Red Blood Cell Function and Anatomy

Red Blood Cell Function

• Red blood cells deliver oxygen from the lungs to all cells in the body.
• Red blood cells carry carbon dioxide back to the lungs for expulsion.
• Red blood cells make up about 40-45% of total blood volume.

Anatomy and Description

• Red blood cells are small, disc-shaped cells without a nucleus, resembling a doughnut.
• Their small size allows them to pass through tiny capillaries for oxygen-carbon dioxide exchange.
• Red blood cells contain hemoglobin, a protein with heme, which contains an iron ion that binds to oxygen.

Life Cycle

• Red blood cells live for about 120 days, circulating in the blood.
• They are produced in bone marrow and destroyed by cells in the liver and spleen.

Production

• Red blood cells are made in red bone marrow found in the center of long bones, as well as in spongy bone.
• Hemocytoblasts, stem cells in red bone marrow, differentiate into proerythroblasts, immature red blood cells with a nucleus.
• Proerythroblasts make hemoglobin and lose their nucleus to become mature red blood cells (erythrocytes).

Mature Red Blood Cells

• Mature red blood cells are released into the bloodstream from bone marrow.
• They have a long lifespan (about 120 days) and circulate continuously.
• Approximately 1% of red blood cells are replaced daily.

Death of Red Blood Cells

• After 120 days, red blood cell membranes break down.
• Cells in the spleen and liver destroy dying red blood cells and recycle their hemoglobin.

Functions

• Primary functions of red blood cells are oxygen transport and carbon dioxide removal.
• They also play a role in blood clotting by :
  • Increasing blood viscosity, making clots more likely.
  • Clotting is impaired in people with low red blood cell counts.

Oxygen and Carbon Dioxide Transport

• Hemoglobin in red blood cells binds to oxygen in the lungs.
• Oxygen is released from red blood cells in tissues and organs.
• Carbon dioxide from cellular respiration enters red blood cells and is converted for storage.
• Red blood cells return to the lungs, release carbon dioxide, and pick up more oxygen.

Red Blood Cell Disorders

• Anemia: low red blood cell count.
  • Causes: blood loss, iron deficiency, underlying disorder.
  • Treatment: depends on the cause, may include iron supplements or blood transfusions.
• Sickle Cell Disease: abnormally shaped red blood cells increase the risk of clotting.
  • Causes: genetic mutation.
  • Symptoms: significant pain and anemia.
  • Treatment: medications to prevent clotting, blood transfusions, stem cell transplants.
• Thalassemia: red blood cells contain abnormal hemoglobin, leading to chronic oxygen deficiency.
  • Causes: genetic mutation.
  • Symptoms: growth delays, heart and spleen damage.
  • Treatment: blood transfusions, stem cell transplants.
• Polycythemia vera: blood cancer with excessive red blood cell production due to a genetic mutation.
  • Symptoms: increased risk of blood clots leading to stroke or heart attack.
  • Treatment: regular bloodletting.