Lecture Notes: Components of Blood

Overview

• Blood is composed of four main components:
  • Red Blood Cells (RBCs)
  • White Blood Cells (WBCs)
  • Platelets
  • Plasma
• Understanding each component is essential, especially when considering blood replacement for those with inadequate blood levels.

Red Blood Cells (RBCs)

• Composition: Make up almost half of the blood by volume.
• Function:
  • Transport oxygen from the lungs to tissues for cellular respiration.
  • Contain hemoglobin, a red pigment that binds with oxygen to form oxyhemoglobin.
  • Oxyhemoglobin releases oxygen into tissues for diffusion.
• Adaptations:
  • Lack of nucleus to provide more space for hemoglobin and oxygen.
  • Biconcave disc shape increases surface area for oxygen absorption.

White Blood Cells (WBCs)

• Composition: Constitute less than 1% of blood volume.
• Function: Crucial part of the immune system, defending against infections.
  • Perform phagocytosis (engulfing pathogens).
  • Produce antibodies and antitoxins to neutralize toxins.
• Structure: Contain a nucleus, unlike RBCs.

Platelets

• Nature: Small cell fragments, not actual cells, without a nucleus.
• Function:
  • Facilitate blood clotting to prevent blood loss from cuts.
  • Protect the body from infection by sealing wounds.

Plasma

• Composition: Makes up just over half the blood's volume.
• Appearance: Pale, straw-colored liquid.
• Function:
  • Facilitates flow of blood.
  • Carries RBCs, WBCs, and platelets.
  • Transports nutrients, waste products, hormones, proteins, antibodies, and antitoxins.

Blood Volume and Replacement

• Normal Volume: Adults have approximately 5 liters of blood.
• Blood Loss: Significant reduction (e.g., due to injury) may impair oxygen delivery to tissues.
• Replacement Options:
  • Artificial Blood: A substitute fluid mainly consisting of salt water.
    • Adds volume to circulatory system.
    • Does not contain RBCs, hence limited oxygen transport capability.
    • Only a third of blood can be replaced with it.
  • Blood Transfusion: Use of donor blood containing RBCs for effective oxygen transport.

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