Transcript Document

Hematology
&
Immune Mechanisms
Tutor: Prof Mohan Dikshit
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Objectives: Composition of blood & RBC
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Describe the cellular and non-cellular components of blood
Enumerate functions of the non-cellular part.
Describe the physical characteristics of the RBC
Describe functions of RBC.
Describe the life cycle of RBCs
Describe the process of erythropoiesis
List the factors that affect erythropoiesis
State the normal values for Hemoglobin percentage and RBC count in
males and females
Define anemia, and recognize different types of anemia, and that iron
deficiency anemia is the commonest variety world wide
List the common symptoms of anemia
Define Polycythemia and give an example
Recommended reading: Tortora & Derrickson . Principles of Anatomy and
Physiology.12th edn. 2009. Volume 2
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Physical characteristics of blood
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Thicker than water with a Specific gravity around 1.58
pH 7.35-7.45
Colour: bright red when oxygenated
dark red when de-oxygenated
8% body weight
20% of ECF
Volume about 5 l (70 ml/Kg body wt.)
Sampling by venipuncture; finger pick/heel prick
arterial puncture
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Constituents of blood
Plasma 55%
Formed elements 45%
RBCs
5 million/cumm (µl)
91.5% water
7% gm% proteins
3.8gm % albumin (54%)
2.7gm% globulin (38%)
0.5gm % fibrinogen (7%)
1.5%
Electrolytes
Nutrients
Gases
Regulatory substances
Waste products
WBCs 10,000/cumm (µl)
Neutrophils
Eosinophils
Basophils
Monocytes
Lymphocytes
Platelets 140-400000/µl
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Constituents of blood
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Functions of blood
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1. Transportation of
respiratory gases; nutrients ; hormones;
waste products
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2. Regulatory: body temperature; pH
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3. Protection
against disease (immune functions);
against blood loss (coagulation) ( ‫) َت َخ ُّثر‬
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Origin: STEM CELLS (stem cell pool) in the bone marrow
Stem cells may be
i. Pluripotent (multipotential),
ii. Committed (unipotential) COLONY forming Units
(CFUs).
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Hematopoesis : process of forming blood cells
continues life long,
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is modulated by requirements of the body.
- It increases in anemia, blood loss, infection by:
i. reconversion of old yellow bone marrow into red marrow;
ii. daughter cells differentiate faster; iii. faster proliferation of stem cells
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Some times even in adults EXTRA MEDULLARY
hematopoesis occurs in liver, spleen
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In blood cancer, hematopoesis becomes abnormal
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Red Blood Cells (eryrthrocytes)
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No. 4-5 million/cumm (μL)
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Size 7μ, bi-concave discs
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No nucleus: can not reproduce =
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More surface area & center becomes
thinner (biconcave):
- More O2 can be carried
- Squeeze into narrow capillaries
- Allow O2 & CO2 Diffusion
NO mitochondria: ATP by anaerobic
means (advantage: do not use up O2
they carry)
Life span 120 days
Destroyed in the body by RE cells: by
products are recycled (mostly at
Spleen)
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Live only 120 days, Why?
While Moving in and out of
capillaries the RBC are torn and
damaged, and due to the absence
of Nucleus, healing doesn’t
occur.
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Physiology of RBCs
1. Main function: transport of OXYGEN bound to
Hemoglobin
4 Heme mols
Each having Iron mol
Globin
2 alpha chains
2 beta chains
Thus each Hb molecule carries 4 O2 molecules
- Iron is what attaches Oxygen
Hb and O2 binding is a loose chemical one: easily released by Hb
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Hb : also carries
CO2 but only about 15%
Nitric Oxide (NO) – allows blood to go through narrow capillaries
RBCs carry blood group antigens (A,B, O) on their cell membranes
RBC Life cycle: 120 days
Macrophages in spleen liver, marrow
break up RBCs
heme
Iron
recycled
biliverdin
globin
Amino Acids
Bilirubin in liver
excreted
increase leads to jaundice
recycled
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Erythropoeisis: formation of RBC
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Before birth in
yolk sac
liver and spleen
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After birth
In bone marrow
long bones up to about 20 yr
flat bones later in life
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About 2.5 million RBC are formed/sec
Extra medullary erythropeisis
Under severe stress of anemia in post natal life
Liver and spleen
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Normal erythropoiesis
Progenitor cell in bone marrow:
Pluripotent hemopoeitic stem cell
Colony forming unit Erythrocyte
(Stimulated by erythropoeitin)
Proerythroblast
Basophil erythroblast
( Hb just introduced); B9 B12 Process takes about 1 week
Polychromatophil
erythroblast
Orthochromatic erythro
Reticulocyte
In circulation for 1-2 days
ERYTHROCYTE
Large no of Reticulocytes means that the bone marrow is working
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Factors affecting erythropoeisis:
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Erythropoeitin from the kidneys is most important
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Erythropoietin increases in
hypoxia, chronic lung disease, anemia, low blood volume
that’s why people living in high mountains have larger numbers of RBC =
HYPOXIA
(other sources of Erythropoietin: liver)
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Testosterone
Vit B12, Folic acid (B9),
Iron
Thyroid hormone
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Normal Reticulocyte count about 1% of RBC
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If bone marrow is hypoactive
reticulocyte count will go down
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Normal HB level
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Male: about
Female about
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Clinical implications
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Anemia means a deficiency of Hb which can be
caused by either too few RBCs or too little Hb in the
cells.
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For diagnosis of anemia:
Hemoglobin
<13.0 g/dl
for males
< 12.0 g/dl. for females
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13-15 gm%
12-14 gm%
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Causes of anemia
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i. reduced/defective RBC formation
ii. blood loss
iii. excessive destruction ( ‫) َت ْخريب‬:
iv. combination of all the above
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The commonest cause of anaemia world
wide is IRON deficiency : IDA
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Common symptoms of anemia
weakness
lethargy
lack of concentration
breathlessness – to begin with on exercise
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heart failure in severe anemia
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Investigations:
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Hb/RBC count
Treatment: iron; diet; remove obvious cause
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Polycythemia:
Excess formation of RBC (> 6-7 million/µl)
i. Classically : high altitude exposure
ii. Polycythemia Rubra
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RECAP
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Blood constituents
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Functions of the non-cellular part.
RBC: characretristics, functions & and formation
Life cycle of RBCs
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Normal values for Hemoglobin percentage and RBC
count in males and females
Anemia, and recognize different symptoms of anemia
Iron deficiency anemia is the commonest variety world
wide
Define Polycythemia and give an example
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