Blood Components and Functions

• Module II focuses on the circulatory, lymphatic, and respiratory systems
• Unit 1 covers blood components

Blood Component Functions

• Blood transports nutrients, hormones, gases, and wastes through red blood cells (RBCs)
• Blood provides protection against foreign invaders via white blood cells (WBCs) and enables clotting through platelets
• Blood regulates the internal environment, including pH (7.35-7.45) and osmolarity of tissues

Blood Composition

• Blood comprises plasma and formed elements
• An adult human typically has 4-6 liters of blood

Plasma

• Plasma constitutes about 55% of blood volume and is the fluid component
• Plasma is mostly water, containing ions, nutrients, wastes, hormones, and gases
• Plasma proteins include:
  • Albumin: The most abundant protein, thickens blood
  • Globulins: Antibodies that attach to foreign microbe antigens, small proteins
  • Fibrinogen and prothrombin: Important for clot formation
• Serum is plasma without clotting proteins

Formed Elements

• Formed elements are cells and cell fragments suspended in plasma, making up roughly 45% of blood volume
• All formed elements originate in red bone marrow, especially in bones like the sternum, ribs, and coxal bones
• Some WBCs migrate to lymphatic tissues, such as the spleen, thymus, and lymph nodes, to mature
• Red blood cells (RBCs), also known as erythrocytes, are the most abundant formed element
  • Shape: biconcave disc
  • Anucleated: survive for about 4 months
  • Lack organelles
  • Purpose: involved in the transport of oxygen, carbon dioxide, and hydrogen ions within the blood
  • Oxygen and carbon dioxide bind to hemoglobin (Hb), an iron-containing protein that gives blood its red color
  • Erythropoiesis: RBC formation in bone marrow
  • Regulation: Erythropoietin (EPO), produced by kidneys in response to low oxygen levels, stimulates RBC production in the red bone marrow

Hematocrit

• Hematocrit is a blood cell analysis that involves spinning a blood sample in a centrifuge to analyze its components

Anemia

• Anemia is the inability to carry enough oxygen in the blood, often due to RBC deficiency or lack of hemoglobin
• Pernicious anemia: Low RBC count caused by vitamin B12 deficiency
• Iron deficiency anemia: Lack of iron, a hemoglobin component needed for carrying oxygen
• Sickle cell anemia: Abnormal hemoglobin causes RBCs to sickle when oxygen is released
  • Sickled RBCs clog capillaries, preventing blood flow
  • Erythropoiesis cannot compensate for the loss, resulting in anemia

Polycythemia

• Polycythemia occurs when red bone marrow overproduces RBCs, potentially increasing blood viscosity
• A more viscous (thick) blood forces the heart to work harder and increases the risk for heart attack and stroke

White Blood Cells (WBCs) or Leukocytes

• White blood cells (WBCs) or leukocytes defend the body against invading microorganisms (pathogens)
• They have a nucleus
• Live for a few days to several months
• Can leave blood vessels to move through surrounding tissues
• Neutrophils and monocytes: Phagocytize microbes
• Eosinophils: Phagocytize antigen-antibody complexes, an increase in number if exposed to an allergen
• Basophils: Release histamine and heparin, which prevents formation of blood clots and increase inflammation, responsible for symptoms of an allergic reaction
• Lymphocytes:
  • B-lymphocytes: Produce antibodies (globulin proteins) that target foreign microbes
  • T-lymphocytes: Directly attack foreign microbes (as killer T-cells)
  • Antigen-Antibody response: involves the binding of an antigen to a B-lymphocyte receptor, activating the B-lymphocyte to produce plasma cells which manufacture antibodies for that specific antigen
  • Some activated B-lymphocytes remain as memory cells for quicker response to future attacks
  • Antibodies bind to antigens for eosinophil phagocytosis and microbe neutralization

Vaccinations and Autoimmune Disorders

• Vaccinations use weakened or dead cell fragments to generate memory cells
• Autoimmune disorders occur when antibodies attack the body's own cells

Abnormal White Blood Cell Conditions

• Leukopenia: Abnormally low WBC count (e.g., AIDS)
• Leukocytosis: Abnormally high WBC count, often during infection
  • Leukemia: High WBC count where WBCs are cancer cells that do not properly function

Platelets

• Platelets are small, anucleated cell fragments from megakaryocytes with a lifespan of 5-9 days
• Platelets form clots to plug holes in vessel walls and stop bleeding

Hemostasis and Blood Types

• Unit 2 addresses hemostasis and blood types

Hemostasis

• Hemostasis is the process of controlling blood flow through:
  • Vascular spasm: Smooth muscle constriction upon damage, aided by platelet factors reducing blood flow
  • Platelet plug formation: Platelets adhere to vessel wall tears and release chemicals like thromboxane A2, serotonin, and ADP
  • ADP causes platelets to become sticky, gather, and form a plug
  • Coagulation (clotting): Goal is to make fibrin
    • Extrinsic pathway: Chemicals from damaged tissues activate prothrombinase
    • Intrinsic pathway: Platelets release substances that activate prothrombinase
    • Vitamin K is needed to synthesize for clotting factors
    • Factors are calcium needed

Fibrin

• Fibroblasts generate connective tissue around the vessel
• Fibrin is made with simultaneous occurence after injury
• Activated platelets start the clotting process

Hemophilia

• Hemophilia is the result of an inability to properly form fibrin, because of clotting factor issues

Blood Vessel Sections

• Endothelium: keeps it smooth
• Prostacyclin: all stuff in blood vessel
• Smooth muscle around tissue