Lymphatic System & Immunity

Vocab

• -gen: be produced• Humor-: fluid• Nod-: knot• Immun-: free• Inflamm-: set on fire• Patho-: disease• Lymph: the fluid inside lymph vessels and

capillaries

Lymphatic System

• The lymphatic system: A collection of cells and biochemicals that travel through lymph vessels, organs and glands

Functions

• Launch immune attacks against foreign particles• Protects against toxins and cancer• Filters blood plasma

Pathways

• Begin at capillaries and merge with larger vessels• Capillaries → Vessels → lymph nodes → lymph

trunks → ducts

Lymph Nodes

• Lymph nodes: specialized glands that contain lymphocytes• B & T cells of the immune system• Macrophages that kill microorganisms

• found all over the body except in the nervous system• Functions:• Filters harmful particles from lymph• Immune surveillance= lymphocytes attack viruses,

bacteria and parasites

Lymphatic System

• Hilum- where blood vessels and nerves join a lymph node• Lymphatic trunks: collecting ducts that receives

lymph fluid from distal parts of the body

Lymphatic System

• Lymph Modules: the functioning unit of a lymph node• Lymph Sinuses: a network of chambers in a lymph

node

Lymph Movement

• One way • Exercise and movement increase lymph flow• Breathing stimulates lymph movement• Impaired lymph movement: Causes edema

(swelling)

Lymphatic System

• Thymus= a soft gland located posterior to the sternum• Large when you are born – shrinks when you get older• Secretes lymphocytes and hormones

Spleen

• The largest organ in the lymphatic system• Filled with blood vessels, not lymph• Contains lymphocytes and macrophages• Filters blood as much as lymph nodes do

Defense Against Infection

• Pathogen: disease-causing agent• virus, bacteria, fungus

Nonspecific (innate responses)• Inflammation= swelling, heat, pain, redness and pus• Fever= makes body inhospitable to pathogens• Phagocytosis= digests foreign material• Chemical barriers= body fluid, stomach acid, (low pH)• mechanical barriers= skin, mucus membranes, hair,

sweat• Species resistance= organism can’t survive in human

body• Natural killer cells= cells that secrete cytolytic (“cell

cutting”) substances that cut through cell membranes

Specific Immune Responses • Specialized cells recognize foreign invaders• Respond more slowly than non-specific responses• Antigens= proteins, sugars or lipids on a cell’s

surface recognize foreign invaders

Lymphocytes

• T cells: require antigen-presenting cells to be activated• Enter tissues and Kill foreign invaders• Have a memory once exposed to a pathogen

Lymphocytes

• B-cells: activated by specific antigens or T-cells• Have a memory once exposed to a pathogen• Never enters tissues• Produce antibodies

Antibodies

• Immunoglobins: present in plasma, interstitial fluid, breast milk, tears, bile, stomach acid, nasal mucus, urine• Act on allergens, bacteria, viruses, fungus and toxins

• Reaction to antigens: • Tries to contain the pathogen or toxin to the area it

is in• direct attack, stimulate inflammation, or activate

cells to act

Allergic Reactions

• Allergic reactions: an immune response to a non-harmful substance• can damage tissues

• Allergens: antigens that cause allergic reactions

Allergic Reactions

• Immediate-reaction allergies: within minutes of contact with allergen• Activates B-cells• Release histamines and prostaglandins that:• Causes blood vessel dilation• Swelling• Increased mucus production• Contraction of bronchial muscles

Transport/Tissue Rejection

• Transplant/Tissue Rejection: donor part is recognized as an invader and the body reject it• Immunosuppressive drugs: used to reduce the

chance of tissue rejection• Interfere with immune response by suppressing T-cells

and antibody formation

Auto Immunity

• Auto immunity: immune system turning against itself• Autoantibodies: attack tissues and organs• Examples: type 1 diabetes, mellitus, rheumatoid

arthritis, lupus• Caused by:

• Viruses• T-cells not “learning” to recognize other threats• Genetics

Active Immunity

• Naturally Acquired: exposure to pathogens stimulates immune response• ex: chicken pox

• Artificially Acquired: a vaccination containing weak or dead pathogens is given to stimulate an immune response• ex: polio vaccination

Passive Immunity

• Naturally Acquired: antibodies passed from mother to fetus through umbilical cord or breast milk• Artificially Acquired: antibodies injected into the

blood stream