Blood Cells and Hemoglobin

Blood Cells

• Erythrocytes (RBCs) undergo Oxythropoiesis, a process that produces red blood cells.

Structure and Function of RBCs

• RBCs have a biconcave shape, allowing them to pass through the lumen of blood vessels.
• The biconcave shape is maintained by the protein spectrin.
• RBCs have a diameter of approximately 7.5-8.7 μm.
• The surface area-to-volume ratio of RBCs is 1.3-1.4 μm²/μm³.

Haemoglobin

• Haemoglobin is a protein found in RBCs that transports oxygen.
• Haemoglobin is synthesized in the bone marrow.

Life Span of RBCs

• The average life span of RBCs is 110 days.

Metabolism of RBCs

• RBCs undergo glycolysis to generate energy (EMP pathway).
• They also use the hexose monophosphate (HMP) pathway to generate energy.

Erythropoiesis

• Erythropoiesis is the process of RBC production, which occurs in the bone marrow.
• During intrauterine life, erythropoiesis occurs in the following stages:
  • Mesoblastic stage (up to 3 months): RBCs are produced in the yolk sac.
  • Hepatic stage (3-5 months): RBCs are produced in the liver and spleen.
  • Myeloid stage (after 5 months): RBCs are produced in the bone marrow.

Developmental Stages of Erythropoiesis

• In children, erythropoiesis occurs in the liver, spleen, and bone marrow.
• The bone marrow becomes the primary site of erythropoiesis around age 6.
• The liver and spleen stop producing RBCs around age 5 and 6, respectively.