4.21 The Lymphatic and Immune Systems

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4.21 The Lymphatic and Immune Systems
2010-11-16 03:37:51
Lymphatic Immune Systems Disorders Throughout Life

The Lymphatic and Immune Systems; Disorders of; Throughout Life
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  1. The Lymphatic System
    General Overview
    Main function is to return excess tissue fluid to blood vascular system

    • Lymphatic vessels collect tissue fluid from loose connective tissue
    • • Carry fluid to great veins in the neck
    • • Fluid flows only toward the heart
    • • Once tissue fluid is within lymphatic vessels it is termed lymph
    • **blockage of lymphatic vessels causes swelling with excess tissue fluid, a condition called edema

    • Collect excess blood proteins and return them to the blood stream to maintain osmotic balance

    • Lymph capillaries: smallest lymph vessels; first to receive lymph; drain into..
    • • Lymphatic collecting vessels: Collect from lymph capillaries; drain into lymph trunks
    • Lymph nodes are scattered along collection vessels

    Lymph trunks: Collect lymph from collecting vessels; unite to form lymph ducts

    Lymph ducts: Empty into veins of the neck
  2. Lymphatic Capillaries
    • Located near blood capillaries, single layer of endothelial cells
    • Permeability results from structure and arrangement of endothelial cells; few intercellular junctions, edges of cells overlap, forming minivalves

    • • Receive tissue fluid from CT
    • • Increased volume of tissue fluid
    • • Minivalve flaps open and allow fluid to enter

    • High permeability allows entrance of
    • • Tissue fluid and protein molecules
    • • Also Bacteria, viruses, and cancer cells (lymph nodes help avert the spread of these)

    • Lacteals—specialized lymphatic capillaries
    • • Located in the villi of the small intestines
    • • Receive digested fats
    • • Fatty lymph—chyle
  3. Lymphatic Collecting Vessels
    • Accompany blood vessels

    • • Composed of the same three tunics as blood vessels, but walls are much thinner (lower pressure)
    • • Contain more valves than veins do; bulges at the base, collecting fluid to close valves
    • - Helps direct the flow of blood

    • Lymph propelled by:
    • • Skeletal muscles bulging
    • • Nearby arteries pulsing
    • • Muscular tunica media of the lymph vessels
    • • Normal movements of limbs and trunk
  4. Lymph Nodes
    Gross Anatomy
    •Cleanse the lymph of pathogens

    •Human body contains around 500

    • Superficial lymph nodes located in
    • • Cervical (along jugular veins and carotid arteries)
    • • Axillary (armpits)
    • • Inguinal regions (superior thigh)

    • Deep nodes are
    • • Tracheobronchial (thoracic viscera), aortic (posterior abdominal wall), and iliac (pelvic organs) lymph nodes
  5. Microsopic Anatomy of a Lymph Node
    Fibrous capsule—surrounds lymph nodes

    Trabeculae—connective tissue strands; extends inward forming compartments

    • Lymph vessels
    • Afferent lymphatic vessels: through which lymph enters convex portion of the node
    • Efferent lymphatic vessels: where lymph exits on the indented region

    • • Cortex: contain lymphoid follicle (purple ring) and germinal center (granules in center of ring)
    • • Medulla: contains medullary cord (purple blobs) and medullary sinus (outer pink regions)
  6. Lymph Trunks
    • Lymphatic collecting vessels converge to form five major lymph trunks
    • From inferior to superior
    • 1. Lumbar trunks: Receives lymph from lower limbs, pelvic organs; paired
    • 2. Intestinal trunk: Receives chyle from digestive organs; unpaired
    • 3. Bronchomediastinal trunks: Collects lymph from thoracic viscera; paired
    • 4. Subclavian trunks: Receive lymph from upper limbs and thoracic wall; paired
    • 5. Jugular trunks: Drain lymph from the head and neck
  7. Lymph Ducts
    • Cisterna chyli
    • • Located at the union of lumbar and intestinal trunks

    • Thoracic duct
    • • Ascends along vertebral bodies
    • • Empties into venous circulation at junction of left internal jugular and left subclavian veins
    • • Drains three quarters of the body: left side of the head, neck, and thorax; upper limb, and body's entire lower half

    • Right lymphatic duct
    • • Empties into right internal jugular and subclavian veins
    • • Drains lymph from the right upper extremity, head and thorax
    • • Is absent in some individuals
  8. The Immune System
    Brief Overview
    • Protects our bodies from foreign organisms
    • • Confers immunity to disease

    • Main components
    • :• Lymphocytes, lymphoid tissue, and lymphoid organs

    • Recognizes specific foreign molecules (antigens)

    • Destroys pathogens effectively

    • • Key cells—lymphocytes (type of white blood cell)
    • **two types of cells: T-cells (attack cells directly) and B-cells (differentiate into plasma cells that secrete antibodies)
    • • Also includes lymphoid tissue and lymphoid organs

    • Lymphoid organs
    • •Lymph nodes, spleen, thymus, tonsils, aggregated lymphoid nodules, and appendix
  9. Lymphoid Organs
    • Primary lymphoid organs
    • • Bone marrow (produce B cells)
    • • Thymus (T cells)

    • Secondary lymphoid organs (store lymphocytes and gather and destroy infections microorganisms)
    • • Lymph nodes, spleen, tonsils
    • • Aggregated lymphoid nodules in small intestine and appendix

    • Spleen
    • • Largest lymphoid organ
    • • Two main blood-cleansing functions
    • 1. Removal of blood-borne antigens
    • 2. Removal and destruction of old or defective blood cells
    • • Storage of platelets
    • • Site of hematopoiesis in the fetus

    • Tonsils
    • • Simplest lymphoid organs
    • • Four groups of tonsils
    • - Palatine (largest tonsils, often removed), lingual, pharyngeal, and tubal tonsils
    • • Arranged in a ring to gather and remove pathogens from inspired air or swallowed food