Blood Chapter 18 Part 3 – Key Terms (WBCs, Platelets, Hemostasis)

Vocabulary flashcards covering key terms related to white blood cell production, platelets, and the hemostasis/coagulation process from the lecture notes.

Hemocytoblasts

Stem cells in red bone marrow that give rise to all blood cells via myeloid and lymphoid lines.

Myeloid stem cells

Stem cells that produce all WBCs except lymphocytes; mature in red bone marrow.

Lymphoid stem cells

Stem cells that produce lymphocytes; lymphopoiesis; T cells mature in the thymus.

Lymphopoiesis

Production of lymphocytes.

Lymphocytes

White blood cells responsible for adaptive immunity (B, T, and NK cells).

Monocytes

WBCs that enter tissues to become macrophages and phagocytose pathogens or debris.

Neutrophils

Most abundant WBC; granulocyte that phagocytizes pathogens.

Eosinophils

Granulocytes that attack parasites and modulate allergic reactions; involved in inflammatory responses.

Basophils

Granulocytes that release histamine and heparin to promote inflammation.

Platelets

Cell fragments from megakaryocytes; lack nucleus; essential for clotting; circulate 9–12 days.

Megakaryocyte

Giant bone marrow cell that sheds platelets.

Thrombopoietin (TPO)

Hormone that increases platelet formation and megakaryocyte production.

Thrombocytopoiesis

Platelet production in the bone marrow.

Colony-stimulating factors (CSFs)

Hormones that stimulate production of specific blood cells (e.g., M-CSF, G-CSF, GM-CSF, Multi-CSF).

M-CSF

CSF that stimulates monocyte production.

G-CSF

CSF that stimulates production of granulocytes (neutrophils, eosinophils, basophils); drug neupogen is an example.

GM-CSF

CSF that stimulates granulocyte and monocyte production.

Multi-CSF

CSF that accelerates production of granulocytes, monocytes, platelets, and RBCs (not lymphocytes).

Platelet count

Normal range: 150,000 to 500,000 platelets per μL of blood.

Thrombocytopenia

Abnormally low platelet count; major sign is bleeding.

Thrombocytosis

Abnormally high platelet count; may signal infection, inflammation, or cancer.

Hemostasis

Cessation of bleeding; occurs in three phases: vascular, platelet, and coagulation.

Vascular phase

Vascular spasm; endothelial cells contract, expose basement membrane, and release factors (e.g., endothelins) to promote clotting and platelets adhesion.

Platelet phase

Platelet adhesion and aggregation forming a platelet plug; activated platelets release chemicals that promote further aggregation.

Coagulation phase

Clotting phase; a cascade of clotting factors converts fibrinogen to fibrin, forming a clot.

Endothelins

Endothelial factors that stimulate smooth muscle contraction and endothelial growth; contribute to vascular phase.

Tissue factor (TF, Factor III)

Released by damaged tissue; together with Ca2+ activates Factor X in the extrinsic pathway.

PF-3 (Platelet Factor 3)

Phospholipid released by platelets that supports coagulation reactions (intrinsic pathway).

Ca2+ (Calcium ions)

Essential cofactor in many clotting reactions.

Extrinsic pathway

Clotting pathway initiated by tissue factor outside the blood; TF + Ca2+ activates Factor X.

Intrinsic pathway

Clotting pathway initiated by exposed collagen; involves Factors XII, XI, IX, VIII, and X with PF-3.

Common pathway

Convergence of intrinsic and extrinsic pathways; Factor X activates prothrombinase, which converts prothrombin to thrombin; thrombin converts fibrinogen to fibrin.

Vitamin K

Fat-soluble vitamin required to synthesize several clotting factors; produced by gut bacteria.

Antithrombin-III

Inhibits thrombin and other clotting factors; an anticoagulant.

Heparin

Accelerates antithrombin III activity; used as an anticoagulant.

Thrombomodulin

Endothelial protein that binds thrombin and activates Protein C.

Protein C

Anticoagulant that inactivates factors and promotes fibrinolysis; requires thrombomodulin–thrombin complex.

Prostacyclin

Endothelial product that inhibits platelet aggregation and vasodilates.

Plasmin

Enzyme that digests fibrin and dissolves clots (fibrinolysis).

t-PA (tissue plasminogen activator)

Activates plasminogen to plasmin, promoting fibrinolysis.

Fibrinolysis

Dissolution of a clot by plasmin breaking down fibrin.

Hemophilia

Genetic disorder (often X-linked) with deficiency of clotting factors, typically VIII or IX.

Factor VIII

Clotting factor missing in Hemophilia A.

Factor IX

Clotting factor missing in Hemophilia B.

Warfarin

Anticoagulant that inhibits vitamin K–dependent clotting factor production.