Blood

• Functions of the Blood

  • Distribution
  • Regulation
  • Protection
• Distribution


  • Blood transports nutrients, wastes, hormones, body heat
• Regulation


  • Maintains body temperature, pH in body tissues, adequate fluid volume in circulatory system
• Protection


  • Prevents blood loss by constriction, prevents infections by containing white blood cells
• Components of Blood


  Blood (only fluid tissue), Formed elements (living cells), Plasma (nonliving fluid matrix)

  
• When blood is separated

  Formed elements (erythrocytes) sink to the bottom, Buffy coat (leukocytes and platelets) forms a thin layer, Plasma rises to the top
• Constituents of Plasma


  • Nutrients
  • Salts (electrolytes)
  • Respiratory gases
  • Hormones
  • Plasma proteins
  • Waste products
• Constituents of Formed Elements

  • Erythrocytes (red blood cells)
  • Leukocytes (white blood cells)
  • Platelets
• Blood characteristics

  • Sticky, opaque fluid
  • Heavier and thicker than water
  • Oxygen-rich blood is scarlet red, oxygen-poor blood is dull red or purple
  • Metallic, salty taste (due to iron content in RBC)
  • Slightly alkaline pH (7.35-7.45)
  • Slightly higher than body temperature (38C or 100.4F)
• Blood volume

  5–6 liters, or about 6 quarts of blood found in a healthy adult, Blood makes up 8% of body weight
• Plasma

  90 percent water, Straw-colored fluid, Includes many dissolved substances
• Plasma proteins


  • Most abundant solutes in plasma, Mostly made by the liver, Include albumin, clotting proteins, antibodies
• 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
• Erythrocytes (Red blood cells or RBCs)

  Carry oxygen, Anucleate, Contain few organelles but lack mitochondria, Essentially bags of hemoglobin, Shaped like biconcave discs, Normal count is 5 million RBCs per cubic millimeter (mm3) of blood
• Hemoglobin


  Iron-bearing protein, 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 milliliters (ml) of blood
• Anemia


  Decrease in the oxygen-carrying ability of the blood due to lower-than-normal number of RBCs or abnormal/deficient hemoglobin content
• Sickle cell anemia (SCA)


  Results from abnormally shaped hemoglobin, More RBCs are destroyed, Less RBCs are able to carry oxygen
• Polycythemia


  Excessive or abnormal increase of RBCs due to bone marrow cancer or life at higher altitudes, Increase in RBCs slows blood flow and increases blood viscosity
• Leukocytes (White blood cells or WBCs)


  Crucial in body's defense against disease, Complete cells with nucleus and organelles, Able to move into and out of blood vessels, Respond to chemicals released by damaged tissues, Move by amoeboid motion, Normal count is 4,800 to 10,800 WBCs per mm3 of blood

  
• Leukocytosis


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


  Abnormally low WBC count, Caused by certain drugs
• Leukemia


  Bone marrow becomes cancerous, Numerous immature WBC are produced
• Types of leukocytes


  • Granulocytes (neutrophils, eosinophils, basophils)
  • Agranulocytes (lymphocytes, monocytes)
• List of the WBCs, from most to least abundant

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


  • Most numerous WBC, Having a neutral pH, Multilobed nucleus, Cytoplasm stains pink and contains fine granules, Function as phagocytes at active sites of infection, Numbers increase during infection, Normal count is 3,000–7,000 per mm3 of blood (40–70 percent of WBCs)

  
• Eosinophils


  • Nucleus stains blue-red, Brick-red cytoplasmic granules, Function to kill parasitic worms and play a role in allergy attacks, Normal count is 100–400 per mm3 of blood (1–4 percent of WBCs)
• Basophils


  • Rarest WBC, Large histamine-containing granules that stain dark blue, Contain heparin (anticoagulant), Normal count is 20–50 per mm3 of blood (0–1 percent of WBCs)
• Lymphocytes


  • Reside in lymphatic tissues, Large, dark purple nucleus, Slightly larger than RBCs, Play a role in immune response, Normal count is 1,500–3,000 per mm3 of blood (20–45% of WBCs)

  
• Monocytes


  • Inactive form in the blood, Largest WBC, U or kidney-shaped nucleus, Function as macrophages when they migrate into tissues, Important in fighting chronic infection, Normal count is 100–700 per mm3 of blood (4–8 % of WBCs)

  
• Platelets


  Fragments of megakaryocytes, Needed for clotting process, Normal platelet count is 300,000 per mm3 of blood
• Hematopoiesis


  Process of blood cell formation, Occurs in red bone marrow (myeloid tissue), All blood cells are derived from a common stem cell (hemocytoblast)
• Hemocytoblasts


  Form 2 types of descendants: Lymphoid stem cell (produces lymphocytes), Myeloid stem cell (produce all other formed elements)
• Formation of Red Blood Cells

  • RBCs are anucleate, Unable to divide, grow, or synthesize proteins, RBCs wear out in 100 to 120 days, Lost cells are replaced by division of hemocytoblasts in the red bone marrow, Rate of RBC production is controlled by erythropoietin hormone produced mainly by the kidneys, Homeostasis is maintained by negative feedback from blood oxygen levels

  
• Formation of White Blood Cells and Platelets

  • Hormones control production of WBC and platelets, Colony stimulating factors (CSFs) and interleukins prompt bone marrow to generate leukocytes, Thrombopoietin stimulates production of platelets from megakaryocytes

  
• Hemostasis


  Process of stopping the bleeding that results from a break in a blood vessel
• Myeloid stem cell


  Produces all other formed elements
• Hemacytoblasts


  Stem cells - origin of all White blood cells
• Formation of Red Blood Cells

  1. RBCs are anucleate

  2. RBCs wear out in 100 to 120 days

  3. Lost cells replaced by division of hemocytoblasts in the red bone marrow

  4. Rate of RBC production controlled by erythropoietin

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

  6. Homeostasis maintained by negative feedback from blood oxygen levels

  
• Formation of White Blood Cells and Platelets

  1. Hormones control production of WBC and platelet

  2. Colony stimulating factors (CSFs) and interleukins prompt bone marrow to generate leukocytes

  3. Thrombopoietin stimulates production of platelets from megakaryocytes