In-Depth Notes on Blood

Blood Content

• Blood consists of two main components:

  • Plasma

  • Non-living fluid matrix, constituting 63% of blood.

  • Composed mainly of:

    • Water: 90%

    • Nutrients: 1%

    • Proteins: 60% albumin, 36% globulins, 4% fibrinogen

    • Wastes and Gases

  • Formed Elements (Living blood components):

  • Erythrocytes (RBCs): Red Blood Cells

  • Leukocytes (WBCs): White Blood Cells

  • Platelets: Cell fragments

• Blood has a sticky, opaque, metallic taste with a pH range of 7.35-7.45.

• Blood volume is approximately 5-6L in men and 4-5L in women.

Blood Functions

Blood serves three main functions:

1. Distribution:

   • Delivers oxygen and nutrients to body cells (O_2) and transports metabolic wastes to lungs and kidneys for elimination.

   • Transports hormones from endocrine organs to target organs.

2. Regulation:

   • Maintains body temperature by absorbing and distributing heat.

   • Maintains normal pH through buffers.

   • Maintains adequate fluid volume in circulatory system.

3. Protection:

   • Prevents blood loss through clot formation aided by plasma proteins and platelets.

   • Prevents infection.

Erythrocytes (RBCs)

• Structural Features:

  • Biconcave disks, anucleate (no nucleus), and lack organelles.

  • Contain spectrin which provides flexibility to change shape.

• Function:

  • Main function is respiratory gas transport;

  • Hemoglobin (Hb): A protein that carries oxygen, constituting 97% of the RBC's content.

  • Structure of Hemoglobin:

  • Composed of 4 polypeptide chains:

    • 2 alpha chains and 2 beta chains.

    • Heme: Pigment bonded to globin that gives blood its red color.

  • Oxygen Transport:

  • Oxyhemoglobin: Ruby red, formed during (O_2) loading in lungs.

  • Deoxyhemoglobin: Dark red, formed during (O_2) unloading in tissues.

  • Carbaminohemoglobin: 20% of (CO_2) in blood binds to hemoglobin.

• Each RBC contains approximately 250 million hemoglobin molecules, and each hemoglobin can transport 4 molecules of oxygen (O_2).

Hematopoiesis

• The formation of blood cells, occurring in red bone marrow.

• Hemocytoblasts: Hematopoietic stem cells that give rise to all blood cells.

• Hematocrit: Percentage of blood volume that is composed of RBCs:

  • Approximately 47% ± 5% in males.

  • Approximately 42% ± 5% in females.