Download Ms. S Lymphatic Notes File

Lymphatic System
Chapter 14
• -Part of the circulatory system
• -2 major roles
• 1) carries fluid from the extracellular environment into the
bloodstream which helps with fluid balance
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2) immunity – defends the body against disease
• -Parts included: lymphatic network (vessels, capillaries),
lymph nodes, spleen, thymus, tonsils, Peyer’s patches
Lymph network
• -Interstitial fluid is plasma that is pushed through the
walls of capillaries. It serves as a transport medium for
gases, nutrients, and other molecules that travel between
cells and blood
• -90% of all interstitial fluid is returned to the blood stream;
the rest slowly returns to the heart by way of the
lymphatic vessels
• -network includes lymphatic capillaries, vessels, trunks,
and collecting ducts
•  Lymphatic capillaries
• -found between cells and among capillary beds of nearly
all tissues and organs
• -not found in the brain, spinal cord, bone tissue, and
epidermis
• -made of a single layer of endothelium that overlaps at
times; when pressure is greater in the capillaries, this
overlap does not allow the lymph to leak back into the
extracellular space
•  Lymphatic vessels
• -formed when the capillaries merge w/ one another and
are located closer to the heart
• -thicker walls than the capillaries
• -have valves to prevent the backflow of lymph (keep
lymph traveling toward the heart)
• -as the vessels extend toward the heart, they increase in
size and form larger lymphatic trunks and collecting
ducts; they lead to small oval organs called lymph nodes
• -the lymph will pass through nodes and continue on its
way
Lymphatic Trunks and Collecting Ducts
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-formed from the merging of numerous lymphatic vessels
- they drain lymph from a large part of the body
(ex: right upper limb, pelvic region)
-they merge and form one of the two collecting ducts:
1) thoracic duct
2) right lymphatic duct
•  Thoracic duct – main collecting vessel; drains the left
side of the head, neck, and thorax, the left upper limb, the
entire body below the diaphragm
• It starts in the lower abdomen and travels up the back
wall of the upper chest; unites with the left subclavian
vein
• Right lymphatic duct – drains lymph from the right side of
the head, neck, and thorax, the right upper limb; empties
into the right subclavian vein
Movement of Lymph
• lymph is moved by pressure gradients caused by
accumulation of protein, skeletal muscle contraction and
breathing movements
Lymphatic Organs
• Any structure that contains lymphoid tissue (connective
tissue) is a lymphatic organ
Lymph nodes
• small oval masses of lymphoid tissue that lymph passes
through on the way to the heart
• clusters found in neck, armpit, groin, deep w/in abdominal
cavity
• vary in shape and size; frequently shaped like a kidney
bean and 1 inch long
Lymph Nodes
• fibrous capsule – shell of
connective tissue
• lymph nodules – compact
clusters of lymphocytes in
the lymph node
• cortex – outer area where
lymphocytes mature
• medulla – inner area where
lymphocytes are arranged in
strands called medullary
cords
• as lymph passes through
nodes, it is filtered by
WBC’s (lymphocytes +
macrophages) to trap
bacteria, viruses, and toxins
Spleen
• largest lymphatic organ located on the left side of the
body under the diaphragm
• contains both red pulp area (contains RBC’s) and white
pulp area (contains WBC’s)
• functions as a large filter; rids the blood of foreign
particles, old/defective RBC’s + platelets
• stores blood that is used in case of emergency (ex:
trauma w/ major blood loss)
Thymus gland
• also functions in endocrine system
• most active during ages 6 months to 5 years in immune
response
• by adulthood, it is replaced with fatty tissue and no longer
active
Tonsils
• -3 kinds (palatine,
pharyngeal, lingual)
• -lymphatic tissue gathers
and engulfs diseasecausing microorganisms
in the mouth and throat
regions
• -removed if there are
chronic infections
Peyer’s patches
• located in the walls of the distal end of the small intestine
• believed to be a protective barrier between the walls of
the intestine and abdominal cavity
Defense Mechanisms of the Body
• pathogen – disease-causing agents that include living
bacteria, fungi, and protozoans
• pathogens cause harm by destroying cells or releasing
toxins (poisonus substances) that interfere w/ cell
functioning
• self-cells – cells that belong to the body
• nonself cells – cells that do not belong to the body
• WBC’s can tell the difference between the 2 b/c all self
cells have specific marker proteins (MHC proteins) on the
surface identifying them
• MHC (majorhistocompatibility) complex – group of genes
coding for marker proteins
Nonspecific (Innate) Defense Mechanisms
• -not selective
• -defend against all foreign invaders
• Physical/Mechanical Barriers – prevent substances from
entering body
– skin – 1st line of defense
• mucous membranes line all body cavities (produce
chemicals that can trap invaders)
• infection – invasion by a pathogen that penetrates the
body’s physical barriers
• Chemical Barriers – fluid that contains a substance that
destroys pathogens
• gastric juice in stomach has low pH (HCl) and pepsin
enzyme
• tears contain lysozyme enzyme – destroys bacteria in
eyes
• sweat – kills some bacteria on skin
• Phagocytosis – ingestion and destruction of particles by
specialized cells called phagocytes
– 1) extend pseudopod (cytoplasmic “foot”) to reach invader
– 2) trap invader
– 3) enzymes destroy invader
• performed by most WBC’s
• monocytes and neutrophils are most active b/c they can
squeeze through blood vessels (diapedesis) and travel to
sites of infection
• monocytes become macrophages which attach to
lymphatic vessels and organs
• Natural Killer Cells
• WBC’s that kill cancer cells and virus-infected cells by
puncturing their membranes (lysis)
• Proteins
• 1) complement – a group of 20 types of plasma proteins
– only active during infection
– label invaders as unwanted so phagocytes can destroy them
– help move phagocytes to area of infection
• 2) interferons – proteins released by virus-infected cells
– travel to surrounding cells and prevent virus from invading
• Inflammation – response to body stress following an
infection or physical injury
• damaged cells release substances (histamine +
serotonin) into bloodstream which causes 2 responses:
• 1) Vasodilation – blood vessels widen
– allows more blood flow to the site bringing clotting proteins,
antibodies, and WBC’s (accumulates causing pus to form);
results in redness and heat
• 2) Increased permeability of blood vessels – pores in
capillary walls widen which cause fluids to leak across
capillary walls into extracellular space (edema); results in
swelling and pain
• Fever
• increased temperature makes body inhospitable to
pathogens
• liver/spleen hold iron, making less iron in bloodstream;
Iron is needed by bacteria and fungi to reproduce
• phagocytic white blood cells are more active at higher
temps.
Specific Responses: The Immune Response
• directed at a particular pathogen or toxin
• immune response (immunity): state of resistance to
infection
• 2 types of immune response
– Cell-mediated immunity (T-cells)
– Humoral Immunity (antibodies and B-Cells)
Components of Immunity
• Antigens – substances that provoke an immune response when they enter the
body
– recognized as foreign by WBC’s
• autoimmune response – immune failure when the immune system recognizes a
person’s own cells as being foreign
• Antibodies – a protein molecule produced in response to an antigen
• antigen-antibody complex – when antigen binds to antibody and inactivates the
toxic effects of the antigen
• immunoglobulins (Ig) – family of proteins that antibodies belong to
– 5 classes (IgG, IgA, IgM, IgD, IgE) p. 391
• Lymphocytes – most important WBC form in red bone marrow
before birth: nonfunctional form
– T cell line  thymus gland (T-cells mature)
– B cell line  small intestine – spleen, stay in RBM
• Lymph nodes and other lymphoid tissue
• B and T cells are programmed to recognize self/non-self cells
= immunocompetent
• T cells
– are immunocompetent shortly before/after birth
– very active
– destroy non-self cells in a # of ways
– maintain the # of T cells by continuous mitosis
(immunocompetent)
– T cells become activated or sensitized (happens in lymphoid
tissue) and form types of T cells
Sensitization
• macrophage identifies, phagocytizes, and processes an
antigen
• processed antigen is expressed on macrophage plasma
membrane
• macrophage presents processed antigen to a T cell,
which enlarges and divides
• 1) Killer (cytolytic) T-cells – destroy virus-infected cells, cancer cells, and foreign
cells from transplants
– binds to cells and releases lymphotoxins (toxic chemicals), causing cells to rupture
• 2) Helper T-cells – stimulate/control defensive activities of other cells
– release lymphokines (proteins) into bloodstream when they identify an antigen
• 3) Suppressor T-cells – slow down and stop defense mechanisms controlled by
helper T-cells
– prevents unnecessary activity that can destroy healthy self cells
• 4) Memory T-cells – remember antigens; T cells respond very fast when you are
exposed to an antigen for a 2nd time
• B cells
– sensitization of B cells is same as for T cells
– 1) Plasma cells – rest after they are formed and then produce
antibodies (2000/second)
– 2) Memory B cells – found in bone marrow, lymph nodes, and spleen
– remember antigens so antibodies can be produced faster if exposed
to antigen again (occurs w/in hours)
– immunization – the ability of the immune response to activate itself
quickly when exposed to a 2nd invasion
The Allergic Response
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type of humoral response involving the release of antibodies by plasma cells
allergic – intolerance to a certain antigen coming in contact with skin
allergen – antigens that cause an allergic response
an allergic individual secretes different antibodies (IgE) than nonallergic
individuals (IgG or IgM)
• IgE antibodies circulate in blood and eventually come in contact w/ a mast cell 
found throughout body, mainly in skin and mucous membranes; store chemicals
that cause inflammation
• when IgE binds to mast cells, chemicals are released and mucous membranes
increate the rate of mucous production
• Acquired Immunity - person’s ability to mount a defensive immune
response b/c of previous contact w/ an antigen
• Naturally Acquired Active Immunity – develops from exposure to
pathogens or toxins during the course of daily living
– symptoms of disease are expressed during 1st exposure
• Naturally Acquired Passive Immunity – the transfer of antibodies from a
person w/ immunity
• during pregnancy, antibodies pass across the placenta to the fetus (last
few months)
– breast milk also passes antibodies to baby
• Artificially Acquired Active Immunity – deliberate, artificial
introduction of an antigen to stimulate the immune response
• vaccine – killed or weakened living pathogen, or inactivated
toxin
• vaccination – process of introducing a vaccine
• Artificially Acquired Passive Immunity – transferring human or
animal antibodies to an individual by injection
Homeostasis
• immunodeficiency – impairment of the body’s ability to defend
against pathogens and toxins due to damage or loss of WBC’s
• Acquired Immunodeficiency Syndrome (AIDS) – lethal disease that
acts by lowering a victim’s immunity, allowing a 2nd, unrelated
infection to produce fatal symptoms
• HIV (Human Immunodeficiency Virus) – virus that causes AIDS
• blood test measures HIV antibodies  produced by B cell
lymphocytes in response to HIV exposure
HIV: Mode of Infection
• typical virus structure = RNA or DNA surrounded by proteins
• HIV virus has an additional layer of lipids
• Virus infects cells:
– 1) Injects genetic information into host cell
– 2) Host cell follows genetic information of virus and assembles new
viruses
– 3) Viruses burst host cell and infect nearby cells
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Development of AIDS
helper T cells decline
HIV activation suppresses cell-mediated immunity
secondary diseases that commonly cause death:
pneumonia, Kaposi’s sarcoma, hepatitis B,
toxoplasmosis, HIV wasting syndrome, AIDS dementia
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Transmission and Prevention
transmitted by transfer of blood or reproductive fluids
outside the body, HIV is fragile
cannot exist in air (20% oxygen), 135° water for 10
minutes, 30% hydrogen peroxide, rubbing alcohol, bleach