Lymphatic System:Structures & Immune

ResponseHonors Anatomy & Physiology

Wbc engulfs bacteria: http://www.youtube.com/watch?v=JnlULOjUhSQ

Lymph Vessels

Lymphatic vessels – drainage of excess interstitial fluid (lymph) that is returned to blood vessels

Lymphatic capillaries weave between tissue cells and blood capillaries in areolar tissue

Very permeable◦ Lacteals – specialized

capillaries found in villi of intestinal mucosa to help absorb fats

Flows to collectively larger vessels

Lymphatic Vessel Drainage

•Right lymphatic duct• Right arm, side of head

and upper thorax

• Empties into the right subclavian vien

•Thoracic duct• Much larger• Rest of the body

• Empties into junction of left subclavian vein & jugular vein

•About 3L enters blood every 24 hours

What is elephantiasis? Lymphatic ducts get

clogged with parasitic roundworms

Swelling of lower limbs and scrotum due to edema

Lymph Nodes

Filters lymph fluid◦ Macrophages destroy microorganisms

Help activate the immune system◦ Lymphocytes monitor & attack

antigens 100’s of these small organs Bean shaped <1inch long Cortex (outer region)

◦ Dividing B cells◦ Circulating T cells

Medulla (inner region)◦ Plasma cells◦ macrophages

Fewer efferent lymph vessels than afferent vessels

Lymph Organs

Spleen – monitors blood◦ Red pulp -extracts aged & defective blood

cells◦ Stores hemoglobin & platelets (recycled)◦ White Pulp -contains lymphocytes &

macrophagesThymus – T cells become immunocompetent

(specific)◦ Atrophy after puberty (replaced by adipose

tissue)◦ Does not directly fight pathogens

Tonsils – invaginations trap pathogens◦ Contains lymphocytes & macrophages

Palatine tonsils Lingual tonsils Pharyngeal tonsil Tubal tonsils

Lymphatic Tissues

MALT: Mucosa Associated Lymphatic Tissue

Protects passages open to exteriorProduces memory cells against

invadersIncludes:

◦Peyers Patches Clusters of lymph tissue on small

intestine◦Appendix

Off shoot of large intestine Destroys any bacteria may leave

intestine

Innate (Non Specific) Defenses

1st line defense- Surface Barriers: ◦Skin & Mucous Membranes Physical barrier Acidity of skin secretions

(ph 3-5) Sebum – toxic to bacteria HCl of stomach Saliva & lacrimal fluid

contain lysozyme◦Enzyme destroys bacteria

Mucus traps microorganisms

Innate (Non Specific) Defenses (20 Defense)

Cells◦Phagocytes – engulfs & digests

Macrophages from WBC monocytes◦ Free (mobile) or fixed (liver, brain)

Neutrophils (WBC)◦ Become phagocytic after encounters pathogen◦ Destroy self in process

Eosinophils (WBC)◦ defend against parasitic worms

◦Natural Killer (NK) Cells “police” blood & lymph Detect lack of “self” antigens Direct contact induces target cell to

undergo apoptosis Lyse & kill cancer cells & viral infected

cells

Innate (Non Specific) Defenses

Chemicals◦ Inflammation -Prevents spreading of pathogen &

disposes pathogens & cell debris Redness & heat

◦Mast cells release histamines causing vasodilatation Swelling & pain

◦ Increased permeability of capillaries ◦Clotting factors, antibodies & fluid leak into tissues

◦Antimicrobial proteins Interferons (IFNs)

◦Secreted by viral infected cells to prevent other cells from becoming infected

◦Stimulate synthesis of proteins that interfere w/viral protein synthesis (not specific)

◦Fever Response to widespread infection Macrophages and WBC release pyrogens

◦Chem that resets thermostat in Hypothalmus◦ Increases metabolism

Adaptive Defenses (Specific)

Must be primed by initial exposure before it can defend against it

3 important features:Specific against a particular pathogenSystemic – not restricted to infection site

◦Humoral Immunity – circulating antibodies in body fluids

◦Cell Mediated Immunity – lymphocytes attack pathogens

Memory – recognizes and mounts strong attacks against previously encountered pathogens

Antigens

Antigens – Foreign substances that provoke an immune response◦ Non-self - not normally found in the

body◦ Cause proliferation of lymphocytes &

antibodiesSelf-Antigens

◦ MHC (major histocompatibility complex) proteins on surface of “self” cells

◦ Variety - genetically determined

Antibodies

AKA immunoglobulin (Igs)Secreted by B cells or plasma cellsStructure:

◦‘Y’ shaped; 4 polypeptide chains (2 Heavy, 2 Light)◦Variable region – 2 binding sites that responds to

specific antigens◦Constant region – determines Ig class

Antigen-antibody complex:◦Neutralizes - no longer harmful◦Agglutination – cross linked causing clumping

Inactivates pathogens and tags for destruction

Humoral Immune Response

Antigen binding to receptor on specific B lymphocyte stimulates proliferation forming clones that differentiate into:

Plasma cells – secrete 2,000 antibodies per second (for about 5 days then dies)!!!

Memory cells – will respond to subsequent exposures to same antigen

How do Vaccines work?

Contain dead or attenuated (weakened) pathogens or their components

Spares us symptoms of disease that would normally occur during a primary response

Memory cells are formed against antigen (humoral only)

Cell Mediated Response

T cells mature in Thymus Targets infected cells, cancer cells,

foreign tissues Helper T cells (CD4)

◦ Stimulates production of cytotoxic T cells and B cells, activates macrophages, and releases cytokines (chemicals that trigger proliferation and inflammation)

Cytotoxic T cells (CD8)◦ Binds to infected cells and inserts

chemicals causing apoptosis Regulatory T cells

◦ Suppresses immune activity Memory T cells

◦ Responds quickly to subsequent infections (last years)

Double recognition on an antigen presenting cell:◦ Non self antigen◦ MHC proteins indicating “self” cell

Types of immunity

Innate – genetically determinedAcquired – arises during life

◦Active – appears after exposure to antigen Naturally- continually induced as encounter “new”

pathogens or antigens Induced – stimulated under controlled conditions

◦Vaccine: dead/inactive pathogen that induces an immune response

◦Passive – transfer of antibodies from another source Naturally – mother to baby

◦Gestation – via placenta◦ Infancy – via breast milk

Induced – antibodies administered to fight infection or prevent disease after exposure

Select your Task…

Create a comic strip depicting the specific response of lymphatic system (combating a pathogen of your choice)

Write a script for a mini-play describing specific response of lymphatic system

May work in pairsEither choice should include: B cells, plasma

cells, antibodies, helper T cells, cytotoxic T cells, memory cells, suppressor (regulator) T cells, and macrophages