Hemic and Immune Systems
The hemic and immune systems comprise blood, blood-forming tissues, lymphatic structures, and defenses that recognize and respond to threats.
Blood: A circulating tissue of plasma, red blood cells, white blood cells, and platelets. It carries the cells and proteins that connect the system’s organs and defenses.
Hematopoiesis: The formation of blood cells from hematopoietic stem and progenitor cells. It replenishes the cellular components circulating through the system.
Complete Blood Count: A laboratory test measuring major blood-cell types and related indices. It gives a routine snapshot of blood-cell production and circulating cell levels.
Hemostasis: The process that stops bleeding through vascular constriction, platelet activity, and coagulation. It is a blood function that prevents blood loss, rather than primarily defending against infection.
Bone Marrow: The tissue inside many bones where blood cells are produced. It continually supplies the blood with immune cells and other blood cells.
Innate Immunity: Rapid defense based on inherited recognition mechanisms and responses that do not require prior exposure. It provides immediate defenses while adaptive responses develop.
Blood Transfusion: The transfer of donated blood or blood components into a patient's circulation. It replaces components lost or deficient through disease, injury, or treatment.
Coagulation: The conversion of blood into a clot through a cascade of clotting-factor activation. It is often grouped with blood functions but is distinct from immune recognition.
Lymphatic System: A network of vessels, tissues, and organs that returns tissue fluid to blood and supports immune responses. It links immune tissues and transports lymph, cells, and antigens.
Adaptive Immunity: Antigen-specific defense mediated by B and T lymphocytes, with the capacity for immunological memory. It supplies targeted responses and lasting protection against particular threats.