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All about the lymphatic and immune systems
Lymphatic system
consists of the lymphatic vessels and lymphatic organs
Homeostasis Functions - Lymphatic system
lymphatic capillaries absorb excess interstitial fluid
lymphatic capillaries absorb fats from the digestive tract and transport them to the bloodstream
lymphoid organs help defend the body against disease
Lymphatic vessels
form a one-way system of vessels that move fluid from tissues to the cardiovascular system
Lymph
fluid inside lymphatic vessels
Interstitial fluid
the primary component of lymph
mostly water, but also contains solutes (nutrients, electrolytes, and oxygen) derived from blood plasma
Additionally, interstitial fluid contains cellular products (hormones, enzymes, and cellular waste)
Lymphatic organs
divided into primary and secondary lymphatic organs
Primary Lymphatic Organs
red bone marrow and the thymus
Secondary lymphatic organs
the lymph nodes and the spleen
Red bone marrow
produces all types of blood cells
children have red bone marrow in most bones
adults have red bone marrow in the sternum, vertebrae, ribs, pelvic girdle, humerus, femur
produces red blood cells and five types of white blood cells: neutrophils, eosinophils, basophils, lymphocytes, monocytes
Lymphocytes
divided into B cells and T cells
B cells (B lymphocytes)
mature in the bone marrow
any B cell that reacts to body cells is destroyed in the bone marrow and does not enter circulation to prevent autoimmune disorders
T cells (T lymphocytes)
mature in the thymus
Thymus
soft-bodied and bilobed organ located in the cavity between the trachea and the sternum which decreases in size as children grow into adulthood
Thymus functions
produce hormones (like thymosin - aids in the maturation of t lymphocytes)
maturation site of T lymphocytes: only ~5% of these cells ever leave the thymus
to leave the thymus, T cells have to demonstrate that they can attack a pathogen and that they will not attack body cells
without mature T cells, the body cannot adequately respond to specific infections
Spleen
filters blood
largest lymphatic organ, located in the upper left part of the abdominal cavity
within the spleen, macrophages engulf pathogens and debris
Lymph nodes
occur along lymphatic vessels
each of their multiple compartments are filled with lymph, and lymphocytes and macrophages (which attack pathogens and cancer cells)
Immunity
the capability of killing or removing foreign substances, pathogens, and cancer cells
innate (non-specific immunity)
adaptive immunity
Innate (non-specific) immunity
include physical and chemical barriers
serve as a first line of defense against infection by pathogens
Physical Barriers - innate immunity
skin: prevents the entry of microbes
mucous membranes: trap invading pathogens
Chemical Barriers - innate immunity
perspiration, saliva, and tears: contain lysozyme (antibacterial enzyme)
acidic pH: stomach and vagina
microbiome: beneficial bacteria in our systems
Inflammatory Response
second line of defense
employs neutrophils and macrophages to surround and kill invading pathogens
symptoms of IR: redness, heat, swelling, pain
excess fluid from leaky capillaries causes swelling (which presses on nerves) and pain
these summon white blood cells to the region
neutrophils are the first WBCs to arrive, and they phagocytize (eat) debris, dead cells, and bacteria
if neutrophils are overwhelmed, they released cytokines
monocytes are longer-lived cells that become macrophages
Histamine
a chemical mediator released by damaged tissue cells and mast cells which cause the capillaries to dilate and become more permeable
Cytokines
proteins that attract more WBCs, including monocytes
Macrophages
more powerful phagocytes than neutrophils
Complement system
composed by a number of blood plasma proteins that increased the immune response of one or more specific immune responses
Complement proteins can…
trigger mast cells to release histamine
attract phagocytes to a specific location
bind directly to bacteria can cause them to burst
Interferons
proteins produced by virus-infected cells that cause uninfected cells to prepare for viral infection by producing substance that interfere with viral replication
Antigen
a large protein structure that the immune system recognizes as a foreign body
Fragments that can be antigenic
bacteria, viruses, molds, parasitic worms
Adaptive defenses
primarily depend on B and T cells (B and T lymphocytes)
each lymphocyte has a single kind of receptor to combine with a specific antigen (like a lock and key)
Adaptive Immunity Pathways
cell-mediated immunity and antibody-mediated (humoral) immunity
Cell-mediated immunity
T-cells target and destroy any cells that present a specific antigen
helper t cells may come into contact with an antigen and release cytokines to call cytotoxic T cells to the area
cytotoxic t cells either phagocytize or trigger apoptosis in infected cells
Antibody-mediated (humoral) immunity
an antigen binds with a B cell’s receptor
the B cell then undergoes rapid clonal expansion, creating B memory cells, and plasma cells
the plasma cells created secrete antibodies for the original antigen
Antibody Structure
Y-shaped with two antigen binding sites
Antibody function
many antibodies will bind with the antigens, covering the offending molecule so that it can’t bind
antibodies then call for other white blood cells
Antibody classes
IgG, IgM, IgA, IgD, IgE
IgG
main antibody type in circulation
crosses the placenta from mother to fetus
binds to pathogens
activates compliments
enhances phagocytosis by WBCs
IgM
found in circulation
largest antibody
first antibody formed by newborns
first antibody formed in any new infection
activates compliment and clumps cells
IgA
main antibody in saliva and breast milk
prevents pathogens from attaching to epithelial cells in the digestive and respiratory tracts
IgD
antibody found on the surface of immature B cells
signifies readiness of B cells
IgE
antibody found as antigen receptors on mast cells
responsible for immediate allergic response and protection against certain parasitic worms
Cytotoxic T Cells
specialized T lymphocytes with storage vacuoles that contain perforins and storage vacuoles that contain granzymes
Granzymes
an enzyme that causes apoptosis
Helper T cells
specialized T lymphocytes that regulate immunity by secreting cytokines
B lymphocytes cannot be activated without T cell help
HIV (which causes AIDS) attacks T cells, which leaves patients vulnerable to opportunistic infections, which may eventually cause death
Memory T cells
remain within the body and can jump-start an immune response to an antigen previously present in the body
Active immunity
occurs when an individual produces antibodies against an antigen
develops naturally after a person is infected with a pathogen
can be artificially developed by exposure to the antigen
Passive immunity
occurs when an individual is given prepared antibodies via an injection
commonly achieved in infants from IgG antibodies that have crossed the placenta from their mother
Immunization
involves the use of vaccines to expose the immune system to the antigen
part of active immunity
Vaccine
substances that contain an antigen to which the immune system responds
AIDS
acquired immunodeficiency syndrome
inability of the acquired immune system to respond to opportunistic pathogens because of a low helper T cell count; caused by HIV
HIV
human immunodeficiency virus
virus that infects and destroys T helper cells and macrophages; causes AIDS if untreated
Opportunistic infection
an infection that can only occur because the patient’s immune system is compromised
Allergies
a hypersensitivity to a substance, like pollen, food, animal hair, or mold, that would ordinarily do no harm to the body
Allergen
an antigen that elicits an allergic response
Immediate allergic response
response within seconds to be exposed to an allergen
caused by IgE antibodies attached to receptors on mast cells and basophils
Anaphylactic shock
an immediate allergic response that occurs when an antigen enters the bloodstream
characterized by a life-threatening sudden drop in blood pressure due to the increased permeability of capillaries in the response to a flood of histamine
often treated with epinephrine
Delayed allergic response
immune response initiated by T cells at the site where an allergen contacts the body
used to test for tuberculosis (TB)
SCID
severe combined immunodeficiency disease
characterized by both the antibody and cell-mediated immune responses being either inadequate or lacking
has been successfully treated with bone marrow transplant and or gene therapy
Autoimmune Disease
occurs when cytotoxic T cells or antibodies attack the body’s own tissues
exact cause is unknown, but it appears to have both genetic and environmental components
women more likely to develop autoimmune disorders than men
Rheumatic fever
antibodies introduced into throat to fight the streptococcal infection also react with the heart muscle
causes an inflammatory response in the heart that damages the heart muscle and valves
Rheumatoid arthritis
causes chronically inflamed joints
antibodies, compliments, neutrophils, activated T cells, and macrophages all attack the cartilage of the joints
SLE
systemic lupus erythematosus
various symptoms including facial rash, fever, and joint pain
patients produce high levels of anti-DNA antibodies, which interferes with tissues throughout the body
damage to the central nervous system, heart, and kidneys can be fatal
Myasthenia gravis
antibodies attach to muscle cells
causes muscle weakness and eventual death from respiratory failure
