Blood Composition and Function

Blood Overview

• The heart pumps 75 ml of blood with each contraction.
• The average heart beats 70 times per minute.
• 5250 ml of blood is circulated per minute.
• Blood functions include transport, defense, and regulation.

Blood Composition

• Formed elements are produced in red bone marrow.
  • Red blood cells (erythrocytes)
  • White blood cells (leukocytes)
  • Platelets (thrombocytes)
• Plasma: 91% water, 9% salt and organic molecules.
  • Solutes maintain osmotic pressure.
  • Salts act as buffers.
  • Solutes include nutrients, waste, and hormones.
  • Plasma proteins are the most abundant organic molecules.
  • Most are created in the liver, establishing osmotic pressure in the blood.

Types of Plasma Proteins

• Albumins: most abundant plasma protein, contribute significantly to osmotic pressure, and transport molecules.
• Globulins: Some transport substances in the blood; others (gamma globulins) fight pathogens.

Red Blood Cells (Erythrocytes)

• Biconcave shape increases surface area.
• Specialized for oxygen transport.
• Hemoglobin: a pigment that binds up to 4 oxygens.
  • Oxyhemoglobin: bound to oxygen
  • Deoxyhemoglobin: when oxygen leaves hemoglobin in tissues.
• Carbon Dioxide Transport:
  • 7% of CO2 dissolved in plasma.
  • 23% binds to the globin portion of hemoglobin (carbaminohemoglobin).
    • 70% transported as bicarbonate ion in the plasma.

Red Blood Cell Production

• Red blood cells are produced in bone marrow.
• Lose their nucleus and most organelles during development.
• Erythropoietin: a hormone produced by the kidneys which stimulates red blood cell production when oxygen levels are low.

Blood Disorders/Disorders Involving RBCs

• Jaundice: a buildup of heme in the blood (liver problems)
• Anemia: too few red blood cells/low hemoglobin.
  • Iron-deficiency anemia: caused by insufficient dietary iron
  • Pernicious anemia: lack of vitamin B12
  • Folic-acid deficiency anemia: lack of folic acid
• Hemolytic anemia: too much red blood cell breakdown (hemolysis)
• Sickle-cell disease: defective hemoglobin structure causing sickle-shaped red blood cells prone to rupture.

White Blood Cells (Leukocytes)

• Large cells; translucent unless stained, less numerous than red blood cells.
• Produced in red bone marrow, production regulated by colony-stimulating factors.
• Fight infection (immune system).
• Some live for days, others for months/years.
  • Granular Leukocytes:
    • Neutrophils: most abundant white blood cell (50-70%), multi-lobed nucleus, first responders to infection, engulf pathogens via phagocytosis.
    • Eosinophils: bilobed nucleus, many large granules, involved in parasitic infections and allergies.
    • Basophils: rarest white blood cell, U-shaped nucleus, develops into mast cells, release histamine during allergic reactions, histamine dilates blood vessels but constricts breathing passages.
  • Agranular Leukocytes:
    • Lymphocytes: 25-35% of white blood cells, B and T cells. (B cells produce antibodies. Some cytotoxic T cells directly destroy pathogens).
    • Monocytes: largest of the white blood cells. Develop into larger macrophages in tissues, engulf pathogens, old cells and debris.

Disorders Involving WBCs

• Severe Combined Immunodeficiency Disease (SCID): inherited disease where lymphocytes do not develop.
• Leukemia: cancer in which white blood cells proliferate uncontrollably.
• Infectious mononucleosis: viral infection of lymphocytes resulting in fatigue, sore throat, swollen lymph nodes.

Platelets (Thrombocytes)

• Result from fragmentation of large cells called megakaryocytes in red bone marrow.

Blood Clotting

• Blood clotting (coagulation) important to prevent blood loss.
• 13 clotting factors, calcium ions and enzymes contribute in clot formation.
• Platelets and damaged tissue cells release prothrombin activator.
• Fibrin thread forms, trapping red blood cells.

Disorders Related to Blood Clotting

• Thrombocytopenia: too few platelets.
• Thromboembolism (stationary clot forms, then travels): forms, travels (caused by leukemia/drugs, etc.).
• Hemophilia (A, and B Christmas disease, Von Willebrand Disease): genetic deficiencies of clotting factors, unable to fully form blood clots.

Blood Types

• Determined by proteins on the surface of red blood cells (RBCs) (antigens).
• ABO blood groups: presence/absence of type A and B antigens.
  • Blood compatibility is crucial (mixing small amounts of blood to test for agglutination).
    • O is universal donor (lacks antigens)
• Rh blood groups: presence or absence of Rh antigen.
  • Anti-Rh antibodies can develop, leading to hemolytic disease in newborns involving mixing of fetal and paternal blood.

Homeostasis

• Organ systems interact to maintain homeostasis (internal balance).
• Cardiovascular system interacts with:
  • lymphatic system
  • respiratory system
  • digestive system
  • muscular system
  • endocrine system
  • urinary system

Overview of blood, including its composition of formed elements and plasma. Discusses the role of red blood cells, white blood cells, and platelets. Explains the function of plasma proteins like albumins and globulins in transport and immunity.