Blood

• Cardiovascular system:

  Transport system

  • Gases oxygen and carbon dioxide)
  • Nutrients
  • Waste
  • Hormones

  Composed of 3 parts

  • Blood: transport medium
  • Heart: pump
  • Blood vessels: conduits
• Characteristics:

  More viscous than water (thicker, 5x)

  pH = 7.35 -7.45

  ~7% of body mass

  4-6 liters

  Connective tissue
• Functions of blood:

  Transportation

  • Gases
  • Nutrients
  • Wastes
  • Hormones

  Regulation

  • pH
  • Ion composition
  • Body temperature
  • Maintain fluid balance

  Protection

  • Blood loss by clot formation
  • Invasion by foreign particles
• Plasma:

  ~55% of blood volume

  Mostly water (92%)

  Other components

  • 7% proteins
  • Plasma proteins
  • Fibrinogen
  • Globulins
  • Albumin
  • 1% other solutes (ions, gases, hormones, nutrients, wastes)
• Formed elements:

  ~45% of blood volume

  Red blood cells (erythrocytes)

  White blood cells (leukocytes)

  Platelets (thrombocytes)
• Red blood cells:

  Erythrocytes

  99.9% of formed elements

  ~40% of total blood volume

  Primarily transport oxygen
• White blood cells:

  <0.1% of formed elements

  Many different types

  Primarily used in immune response
• Platelets:

  Thrombocytes

  <0.1% of formed elements

  Clot formation

  Prevention of blood loss during injury
• Hemopoiesis:

  Formation of formed elements

  Red bone marrow (myeloid bone) -( in end bones & flat bones)

  Pluripotent stem cells - in red bone marrow, undifferentiated with the ability to become any formed element

  Under hormonal regulation (hormones)

  • Erythropoietin: RBCs
  • Thrombopoietin: platelets
  • Cytokines and thymes hormones: white blood cells

  (Hormone stimulates pluripotent stem cells to create formed elements)
• Erythrocytes:

  Most numerous

  Account for viscosity (thickness)

  Contain hemoglobin

  Do not contain nuclei at maturity spit out nucleus & most organelles

  • Lacks organelles (Cannot divide, mainly just hemoglobin)
• Structures of erythrocytes:

  Don’t reproduce in circulation; cannot repair themselves

  Biconcave disc

  • High surface area - speeds up rate of gas exchange
  • Stacking - closer together, more through small areas faster
  • Flexible - can bends → go through areas smaller than blood cell
• Erythrocyte transportation:

  Primarily for oxygen transport

  Done via hemoglobin (Hb)

  • Composed of globin (protein), heme, and iron
  • Iron is the oxygen binding site

  Hemoglobin aids in CO2 transportation to lungs (to get rid of)

  • 23% CO2 transported bound to hemoglobin (Hb)
  • Binds to protein (globin), not heme/iron
  • Only binds to deoxygenated hemoglobin
• Erythropoiesis:

  Formation of red blood cells

  Occurs in the red bone marrow

  Controlled by hormone erythropoietin

  • Secreted by kidneys
  • Released when low oxygen levels in the blood
• Erythropoiesis process:

  Multiple erythroblast stages

  Lose nucleus (exocytosis) before going into circulation

  • Reticulocyte - final stage, getting rid of nucleus
  • Takes about 5-7 days

  Stimulated by decreased oxygen levels in the kidneys

  • Blood loss due to injury or donation
  • Reduced availability of oxygen in environment
  • Increased oxygen demand by the tissues - sustained exercise
• Red blood cell recycling:

  Lifespan is 100-120 days

  • Replaced at rate of 2 million/sec
  • RBCs become fragile with age
  • Hemoglobin begins to break down

  Damaged/dying cells are removed by the spleen

  • Liver and macrophages
  • Hemoglobin recycled
  • Globin is broken down for amino acids
  • Heme: bilirubin and bile (breakdown products)
  • Iron: transferrin (transporting molecule) transports iron to liver
• Human blood groups:

  Markers (antigens) on surface of RBCs

  • Substances that stimulate immune response
  • React with antibodies or cells from immune system
  • Self vs. Non-self
• Blood group antigens:

  Important in blood donations, transfusions, and pregnancy

  • Antigens on donor blood cell may stimulate antibodies in recipients blood to cause agglutination (lumping)
  • Decrease in oxygen carrying capacity
  • Flat formation ( strokes, heart attacks)
  • Kidney failure
• Human blood groups categorized:

  Categorized by the presences/absense of antigens onRBCs

  • 24 blood types
  • > 100 antigens

  Most commonly encountered are

  • ABO
  • Rh (+/-)
• ABO groups:

  Based on 2 antigens: A and B

  4 blood types based on genetic factors

  • Single gene codes for antigen
  • Three forms: A, B, O
  • Each person has 2 copies of gene
  • Genetic makeup of different blood types
  • Type A = AA or AO
  • Type B = BB or BO
  • Type O = OO
  • Type AB = AB
• ABO group antibodies:

  Antibodies are also present

  • Type A has antiB antibodies
  • Type B has antiA antibodies
  • Type AB has no antibodies
  • Type O has antiA and antiB antibodies

  Person has antibodies for whatever they are NOT

  Example

  • Person with type A gets transfusion of type B
  • antiB antibodies bind to antigens on type B RBCs
  • Agglutination occurs causing cellular and tissue damage
• Rh groups:

  Named for factor found in rhesus monkeys

  Antigens are coded by 3 genes

  • People having antigens are Rh+
  • People lacking antigens are Rh-
  • these people normally do not produce antibodies against Rh
  • will only produce if exposed to Rh+ blood
  • agglutination occurs on second exposure
  • hemolytic disease of fetus
• Hemolytic disease:

  occurs when Rh- woman carries and Rh+ child

  first pregnancy is normal

  during birth process, maternal and fetal blood may mix

  mother produces antibodies against Rh

  if next pregnancy is Rh+ child, antibodies from mother will cross placenta and attack fetus

  can be prevented is mother is given injection of RhoGAM after birth of first child
• White blood cells (leukocytes):

  do not contain hemoglobin (colorless)

  have a large nucleus and organelles - larger the RBCs

  function to protect the body

  emigration: can leave blood vessels and enter tissues (leave to infection sites)

  • Diapedesis - process of WBCs leaving blood vessels
  • Uses adhesion molecules
  • ameboid movement
  • are attracted by chemical signals (chemotaxis)
• Types of Leukocytes:

  Two types:

  • Granulocytes
  • Agranulocytes
• Granulocytes:

  contain darkly staining granules

  • larger than RBCs
  • functions as phagocytes (eat/engulf other cells)
  • characterized by how they stain
  • Cells: neutrophils, eosinophils, basophils
• Neutrophils:

  most numerous

  nucleus has 2-5 lobes

  granules contain digestive enzymes and defensins (help breakdown material)

  ingest fungi, viruses, and bacteria
• Eosinophils:

  nucleus has 2 lobes

  granules stain red

  secrete toxic compounds

  • attack parasitic worms

  involved in allergies - allergic reaction
• Basophils: :

  rarest of the leukocytes (<0.5% of all WBCs)

  nucleus has 2 lobes

  contain histamine granules (stain blue)

  responsible for vasodilation during inflammation
• Agranulocytes:

  lack membrane bound granules

  two types:

  • lymphocytes
  • monocytes
• Lymphocytes:

  20-25% of all leukocytes

  help mediate immune response (specific/adaptive immunity)

  T cells, B cells, and natural killer cells (not phagocytes → don’t engulf; use chemicals)
• Monocytes:

  3-8% of leukocytes

  phagocytes

  macrophages - becomes once it leaves the cell

  • fixed or wandering

  nucleus is kidney-bean or horse shoe shaped
• Platelets:

  Cell fragments → no nucleus or organelles

  • megakaryocyte (thrombopoietin triggers stem cell to make; then breakdowns into smaller pieces)
  • 4000 platelets
  • thrombopoietin

  last 5-9 days
• Platelet function:

  initiate clotting process

  formation of platelet plug

  reduce size of blood vessel break
• Hemostasis:

  3 phases

  • Vascular
  • contraction of injured vessel
  • platelet
  • plug formation
  • coagulation
  • platelets release thrombin
  • converts fibrinogen to fibrin