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Lymphatic System. Functions. Put excess fluid in tissue spaces back into the blood stream Immunity. Flow of Lymph. Lymphatic capillaries → Lymphatic vessels → Lymphatic Trunks → Collecting Ducts → Veins - PowerPoint PPT Presentation
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Put excess fluid in tissue spaces back into the blood stream
Immunity
Lymphatic capillaries → Lymphatic vessels →
Lymphatic Trunks → Collecting Ducts → Veins
The lymph will also pass through lymph nodes found along these vessels
Closed-ended tubes Form network with
blood capillaries Thin-walled Fluid inside is
called lymph
Lymphatic vessels• Structure is very similar to veins
Lymphatic Trunks• Larger vessels than lymphatic vessels; drain
into collecting ducts
Two Main Ducts• Thoracic Duct- collects
lymph drained from the lower limbs, the abdomen, the left upper limb, and the left side of the thorax, head, and neck
• Right Lymphatic Duct- collects lymph drained from the right upper limb and the right side of the thorax, neck, and head
Interstitial fluid surrounding capillaries
Constant movement in and out of capillaries
Generally same composition as plasma except plasma proteins
Some excess fluid stays and is not recollected by capillaries
Volume pressure of interstitial fluid causes some of the fluid to enter lymphatic capillaries
Lymph will return to the bloodstream but will be filtered along the way
Controlled by• Skeletal muscle movement • Pressure changes due to breathing
Valves keep the movement going in one direction
Usually small and bean shaped Afferent lymphatic vessels
• carry lymph into lymph node• Come in at various points along convex
surface Efferent Lymphatic vessels
• Carry lymph out of lymph node• Come out at hilum (area on the concave
side) Blood Vessels and nerves enter at
hilum
Connective tissue encloses lymph node and creates sub-compartments inside
Compartments are lymph nodules Space inside the nodule is called a
lymph sinus Sinuses are filled with lymphocytes
and macrophages
Filter foreign particles from blood before returning the lymph to the blood stream
Immune surveillance
Bilobed structure found in the mediastenum
Largest during childhood
Creates T-cells Also endocrine
gland- releases thymosins to make T-cells mature after leaving the thymus
Largest lymphatic organ Found in upper left
quadrant near stomach Similar structure to
lymph nodes except sinuses contain blood instead of lymph
White pulp- high in lymphocytes
Red pulp- high in red blood cells, lymphocytes, and macrophages
Filters Blood
Protection against pathogens Pathogens include
• Viruses• Bacteria• Fungi• Protozoans
Innate vs Adaptive
Natural vs Artificial
Active vs Passive
Species resistance First line of defense- skin and mucous
layers Second line of defense
• Chemical barriers Tears, gastric juices, and sweat interferons
• Fever• Inflammation• Phagocytosis
Third line of defense
Lymphocytes are responsible
Responds to specific antigen on the invading pathogen
Undifferentiated lymphocytes made by fetal bone marrow
T cells• Lymphocytes travel to thymus and become T
cells• T cells either circulate in blood or are found in
lymph system B cells
• Made in marrow• B cells either circulate in blood or found in the
lymph system
Cellular Immune response• Attack up close• Performed by T cells
Humoral immune response• Attack from afar• Performed by B cells
Antigen-presenting cells processes and displays antigen of pathogen
Displayed antigen must be matched with a circulating helper T cells antibody receptor
Helper T cell is activated
Cytotoxic T cells- attack cells infected virus or cancerous cells
must be activated by a matching antigen
B cell must match with an antigen Activated Helper T cell secrete
cytokines Cytokines make B cell proliferate to
form plasma cells and memory cells Plasma cell secrete antibodies
Globular proteins Five Types
• Immunoglobulin G (IgG)- in plasma and tissue fluids; activates complement system
• IgA- in exocrine gland secretions• IgM- in plasma; activates complement system• IgD- found on surfaces of B cells; activates B
cells• IgE- in exocrine gland secretions; associated
with allergic reaction
Attack Directly• Agglutinate- clump pathogens together• Precipitate- make pathogen insoluble• Neutralize- cover or destroy toxic part of
antigen
Activate compliment• Done by shape change of IgG and IgM• Starts a series of rxns that activate the
compliments circulating in the plasma Compliment Function
• Opsonization- coating antigen-antibody complex
• Chemotaxis- bringing macrophages to the area• Lysis- rupturing membranes• Agglutination• Neutralization
Memory T and B cells- circulate after primary immune response
Body will be able to respond quickly during secondary immune response
Immune response to everyday, non-harmful antigens (allergens)
Delayed-reaction allergy• Exposure to allergen on skin • Collects T cells and macrophages in the
area• Causes dermatitis
Immediate-reaction allergy• Occurs within minutes• First exposure- B cells become sensitized;
IgE is attached to basophils and mast cells• Subsequent exposures- mast cells and
basophils secrete several substances including histamine
• These substances produce the reactions seen in allergy reactions
Transplant tissue or organ Antigen is recognized as foreign and
starts immune response Tissue matching helps minimize
reaction Immunosuppressive drugs- suppress
immune reaction
Cytotoxic T cells cannot correctly identify self cells and attacks self cells
Why?• “catalogue” is incomplete• Pathogen borrows self antigens during
attack • Pathogen antigen is very similar to a self
antigen