Blood

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dallas.dawn
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206212
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Blood
Updated:
2013-03-12 01:31:55
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anatomy
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  1. blood
    Blood is a specialized fluid connective tissue that contains cells suspended in a fluid matrix
  2. Functions of blood:
  3. Transporting dissolved gases, nutrients, hormones, and metabolic wastes
    • Regulating the pH and ion composition of interstitial fluids
    • Restricting fluid losses at injury sites
    • Defending against toxins and pathogens
    • Stabilizing body temperature
  4. Physical characteristics of blood:
  5. Blood temperature is about 100.4°F (38°C) – slightly above body temp
    • Blood is 5x as viscous as water
    • Blood is slightly alkaline – pH 7.35-7.45
  6. Blood consists of a matrix called plasma (46-63%)and the formed elements (37-54%)
    Formed elements are the red and white blood cells
  7. Plasma
    •  contains significant quantities of dissolved proteins
    • The liver synthesizes and releases more than 90% of the plasma proteins
  8. albumin 
    60% of plasma proteins 

    major contributor to osmotic pressure of plasma 
  9. globulin 
    35% of plasma proteins 

    form antibodies 
  10. fibronogen
    • 4% of plasma proteins 
    • function in clotting 
  11. Other plasma proteins 
    the remaining 1% of plasma proteins is composed primarily of hormones circulating throughout the blood 
  12. RED blood cells 
    • Account for 99.9% of the formed elements
    • The percentage of a blood sample that consists of formed elements is known as the hematocrit
  13. Structure of RBCs 
    Each RBC is a biconcave disc with a thin central region and a thicker outer margin
  14. The unusual shape has 3 important functional advantages for RBCs
    Gives each RBC a large surface area to volume ratio

    Enables RBCs to form stacks that smooth the flow through narrow blood vessels

    Stacks are known as rouleaux

    Enables RBCs to bend and flex when entering small capillaries and branches
  15. RBCs do not contain many organelles, only retain cytoskeleton (NO nucleus)
    Because of this, lifespan is relatively short

    120 days 
  16. hemoglobin 
    Molecules of hemoglobin account for more than 95% of a RBC intracellular proteins
  17. Structure:
    Each hemoglobin molecule has 2 alpha and 2 beta chains of polypeptides

    Each chain is a globular protein subunit that resembles the myoglobin__ in skeletal and cardiac muscle

    Like myoglobin, each hemoglobin chain contains a single molecule of heme
  18. structure of hemoglobin (2) 
    Each heme holds an iron ion in such a way that the iron can interact with an oxygen molecule, forming oxyhemoglobin

    Blood containing oxyhemoglobin is bright red

    • The iron-oxygen interaction is very weak (can easily dissociate)
    • A hemoglobin molecule whose iron is not bound to oxygen is called deoxyhemoglobin

    Blood containing deoxyhemoglobin is dark red (burgundy)
  19. function:
    Each RBC contains 280 million hemoglobin molecules

    Each hemoglobin contains 4 heme units, so each RBC can potentially carry more than a billion molecules of oxygen at a time

    The amount of oxygen bound to hemoglobin depends mostly on the oxygen content of the plasma

    When the plasma oxygen levels are low, hemoglobin releases oxygen.
  20. functions:

     peripheral capillaries
    plasma co2 levels rise 

    the alpha and beta chain of hemoglobin then bind co2 forming carbominohemoglobin 
  21. functions
    in the capillaries of lungs
    • Plasma oxygen levels are high and CO2 levels are low
    • Upon reaching these capillaries, RBCs absorb oxygen and release CO2
  22. functions 
    • Normal activity can be sustained only when tissue oxygen levels are kept within normal limits
    • Anemia – a lack of oxygen – can be due to a low hematocrit, or reduction in hemoglobin content in the RBCs
  23. RBC formation and turnover 
    • RBCs are exposed to severe mechanical stresses
    • Each RBC will travel about 700 miles in its 120 day life span
    • New RBCs enter the bloodstream at a comparable rate as the recycling of the old RBCs
    • About 1% of the circulating RBCs are replaced each day (3 million RBCs/second)
  24. Hemoglobin conservation and recycling
    _macrophage_____ in the spleen, liver, and bone marrow detect and remove hemoglobin molecules from ruptured RBCs

    If the hemoglobin is released by the rupturing RBC and is not phagocytosed by a macrophage, the hemoglobin will not be recycled

    The alpha and beta chains are filtered by the kidneys and eliminated in urine
  25. Hemoglobin conservation and recycling

    Once an RBC has been engulfed and broken down by a macrophage, each component of hemoglobin has a different fate
    • Globular proteins broken down to amino acids
    • Each heme is stripped of its iron and converted to biliverdin, which is converted to bilirubin

    • Bilirubin is an orange-yellow protein that is released into the blood where it binds to albumin and is transported to the liver for excretion in bile
    • Jaundice – occurs when the bile ducts are blocked or the liver cannot absorb or excrete bilirubin
  26. Iron recycling
    • Large quantities of free iron are toxic to cells
    • Iron is generally bound to transport or storage proteins

    In the blood, iron binds to transferrin

    In the liver and spleen, iron is stored in 2 special protein-iron complexes: ferritin and hemosiderin
  27. RBC production
    Blood cells appear in the fetus during the 3rd week of development
    Red blood cell formation (erythropoiesis) occurs only in the red bone marrow
    • Located in portions of vertebrae, sternum, ribs, skull, scapulae, pelvis, and proximal limb bone
    • It takes 5-7 for rbc to fully mature 
    • Erythropoiesis is stimulated directly by the peptide hormone EPO

    EPO appears in the plasma when peripheral tissues, especially kidneys, are exposed to low oxygen concentrations
  28. Blood types 
    Antigens
     are substances that trigger a protective defense mechanism called an immune response

    Most antigens are proteins

    Your plasma membrane contain surface antigens, which are substances that your immune system recognizes as ‘normal’
  29. blood type is determined by
     presence or absence of specific surface antigens on rbc plasma proteins 
  30. type A 
    Type A has surface antigen A only
  31. type b 
    type B has surface antigen B only

    (will attack the type a surface antigen ) 
  32. type ab 
    Type AB has both A & B antigens (universal acceptor)

    has no antibodies 
  33. type O 
    has neither a or b antigens (universal donor) 

    no antigens- can give to everyone
  34. Rh positive (Rh+)
     indicates the presence of the Rh surface antigen, commonly called the Rh factor
  35. Rh negative (Rh-) 
    is when you do not have the Rh antigen

    When talking about blood type, the Rh is usually omitted, just say O negative, etc.
  36. Rh factor can be an issue during pregnancy:=
    •  If mother is Rh-, she does not have the Rh antigen
    • Problems seldom develop during the 1st pregnancy

    But, if baby is Rh+, the blood will mix during childbirth and the mother will now make antibodies (that will attack) the Rh+

    During a subsequent pregnancy, if the baby is Rh+ the mother’s antibodies will attack the baby’s blood because it recognizes the Rh+

    Can be prevented during weeks 26-28 by medication
  37. White blood cells (leukocytes)
    • WBCs have nuclei and other organelles, but they lack ___hemoglobin__________
    • help defend the body against invasion by pathogens and remove toxins, wastes, and abnormal or damaged cells

    WBCs circulate for only a short time of their life span

    WBCs can migrate through the connective tissues of the body
  38. characteristics of wbc 
    All can migrate out of the bloodstream

    All are capable of amoeboid (gliding) movement

    • All are attracted to specific chemical stimuli
    • Neutrophils, eosinophils, and monocytes are capable of phagocytosis
  39. Neutrophils
    50-70% of WBCs

    Highly mobile and usually 1st to arrive at site of injury

    Specialize in attacking and digesting bacteria that have been ‘marked’ with antibodies

    Upon encountering a bacteria, a neutrophil quickly engulfs it and the metabolic rate of the neutrophil increases dramatically

    Most neutrophils have a short life span, surviving in blood stream for ~10 hours
  40. Eosinophils
    2-4% of circulating WBCs

    attack objects coated with antibodies 

    Will engulf antibody-marked bacteria, protozoa, or cellular debris

    • Increase in numbers during allergic reactions
    • Also attracted to sites of injury where they release enzymes that reduce inflammation
  41. Basophils
    • Less than 1% of circulating WBCs
    • Migrate to injury sites and accumulate in damaged tissues

    • Discharge their granules into the interstitial fluids
    • Granules contain histamine which dilates blood vessels(releases histamine dilates bv, more blood:)
  42. Monocytes
    2-8% of circulating WBCs

    In blood ~24 hrs before entering peripheral tissues to become a macrophage

    Macrophage are aggressive phagocytes 

    Macrophages also release chemicals to attract and stimulate neutrophils, monocytes, and other phagocytic cells
  43. Lymphocytes
    20-30% of circulating WBCs

    Continuously migrate from the blood stream through peripheral tissues and back to the blood stream
  44. 3 classes of lymphocytes:T cells
    Responsible for defense against invading foreign cells
  45. B cells
    Produce antibodies that will produce an immune defense
  46. Natural killer (NK) cells
    Responsible for immune surveillanceDetect and destroy abnormal cells
  47. WBC production 
    Stem cells responsible for the production of WBCs originate in the red bone marrow

    Basophils, eosinophils, and neutrophils complete their development in the red bone marrow

    Monocytes complete their development when they become free macrophages in peripheral tissues

    Lympocytes migrate to peripheral lymphatic tissues (thymus, spleen, lymph nodes) and complete their development
  48. Platelets
    • Are small fragments of a cell
    • Do not have a nucleus
    • Participate in the clotting process
    • Platelets circulate for 9-12 days
  49. Function of Platelets
    • Release chemicals important for the ____clotting process______
    • Forms a temporary patch in the walls of damaged blood vessels
    • Reduces the size of a break in the vessel wall
  50. Production of platelets
    • Occurs in the red bone marrow
    • Normal red bone marrow contains megakaryocytes and these cells will break up and the fragments of the megakaryocytes are called platelets
  51. Vascular phase
    Blood clotting (hemostasis) 
    • Cutting of the vessel triggers a contraction in the vessel (vascular spasm)
    • Slows or even stops the loss of blood
    • Can last for about 30 minutes
  52. Platelet phase
    • Begins when platelets attach to the injury site
    • As more platelets arrive a platelet plug forms

    The platelets become more activated and release a wide variety of compounds that promotes a positive feedback loop to stimulate further platelet aggregation
  53. Coagulation phase
    The vascular and platelet phase begin within a few seconds after injury, coagulation phase does not begin until 30 seconds or more after injury

    Normal blood clotting depends on the presence of clotting factors (Table 19-4)

    When a blood vessel is damaged, both the extrinsic and intrinsic pathways respond

    The extrinsic pathway is usually the first to initiate clotting

    Best way to think of it is the extrinsic pathway forms a quick patch and the intrinsic pathway reinforces that patch

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