peripheralblood

Peripheral blood refers to the circulating component of the blood within the vascular system, as opposed to blood contained in the heart, vessels, or bone marrow. It consists of plasma, the liquid matrix, and formed elements including erythrocytes (red blood cells), leukocytes (white blood cells), and platelets. Erythrocytes transport oxygen via hemoglobin, leukocytes provide immune defense, and platelets participate in blood clotting. In a typical sample, hematocrit values reflect the proportion of red cells, with adult ranges roughly around 38–46 percent for women and 40–54 percent for men.

Peripheral blood can be collected by venipuncture and processed to obtain plasma (blood with anticoagulant) or serum (blood allowed to clot). Plasma contains clotting factors, while serum does not. The formed elements are typically analyzed through a complete blood count (CBC) with differential, which enumerates red cells, platelets, and various white cell types. Additional tests may include coagulation studies, chemical and protein analyses, and pathogen testing. Flow cytometry can characterize lymphocyte subsets, and peripheral blood mononuclear cells (PBMCs) can be isolated for research.

Clinical relevance is broad: peripheral blood testing aids in diagnosing anemia, infection, inflammation, and hematologic disorders such as leukemia or myelodysplasia. It is also the primary source for transfusion products, including red blood cells, platelets, and plasma, obtained from donors. Peripheral blood studies complement bone marrow examination in the evaluation of hematologic health and disease.