[ANAPHY] Blood

• Blood is the only fluid tissue, a type of connective tissue, in the human body
• Blood transports everything that must be carried from one place to another
• Components of blood


  • Erythrocytes
  • Leukocytes
  • Platelets
  • Plasma
• Erythrocytes


  Tend to sink to the bottom and comprise about 45 percent of blood
• Buffy coat


  Less than 1 percent of the blood, contains leukocytes and platelets
• Plasma


  Around 55 percent of the blood, rises to the top
• Plasma


  • It is an extracellular fluid that distributes nutrients, hormones, and other substances
  • It contains proteins that play a role in blood clotting and prevent infection
  • It is involved in the transport of waste products for excretion
• Blood is a fluid tissue
• Plasma


  Straw-colored fluid of blood, 90% of its composition is water, contains dissolved substances like electrolytes, respiratory gases, hormones, waste products, and plasma proteins
• Dissolved substances in plasma

  • Electrolytes
  • Respiratory gases
  • Hormones
  • Waste products
  • Plasma proteins
• Plasma proteins


  Most abundant solutes in the fluid portion of the blood, majority are manufactured by the liver
• Most common and important plasma proteins

  • Albumin (acts as a buffer and contributes to osmotic pressure)
  • Clotting proteins (play an important role during vascular injury)
  • Antibodies (involved in the body's defense against pathogens)
• Blood composition varies as cells exchange substances with the blood
• Liver makes more proteins when levels drop
• Respiratory and urinary systems restore blood pH to normal when blood becomes too acidic or alkaline
• Formed elements


  Help protect the body from pathogens
• Erythrocytes (red blood cells, RBCs)


  Main function is to carry oxygen, anucleate, contain few organelles, lack mitochondria, essentially bags of hemoglobin, shaped like biconcave discs
• Hemoglobin


  Iron-bearing protein in erythrocytes that attracts and binds oxygen, each hemoglobin molecule can bind 4 oxygen molecules, each erythrocyte has 250 million hemoglobin molecules, normal blood contains 12-18 g of hemoglobin per 100 ml
• Leukocytes (white blood cells, WBCs)


  Cells contain complete set of organelles with nucleus, able to move into and out of blood vessels, respond to chemical signals released by damaged tissues, have amoeboid motion
• Types of leukocytes from most to least abundant (Never Let Monkeys Eat Bananas)

  • Neutrophils
  • Lymphocytes
  • Monocytes
  • Eosinophils
  • Basophils
• Granulocytes


  • Have granules present in their cytoplasm that react to stain, include neutrophils, eosinophils, and basophils
• Neutrophils


  Most numerous WBC, multilobed nucleus, pink cytoplasm with fine granules, function as phagocytes at active sites of infection, numbers increase during infection
• Eosinophils


  Nucleus stains blue-red, brick-red cytoplasmic granules, function is to kill parasitic worms and play a role in allergy attacks
• Basophils


  Rarest of the WBC, large histamine-containing granules that stain dark blue, contain heparin (anticoagulant)
• Agranulocytes


  Lack visible cytoplasmic granules, nuclei are spherical, oval, or kidney-shaped, include lymphocytes and monocytes
• Lymphocytes


  Large, dark purple nucleus, slightly larger than RBCs, reside in lymphatic tissues, play a role in immune response
• Monocytes


  • Largest of the white blood cells
  • Distinctive U-or kidney-shaped nucleus
  • Function as macrophages when they migrate into tissues
  • Important in fighting chronic infection
• Monocyte count


  100-700 monocytes per mm³ of blood (4-8 percent of WBCs)
• Platelets


  • Fragments of megakaryocytes (multinucleate cells)
  • Needed for the clotting process
• Normal platelet count


  300,000 platelets per mm³ of blood
• Anemia is a decrease in the oxygen-carrying ability of the blood due to: lower-than-normal number of RBCs, abnormal or deficient hemoglobin content in the RBCs
• Sickle cell anemia (SCA)


  Results from abnormally shaped hemoglobin
• Polycythemia


  Disorder resulting from excessive or abnormal increase of RBC due to: Bone marrow cancer (polycythemia vera), Life at higher altitudes (secondary polycythemia)
• Increase in RBCs


  Slows blood flow and increases blood viscosity
• Leukocytosis


  WBC count above 11,000 cells per mm³ of blood, Generally indicates an infection
• Leukopenia


  Abnormally low WBC count, Commonly caused by certain drugs, such as corticosteroids and anticancer agents
• Leukemia


  Bone marrow becomes cancerous, Numerous immature WBC are produced
• Hematopoiesis


  1. The process of blood cell formation

  2. Occurs in red bone marrow (myeloid time)

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

  4. Hemocytoblasts form two types of descendants: Lymphoid stem cell, which produces lymphocytes, Myeloid stem cell, which can produce all other formed elements
• Red blood cell (RBC) formation

  • Since RBCs are anucleate, they are unable to divide, grow, or synthesize proteins
  • RBCs wear out in 100 to 120 days
  • When worn out, RBCs are eliminated by phagocytes in the spleen or liver
  • Rate of RBC production is controlled by a hormone called Erythropoietin
  • Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood
  • Homeostasis is maintained by negative feedback from blood oxygen levels
• White blood cell (WBC) and platelet formation

  • WBC and platelet production is controlled by hormones
  • Colony stimulating factors (CSFs) and interleukins prompt bone marrow to generate leukocytes
  • Thrombopoietin stimulates production of platelets from megakaryocytes