lecture recording on 11 March 2025 at 15.54.39 PM

Blood Composition

• Plasma

  • Makes up 55% of blood

  • Yellowish liquid primarily composed of water

  • Contains vital proteins such as:

    • Albumin: Helps maintain osmotic pressure; produced in the liver

    • Clotting proteins: Assist platelets

    • Immune proteins: Support leukocytes' function

    • Transport proteins: Aid in transporting substances in the blood

    • Nutrients like glucose and gases

• Formed Elements

  • Comprise erythrocytes (red blood cells), leukocytes (white blood cells), and platelets

  • Each plays unique roles:

    • Erythrocytes (Red Blood Cells)

      • Function: Gas transport (O2 and CO2)

      • Structure: Biconcave, lack nucleus to maximize surface area for gas exchange

      • Contain hemoglobin which binds O2, CO2, and carbon monoxide (creating carboxyhemoglobin)

    • Leukocytes (White Blood Cells)

      • Function: Immune defense against infections

      • Types: Granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (monocytes, lymphocytes)

    • Platelets

      • Function: Blood clotting and controlling bleeding

Clinical Connection

• Common Blood Disorders

  • Anemia

    • Definition: Decreased oxygen carrying capacity of blood

    • Symptoms: Fatigue, pale skin, weakness, shortness of breath, elevated heart rate

    • Causes include:

      • Decreased hemoglobin (often due to dietary iron deficiency)

      • Decrease in erythrocyte count (e.g., from blood loss)

      • Abnormal hemoglobin (e.g., sickle cell anemia)

• Leukocytes in Infection

  • Frequent infections signal possible decrease in leukocyte function

  • If leukocytes are dysfunctional, increased susceptibility to infections and longer recovery times

Erythropoiesis (Production of Erythrocytes)

• Stem cells in red bone marrow differentiate into:

  1. Erythrocyte Colony Forming Units (CFUs)

  2. Proerythroblasts (which eventually lose their nucleus)

  3. Reticulocytes (immature erythrocytes)

  4. Mature Erythrocytes (released into circulation)

• Hormonal Control:

  • Erythropoietin (EPO) from kidneys stimulates erythropoiesis in response to low O2 levels.

Functions of Blood Cells

• Erythrocytes

  • Primary role: Gas transport (O2 and CO2)

• Leukocytes

  • Neutrophils: Fight bacterial infections by ingesting bacteria; inflammation mediator

  • Eosinophils: Combat parasitic infections and mediate allergic reactions

  • Basophils: Least common; release histamine during inflammatory responses

  • Monocytes: Differentiate into macrophages that ingest pathogens and dead cells

• Platelets

  • Essential for clotting: Form a temporary plug in damaged blood vessels and secrete clotting factors

Implications of Dysfunction in Blood Cells

• Erythrocyte Dysfunction

  • Leads to reduced gas exchange, causing fatigue and hypoxia.

• Leukocyte Dysfunction

  • Increases vulnerability to infections; could indicate weakness in immune response, potentially linked to abnormalities like leukemias.

• Platelet Dysfunction

  • Causes prolonged bleeding and hemophilia, resulting in increased risk of hemorrhage.

Assessing Blood Health

• White Blood Cell Count: Elevated in infections; used for diagnosing conditions like leukemia.

• Red Blood Cell Count: Crucial for determining anemia.

• Platelet Count: Helps assess clotting ability and detect bleeding disorders.