Lymphatic System and Immunity The super cool ways your body keeps you healthy

What is it? It is a network of vessels that assist in circulating body fluids It is made up of different types of cells and proteins that all have a different job

What does it do? Transports excess fluid away from interstitial spaces Transports fluid to the bloodstream Transports digested fats to the bloodstream Defends the body against foreign invaders

What is its pathway? Begins as lymphatic capillaries Capillaries merge to form lymphatic vessels Lymph is passed through the lymph nodes while in the lymphatic vessels Vessels merge to form lymphatic trunks Lymphatic trunks join one of two collecting ducts Collecting ducts transport lymph into venous system through the subclavian veins Venous system carries it as plasma in blood’s return to the right atrium

What is LYMPH? Our blood capillaries tend to seep fluid into the surrounding tissues This fluid contains food that must be taken to the cells and waste that must be taken away from the cells Although this fluid is important, if it builds up, it causes edema The lymphatic system drains off this fluid so that there is no swelling! Once this fluid is in the lymphatic system, it is called lymph Lymph is composed of proteins, fats, foreign particles, gases, hormones, and other small molecules

Lymph Nodes Bean-shaped masses of lymphatic tissue located in groups along the lymphatic vessels Filter lymph by getting rid of any potentially harmful material Contain many lymphocytes and macrophages which attack the harmful particles Afferent vessels bring lymph into the node; efferent vessels carry lymph away from the node Several major regions of clusters, including the cervical region and the axillary region

Lymphatic System Organs Thymus (thymus gland): Located between lungs, above heart, behind sternum Provides place where some inactivated lymphocytes called thymocytes can mature into T-lymphocytes Spleen: Located under the left side of diaphragm Contains two types of tissues 1. red pulp: contains red blood cells; filters blood of any unwanted particles 2. white pulp: contains lymphocytes; helps fight infections

Lymphatic System Organs Lymph Vessels Located parallel to veins, branch throughout body Provides unidirectional transport from tissues to the heart Tonsils Are masses of lymphatic tissues, produce lymphocytes and filter bacteria

Innate (nonspecific) defenses Species Resistance: diseases are unique to a certain species; another species cannot get that disease Mechanical Barriers: prevent entrance of infectious agents; skin first line of defense

Innate (nonspecific) defenses continued Chemical Barriers: enzymes, low pH, excess salt can destroy bacteria Interferons: proteins that tell other cells to block viral replication Defensins: proteins that destroy bacterial cells by making holes in the cell walls Collectins: proteins that detect and bind to sugar molecules on pathogens, making the pathogens more easily phagocytized

Innate (nonspecific) defenses continued Fever: lymphocytes send signal to hypothalamus to maintain a higher body temperature Higher temp makes liver and spleen retain their iron, which the viral and bacterial cells can’t survive without Natural Killer (NK) Cells: secrete perforins which cause cell walls of viral and cancer cells to disintegrate

Innate (nonspecific) defenses continued Inflammation: Tissue response of localized redness, swelling, heat, and pain that kills pathogens in the area, prevents spread of pathogens, and promotes healing Phagocytosis: Removes foreign particles from lymph, blood vessels, and tissues by engulfing and digesting foreign particles and cells

Naturally Acquired Immunity Naturally acquired passive immunity is immunity you get from your mother while still in the womb Some of the antibodies your mother has acquired over her lifetime gets passed through the placenta to the fetus The other type of naturally acquired immunity is your body’s response to the antigen (discussed later)

Artificially Acquired Immunity Artificially acquired immunity is the immunity we get from vaccinations Vaccinations can be the transfer of antibodies, or they can be injection of a non-active form of a virus Transfer of antibodies can be used for things like snake bites, as a treatment Vaccinations are used prophylactically in hopes of preventing you from getting something

Vaccinations

Vaccinations 1st vaccination: small pox “vacca” = cow Started in India or China before 200 BC! “vacca” = cow First vaccine was against small pox and was taken from a cow virus called cowpox

What Are Vaccinations? Vaccinations are usually either inactivated or weakened forms of a virus Your body produces antibodies in response to these inactivated or weakened viruses Some of these antibodies are the Memory T and B cells, which stay with you for a very long time

Vaccination Schedule In the US, we have a vaccination schedule for infants and minors Vaccination schedule is from the American Academy of Pediatrics Everyone is required to follow this, except for religious reasons Most vaccinations are required in the first year of life The rest are required by the age of 5-6 Most vaccinations have to given again in adolescence, before the age of 18 Some also depend on the state you live in

Vaccination Debate Some people believe that early childhood vaccinations cause autism Some of these people are trying to refuse to give their children vaccinations The problem with this is that if we have too many unvaccinated children, the diseases that we have essentially eradicated may come back