ANAPHY 1

• Blood


  The only fluid tissue in the human body<|>Classified as a connective tissue
• Formed elements


  Living cells in blood
• Plasma


  Non-living matrix in blood
• Physical characteristics of blood

  • Color range (oxygen-rich blood is scarlet red, oxygen-poor blood is dull red)
  • pH must remain between 7.35–7.45
  • Blood temperature is slightly higher than body temperature
• Substances in blood plasma

  • Nutrients
  • Salts (metal ions)
  • Respiratory gases
  • Hormones
  • Proteins
  • Waste products
• Plasma proteins


  Albumin - regulates osmotic pressure<|>Clotting proteins - help to stem blood loss when a blood vessel is injured<|>Antibodies - help protect the body from antigens
• Formed elements


  • Erythrocytes (red blood cells)
  • Leukocytes (white blood cells)
  • Platelets (cell fragments)
• Erythrocytes (red blood cells)

  • Main function is to carry oxygen
  • Biconcave disks
  • Essentially bags of hemoglobin
  • Anucleate (no nucleus)
  • Contain very few organelles
  • Outnumber white blood cells 1000:1
• Hemoglobin


  Iron-containing protein that binds strongly, but reversibly, to oxygen<|>Each hemoglobin molecule has four oxygen binding sites<|>Each erythrocyte has 250 million hemoglobin molecules
• Leukocytes (white blood cells)


  • Crucial in the body's defense against disease
  • Complete cells, with a nucleus and organelles
  • Able to move into and out of blood vessels (diapedesis)
  • Can move by ameboid motion
  • Can respond to chemicals released by damaged tissues
• Normal leukocyte levels


  Between 4,000 and 11,000 cells per millimeter
• Leukocytosis


  Above 11,000 leukocytes/ml, generally indicates an infection
• Leukopenia


  Abnormally low leukocyte level, commonly caused by certain drugs
• Types of leukocytes


  • Granulocytes (neutrophils, eosinophils, basophils)
  • Agranulocytes (lymphocytes, monocytes)
• Granulocytes


  • Neutrophils - multilobed nucleus with fine granules, act as phagocytes at active sites of infection
  • Eosinophils - large brick-red cytoplasmic granules, found in response to allergies and parasitic worms
  • Basophils - have histamine-containing granules, initiate inflammation
• Agranulocytes


  • Lymphocytes - nucleus fills most of the cell, play an important role in the immune response
  • Monocytes - largest of the white blood cells, function as macrophages, important in fighting chronic infection
• Platelets


  Derived from ruptured multinucleate cells (megakaryocytes)<|>Needed for the clotting process<|>Normal platelet count = 300,000/mm3
• Hematopoiesis


  1. Blood cell formation occurs in red bone marrow

  2. All blood cells are derived from a common stem cell (hemocytoblast)

  3. Lymphoid stem cell produces lymphocytes

  4. Myeloid stem cell produces other formed elements
• Fate of erythrocytes

  • Unable to divide, grow, or synthesize proteins
  • Wear out in 100 to 120 days
  • When worn out, are eliminated by phagocytes in the spleen or liver
  • Lost cells are replaced by division of hemocytoblasts
• Control of erythrocyte production


  1. Rate is controlled by erythropoietin hormone

  2. Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood

  3. Homeostasis is maintained by negative feedback from blood oxygen levels
• Hemostasis

  1. Platelet plug formation

  2. Vascular spasms

  3. Coagulation
• Platelet plug formation


  1. Collagen fibers are exposed by a break in a blood vessel

  2. Platelets become "sticky" and cling to fibers

  3. Anchored platelets release chemicals to attract more platelets

  4. Platelets pile up to form a platelet plug
• Vascular spasms


  1. Anchored platelets release serotonin

  2. Serotonin causes blood vessel muscles to spasm

  3. Spasms narrow the blood vessel, decreasing blood loss
• Coagulation


  1. Injured tissues release thromboplastin

  2. PF3 (a phospholipid) interacts with thromboplastin, blood protein clotting factors, and calcium ions to trigger a clotting cascade

  3. Prothrombin activator converts prothrombin to thrombin (an enzyme)

  4. Thrombin joins fibrinogen proteins into hair-like fibrin

  5. Fibrin forms a meshwork (the basis for a clot)
• Blood clotting


  • Blood usually clots within 3 to 6 minutes
  • The clot remains as endothelium regenerates
  • The clot is broken down after tissue repair
• Thrombus


  A clot in an unbroken blood vessel, can be deadly in areas like the heart
• Embolus


  A thrombus that breaks away and floats freely in the bloodstream, can later clog vessels in critical areas such as the brain
• Thrombocytopenia


  Platelet deficiency, even normal movements can cause bleeding from small blood vessels that require platelets for clotting
• Hemophilia


  Hereditary bleeding disorder, normal clotting factors are missing
• Consequences of large blood loss

  • Loss of 15 to 30 percent causes weakness
  • Loss of over 30 percent causes shock, which can be fatal
• Transfusions are the only way to replace blood quickly
• Transfused blood must be of the same blood group
• Blood contains genetically determined proteins

  A foreign protein (antigen) may be attacked by the immune system
• Blood typing


  1. Blood samples are mixed with anti-A and anti-B serum

  2. Coagulation or no coagulation leads to determining blood type

  3. Typing for ABO and Rh factors is done in the same manner

  4. Cross matching - testing for agglutination of donor RBCs by the recipient's serum, and vice versa
• Developmental aspects of blood

  • The fetal liver and spleen are early sites of blood cell formation
  • Bone marrow takes over hematopoiesis by the seventh month
  • Fetal hemoglobin differs from hemoglobin produced after birth