Red cell structure

• Red Cell structure and metabolism
• Lecture objectives
• Maturational sequence of RBC

  1. Size

  2. Nucleus

  3. Nucleolus

  4. Haemoglobinization

  5. Specialization
• Mature erythrocyte


  • Biconcave disc shape
  • Diameter 6.7-7.7um
  • MCV 76 - 96 fl (80-100 fl)
• Life Span of RBC


  ~120 days. Depends on: Structural integrity of the membrane and cytoskeleton, Sufficient energy ATP to maintain cation pump
• Mature RBC


  • No nucleus - no RNA production
  • No Ribosomes
  • No protein synthesis
  • No Mitochondria - No cytochrome mediated oxidative phosphorylation
• Cell Survival


  Relies on preformed protein and glycolysis for ATP production
• RBC membrane


  • Plasma membrane envelope composed of lipid molecules anchored to an elastic network of skeletal proteins
  • Cytoskeleton-complex network of fibrous proteins within the cytoplasm binding the membrane
• Major skeletal proteins: a & ẞ spectrin, ankyrin-confer the biconcave shape and deformability
• Transmembrane proteins (>50) - embedded in the lipid bilayer act as tethering sites
• Structural organization of RBC confers high elasticity, high structural resistance, ability to respond rapidly to applied fluid stress, highly deformable can traverse microvasculature 1/3 its diameter
• Deformability of RBC


  Regulated by: Cell geometry - SA to vol. ratio, Cytoplasm viscosity - haemoglobin, Membrane elasticity
• Red cell Metabolism


  1. Gycolysis - Glucose

  2. 2 ATPS lactate

  3. 2,3DPG (interacts with Hb to regulate oxygen affinity)

  4. NADP

  5. Pentose phosphate pathway: NADP/NADPH system (provides redox potential & Glutathione reductase)
• Hbfe2+ (reduced iron) from met Hb
• Red cell values & Indices
• Red blood cell count values

  • Manual - Neubauer counting chamber
  • Automated haematology analyzer
  • Red Cell Mass (not used much) - comparison of total blood volume to plasma volume (Males 36mls/kg, females 32mls/Kg)
• Red cell Indices


  • Packed Cell Volume (PCV)/Haematocrit (Hct)
  • Mean corpuscular volume - Femtolitres (fl)
  • Mean Cell Haemoglobin (MCH) - Picograms(pg)
  • Mean Cell Haemoglobin Concentration (MCHC) - g/dl
• Indices useful in classification of red cell morphological changes (size, shape, haemoglobinization) that occur in various pathological states
• Values and indices can be determined or derived by automated and manual methods as part of the Total Blood Count (TBC) in diagnostic haematology
• Components of TBC


  • HB, Hct/PCV, RBC count, MCV, MCH, MCHC
  • WBC total count/differential count
  • Platelet count
• The RBC life span is dependant on the structural integrity of the membrane and cytoskeleton and provision of ATP for energy
• Cell Survival relies on preformed protein and glycolysis for ATP
• The red cell structure is related to its internal (metabolism) and external environment
• Red cell values are age and sex dependent, and are also influenced by geographic location