Introduction
Red blood cells are the non-nucleated formed elements in the blood involved principally in the transport of gases (Oxygen & Carbon Dioxide)
Features
MORPHOLOGY
- Normal shape: Disk-shaped and biconcave (dumbbell-shaped)
- Normal size:
- Diameter – 7.8µm
- Thickness:
- At the periphery: 2.5 µm
- At the center: 1.0 µm
- Surface area –
- Volume – 87mm3
- Normal structure:
- Non-nucleated
- Lack organelles such as mitochondria and Golgi apparatus
- Cytoskeleton made up of actin and spectrin which are anchored to transmembrane protein by ankyrin
LIFESPAN
- Average lifespan of RBCs – 120 days
PROPERTIES
- Rouleaux formation: the ability of RBCs to pile up above one another like a pile of coins due to excessive globulin & fibrinogen levels in the blood
- Packed cell volume: is the percentage of the blood occupied by RBCs. Also called haematocrit value, it is 45% of the blood. Plasma volume is 55%
- Suspension stability: the ability of RBCs to remain suspended uniformly in the blood during circulation
- Transport of Oxygen from the Lungs to the Tissues
- Transport of Carbon Dioxide from the Tissues to the Lungs
- Buffering action: Haemoglobin regulates hydrogen ion concentration
- Blood group determination
Variations
NORMAL COUNT
- Males – 5.4 × 1012/L
- Females – 4.8 × 1012/L
VARIATION IN NUMBER
- Physiological variations
- Age – more in infants (decreases within 10 days after birth)
- Sex – More in males
- High altitude – Increases at higher altitudes due to hypoxia
- Muscular exercise – increases during muscular exercises due to increased oxygen need
- Emotional conditions – Increases during emotional conditions
- After meals – slightly increases after meals
- High barometric pressures – RBC count decreases
- During sleep – Count decreases slightly
- Pregnancy – decreases due to increased extracellular fluid
- Pathological variations
- Polycythaemia – abnormal increase in RBC count
- Anaemia – decrease in RBC count
VARIATION IN SIZE (Anisocytosis)
- Normocytes – normal cell size
- Microcytes – smaller than normal
- Macrocytes – larger than normal
VARIATION IN SHAPE (Poikilocytosis)
- Spherocytosis – cell is spherical in shape
- Stomatocytosis – a slit (called stoma) in between the cell
- Acanthocytosis – multiple irregular surface projections on the cell (mainly found in liver diseases)
- Target cells – hollow appearance in the middle of the cell due to iron deficiency
- Elliptocytosis – cells are elliptical or oval in shape
- Cigar cells – cigar or penal shaped cells
- Sickle cells – cells are sickle-shaped due to haemoglobin disease
- Crenation – shrinkage as in hypertonic conditions
VARIATION IN STRUCTURE
- Punctate Basophilism – striated appearance of RBCs due to the presence of dots of basophilic materials (Porphyrin) as in lead poisoning
- Ring in RBCs (Goblet rings) – rings or twisted strands of basophilic material in the periphery of the RBCs
- HOWELL-JOLLY BODIES – Nuclear fragments (Howell-Jolly bodies) present in the cytoplasm of RBCs
Variation In Colour
- Normochromasia – normal cell colour [Red – oxygenated,
- Hypochromasia – small and not brightly red due to a reduction in the amount of haemoglobin
- Polychromasia – cells having grains of blue-grey colour when stained with eosin or basic dye. Occurs in reticulocytosis
Production And Fate
RBCs are produced in the bone marrow and after circulating a lifespan of 120 days, are eventually destroyed and broken down by the reticuloendothelial system
Anaemia
Megaloblastic anaemia
Polycythaemia Vera
Secondary Polycythaemia
