Hematology_Comprehensive Blood Physiology Review

1. Hematology Basic Medical Science
Global Overview/Review
Marc Imhotep Cray, M.D.
Basic Medical Sciences Teacher
http://www.imhotepvirtualmedsch.com/

2. Lecture Outline
• Basic properties & functions
• Blood plasma
• Red blood cells (erythrocytes)
• White blood cells (leukocytes)
• Platelets
• Coagulation
• Fibrinolysis
• Defense mechanisms
2
Related resources:
•WebPath Hematopathology: 70 Images
The peripheral blood, bone marrow, lymph nodes, and spleen
• HEMATOPOIESIS

3. Blood
Properties
• Sticky
• Opaque
• Salty-metallic taste
• Color varies according to oxygen content
• More dense than water and 5x more viscous
• pH: 7.35-7.45 (reservoir for bicarbonate ions)
• Temperature: 38°C
• Volume (4-6 litres; adult).
3

4. Blood
Basic Functions
• Distributes
– oxygen and nutrients (removes waste products)
– hormones delivered to target organs
• Regulates
– body temperature, pH
• Protects
– against blood/fluid loss via hemostasis (coagulation)
– against infection via contribution to inflammatory and
immune responses.
4

5. Blood Plasma
• Blood is composed of cellular and non-cellular
elements.
• If the cellular components are removed: plasma
remains.
5

6. Blood Plasma
• Contains all soluble elements including:
– 90% water
– 7% protein
– 3% salts, sugars, lipids, gases, nutrients,
metabolites.
• Plasma proteins:
– Albumin (60%): osmotic effect.
– Globulins (36%):
• alpha and beta globulins, transport proteins.
• gamma globulins (antibodies/immunoglobulins).
– Clotting proteins (4%): eg. fibrinogen and prothrombin
Liver
6

7. Blood
Cellular elements
• Red blood cells:
– anucleated, discoid structures, designed for O2
transport.
• White blood cells:
– mononuclear cells: monocytes and lymphocytes.
• Vital for functioning of immune system.
– polymorphonuclear cells: neutrophils, eosinophils and
basophils.
• Vital for non-specific defenses (ie inflammation)
• Platelets (thrombocytes):
– cell fragments derived from megakaryocytes.
• Role during clot formation.
7

8. Cellular Elements
Relative Numbers
• Red blood cells: 5 x
106/mm3
8

9. Cellular Elements
Relative Numbers
• Red blood cells: 5 x
106/mm3
• White blood cells: 5 x
103/mm3
9

10. Cellular Elements
Relative Numbers
• Red blood cells: 5 x 106/mm3
• White blood cells: 5 x 103/mm3
• Platelets: 2.5 to 5 x 105/mm3
10

11. Red blood cells
Erythrocytes
• Survive for 100-120 days in circulation.
• Remnants broken down by liver and spleen.
• Renewed by division and differentiation of stem
cells found in the bone marrow: 2 million/second!
• Formation controlled in part by the hormone
erythropoietin (EPO).
– produced by kidney in response to low oxygen levels.
• Other regulatory factors:
– supplies of iron, amino acids and certain B vitamins
– testosterone enhances EPO production.
11

12. Red blood cells
Regulation of Erythropoiesis
12

13. Red blood cells
Fate and Destruction
• Dead red blood cells are removed by liver & spleen
• Heme and globin components are re-used
SPLEEN
LIVER
13

14. Red blood cells
Iron Requirements
• 0.6 - 2mg required per day.
• Absorbed in small intestine.
• How is iron used?
14

15. Red blood cells
Hemoglobin
• 0.6 - 2mg required per day.
• Absorbed in small intestine.
• How is iron used?
–To produce hemoglobin
15

16. Red blood cells
Hemoglobin
• Hemoglobin is a molecule
specialized for transport of
oxygen
• Consists of four peptide
chains or globins, and four
heme molecules
HEME
16

17. Red blood cells
Hemoglobin
• Each molecule of heme
contains an iron atom
• Each heme binds one
molecule of oxygen
17

18. Red blood cells
Iron Storage and Use
• Free iron is toxic to body.
• Majority is stored as
hemoglobin/myoglobin.
• Some of the remainder is
stored inside cells as a
protein-iron complex called
ferritin.
– Marrow, liver & spleen.
• Transported in blood bound
to transferrin.
• Utilized by electron transport
chain (cytochromes)
18

19. Red blood cells
Iron Cycle
• Majority of iron comes from recycling dead RBCs
19

20. Red blood cells
Vitamin Requirements
• Proliferation of RBC precursors requires:
– DNA synthesis (ie. precursors have a nucleus).
– Protein synthesis (synthesis of some amino acids)
• Two B-complex vitamins play critical role:
– Folate (50-100 g/day)
• required for synthesis of purines and pyrimidines (ie. A,
T, C, G and U bases found in nucleic acids).
– Vitamin B12 (approximately 3g/day )
• required for synthesis of some amino acids.
20

21. Blood Typing
• Based on type of glycoproteins present on the
surface of red blood cells.
• If foreign glycoproteins are presented to the
immune system (ie transfusion of incompatible
blood), then the RBC are clumped together and
destroyed.
• ABO blood groups are based on the expression of
type A and type B glycoproteins (agglutinogens).
• Rhesus groups: based primarily on agglutinogen D.
21

22. Blood Typing
• AB: produce both glycoproteins
– rare, can receive donations from A, B, AB or O.
• A: produce type A glycoprotein.
– Can receive donations from A or O.
• B: produce type B glycoprotein.
– Can receive donations from B or O.
• O: produce neither A nor B.
– Most common, can receive only O type.
22

23. Blood Typing
• Rhesus (+) Most Common
– produce agglutinogen D.
• Rhesus (-)
– don’t produce agglutinogen D.
Antibodies to agglutinogen D are produced more slowly than those to
types A and B.
Rhesus (-) mothers have to be treated if carrying a rhesus (+) baby.
23

24. Blood
Hematocrit
• The % volume
occupied by red
blood cells is known
as the hematocrit.
• Volume occupied by
white blood cells is
relatively small.
24

25. White Blood Cells
(Leukocytes)
 Granular leukocytes
– Neutrophils (40-70%)
– Eosinophils (acidophils, <5%)
– Basophils (<1%)
 Agranular leukocytes
– Lymphocytes (20-45%)
– Monocytes (<10%)
25

26. Lymphocyte
Monocyte
Eosinophil
Basophil
Neutrophil
GranulocyteAgranulocyte
Leukocyte
White Blood Cells
26

27. GRANULOCYTES
1. Neutrophils
• 40 - 75% of leukocytes
• 10 - 14um diameter
• Exhibit multi - lobed nuclei
• Cytoplasm lightly stippled with indistinct granules
- represents large lysosomes
• Active phagocytes that ingest bacteria & cell
fragments
27

28. NEUTROPHIL
Multi - lobed
nucleus
Cytoplasm
Erythrocyte
28

29. • 1 - 6% of leukocytes
• 10 - 14um diameter
• Bilobed nucleus
• Abundant large ovoid granules
- stain bright red with eosin
• Phagocytes that ingest antibody + antigen complexes
• Release histaminase that inhibits inflammation
GRANULOCYTES
2. Eosinophils
29

30. EOSINOPHIL
Bi - lobed
nucleus
Cytoplasmic
granules
30

31. • < 1% of leukocytes
• 10 - 16um diameter
• U- or S-shaped bi-lobed nucleus
• large blue cytoplasmic granules
- exhibit basophilic staining
• Granules contain materials that mediate inflammation
- eg. histamine
GRANULOCYTES
3. Basophils
31

32. BASOPHIL
Bi - lobed
nucleus
Cytoplasmic
granules
32

33. • 20 - 30% of leukocytes
• 6 - 9um diameter (small)
• 9 - 15um diameter (large - 3%)
• Round, densely stained nuclei
• Pale non-granular cytoplasm
• Small lymphocytes have relatively little cytoplasm
- attack pathogens & regulate immune responses
• Large lymphocytes make antibodies
AGRANULOCYTES
1. Lymphocytes
33

34. LYMPHOCYTES
Small
Large
Rounded
nuclei
34

35. • 2 - 10% of leukocytes
• 14 - 24um diameter
• Large, often indented, nuclei
• Abundant grey-blue cytoplasm with fine granules
• Cytoplasmic vacuoles often evident
• Highly motile
• Differentiate into macrophages which phagocytose
pathogens & dead tissue
AGRANULOCYTES
2. Monocytes
35

36. MONOCYTE
Indented
nucleus
Abundant
cytoplasm
36

37.  Eating-like behavior of cells.
 Performed by:
–Neutrophils
–Monocytes
 Targets:
–Bacteria or other foreign
materials.
–Damaged/infected/abnormal
cells.
Phagocytosis
37

38. Phagocytosis
Foreign cell
being engulfed
Monocyte
38

39. • Small cell fragments
• Possess granules
• 2.5 to 5 x 105/mm3
• Produced by
megakaryocytes in marrow.
• Regulated by
thrombopoietin.
• Contain granules.
• Role in clotting
Platelets
39

40. Platelets
Role during clotting
• React with extracellular
matrix proteins when
blood vessels are
severed.
• Stick to collagen and
form plug.
• Release variety of
chemical mediators from
granules.
• Stimulate coagulation
and wound healing. 40

41. Blood Clotting
Consists of three basic
phases:
• Constriction of vessels
• Reduces blood flow.
• Platelet aggregation
• Plugs hole in vessel
wall.
• Coagulation.
• Reinforces platelet
plug by forming fibrin
mesh.
41

42. Coagulation
• Cascade of chemical reactions that result in formation
of a fibrin mesh.
• Involves 12 different clotting factors
– factor IV is calcium, (factor VI now recognised as
V)
•Critical events
– Formation of prothrombin activator (Ca2+/TF or
PF3).
– Conversion of prothrombin (factor II) into
thrombin.
– Conversion of fibrinogen (factor I) into fibrin. 42

43. There are three pathways to consider:-
COAGULATION PATHWAYS
1. Extrinsic pathway
2. Intrinsic pathway
3. Common pathway
43

44. 44

45. EXTRINSIC PATHWAY
1.There is a rapid initiation of coagulation when "Tissue Factor”
(a protein-phospholipid complex normally present on vascular cells
and activated monocytes), is exposed to factor VII in the presence of
calcium.
2.The activated Tissue factor-VII complex activates factors IX and X
(Factor IXa enhances the production of Xa, especially in the presence
of the co-enzyme VIIIa).
Blood clotting through the extrinsic system is quick (10 - 13 secs).
45

46. When tissue or endothelial cells are damaged they release
tissue factor, which combines with two clotting factors to
make the enzyme tissue thromboplastin
EXTRINSIC PATHWAY
46

47. The pivotal molecule in both pathways is thromboplastin.
The intrinsic pathway is triggered when thromboplastin is released
from the platelets and the intermediates of the pathway
are activated on the platelet surfaces.
Each pathway requires Ca2+ and involves the activation of a
series of procoagulants each serving to activate the next
coagulant in line.
The intermediate steps of each pathway fall to a common
intermediary factor X.
INTRINSIC PATHWAY
47

48. INTRINSIC PATHWAY
48
The aggregated platelet plug releases
platelet factor 3, which combines with
two clotting factors to make the
enzyme platelet thromboplastin

49. The common pathway begins once either of the two types of
thromboplastin are formed.
When this happens, prothrombin is converted into the enzyme
thrombin. Thrombin then takes the final step in the coagulation
process by converting fibrinogen into fibrin.
COMMON PATHWAY
49

50. • Platelets have inside them contractile proteins called
thrombasthenins
• When the platelets contract they reduce the size of
the entire blood clot pulling the torn edges of the
vessel closer together, reducing the size of the
damaged area, and making repairs easier.
CLOT RETRACTION
50

51. The continuous generation of cross-linked fibrin would create a clot
capable of obstructing normal blood flow
The Fibrinolytic system is present to keep clot formation in check by
actually degrading the fibrin
FIBRINOLYSIS
51

52. Once hemostasis is restored and the tissue is repaired, the clot must
be removed from the injured tissue. This is achieved by the fibrinolytic
pathway. The end product of this pathway is the enzyme plasmin,
a potent proteolytic enzyme with a broad spectrum of activity.
FIBRINOLYSIS
Plasmin is formed by activation of the proenzyme, plasminogen by
either plasma or tissue activators.
Tissue plasminogen activators are found in most tissues, except the
liver and the placenta,
where they are synthesized by endothelial cells and are found
concentrated in the walls of blood vessels. The two best
characterised are vascular activator (commonly
known as tissue plasminogen activator -- tPA) and urokinase.
52

53. Fibrinolysis works in a steady state with haemostasis.
Damaged endothelium releases tissue plasminogen activator as well
as plasminogen - both of which are adsorbed to the fibrin surface
FIBRINOLYSIS
53

54. Inflammation
Immune system
Defense Mechanisms
54

55. • Inflammation: non-specific.
• Immune system: specific
Defense Mechanisms
55

56. The body’s response to injury
Inflammation
56

57. Anatomical:
Redness, swelling, heat, pain, poor
function.
Histological:
Leukocytes accumulate in inflamed tissues.
Inflammation
Signs and Symptoms
57

58. Acute:
Short duration (hours, days)
Possible neutrophil influx
Chronic:
Long duration (weeks, months)
Immune system recruited (lymphocytes)
Inflammation
Degrees of severity
58

59. Blood vessels: changes in diameter and
permeability.
Leukocytes: chemotactic emigration.
Both regulated by the production and release
of inflammatory mediators.
Inflammation
Underlying Mechanisms
59

60.  Crawling-like motility of cells.
 Powered by actin cytoskeleton.
 Displayed by variety of cell types.
 Utilised by leukocytes to emigrate
and seek-out bacteria.
Inflammation
Amoeboid Migration/Diapedesis
60

61.  Directed migration of cells in
response to a concentration
gradient of soluble stimulus:
–eg. Products secreted by
bacteria.
–eg. Inflammatory mediators.
Inflammation
Chemotaxis
61

62. • Derived from plasma proteins:
– e.g. products released during clotting.
• Derived from cells:
– e.g. histamine, cytokines.
Only released/act locally.
(hormonal-like specificity)
Inflammation
Inflammatory Mediators
62

63. Tissue
damage
Chemical
mediators
releasedIncreased
vascular
permeability
Chemotaxis
Pathogen
Inflammatory
Response
63

64. Tissue
damage
Chemical
mediators
releasedIncreased
vascular
permeability
Chemotaxis
Fibrin mesh
isolates injury site
Increased numbers of
white blood cells
at injury site
Pathogens contained
& destroyed
Pathogen
Inflammatory
Response
64

65. Additional Nonspecific Resistance
Chemical defenses
1. Complement
• group of about 20 serum proteins
• when combined with foreign substances a
“complement cascade” is activated
• complement proteins rupture bacterial
membranes
2. Interferon
• stimulate body cells to resist viral infection
• inhibits viral replication
65

66. Complement
Inrushing
fluid
Bacterial
membrane
66

67. The Immune System
• Specific: via receptor ligand interactions.
• Acquired: via “education” of lymphocytes.
• Systemic: via emigration of lymphocytes.
• Memory: via survival of lymphocytes.
67

68. The Immune System
Specificity is driven by receptor-ligand type
interactions.
Two main pathways:
1. Humoral pathway (involves B lymphocytes).
2. Cell mediated pathway (uses T lymphocytes)
68

69. Humoral Pathway
ANTIBODIES: proteins secreted
by activated B lymphocytes, that
bind to antigens
(immunoglobulins).
ANTIGENS: any chemical which
elicits an immune response
(usually foreign).
69

70. Basic Antibody Structure
Antigen binding site
Heavy chain
Light chain
Constant
region
Variable
region
70

71. B-lymphocytes
Produce antibodies against foreign proteins
Antibodies (immunoglobulins - Ig)
• proteins produced by plasma cells (mature form of
B-lymphocytes)
• bind to SPECIFIC foreign proteins
5 main classes
1. IgG - most abundant
2. IgM - first circulating Ig released
3. IgE - involved in inflammatory responses
4. IgA - body secretions
5. IgD - surface receptor
71

72. Humoral Pathway
Antibodies and antigens bind each other to
form IMMUNE COMPLEXES.
ANTIGENIC DETERMINANT:
The region of an antigen that is recognised.
72

73. Antigen
Different
antigenic
determinants
Antigenic Determinants
73

74. Humoral Response
74

75. Humoral Response
Consequences of immune complex
formation.
1. Neutralisation of toxic antigens.
2. Activation of leukocytes.
3. Formation of inflammatory mediators.
4. Destruction of bacteria.
75

76. • Antigen-receptor interactions occur on the
cell surface.
• Two types of interaction:
– Antigen presenting cells (APC) and Helper T
cells.
– Cytotoxic T cells and abnormal cells.
Cell Mediated Response
76

77. APC
MHCII-antigen
complex
Antigen
MHCII
T-cell
receptor
Helper T cell
Cytokines
Released
MHC = Major-Histocompatibility-Complex molecule.
Cell Mediated Response
77

78. Infected Cell
MHCI-antigen
complex
Virus
MHCI
T-cell
receptor
Cytotoxic
T cell
Infected cell
Killed
Cell Mediated Response
78

79. Virus infected cell
Killer T cell
Cell lysis
initiated
Time
Cytotoxic T-cell Response
79

80. “Education” by Clonal Selection
Memory cells
ATTACK
80