UNIT 1 Blood - Part 1 of 2

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UNIT 1 Blood - Part 1 of 2

• Overview of Blood
• Plasma
• Formed Elements RBCs and WBCs

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Overview of the Circulatory Systems

• Cardiovascular System
• Blood (Unit 1 of this course)
• Heart (Unit 2 of this course)
• Blood Vessels and Blood Pressure (Units 3 4 of
  this course)
• Lymphatic System (Unit 6 of this course)

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Overview of Blood - blood is a connective tissue

• Blood Circulation is powered by the pumping
  action of the Heart
• Blood carries respiratory gases (e.g. oxygen and
  carbon dioxide), nutrients (e.g. glucose), and
  hormones (e.g. insulin)
• Blood volume Males approx. 5-6 liters
  Females approx. 4-5 liters
• Blood pH - slightly alkaline (basic) typically
  ranging 7.35-7.45
• Components of Blood
• PLASMA - the extracellular fluid component
  approx. 55 of blood volume
• FORMED ELEMENTS - blood cells (i.e. red blood
  cells or erythrocytes and white blood cells or
  leukocytes) and platelets constitute approx. 45
  of blood volume

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Overview of Blood

• HEMATOCRIT (fig. 17.1) erythrocytes (red blood
  cells) as a
• percentage of total blood volume leukocytes and
  platelets
• constitute less than 1 of blood volume, so they
  are not counted in
• The hematocrit thus, the hematocrit is a measure
  of erythrocyte
• content of a sample of blood
• normal hematocrit values vary, but on average
•  
• males 47 5
• females 42 5
•  
• BUFFY COAT - thin, whitish layer which includes
  the leukocytes and platelets
• hematocrits increase with dehydration and
  decrease with anemia's

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General Functions of Blood

• Distribution
•  
• delivering oxygen from lungs and nutrients from
  digestive tract to all body cells
• transport metabolic waste products from cells to
  elimination sites e.g. to lungs for elimination
  of carbon dioxide
• transport hormones from endocrine organs to their
  target organs
• Regulation
• maintain appropriate body temperature by
  absorbing and distributing heat throughout the
  body heat loss occurs at the skins surface
• maintain normal pH in body tissues buffers to
  prevent excessive or abrupt changes in blood pH
  reservoir (for alkaline) bicarbonate atoms
• maintain adequate fluid volume in the circulatory
  system e.g. salts and blood proteins act to
  prevent excessive fluid loss
• Protection
•  
• preventing blood loss platelets and plasma
  proteins repair damaged blood vessels to halt
  blood loss
• preventing infection antibodies and white blood
  cells (leukocytes) defend body against foreign
  invaders such as bacteria and viruses

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Blood Plasma

• fluid portion of blood it is extracellular fluid
  that is very similar in composition to
  interstitial fluid
• Approximately 90 water
• Contains solutes including ions, nutrients,
  wastes, and proteins (table 17.1)
• plasma proteins - albumin (60 of plasma
  protein), globulins, and fibrinogen most plasma
  proteins are produced by the liver
• albumins
• are major contributors to the osmotic pressure of
  plasma
• do not leave the blood, and thus maintain a high
  level of solute concentration within the plasma
• transport fatty acids and some hormones
• fibrinogen - forms fibrin threads of blood clots
• nonprotein nitrogenous substances - urea, uric
  acid, creatine, and ammonium salts
• nutrients - e.g. glucose, amino acids, fatty
  acids, cholesterol, and vitamins
• electrolytes - e.g. sodium, potassium, calcium,
  chloride, and bicarbonate
• respiratory gases - oxygen (O2) and carbon
  dioxide (CO2)
• Plasma composition is kept relatively constant by
  various homeostatic mechanisms

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Overview of the Formed Elements (fig. 17.2)

• include the Erythrocytes (red blood cells or
  RBCs), Leukocytes (white blood cells or WBCs),
  and Platelets
• Staining of Blood Cells
• acidic dye - e.g. eosin stains pink
• basic dye e.g. methylene blue stains blue and
  purple note that nuclei stain darker than the
  rest of the cell that is because methylene blue
  binds to the DNA in the nucleus

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ERYTHROCYTES

• Structural Characteristics (fig. 17.3)
• biconcave shape this unique shape has 3
  important effects on their function
• it gives them a greater surface area to volume
  ratio this allows for a fast exchange of
  materials across the cell membrane the RBC is
  designed to transport oxygen and this shape
  allows O2 to move quickly into and out of the
  cell
• it enables RBCs to stack stacking facilitates
  the movement of large numbers of RBCs passing
  through capillaries only slightly larger in
  diameter than the RBCs themselves
• it enables them to flex and bend bending is
  necessary in moving through small capillaries
  that are smaller in diameter than the RBCs
  themselves
• have no organelles or nuclei
• because they have no nuclei RBCs cannot divide
• because they have no mitochondria they cannot
  carry on aerobic respiration to generate ATP
• because they have no ribosomes they cannot
  produce proteins, including enzymes thus, they
  cannot perform repairs
• thus, RBCs are stripped down cells designed to
  carry oxygen and CO2
• RBCs have a relatively short life span of less
  than 120 days
• smaller than most white blood cells most
  numerous of the formed elements single drop of
  blood contains approx. 260 million RBCs
• contain hemoglobin oxygen and carbon dioxide
  carrying protein

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ERYTHROCYTES

• Function - dedicated to respiratory gas (oxygen
  or O2 and carbon dioxide or CO2)
• transport
• HEMOGLOBIN (Hb) is the main component of RBCs
  (fig. 17.4)
• the function of hemoglobin is to carry oxygen and
  CO2
• almost all of the oxygen carried by blood travels
  through the bloodstream bound to Hb molecules
  inside RBCs
• it is comprised of 4 globular protein subunits
• each globular subunit contains a HEME molecule
  at the center of each heme molecule is an iron
  ion (Fe) oxygen binds reversibly to this Fe
• because there are 4 hemes per hemoglobin, each Hb
  molecule can carry 4 molecules of O2
• oxyhemoglobin (HbO2) - molecule formed when O2
  binds to the Fe of the Hb blood containing RBCs
  filled with oxyhemoglobin is bright red
• deoxyhemoglobin (Hb) - molecule formed when O2 is
  released from the Fe of the Hb blood containing
  RBCs filled with deoxyhemoglobin is dark red
• carbaminohemoglobin (Hb) - molecule formed when
  CO2 binds to proteins of the Hb hemoglobin can
  transport a smaller amount of CO2 when plasma CO2
  levels are high
• ANEMIA occurs with low hematocrits and low
  hemoglobin content anemia interferes with oxygen
  delivery to all of the tissues of the body and a
  result is weakness and confusion

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ERYTHROCYTES

• Production of Erythrocytes (an overview)
• hematopoiesis (hemopoiesis) is the process of
  blood cell production ERYTHROPOIESIS is the
  process of red blood cell production
• erythropoiesis occurs in the red bone marrow
• Stages of erythropoiesis (fig. 17.5)
• hemocytoblasts produce stem cells
• these stem cells divide to produce RBCs and
  several types of WBCs
• stem cells destined to become RBCs differentiate
  into proerythroblasts
• proerythroblasts differentiate into erythroblasts
  which synthesize hemoglobin
• erythroblasts shed their nuclei and become
  retinculocytes they contain 80 of the
  hemoglobin of a mature RBC
• reticulocytes enter the bloodstream from the red
  bone marrow

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ERYTHROCYTES

• Amino acids, iron, vitamins B12, B6 and folic
  acid are all necessary for the production of RBCs
• The hormone ERYTHROPOIETIN stimulates
  erythropoiesis erythropoietin is released from
  the kidneys in response to low tissue oxygen
  levels caused by situations such as decreased
  numbers of RBCs, defective hemoglobin, increased
  tissue demand from endurance exercise, decreased
  O2 in the lungs due to altitude, lung disease,
  etc. (see fig. 17.6)
• RBCs are passively propelled through the blood
  stream, but are exposed to severe mechanical
  trauma on their journey with this trauma and no
  repair mechanisms in place, RBCs only live about
  120 days about 1 of the circulating RBCs are
  replaced each day
• Old, damaged, and defective RBCs are removed from
  the blood by the liver, spleen and bone marrow.

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ERYTHROCYTES

• Disorders of erythrocytes
• ANEMIAS erythrocyte levels or hemoglobin
  concentrations are low
• hemorrhagic anemias - result from blood loss
• aplastic anemia - results from destruction or
  inhibition of the red bone marrow impairs
  formation of ALL formed elements
• iron-deficiency anemia - low hemoglobin content
  a secondary result of hemorrhagic anemias also
  results from inadequate iron or impaired iron
  absorption
• pernicious anemia - low hemoglobin content due
  to a deficiency of vitamin B12
• SICKLE-CELL ANEMIA (fig. 17.8) an inherited
  condition results from a defective hemoglobin
  molecule erythrocytes distort into a
  sickle-shape with jagged edges

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LEUKOCYTES

• An Overview
• also called white blood cells or WBCs
• WBCs help defend the body against pathogens, and
  remove toxins, wastes, and abnormal or damaged
  cells
• WBCs, unlike RBCs, do have nuclei and other
  organelles
• WBCs do not contain hemoglobin
• WBCs use the bloodstream to get to areas of the
  body where they are needed
• WBCs leave the capillaries and migrate through
  the tissues of the body
• Characteristics of WBCs
• they are capable of amoeboid movement this
  movement allows WBCs to move through tissues
• diapedesis is the means by which they leave
  capillaries and enter tissues they become thin
  and elongate to slip between cells
• positive chemotaxis - WBCs are attracted to
  chemical stimuli the chemical stimuli can be
  coming from pathogens or damaged tissue
• phagocytosis - some WBCs remove pathogens and
  cell debris by engulfing them

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LEUKOCYTES

• Types of Leukocytes
• there are two main categories of leukocytes
  (fig. 17.9)
•  
• granulocytes - cytoplasm contains granules
• agranulocytes - cytoplasm does not contain
  granules
• staining of Blood Cells (17.10)
• acidic dye - e.g. eosin stains pink
• basic dye e.g. methylene blue stains blue and
  purple note that nuclei stain darker than the
  rest of the cell that is because methylene blue
  binds to the DNA in the nucleus

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LEUKOCYTES

• types of granulocytes - cytoplasm contains
  granules (fig. 17.9,
• fig.17.10, table 17.2)
• NEUTROPHIL - most numerous WBC (50-70)
  phagocytizes and destroys bacteria nucleus has
  two to six lobes granules pick up acidic and
  basic stains but are often difficult to see under
  the microscope
•  EOSINOPHIL - compose only about 2-4 of all
  WBCs release toxic chemicals that destroy large,
  multicellular parasites (e.g. tapeworms) also
  play a role in reducing the severity of allergic
  reactions cytoplasm contains large, conspicuous
  red granules that are stained by the acidic eosin
  stain nucleus is bilobed (two lobes) but is
  often difficult to see through the large red
  granules
• BASOPHIL - compose only about 0.5-1 of all WBCs
  granules secrete heparin and histamine histamine
  enhances local inflammation (we take
  antihistamines to help reduce this inflammation,
  and thus feel better) cytoplasm contains
  large, conspicuous blue-purple granules that are
  stained by the basic stain nucleus is bilobed (
  two lobes) but often difficult to see through the
  large blue-purple granules

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LEUKOCYTES

• types of agranulocytes - cytoplasm does not
  contain granules (fig. 17.9,
• fig. 17.10, table 17.2)
• LYMPHOCYTE - compose about 25-40 of all WBCs
  second most common WBC the most important cells
  of the immune system effective in fighting
  infectious organisms lymphocytes become plasma
  cells which secrete antibodies these antibodies
  act against a specific foreign molecule - the
  antigen nucleus stains dark purple most
  lymphocytes are very small (about the size of a
  red blood cell) and contain very little cytoplasm
• there are 3 types of lymphocytes T cells (kill
  foreign cells directly), B cells (differentiate
  into plasma cells which release antibodies), and
  natural killer cells
• MONOCYTE - compose only about 3-8 of all WBCs
  they are the largest of the WBCs nucleus is
  kidney-shaped (or horseshoe-shaped) transform
  into macrophages, which are actively phagocytic

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LEUKOCYTES

• WBC Differential Count
• indicates the number of each type of cell in a
  sample of 100 WBCs
• different conditions are identified by
  characteristic differential counts
• LEUKOPENIA indicates decreased numbers of WBCs
• leukocytosis refers to excessive numbers of WBCs
  a modest leukocytosis is normal during an
  infection extreme leukocytosis generally
  indicates LEUKEMIA (cancer of the blood)

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