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Blood Components and Functions

Sep 7, 2025

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Overview

This lecture covers the components, functions, and disorders of blood, emphasizing cellular elements, plasma, hemostasis, blood typing, diagnostic tests, and key medical terminology.

Composition and Functions of Blood

  • Blood consists of 45% formed elements (RBCs, WBCs, platelets) and 55% plasma.
  • RBCs transport oxygen via hemoglobin and lack a nucleus for efficiency.
  • WBCs defend the body against infection; subtypes include granulocytes (neutrophils, eosinophils, basophils, eosinophils) and agranulocytes (monocytes, lymphocytes).
  • Platelets (thrombocytes) enable blood clotting and vessel repair.
  • Plasma contains proteins: albumin (blood pressure), globulin (immunity), fibrinogen (clotting).
  • Serum is plasma without clotting proteins.
  • Blood is a connective tissue: cells are suspended in liquid plasma.
  • Average blood volume in adults is ~10 pints, varying by age, gender, and size.

Blood Terminology and Formation

  • Medical terms use root elements, prefixes, and suffixes to build meaning (e.g., cyt = cell, cret = separate).
  • Erythropoiesis (RBC production) occurs in bone marrow, regulated by erythropoietin, influenced by iron, B vitamins, folic acid, and amino acids.
  • RBCs live ~120 days, transporting O2, CO2, and nitric oxide.

Major Blood Functions

  • Regulates body temperature by circulating heat.
  • Transports nutrients, vitamins, and hormones.
  • Detoxifies via the liver and kidneys.
  • Maintains pH (buffer system keeps blood at 7.35–7.45).
  • Facilitates osmosis for nutrient/waste exchange.
  • Protects against pathogens and initiates clotting.

Blood Types and Immunity

  • Blood types are defined by RBC surface antigens (A, B, AB, O) and the Rh factor (+/-).
  • Plasma antibodies react to specific antigens, leading to agglutination if mismatched.
  • Rh incompatibility can cause erythroblastosis fetalis in pregnancy; treated with RhoGAM.

Hemostasis and Platelets

  • Hemostasis stops bleeding via vascular spasm, platelet plug formation, and coagulation.
  • Platelets release vasoconstrictors and attract neutrophils to injury sites.
  • Anticoagulants, thrombus, and embolus are related terms for clotting conditions.

Blood Cell and Platelet Disorders

  • Anemia: reduced RBCs, causing fatigue/breathlessness; types include iron deficiency, pernicious, sickle cell, hemolytic, aplastic.
  • Polycythemia vera: overproduction of RBCs/WBCs.
  • Poikilocytosis: irregular-shaped RBCs.
  • Leukemia: cancer of blood-forming tissues, leading to excess abnormal WBCs.
  • Leukopenia: low WBCs, often from viral infections.
  • Pancytopenia: decrease in RBCs, WBCs, and platelets, often from chemotherapy.
  • Hemophilia A: clotting factor VIII deficiency.
  • Von Willebrand disease: defective clotting.
  • Thrombocytopenia: low platelet count, leads to bleeding.
  • DIC (Disseminated Intravascular Coagulation): widespread clotting and bleeding.

Diagnostic Tests and Therapeutic Procedures

  • CBC (Complete Blood Count) measures RBCs, WBCs, platelets, and indices.
  • ESR (Erythrocyte Sedimentation Rate): indicates inflammation.
  • Bone marrow biopsy diagnoses anemia, cancers.
  • Blood transfusions treat severe anemia/blood loss.
  • Bone marrow/stem cell transplant replaces diseased marrow.
  • Therapeutic agents: aspirin, heparin, warfarin, newer anticoagulants, streptokinase, recombinant factor VIII, desmopressin, vitamin B12.

Key Terms & Definitions

  • RBC (Red Blood Cell) — Oxygen-transporting cell lacking a nucleus.
  • WBC (White Blood Cell) — Immune cell combating infections.
  • Hematocrit (HCT) — Percentage of blood volume made of RBCs.
  • Platelet (Thrombocyte) — Cell fragment for clotting.
  • Plasma — Liquid blood component with proteins, nutrients, wastes.
  • Serum — Plasma minus clotting proteins.
  • Hemostasis — Process stopping bleeding.
  • Agglutination — Clumping of RBCs due to antibody-antigen reaction.
  • Thrombus — Clot attached to vessel wall.
  • Embolus — Clot traveling in bloodstream.
  • Anemia — Low RBC count or hemoglobin.
  • Leukemia — Cancer of blood-forming tissues.
  • Hemophilia — Genetic clotting disorder.
  • Thrombocytopenia — Low platelet count.

Action Items / Next Steps

  • Review blood cell types, their functions, and major disorders.
  • Memorize key blood terminology and abbreviations.
  • Study blood typing rules and implications for transfusions.
  • Complete assigned readings on anemia types and hemostasis.
  • Prepare for practice questions on diagnostic tests and blood disorders.

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