Chapter 11: Blood & The Immune System

• Blood


  An average 70-kg person has 5L of blood
• Components of blood


  • 55% plasma (fluid portion)
  • 45% red blood cells
  • Less than 1% white blood cells
  • Less than 1% platelets
• All blood cells are produced by the bone marrow
• Hematocrit


  The percentage of red blood cells in the blood
• Plasma


  The fluid portion of the blood
• Plasma composition


  • About 90% water
  • Blood proteins
  • Glucose
  • Vitamins
  • Minerals
  • Dissolved gases
  • Waste products of cellular metabolism
• Plasma proteins


  • Albumins - Function: Osmotic balance
  • Globulins - Function: Antibodies, immunity
  • Fibrinogens - Function: blood clotting
• Erythrocytes


  A red blood cell that contains hemoglobin and carries oxygen
• Erythrocytes


  • Primary function is to transport oxygen
  • Hemoglobin within it increases oxygen-carrying capacity by a factor of 70
  • Red when saturated with oxygen because of oxyhemoglobin
  • Appears blue (in veins) because the shape of hemoglobin molecules changes, reflecting blue light when not saturated with oxygen
  • Biconcave disk form: concave on both sides, increasing surface area for gas exchange
  • Short life span of 120 days, so they must constantly reproduce
  • Lack a nucleus (enucleated) when mature, increasing the carrying capacity of hemoglobin
  • Formed in the bone marrow from nucleated stem cells
• Anemia


  The reduction in blood oxygen due to low levels of hemoglobin or poor red blood cell production
• Anemia


  • Decreases O2 delivery to the tissues
  • Causes low energy levels
  • The most common cause is hemorrhage (excessive bleeding), but also associated with low iron in the diet
• Leukocytes


  A white blood cell
• Leukocytes


  • Less numerous than red blood cells; outnumbered by a ratio of 700:1
  • Contain nuclei unlike red blood cells
  • Classified by the size and shape of the nuclei and the presence or absence of granules in the cytoplasm
  • Primary function is to destroy invading microbes through phagocytosis
  • Other white blood cells form special proteins (antibodies) which interfere with invading microbes and toxins
  • Their levels are high when the person is fighting an infection
• Platelets (Thrombocytes)


  A component of blood responsible for initiating blood clotting
• Platelets


  • Do not contain a nucleus
  • Produced from large nucleated cells in the bone marrow
  • When a blood vessel is damaged, the cells of the vessel wall release a substance that makes them sticky, and platelets stick to the injured site
  • As the platelets build up, they form a plug to stop the bleeding
  • The platelets change shape from round to spiny, and they release substances that trap more platelets and cause clotting proteins to form
• Blood Clotting


  1. Blood vessel is damaged

  2. Platelets are stimulated and clump together to form a plug to stop the bleeding

  3. Platelets release a protein called thromboplastin which (along with calcium ions) activate prothrombin (a plasma protein) when they're in the blood

  4. Prothrombine is converted to thrombin, which is used to convert fibrinogen molecules to fibrin threads

  5. The fibrin threads warp around the damaged area, trapping red blood cells and platelets to form a blood clot to stop the bleeding
• Thrombus


  A blood cot that forms within a blood vessel and blocks it
• Embolus


  A blood clot that dislodges and is carried by the circulatory system to another part of the body
• Artificial Blood


  • Fluosol is the artificial blood that saved a man's life
  • It contains fluorine and can carry both oxygen and carbon dioxide
  • Requires 0 blood matching
  • When frozen, it can be stored for a long time
  • Does not have to undergo screening procedures before being used in transfusions
  • Will not carry HIV, hepatitis, or any other virus
  • Although it carries oxygen, it is ill-suited for many of the other functions associated with blood (i.e. blood clotting, immunity)
  • It only really provides time until human blood can be administered
  • Can serve as a supplement for patients with diseases like thalassemia (Cooley's anemia) or aplastic anemia, which requires the patient to undergo multiple transfusions
• ABO Blood Groups


  Markers called glycoproteins are located on the membrane of some of the red blood cells
• ABO Blood Types


  • Blood type A: Has an A marker glycoprotein attached to the cell membrane
  • Blood type B: Has a B marker glycoprotein attached to the cell membrane
  • Blood type AB: Have both A and B markers attached to the cell membrane
  • Blood type O: Has neither glycoprotein markers
• ABO Blood Groups


  • If someone with blood type O receives blood from someone with blood type A, the type O blood would recognize the A marker as a foreign invader
  • The A marker acts as an antigen in the body of the person with blood type O
  • Antibodies are produced in response to a foreign invader, which attaches to the antigen markers, causing the blood to clump
  • However, antigen A would not cause the same immune response if transfused into the body of an individual with blood type A
  • The antibodies produced by the recipient act on the invading antigens with agglutination
• Agglutination


  The clumping of blood cells by antigens and antibodies
• Blood Type Compatibility


  • Type AB blood is a universal recipient since it has both A and B antigens, so it can receive A, B, and O blood types, but it cannot donate except to other AB blood types
  • Type O blood is a universal donor since it has no antigens, so it can donate to A, B, and O, blood types, but it cannot receive except to other O blood types
  • Type A can only donate to A and receive from type A or O blood
  • Type B can only donate to B and receive from type B or O blood
• Rhesus Factor


  Another type of antigen found on red blood cells
• Rhesus Factor


  • Just like the ABO blood groups, the rhesus factor is inherited
  • Anyone that has the rhesus factor is said to be Rh+
  • Anyone who doesn't have the rhesus factor is said to be Rh-
  • Individuals who are Rh- can donate blood to Rh+ but cannot receive Rh+, but the immune reaction is not as serious as ABO groups
  • Rhesus factor incompatibilities are important during pregnancy from a Rh+ baby of a Rh- mother
  • If the baby inherits the Rh+ factor from the father, a condition called erythroblastosis fetalis can occur with the second and subsequent pregnancies
• Erythroblastosis fetalis


  A condition that can occur when a Rh+ baby is born to a Rh- mother
• Erythroblastosis fetalis


  • The first child is spared from a reaction because the blood of the mother and baby is separated by the placenta
  • During birth, when the placenta separates from the uterus, capillary beds rupture and the baby's blood comes into contact with the mother's blood
  • The mother's immune system makes antibodies against the Rh+ antigen, and the first baby is no longer connected to the placenta, therefore not in danger
  • If a second pregnancy occurs and the fetus is Rh+, the mother still has these antibodies, and if they cross the placenta, they attach to the antigen on the red blood cells of the fetus, destroying them
  • Symptoms of erythroblastosis fetalis are anemia, jaundice, and an enlarged liver
• Lines of defence to protect the body

  • The skin
  • Lysozyme
  • Cilia
  • Acid & Proteins digesting enzymes
  • Phagocytosis
  • Inflammatory Response
• Phagocytosis


  The process by which a white blood cell engulfs and chemically destroys a microbe
• Phagocytosis


  • The body's nonspecific defence mechanisms rely mainly on this process
  • There are specialized leukocytes that have different phagocytic responses: Monocytes, Macrophages, Neutrophils
• Inflammatory Response


  A localized nonspecific response triggered when tissue cells are injured by bacteria or physical injury, characterized by swelling, heat, redness and pain
• Pus and accompanying inflammation are sure signs that the second line of defence has been at work
• Responses to Severe Damage & Infections

  1. Injured cells emit chemicals that stimulate the production of phagocytic white blood cells and increase their release into the bloodstream

  2. When infectious organisms spread throughout your body, neutrophils and macrophages digest the invaders and release chemicals into the bloodstream

  3. When these chemicals reach your hypothalamus, it triggers a fever response
• Pus


  A thick liquid composed of protein fragments and digested leukocytes and microbes
• Inflammatory Response


  • Localized nonspecific response triggered when tissue cells are injured by bacteria or physical injury, characterized by swelling, heat, redness and pain
• Responses to Severe Damage & Infections

  1. Injured cells emit chemicals that stimulate the production of phagocytic white blood cells and increase their release into the bloodstream

  2. When infectious organisms spread throughout your body, neutrophils and macrophages digest the invaders and release chemicals into the bloodstream

  3. When these chemicals reach your hypothalamus, they reset the body's thermostat to a higher temperature (about 40°C)

  4. Raising body temperature above 40°C is unsafe, as it can cause convulsions (especially in young children) proteins will denature above 43°C, and cells will die
• Reducing your fever by taking aspirin


  May prolong the infection
• Complement Proteins


  A plasma protein that helps defend against invading microbes by tagging the microbe for phagocytosis, punctuation of cell membranes, or triggering the formation of a mucous coating
• Complement Protein Attack


  1. Forming a protective coating around the invader to immobilize it

  2. Puncture the invader's cell membrane, killing it

  3. Attaching to an invader to attract macrophages to engulf them