LYMPHATIC SYSTEM and Immunity
Lymphatic system includes lymph, lymphocytes, lymphatic vessels, lymph nodes, tonsils, the spleen, and the thymus gland.
Functions:
Fluid balance
Fat absorption
Defense
LYMPHATIC CAPILLARIES: tiny, close-ended vessels consisting of simple squamous epithelium.
More permeable than blood capillaries
Join to form larger LYMPHATIC VESSELS
Sequence of fluid flow:
Blood Capillaries >> Interstitial Spaces >> Lymphatic Capillaries >> Lymphatic Vessels >> Lymphatic Ducts >> Subclavian Veins
Major Lymphatic Ducts:
RIGHT LYMPHATIC DUCT - ~1.2 cm
THORACIC DUCT - 38 - 45 cm long
- Begins as a dilation called CISTERNA CHYLI
EDEMA -
LYMPHATIC ORGANS: Include the tonsils, lymph nodes, the spleen, and the thymus gland.
Lymphatic Tissue - consists of many lymphocytes and other cells which are found within lymphatic organs.
TONSILS
3 Groups of tonsils: a. Palatine Tonsils
b. Pharyngeal Tonsil
c. Lingual Tonsil
LYMPH NODES
Rounded structures, varying in size of small seeds to that of shelled almonds
Function to filter lymph.
3 Superficial aggregations of lymph nodes of the body:
Inguinal Nodes
Axillary Nodes
Cervical Nodes
STRUCTURE:
CAPSULE - dense connective tissue that surrounds each lymph node
TRABECULAE - extensions of the capsule that subdivide the lymph nodes into compartments
LYMPH NODULES - dense aggregations of tissue.
LYMPHATIC SINUSES - spaces between lymphatic tissue which contain macrophages on a network of fibers.
METASTASIS -
SPLEEN - roughly the size of a clenched fist; located in the left, superior corner of the abdominal cavity.
Largest single mass of lymphatic tissue.
Filters blood instead of lymph.
Also functions as a blood reservoir.
SPLENECTOMY -
THYMUS - a bilobed gland roughly triangular in shape
Surrounded by a thin connective tissue capsule.
Divided into LOBULES by the trabeculae.
Functions as a site for the production and maturation of lymphocytes.
Infants: 70 g; Old Age: 3 g
IMMUNITY
Immunity - the ability to resist damage from foreign substances.
2 Categories:
Innate Immunity - also called non - specific resistance
Adaptive Immunity - also called Specific Immunity
SPECIFICITY - the ability of adaptive immunity to recognize a particular substance.
MEMORY - the ability of adaptive immunity to "remember" previous encounters with a particular substance.
INNATE IMMUNITY: Accomplished by mechanical mechanisms, chemical mediators, cells, and the inflammatory response.
Mechanical Mechanisms: prevent the entry of microorganisms and chemicals in the body.
a.1 Skin and mucous membranes
a.2 Tears, saliva, and urine
Chemical Mediators: Molecules responsible for many aspects of innate immunity.
b.1 Lysozyme
b.2 Histamine
b.3 Complement
b.4 Prostaglandins
b.5 Leukotrienes
CELLS
CHEMOTAXIS - movement of WBCs toward chemicals known to attract them.
c.1 PHAGOCYTIC CELLS
c.2 CELLS OF INFLAMMATION
c.3 NATURAL KILLER CELLS
INFLAMMATORY RESPONSE
3 basic stages:
Vasodilation and increased permeability of blood vessels.
Emigration of phagocytes from the blood into interstitial fluid.
Tissue repair
d.1 LOCAL INFLAMMATION - an inflammatory response confined to a specific area of the body.
Cardinal S/Sx of Inflammation: redness, pain, heat, and swelling.
d.2 SYSTEMIC INFLAMMATION - an inflammatory response that is generally distributed throughout the body.
ADAPTIVE IMMUNITY
ANTIGENS - substances that stimulate adaptive immune responses.
2 groups:
FOREIGN ANTIGENS - introduced from outside the body.
SELF ANTIGENS - molecules produced by the person's body that stimulate an immune system response.
AUTOIMMUNE DISEASE -
1. ANTIBODY - MEDIATED IMMUNITY
Exposure of the body to an antigen can result in the activation of B cells and the production of antibodies.
ANTIBODIES - proteins produced in response to an antigen.
- Ab are called GAMMA GLOBULINS because they are found mostly in the gamma globulin part of plasma.
- Ab directly inactivate antigens or cause them to clump together.
FIVE CLASSES OF ANTIBODIES:
NAME TOTAL SERUM ANTIBODY (%) FUNCTIONS
IgG 80% Activates complement system; can cross the placenta and provide immune protection to the fetus and newborn; responsible for Rh reactions
IgA 10 - 15 % Secreted into saliva, tears, and onto mucous membranes to provide protection on body surfaces; found in colostrum and milk
IgM 5 - 10 % Activates complement system and acts as antigen binding receptor on the surface of B cells; responsible for transfusion reactions; often the first antibody produced in response to an antigen
IgD 0.2 % Involved in activation of B cells. Acts as an antigen - binding receptors on B cells
IgE < 0.1 % Binds to mast cells and basophils and stimulates the inflammatory response; provides protection against parasitic worms
ANTIBODY PRODUCTION:
PRIMARY RESPONSE - results from the first exposure to an antigen.
- B cells form plasma cells, which produce Ab, and memory B cells.
SECONDARY RESPONSE - results from exposure to an antigen after a primary response.
- Memory B cells quickly form plasma cells and new memory B cells.
2. CELL - MEDIATED IMMUNITY
Exposure to an antigen activates cytotoxic T cells and produces memory T cells.
Cytotoxic T cells lyse virus - infected cells, tumor cells, and tissue transplants.
Cytotoxic T cells produce cytokines, which promote inflammation and phagocytosis.
IMMUNOTHERAPY:
Stimulates or inhibits the immune system to treat diseases.
ACQUIRED IMMUNITY:
ACQUIRED ADAPTIVE
IMMUNITY
ACTIVE IMMUNITY PASSIVE IMMUNITY
Page Updated: January 29, 2007
