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The body’s defense against disease causing organisms, malfunctioning cells, and foreign particles
The dead, outer layer of skin, known as the epidermis, forms a shield against invaders and secretes chemicals that kill potential invaders You shed between 40-50 thousand skin cells every day!
As you breathe in, foreign particles and bacteria bump into mucus throughout your respiratory system and become stuck Hair-like structures called cilia sweep this mucus into the throat for coughing or swallowing
The First Line of Defense (Mucus and Cilia)
Immune system mistakenly recognizes harmless foreign particles as serious threats Launches immune response, which causes sneezing, runny nose, and watery eyes Anti-histamines block effect of histamines and bring relief to allergy sufferers
The First Line of Defense ~Saliva~
What’s the first thing you do when you cut your finger? Saliva contains many chemicals that break down bacteria Thousands of different types of bacteria can survive these chemicals, howeverSwallowed bacteria are broken down by incredibly strong acids in the stomach that break down your food The stomach must produce a coating of special mucus or this acid would eat through the stomach!
The First Line of Defense (Stomach Acid)
If invaders actually get within the body, then your white blood cells (WBCs) begin their attack.WBCs normally circulate throughout the blood, but will enter the body’s tissues if invaders are detected
These white blood cells are responsible for eating foreign particles by engulfing them Once engulfed, the phagocyte breaks the foreign particles apart in organelles called
White Blood Cells (Phagocytes)
Lysosomes
Where could invaders hide from phagocytes?
Viruses enter body cells, hijack their organelles, and turn the cell into a virus making-factory. The cell will eventually burst, releasing thousands of viruses to infect new cells.
Cell before infection… …and after.
Virus-infected body cells release interferon when an invasion occursInterferon – chemical that interferes with the ability to viruses to attack other body cells What happens to already infected cells?
T-Cells, often called “natural killer” cells, recognize infected human cells and cancer cellsT-cells will attack these infected cells, quickly kill them, and then continue to search for more cells to kill
Injured body cells release chemicals called histamines, which begin inflammatory response Capillaries dilate Pyrogens released, reach hypothalamus, and temperature rises Pain receptors activate WBCs flock to infected area like sharks to blood.
The efforts of the WBCs known as phagocytes and T-cells is called the cell-mediated immune system.Protective factor = living cellsPhagocytes – eat invadersT-cells – kill invaders
The other half of the immune system is called antibody-mediated immunity, meaning that is controlled by antibodies This represents the third line of defense in the immune system
Most infections never make it past the first and second levels of defense Those that do trigger the production and release of antibodies Proteins that latch onto, damage, clump, and slow foreign particles Each antibody binds only to one specific binding site, known as an antigen
WBCs gobble up invading particles and break them up They show the particle pieces to T-cells, who identify the pieces and find specific B-cells to help B-cells produce antibodies that are equipped to find that specific piece on a new particle and attach
New particles take longer to identify, and a person remains ill until a new antibody can be crafted Old particles are quickly recognized, and a person may never become ill from that invader again. This person is now immune.
Resistance to a disease causing organism or harmful substance Two types Active Immunity and Passive Immunit Passive Immunity
You produce the antibodiesYour body has been exposed to the antigen in the past either through:Exposure to the actual disease causing antigen – You fought it, you won, you remember itPlanned exposure to a form of the antigen that has been killed or weakened – You detected it, eliminated it, and remember it.
Antigens are deliberately introduced into the immune system to produce immunity Because the bacteria has been killed or weakened, minimal symptoms occur Have eradicated or severely limited several diseases from the face of the Earth, such as polio and smallpox
It depends on the antigenSome disease-causing bacteria multiply into new forms that our body doesn’t recognize, requiring annual vaccinations, like the flu shotBooster shot - reminds the immune system of the antigenOthers last for a lifetime, such as chicken pox
Think again…In 1918, a particularly deadly strain of flu, called the Spanish Influenza, spread across the globeIt infected 20% of the human population and killed 5%, which came out to be about 100 million people
You don’t produce the antibodiesA mother will pass immunities on to her baby during pregnancy - through what organ?These antibodies will protect the baby for a short period of time following birth while its immune system develops. What endocrine gland is responsible for this?Lasts until antibodies die? Why doesn’t the mother just pass on the WBCs that “remember” the antigens? Thymus
Caused by the Human Immunodeficiency Virus Discovered in 1983 Specifically targets and kills T-cells Because normal body cells are unaffected, immune response is not launched
The HIV virus doesn’t kill you – it cripples your immune systemWith your immune system shut down, common diseases that your immune system normally could defeat become life-threateningCan show no effects for several months all the way up to 10 years
Transmitted by sexual contact, blood transfusions contaminated needles As of 2007, it affects an estimated 33.2 million people
Primary lymphoid organs - Bone marrow - Thymus Secondary lymphoid organs - Lymph nodes- - Spleen
Microscopic structure - Less well defined than thymus - Role of stromal cells Function Hematopoiesis B cell maturation B cell selection Puts out mature, naive B-cells
Network of vessels Collects fluid from tissues Major cell is lymphocyte Unidirectional Often first place where antigens are detected
Function 1). Takes in immature T cells and puts out mature (immunocompetent) T cells 2). Increased diversity of T cells 3). T cell selection
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Gross Structure Bi-lobed Lies above heart Microscopic Capsular Lobules with outer cortex and inner medulla
Gross anatomy Structure Bean-shaped structures Drains major segments of lymphatic system
Microscopic Structure Major cell types Lymphocytes Macrophages Dendritic cells Cortex/paracortex/medulla Follicles Primary SecondaryFunction 1st line of response to antigens Secondary follicle (Germinal center) is site of B cell proliferation, mutation, differentiation Specificity is high >90% of B cells die through apoptosis After Ag stimualtion lymphocyte numbers up by 50X in efferent lymphatic vessel Lympadenopathy
Gross Structure Ovoid organ in upper left quadrant of abdomen Microscopic Compartmentalized Red pulp White pulp Periarticualr lymphoid sheath (PALS) Site of Ag presentation Major cell types Lymphocytes Macrophages Dendritic cells RBCs
Function - Filters out older RBCs - Responds to Ag in circulatory system - Produces activated B cells Splenectomy
Follicular structure Contains lymphocytes, macrophages, mast cells Germinal centers appear in response to Ag Protective role in URI (Upper respiratory infection. Infection of the air passages of the nose, the throat, and/or bronchial tubes.)
Associated with intestines Responds to Ag Role in GI immune response
Lymphoid tissues below epithelium Presence of B cells Ag presented through unique cell (M cell) Preferentially responds with IgA antibody