Pathology week 5- Hematopoietic System

Hematopoietic System

Overview of the Hematopoietic System

  • The hematopoietic system is responsible for blood production and includes:

    • Blood

    • Lymphatic tissue

    • Bone marrow

    • Spleen

    • (Also includes the liver due to its role in filtration)

Composition of Blood

  • Blood consists of:

    • Plasma: 55% of blood volume

    • Comprised of:

      • Water

      • Plasma proteins

      • Nutrients filtered from the liver

    • Blood Cells: 45% of blood volume

    • Subtypes include:

      • Red blood cells (erythrocytes)

      • White blood cells (leukocytes)

      • Platelets (thrombocytes)

Blood Cell Production

  • Red Blood Cells and Platelets: Produced in red bone marrow

  • White Blood Cells: Produced in both red bone marrow and lymphoid tissues (e.g., tonsils)

Functions of Blood Components

  • Hemoglobin:

    • An iron-based protein that carries oxygen to the body's tissues.

    • Its presence is significant in diagnostic imaging, particularly in detecting strokes or brain hemorrhages.

  • Leukocytes (White Blood Cells):

    • Can be categorized as granular (basophils, neutrophils, eosinophils) or non-granular (monocytes, lymphocytes).

    • Phagocytosis: The process of engulfing and digesting pathogens.

    • Changes in leukocyte counts can indicate disease presence.

  • Thrombocytes (Platelets):

    • Involved in blood coagulation.

    • Blood thinners prevent their coagulation properties, which is significant in clinical treatments.

Types of Leukocytes

  • Granular Leukocytes:

    • Basophils, Neutrophils, Eosinophils: serve as the body’s first line of defense.

  • Non-Granular Leukocytes:

    • Monocytes and Lymphocytes: important for immune responses.

Lymphatic System

  • Overview:

    • A separate but intertwined circulatory system that ensures immunity and absorbs fats from the GI tract.

  • Components:

    • Composed of lymphatic vessels and nodes, as well as organs:

    • Spleen

    • Thymus

    • Bone marrow

    • Tonsils

  • Functionality:

    • Mainly involved in the production of lymphocytes and antibodies.

    • Supports the maturation process of white blood cells.

Radio Sensitivity of Blood Components

  • In order of decreasing radiation sensitivity:

    • Lymphocytes

    • Leukocytes

    • Thrombocytes

  • Radiation Threshold:

    • Whole body dose of 0.5 to 0.75 Gy leads to detectable changes in blood cells.

    • Not significant in diagnostic radiology due to low exposure levels.

Spleen

  • Definition: The largest lymphoid organ located in the upper left quadrant.

  • Color: Generally appears purple-red due to high blood circulation.

  • Functions:

    • Involved in the production and maturation of white blood cells.