10.2 Blood

• Blood: is a liquid connective tissue that has many different functions: Transports nutrients, wastes, and hormones Regulates body temperature by dispersing body heat Regulates blood pressure (plasma proteins contribute to osmotic pressure of blood) Protects the body against invasion by disease-causing pathogens Clotting mechanisms protect the body against loss of blood.
• Functions of plasma proteins

  • Transport: albumin transports bilirubin; lipoproteins transport cholesterol
  • Blood clotting: fibrinogen
  • Fighting infection: antibodies
  • Maintaining blood volume: plasma proteins are too large to leave the capillaries− Blood in capillaries has a higher solute concentrate than tissue fluid, causing water to diffuse in
• Red blood cells (erythrocytes)


  • Manufactured in the red bone marrow of the skull, ribs, vertebrae, and ends of the long bones
  • Transport oxygen and carbon dioxide in the blood
  • Mature red blood cells have no nuclei and are biconcave
  • Live about 120 days (possibly due to lack of nuclei) and are destroyed in the liver and spleen
  • Biconcave shape increases flexibility (for moving through capillary beds) and surface area (for diffusion of gases)
  • Contain hemoglobin, a respiratory pigment that carries oxygen
  • Iron in hemoglobin acquires oxygen in the lungs and gives it up in the tissues
• kidneys produce an increased amount of the erythropoietin hormone, which speeds up the maturation of red blood cells in the bone marrow
• White blood cells (leukocytes)


  Usually larger than red blood cells, have a nucleus, lack hemoglobin, and appear translucent without staining
• White blood cells

  • Fight infection and play a role in developing immunity
• Types of white blood cells

  • Granular leukocytes
  • Agranular leukocytes
• Granular leukocytes

  • Neutrophils
  • Eosinophils
  • Basophils
• Agranular leukocytes

  • Monocytes
  • Lymphocytes
• Granular leukocytes

  Filled with spheres that contain enzymes and proteins that help white blood cells defend against microbes
• Neutrophils

  Phagocytize pathogens
• Eosinophils


  Phagocytize antigen-antibody complexes and allergens
• Basophils

  Release histamine to promote blood flow to injured tissues
• Agranular leukocytes


  Include cells that can phagocytize pathogens and cells that are involved in specific immunity
• Monocytes

  Largest white blood cells; differentiate into phagocytic dendritic cells and macrophages
• Lymphocytes

  • B lymphocytes (B cells)
  • T lymphocytes (T cells)
• B lymphocytes (B cells)


  Produce antibodies
• T lymphocytes (T cells)

  Helper T cells regulate the responses of other cells; cytotoxic T cells kill other cells
• Disease is present

  Number of white blood cells increases or decreases beyond normal
• Neutrophils


  Increase in response to bacterial infections
• B cells


  Increase in response to infectious mononucleosis
• T cells

  A low number indicates if an HIV-infected person has AIDS
• Leukemia


  A large number of abnormal white blood cells is a characteristic of this form of cancer
• Macrophage


  • Engulfing bacteria
• Platelets


  Involved in blood clotting (coagulation)
• Platelets

  • Also called thrombocytes
  • Result from fragmentation of large cells called megakaryocytes in the red bone marrow
• Blood clotting

  1. Platelets clump at the site of damage and form a plug to partially seal the leak

  2. Platelets and damaged tissue release prothombin activator, which converts prothrombin (a clotting factor) to thrombin in the presence of calcium ions

  3. Thrombin acts as an enzyme on fibrinogen (a clotting factor) to form fibrin threads

  4. Fibrin threads wind around the platelet plug and trap red blood cells to form the framework of the clot
• When blood vessel repair is initiated, plasmin (an enzyme) destroys the fibrin framework and restores the fluidity of the plasma
• Clotting factors in the blood that help platelets in the formation of a blood clot

  • Prothrombin
  • Fibrinogen
• If blood is allowed to clot in a test tube, a yellowish material, called serum, develops above the clotted material
• Hemophilia


  A group of inherited clotting disorders caused by a deficiency in a clotting factor
• Hemophilia A

  • 90% of all hemophilia cases
  • Occurs frequently in males since the faulty gene is on the X chromosome
• Individuals with hemophilia

  • More prone to bleeding
  • Bleeding in the muscles can lead to nerve damage
  • Bleeding into the brain can lead to neurological damage or death
  • Require frequent blood transfusions or injections of the deficient clotting factor
• Stem cells


  Cells that are capable of dividing and producing new cells that go on to differentiate into particular types of cells
• Multipotent stem cells in red bone marrow


  • Have the potential to give rise to other stem cells for the various formed elements
  • Can also differentiate into other cells (liver, bone, fat, cartilage, heart, neurons)
• Researchers prefer using embryonic stem cells since they may be more likely to become any type of cell
• Embryonic stem cells can be collected from unused embryos in fertility clinics, or umbilical cord blood
• Plasma

  Fluid in the blood
• Movement of fluid in the blood through the capillary wall

  1. Controlled by:

  2. Osmotic pressure (causes water to move from the tissue fluid to the blood)

  3. Blood pressure (causes water to move from blood to tissue fluid)
• At the arterial end of the capillary, blood pressure is higher than osmotic pressure of blood, so water exits the capillary