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