Lymphatic System, Immunity, Heart, and Respiratory Functions

Posted on Feb 17, 2025 in Biology

Lymphatic System Functions

The lymphatic system has several crucial functions:

  • Production, maintenance, storage, and distribution of lymphocytes that protect against infections and environmental hazards.
  • Maintenance of fluid balance.
  • Absorption of liquids from the intestine and transportation to the blood.
  • Collection and return of fluid that leaks from blood vessels.
  • Absorption of fats and vitamins.

White Blood Cells (WBCs)

White Blood Cells in blood

T-Cells

T-Cells constitute 80% of lymphocytes. Types include:

  • Cytotoxic T-cells: Attack foreign cells or cells infected by viruses.
  • Helper T-cells: Stimulate the activation and function of T and B cells.
  • Suppressor T-cells: Inhibit the activation and function of T and B cells.
  • Memory T-cells: Respond to previously encountered antigens.

B-Cells

B-Cells make up 10-15% of lymphocytes. They differentiate into plasma cells, which produce and secrete antibodies.

NK Cells

NK Cells constitute 5-10% of lymphocytes.

Inflammation Process

  1. Tissue damage occurs.
  2. Mast cells release histamine and heparin.
  3. Blood vessels dilate, leading to clot formation. Phagocytes are attracted and release cytokines, removing debris and activating specific defenses.
  4. Pathogens are removed, clot erosion occurs, and scar tissue is formed.

Innate Immune System

The innate immune system is the non-specific, first line of defense. It is genetically determined. Key components include:

  • Cells: Phagocytic cells (monocytes/macrophages and PMNs), NK cells, basophils, mast cells, eosinophils, and platelets.
  • Complement System: Proteins circulating in the blood that become sequentially activated in response to microorganisms. There are three types:
    • Classical complement pathway
    • Lectin pathway
    • Alternative complement pathway

Adaptive Immune System

The adaptive immune system is not present at birth. Immunity to a specific antigen is acquired only upon exposure or by receiving antibodies from another source. It includes:

  • Active Immunity: Develops in response to antigen exposure.
    • Natural: Develops after exposure to an antigen in the environment.
    • Artificial: Develops after the administration of an antigen to prevent disease.
  • Passive Immunity: Involves the transfer of antibodies from other sources.
    • Natural: Transfer occurs across the placenta or through breast milk.
    • Artificial: Administration of antibodies to combat infection.

Heart Structure

  • Epicardium: The outside of the myocardium is covered with a thin layer called the epicardium, consisting mostly of connective tissue and fat.
  • Myocardium: The thick layer of cardiac muscle responsible for the contraction and relaxation of the ventricles and atria, composed almost completely of cardiomyocytes.
  • Endocardium: The inner lining of the heart, a smooth membrane of endothelial cells that lines the chambers and valves.
  • Pericardium: A tough, protective membrane enclosing the heart. It has two layers with lubricating fluid in between, allowing for free movement of the heart muscle. Inflammation of this sac is called pericarditis.

Respiratory System Functions

  1. Gas exchange between air and circulating blood.
  2. Moving air to and from the exchange surfaces of the lungs along the respiratory passageways.
  3. Protecting respiratory surfaces from dehydration, temperature changes, and other environmental variations, and defending against pathogen invasion.
  4. Producing sound.
  5. Facilitating the sense of smell and detecting odors.