Blood

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Blood

• Chapter 17

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Introduction

• Circulatory System is subdivided into the
• Cardiovascular system blood, heart, and blood
  vessels
• Lympathetic system lymph and lymph nodes and
  lymph vessels
• First we will look at blood the river of life
• Hematology the study of blood
• - clinicians examine it more often than any
  other tissue when investigating causes of disease
  in their patients

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Blood Circulation

• Initiated by the pumping action of the heart
• - blood leaves the heart in arteries ? tiny
  capillaries ? enter body tissues
• - from capillaries oxygen-deficient blood flows
  into veins which return it to the heart ? lungs ?
  heart
• Functions of blood
• Carries respiratory gases, nutrients, hormones
• Conveys cells of the defense system to infectious
  sites
• Helps regulate body temperature blood is
  diverted to or away from the skin

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Overview Composition of Blood

• Blood accounts for 8 of body mass volume in
  male is 5 6 liters females 4 - 5 liters
• A specialized CT
• - Blood cells (formed elements) are suspended in
  plasma (fluid portion and fibrinogen)
• Hematocrit (blood fraction) - of the blood
  volume that consists of erythrocytes
• - males 47 5
• - females 42 5

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Overview Composition of Blood
Figure 17.1

• Heavier formed elements are packed down
  (erythrocytes red cells) and the less dense
  plasma remains on top
• Buffy coat junction between RBCs and plasma
  contains leukocytes (white cells) platelets
  (thrombocytes)

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Blood Plasma

• Straw-colored, sticky fluid portion of blood
  about 90 water
• Contains
• Ions Na and Cl-
• Nutrients sugars, amino acids, lipids,
• Wastes urea and ammonia, and CO2
• O2, hormones and vitmins
• 3 main types of proteins
• - albumin helps to prevent water from diffusing
  out
• - globulins include both antibodies and blood
  proteins that transport lipids, iron, and copper
• - fibrinogens are invloved in blood clotting

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Formed Elements

• Blood cells
• Erythrocytes lack nuclei and organelles
• Platelets are cell fragments
• Most cannot divide - survive for only a short
  time
• Staining of blood cells cellular structures
  stain
• differentially according to their chemical makeup
• Eosin an acidic dye stains pink
• Methylene blue a basic dye stains blue and
  purple

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Figure 17.2b
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Erythrocytes (RBCs)

• Small, oxygen-transporting cells 7.5 um in
  diameter (capillary diameter 8 10 um)
• - have no organelles or nuclei
• - cytoplasm packed with hemoglobin
• - generate energy by anaerobic mechanisms
• Most numerous of the formed elements females
  4.3 5.2 million cells/cubic ml of blood
• males 5.1 5.8 million

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An Erythrocyte

• 30 more surface area for rapid diffusion of O2
• Sacs of hemoglobin (O2 and CO2)
• Lives 100 -120 days
• Originate in the bone marrow (expel their
  organelles)

Figure 17.3
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Leukocytes (WBCs)

• Less numerous 4,800 11,000 per cubic ml
• - originate in the bone marrow and are released
  continuously into the blood
• Protect the body from infectious microorganism
• Function outside the blood stream in loose CT
  where infections occur
• Diapedesis (leaping through) circulating
  leukocytes leave the capillaries by squeezing
  between endothelial cells of the capillary walls
• - travel by amoeboid motion to infection sites

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WBCs

• Bone marrow stores leukocytes
• -releases in large quantities during serious
  infections
• - count exceeding 11,000 per cubic ml
  leukocytosis
• 5 types divided into 2 groups (presence or
  absence of membrane-bound cytoplasmic granules)
• 1) Granulocytes neutrophils, eosinophils,
  basophils
• 2) Agranulocytes lymphocytes and monocytes
• Relative amount of leukocytes from most to least
  Never Let Monkeys Eat Bananas

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Relative Percentages of the Different Types of
Leukocytes
Figure 17.5
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Granulocytes

• Neutrophils most numerous WBC (60)
• Phagocytize and destroy bacteria
• - also release bacteria-destroying substances
  into ECM of the infected tissue
• - pus is composed of dead neutrophils and other
  WBCs plus tissue debris and dead bacteria
• Nucleus 2 to 6 lobes
• Granules pick up acidic and basic stains
• - membrane-walled sacs of digestive enzymes

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Neutrophil
Figure 17.4a

• Nucleus has two to six lobes
• Granules pick up acidic and basic stains

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Figure 17.4b

• Eosinophils 1 4 of all WBCs that function
  during allergic reactions and parasitic
  infections (gather in digestive tube wall)
• Granules contain digestive enzymes
• - phagocytose allergens then degrade histamine
• - attach to parasites release enzymes that
  digest and destroy the invaders

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Figure 17.4c

• Basophils (base loving) rarest, about 0.5 of
  all leukocytes
• Nucleus usually two lobes
• Granules secrete histamines and molecules
• Function in inflammation mediation

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Agranulocytes

• Lymphocytes (T and B cells) most important
  cells of the immune system (20 45 of WBCs)
• Nucleus occupies most of the cell volume
  (stains dark purple)
• Function in lymphoid CTs play a crucial role in
  immunity
• - effective in fighting infectious organisms
• - act against antigens (induce against) a
  specific foreign molecule that induces a response
• - T cells attack foreign cells directly
• - B cells differentiate and produce antibodies

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Monocytes

• Are the largest - make up 4 8 of WBCs
• Nucleus kidney shaped
• Contain a larger proportion of cytoplasm tiny
  granules
• Like all leukocyes, use the bloodstream to reach
  CT where they transform into macrophages
• phagocytic cells that move by amoeboid motion
• Ingest foreign cells, molecules, debris

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Figure 17.4d,e
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Platelets

• Aka thrombocytes (clotting cells) disc-shaped
  plasma membrane-enclosed fragments of cytoplasm
  (megakaryocytes)
• Plug small tears in BV walls
• - adhere to exposed collagen in large numbers
• - secretory granule signal more platelets to
  arrive
• - release thromboplastin (PF3) helps initiate
  clotting

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Blood Cell Formation

• Hematopoiesis (hemato blood poiesis to make)
• - begins in the early embryo and continues
  throughout life
• - after birth all blood cells originate in the
  bone marrow
• - 100 billion new blood cells formed each day

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Bone Marrow Site of Hematopoiesis

• Bone marrow occupies interior of all bones
• Red marrow (red due to immature erythroctyes)
• - actively generates new blood cells
• - remains in epiphyses, girdles, axial skeleton
• Yellow marrow (contains many fat cells) is
  dormant
• - makes blood cells only in emergencies
• - located in long bones of adults
• Reticular CT basic tissue framework
• - fibroblasts (reticular cells) cover and secret
  reticular fibers contain both fat cells and
  forming blood cells
• - blood sinusoids where mature blood cells enter
  the bloodstream
• - contain macrophages extend psuedopods, capture
  antigens

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Cell Lines in Blood Cell Formation

• All blood cells originate in bone marrow from one
  cell type, the blood stem cell
• - pluripotential hematopoietic stem cell
• Lymphoid stem cells
• - give rise to lymphocytes
• Myeloid stem cells
• - give rise to all other blood cells
• - become committed cells that progressively lose
  ability to become certain cell types

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Genesis of Erythrocytes

• Proerythroblasts (earliest redformers)
  -committed cells that form erythrocytes
• - give rise to early erythroblasts act as
  ribosome-producing factories where hemoglobin is
  made and accumulates during the next 2 stages
• - late erythroblast and normoblast (stage where
  cell division stops)
• - reticulocyte at this stage young erythrocyte
  contains a reticulum of ribosomes (remain here
  for 1-2 after entering bloodstream)
• Reticulocyte count 1 to 2 of all erythrocytes
• gt 2 adapting to life at high altitudes
• lt 1 degenerative bone disease

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Formation of Leukocytes

• Myeloblasts - committed cells in each granulocyte
  line
• Promyelocytes accumulate lysosomes
• Myelocyte stage cell division stops
• Metamyelocyte stage nucleus stops functioning
  and bends into a horseshoe
• Line committing to monocytes, committed
  monoblasts enlarge and obtain more lysosomes to
  become promonocytes and then monocytes

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Platelet Formation

• Immature megakaryoblasts undergo repeated mitoses
  no nuclei or cytoplasmic division
• Megakaryocyte (big nucleus cell) large
  multilobed nucleus with many times the normal
  number of chromosomes
• - from within the reticular CT they send
  cytoplasmic extensions through the walls of
  sinusoids and into the bloodstream
• - extensions break apart into platelets

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Figure 17.8
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Disorders of the Blood

• Disorders of Erythrocytes
• Polycythemia (many blood cells) abnormal
  excess of erythrocytes
• - polycythemia vera cancer of the bne marrow
• Anemia (lacking blood) any condition in which
  erythrocyte levels or hemoglobin concentrations
  are low
• - bloods capacity for carrying O2 is diminished
• - caused by blood loss, iron deficiency,
  erythrocyte destruction excees replacement
• - folic acid deficiency (B12)
• - genetic defect of hemoglobin

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• Sickle cell disease occurs in 1 of every 400
  AAs
• - defect in the hemoglobin molecule causes it to
  crystallize when O2 blood level is low
• - distort into the shape of a crescent
• - fragile, rigid, and easily destroyed
• - cannot pass easily through capillaries
• Hemachromatosis
• - inherited
• - abnormal excess of iron

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Disorders of Leukocytes

• Leukemia form of cancer resulting from the
  uncontrolled proliferation of a leukocyte-forming
  cell line in the bone marrow
• Classified according to
• 1) Cell line lymphoblastic or myeloblastic
• 2) Rate of progression acute (rapidly
  advancing) or chronic (slowly advancing)
• Cancer cells crowd out normal blood cell lines
• - cause anemia, devastating infections and
  hemorrhaging

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Disorders of Platelets

• Thrombocytopenia (lack of platelets)
  -diminished clot formation and internal bleeding
  from small vessels
• Result from damage to the bone marrow,
  chemotherapy, vit B12 deficiency, leukemia,
  auto-inmmune destruction of the platelets,
  over-activity of the spleen (functions to remove
  and destroy platelets and other blood cells)

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The Blood Throughout Life

• First blood cells develop with the earliest BVs
• - in mesoderm around the yolk sac of 3 week old
  embryo
• Mesenchyme cells cluster into blood islands
• - outer cells flatten and become the endothelial
  cells that form the walls of the earliest vessels
  
• - inner cells become the earliest blood cells
• Late in the 2nd month liver and spleen take
  over blood formation
• Bone marrow becomes major hematopoietic organ by
  month 7