and carry oxygen to tissues via hemoglobin. They circulate for about 120 days before being broken down. White blood cells help protect the body from disease. Platelets help the blood clot and stop bleeding from broken blood vessels. The blood also contains proteins, gases, and other nutrients.

1. Blood

4. Blood Composition

5. Origin of Blood Cells

22. Platelet Plug Formation

24. ABO Blood Group

25. Agglutination

26. Preferred and Permissible Blood Types for Transfusion

27. Genotypes of Blood Types Genotype Blood Type (Antigen) Antibody A A A o A B B B B o B A A B AB None o o O A and B D D D - Rh + None - - Rh - None

28. How Rare Is Your Blood? Blood Group and Rh Type How Many Have It? Frequency O Positive One in 3 37.4% O Negative One in 15 6.6% A Positive One in 3 35.7% A Negative One in 16 6.3% B Positive One in 12 8.5% B Negative One in 67 1.5% AB Positive One in 29 3.4% AB Negative One in 167 0.6%

30. Have no fear: they have developed a shot called Rhogam that they can give to women with negative blood to prevent this from hurting the baby.