Dr. Jitendra Patel (MBBS, MD) · Poikilocytosis – Change in shape ... • RBC are formed in bone...
Transcript of Dr. Jitendra Patel (MBBS, MD) · Poikilocytosis – Change in shape ... • RBC are formed in bone...
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Dr. Jitendra Patel (MBBS, MD)
Medical Educator & Researcher
Associate Professor, Department of Physiology
Email: [email protected] Web: www.esphys.weebly.com
OUTLINE
Introduction
Composition and Functions
Red cell membrane
Physiological characteristics
Fate of RBC
Applied Aspect
Summary
Key Terms & Concept 3
INTRODUCTION
• Shape : Biconcave
• Diameter :7.2 μm
• Thickness at periphery:2 μm
• Thickness at centre :1 μm
• Volume :90 μm3
• Surface area :140 μm2
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Advantages of biconcavity of red cells
• They do not easily lyses when
blood becomes hypotonic
• More surface area
• It can easily pass through the
narrow capillaries
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Intro…cont
• Non - nucleated
• Site of formation: BM
• Site of destruction: liver, spleen,
BM
• Development takes : 7–10 days
• Life span : 120 days
• Normal count:
M: 5-6 million/cumm
F: 4-5 million/cumm 6
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RED CELL COMPOSITION
Water : 62.5%
Hb : 35%
Other substances : 2.5%
(Glucose, lipids, proteins, enzymes)
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COMPOSITION: HAEMOGLOBIN
• Hb is a pigment (that is, it
is naturally coloured).
• Because of its iron
content, it appears
reddish when combined
with O2 and bluish when
deoxygenated
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Venous (darker) and arterial (brighter) blood
COMPOSITION: ENZYMES
The glycolytic enzymes are necessary for
generating the energy needed to fuel the active
transport mechanisms involved in maintaining
proper ionic concentrations within the cell.
Ironically, even though erythrocytes are the vehicles for
transporting O2 to all other tissues of the body, for energy
production they themselves cannot use the O2 they are
carrying.
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Enzyme…..cont
The other important enzyme within RBCs,
carbonic anhydrase, is critical in CO2 transport.
This enzyme catalyzes a key reaction that leads to
the conversion of metabolically produced CO2 into
bicarbonate ion (HCO3–), which is the primary
form in which CO2 is transported in the blood.
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G-6-PD Deficiency
• Inborn error of metabolism
• Causes hemolysis – hemolytic anemia
• These individuals are resistant to malaria
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Red cell membrane
• Most thoroughly studied biological membrane
• Three major structural elements: 1. lipid
bilayer 2. integral proteins 3. membrane
skeleton
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Element Physiological/Clinical significance
Phospholipid and
cholesterol
1. Provides an impermeable barrier 2. Slippery exterior – red cells do not stick to the
vascular endothelium
Band-3 protein (AE-I)
Chloride shift
Glycophorins (A to E)
1. Negative charge of membrane 2. Glycophorin-C – Stability and shape
(Eliptocytosis)
Spectrin It maintains cellular shape, provides structural support and regulate lateral mobility (Eliptocytosis and Poikilocytosis)
Ankyrin Provides primary linkage between membrane skeleton and lipid bilayer (Hereditary sherocytosis)
FUNCTIONS
• The functions of red cells
consist of oxygen and
carbon dioxide transport.
• Hb act as a buffer and
help in Regulation of
extracellular fluid pH.
• Red cells contribute to
50% of viscosity of blood
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Funct….cont
Antigen on red cell membrane helps in Blood group classification
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PHYSIOLOGICAL CHARACTERISTIC
1. Permeability
Semipermeable membrane, gas and urea freely
passing through, negative ions easily in or out of
RBC, and positive ions not.
There are Na-k ATPase as pump on the membrane
of RBC
RMP of RBC is : - 10 mV
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Characteristic…..cont
2. Plasticity and Metamorphose
Depend on:
1) Surface area-cubage ratio,
2) Viscosity of Hb,
3) Membrane elasticity and viscosity.
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Characteristic…..cont
3. Suspension stability
It cab be described by ESR which is RBC
descending distance per hour and suspension
stability is inverse proportion to ESR.
Normal value of ESR:
Male, 0~15 mm/h; Female, 0~20 mm/h.
Significance: ESR gives prognostic value rather
than diagnostic.
PCV is opposite to ESR 21
Characteristic…..cont
4. Osmotic fragility
Tendency to rupture.
Aged RBC are more fragile
Isotonic solution :Normal RBC
Hypertonic solution : Crenated RBC
Hypotonic : Swelling of RBC
Significance: congenital hereditary spherocytosis (Spectrin)
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Hypotonic Isotonic Hypertonic
FATE OF RBC
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APPLIED ASPECT: PHYSIOLOGICAL SIGNIFICANCE
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Physiological Variation In RBC Count
• Age : Inverse proportion.
• Sex : Male > Female
• High altitude : ++
• Exercise : ++
• Diurnal : Evening > Morning.
• Temperature : ++
• Excitement : ++
• Meals : ++
APPLIED ASPECT: CLINICAL SIGNIFICANCE
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Abnormal Count
Anaemia:
Decreased RBC count and / or Hb content
Polycythemia:
Increased RBC count
APPLIED ASPECT: CLINICAL SIGNIFICANCE
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Abnormal Shape & Size
Anisocytosis – Change in size
Microcytes – smaller RBCs
Macrocytes – Larger RBCs
Poikilocytosis – Change in shape
Spherical in spherocytosis
Sickle shape in sickle cell anemia
Sickle shape RBC
SUMMARY
• RBCs are biconcave discs without many cell organelles
• RBC are formed in bone marrow and destructed in tissue
macrophage system
• Clinically 5 million/cumm is taken as 100% RBC count
• l=Cumm
• The functions of red cells consist of oxygen transport, carbon
dioxide transport and regulation of extracellular fluid pH.
• Normal count can be altered in many physiological &
pathological conditions
• Source of energy for RBC: Glucose (Anaerobic metabolism)
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KEY TERMS & CONCEPT
Defo rmabil ity
An i so poikiloc ytosis
Sp ec t rin
Bo n e Ma rrow
Red cel l Fra g il ity
T i s su e Ma c ro p hage Sys tem
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For any query/question/idea/suggestion/comment/feedback
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“I honour, and shall always honour, To everyone who advances the noble science of physiology.“ — Charles Darwin