Circulatory System - Blood Manual

There are three main functions of the circulatory system:

  1. Transport

    1. Bring oxygen from lungs to tissues and carbon dioxide from tissues to lungs

    2. Bring nutrients to the body’s tissues from the digestive tract

    3. Metabolic waste → kidneys for removal

    4. Hormones from endocrine cells → target organs

    5. Stem cells from bone marrow → tissues to lodge into and mature

  2. Protection

    1. Role in inflammation

    2. White blood cells/Leukocytes

      1. Destroy microorganisms/cancer cells and remove waste

    3. Antibodies/Blood Proteins

      1. Neutralize toxins and destroy pathogens

    4. Red Blood Cells/Erythrocytes

      1. Bind and transport foreign antigens → liver/spleen for disposal

    5. Platelets/Thrombocytes

      1. Bloodclotting/minimize blood loss, tissue growth, blood pressure maintenance

  3. Regulation

    1. Stabilization of body’s fluid distribution by blood capillaries

    2. Blood proteins stabilize pH of extracellular fluids

    3. Blood flow shifts regulate body temperature

Components of Blood

  1. Liquid connective tissue

  2. Plasma = extracellular blood matrix consisting of over half of the blood volume

  3. Formed Elements = cell/cell fragments suspended in plasma with 3 categories

Formed Elements

  1. Erythrocytes (RBCs):

    1. Responsible for oxygen transport throughout the body, containing hemoglobin which binds to oxygen molecules.

  2. Leukocytes (WBCs):

    1. Play a crucial role in the immune system by defending the body against infections and foreign substances. There are several types of leukocytes, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specific functions.

  3. Platelets: Small cell fragments that are essential for blood clotting. They help prevent bleeding by aggregating at the site of injury and forming a temporary plug.

Leukocyte Subcategories

  1. Granulocytes: These are a subtype of leukocytes characterized by the presence of granules in their cytoplasm, which are involved in inflammatory responses and pathogen destruction.

    1. Neutrophils:These are the most abundant type of white blood cells, accounting for 50-70% of all leukocytes. They are primarily responsible for the phagocytosis of bacteria and fungi, responding quickly to sites of infection.

    2. Eosinophils: These leukocytes make up about 1-4% of the total white blood cell count and are primarily involved in combating parasitic infections and modulating allergic responses.

    3. Basophils: Representing less than 1% of leukocytes, basophils play a role in inflammatory and allergic reactions by releasing histamine and other mediators.

  2. Agranulocytes: These are the second main category of white blood cells, comprising lymphocytes and monocytes, which are vital for adaptive immune responses. Lymphocytes include B cells, responsible for antibody production, and T cells, which are involved in cell-mediated immunity. Monocytes differentiate into macrophages and dendritic cells upon entering tissues, playing crucial roles in phagocytosis and antigen presentation.

    1. Lymphocytes: Comprising about 20-40% of the total white blood cell count, lymphocytes are central to the adaptive immune response, including T cells that kill infected host cells and B cells that produce antibodies.

    2. Monocytes: These cells account for about 2-8% of leukocytes and differentiate into macrophages and dendritic cells upon entering tissues, which are essential for phagocytosis and presenting antigens to lymphocytes.

Blood Serum: This is the clear, yellowish part of the blood that remains after blood clots. It contains water, electrolytes, proteins, hormones, and waste products, playing a crucial role in transporting nutrients and supporting various physiological processes.

Blood Plasma: This is the liquid component of blood, making up about 55% of its total volume, and is primarily composed of water along with dissolved proteins, glucose, electrolytes, hormones, and carbon dioxide. Blood plasma serves as a medium for transporting blood cells, nutrients, and waste products throughout the body, and also plays a key role in maintaining blood pressure and regulating body temperature.

Antigens: These are substances that can provoke an immune response by binding to specific antibodies or lymphocyte receptors, thus playing a crucial role in identifying foreign pathogens and facilitating the body's defense mechanisms.

Antibodies: These are specialized proteins produced by B lymphocytes in response to specific antigens. They play a critical role in the immune system by identifying and neutralizing pathogens such as bacteria and viruses, thus safeguarding the body from infections.