Leukocytes, Thrombocytes, and Blood Grouping

Comprehensive vocabulary flashcards covering the structure, classification, and functions of leukocytes and thrombocytes, the stages of hemostasis, and blood typing principles.

Leukocytes

Also known as white blood cells, these are cells of the immune system derived from hematopoietic stem cells in bone marrow that protect against infectious disease and foreign invaders.

Normal WBC Count

The standard range of white blood cells in a healthy adult, which is between $4,000$ to $11,000 ext{ WBC/microliter}$ of blood.

Neutrophils

The most abundant type of granulocytes (40 ext{%} to 70 ext{%} of all WBCs) that serve as short-lived, highly mobile first responders to inflammation and contain antibiotic proteins called defensins.

Chemotaxis

The process by which neutrophils undergo amoeboid movement toward sites of infection or inflammation in response to chemicals released by microbes and inflamed tissues.

Eosinophils

Acid-loving leukocytes (2 ext{%} to 3 ext{%} of WBCs) that fight viral infections and parasitic worms, and serve as important mediators of allergic responses.

Basophils

The least common type of WBC (0.5 ext{%} to 1 ext{%}) that release granules containing heparin (anticoagulant), histamine, and serotonin to mediate inflammatory and allergic reactions.

Lymphocytes

White blood cells (30.0 ext{%}) including B cells (destroy bacteria), T cells (attack viruses, fungi, and cancer cells), and Natural killer cells (infectious microbes and tumor cells).

Monocytes

The largest leukocyte and part of the innate immune system; they circulate in the blood for 1–3 days before migrating into tissues to differentiate into wandering macrophages and dendritic cells.

Dendritic cells

Mononuclear phagocytes that link innate and adaptive immunity by capturing, processing, and presenting antigens to T-cells.

Leukocytosis

A normal, protective response to stress (such as microbes, exercise, or surgery) where the number of WBCs increases above 10,000/ ext{̇μL}.

Leukopenia

An abnormally low level of white blood cells (below 5,000/ ext{̇μL}) that may be caused by radiation, shock, or chemotherapeutic agents.

Thrombocytes

Also called platelets, these are small, colorless, disc-shaped cell fragments ($150,000$ to $400,000/ ext{microliter}$) derived from megakaryocytes that promote blood clotting.

Thrombopoietin

A hormone produced by the liver, kidney, and bone marrow that influences myeloid stem cells to develop into megakaryocytes and eventually platelets.

Hemostasis

The sequence of physiological responses that stops bleeding, consisting of vascular spasm, platelet plug formation, and blood clotting (coagulation).

Vascular Spasm

A prompt constriction of a broken blood vessel, lasting minutes to hours, caused by damage to smooth muscle, autacoid factors, or nervous reflexes.

Platelet Plug Formation

A three-step process involving platelet adhesion (sticking to damaged endothelium), platelet activation (releasing ADP, thromboxane $A_2$, and serotonin), and platelet aggregation.

Extrinsic Pathway

A blood clotting pathway activated by external trauma that causes blood to escape from the vascular system; it is quicker than the intrinsic pathway.

Intrinsic Pathway

A clotting pathway activated by trauma inside the vascular system, such as contact with exposed endothelium, collagen, or blood proteins.

Thrombomodulin

A protein bound to the endothelial membrane that slows clotting by removing thrombin and activating Protein C, which acts as an anticoagulant.

Agglutinogens

Antigens composed of glycoproteins and glycolipids present on the surface of red blood cells; at least 24 blood groups and 100 antigens exist.

ABO Blood Grouping

A system based on two glycolipid antigens (A and B); Type A has A antigen, Type B has B antigen, Type AB has both, and Type O has neither.

Rh Blood Group

A blood categorization named after the Rhesus monkey; individuals are Rh positive if their RBCs have the Rh antigen (Rh factor) and Rh negative if they lack it.

Erythrocyte Sedimentation Rate (ESR)

A non-specific diagnostic test that monitors inflammatory activity; normal values are $15-20 ext{ mm/hr}$, and it increases when plasma proteins promote Rouleaux formation.