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Lymphatic system
Lymphatic System
• Consists of organs, ducts, and nodes. It transports a
watery clear fluid called lymph. This fluid distributes
immune cells and other factors throughout the body. It
also interacts with the circulatory system to drain fluid
from cells and tissues. The lymphatic system contains
immune cells, which defend against infection and protect
the body
Main functions of lymphatic system:
• to collect and return interstitial fluid, including plasma
protein to the blood, and thus help maintain fluid
balance,
• to defend the body against disease by producing
lymphocytes,
• to absorb lipids from the intestine and transport them to
the blood.
Lymphatic System and Immunity
• Network of vessels that assist circulating body
fluids
• Aids in maintaining blood volume, returns fluid to
the blood
• Closely associated with the circulatory system
• Organs of lymphatic system defend against
infection
• Removes antigens from body
• Exposes antigens to immune system
Pathways
• 1. Lymphatic capillaries -microscopic, closedended tubes
• Extend into interstitial spaces and form
complex networks that parallel blood
capillary networks
• Consist of a single layer of endothelium
designed to allow tissue fluid from interstitial
spaces to enter
• Lymph capillaries located in the small
intestine is known as lacteals
• Fluid inside the capillary is called lymph
Pathways continued
• 2. Lymphatic vessels-similar to vein walls but
thinner
• Consist of an endothelial lining, a middle
layer of smooth muscle and elastic fibers, and
an outer layer of connective tissue
• Also have semilunar valves that prevent
backup of fluids (just like veins)
• Larger lymphatic vessels lead to lymph nodes
Pathways continued
• 3. Lymphatic trunks and collecting ducts
• Trunks drain lymph from lymphatic vessels
and are named for the area they serve
• Lumbar trunk drains the lymph from lower
limbs, lower abdominal wall, and pelvic
organs
• Subclavian trunk drains the upper limbs
• Lymphatic trunks joint one of two collecting
ducts
4. Collecting ducts
• Thoracic duct is larger and longer
• Begins at abdomen and passes through diaphragm
• It empties into the left subclavian vein and drains
lymph from intestinal, lumbar, and intercostal
trunks, left subclavian trunk, left jugular trunk,
and left bronchomediastinal trunks
• Right lymphatic duct is smaller and originates
in right thorax at union of right jugular, right
subclavian and right bronchomediastinal
trunks
• It empties into the right subclavian vein
• Cisterna Chyli – receives lymph from digestive
organs
What’s next?
• After leaving the two collecting ducts, lymph
enters blood stream and becomes part of the
plasma
• Lymph from lower body regions, left upper
limb, and left side of head and neck enters
thoracic duct
• Lymph from right side of head and neck, right
upper limb, and right thorax enters right
lymphatic duct.
• p. 354, Figure 12.2
Lymph is returned to venous
system through:
• Right Lymphatic duct – drains
lymph from right arm and right
side of head and thorax
• Thoracic duct – receives
lymph from rest of body
• Both ducts empty into the
subclavian vein on their side
of the body
Tissue fluid formation
• Lymph has the same composition as plasma
except it doesn’t have plasma proteins
• Filtration from plasma exceeds reabsorption
leading to net formation of tissue fluid
• This increases hydrostatic pressure of tissue
fluid, and favors the movement of this fluid into
the lymphatic capillaries, forming lymph.
Lymph function
• Lymphatic vessels in small intestine play a major
role in absorption of dietary fats
• Lymph returns to the blood stream most of the
small proteins that the blood capillaries filtered
• Lymphatic capillaries are specially designed to
receive proteins and foreign particles
Lymph movement
• Movement of lymph throughout the body assisted
by:
• “Skeletal muscle pump” – contraction of skeletal
muscles against the lymphatic vessels
• Smooth muscle contraction
• Valves in lymphatic vessels
• “Respiratory pump” – pressure changes when
breathing
• Obstruction of system leads to edema (abnormal
accumulation of fluid in body tissues/parts)
Lymph nodes
• Contain large numbers of macrophages and
lymphocytes that fight invading pathogens
• Nodes are surrounded by a capsule, which
extends inside and partially subdivides the node
into nodules which are the structural units of the
node
• Function of nodes is to filter potentially harmful
particles from lymph and to monitor body fluids,
“immune surveillance”
• Nodes and red bone marrow are the centers for
lymphocytes production
central area
-divide nodes into
compartments
Cortex – outer
region of node,
contains the
germinal cells
• Various shapes and sizes, often kidney
shaped
• Lymph passes through several nodes in
filtering process
“in transit” – circulate
continuously
-indented region
-fewer efferent vessel than
afferent vessel which slows
lymph flow allowing more
time to filter
Locations of lymph nodes
• Cervical region
• Axillary region
• Supratrochlear region-medial side of the
elbow
• Inguinal region
• Pelvic cavity
• Abdominal cavity
• Thoracic cavity
Lymphatic tissue
• Clusters of lymphocytes in the connective tissue
of mucous membranes and various organs
• Diffuse lymphatic tissue is scattered in body
passages that open to the exterior and is called
mucosa-associated lymphatic tissue or MALT
• In respiratory it may be called BALT (brochus
associated)
• In digestive it may be called GALT (gut
associated)
Lymphatic tissue
• In some places lymphocytes and macrophages
congregate into masses called lymphatic nodules
(come and go as you get infections.)
• In distal portion of small intestine they form
clusters called Peyer’s patches.
• In some places these nodules are always
present (tonsils, lymph nodes, appendix)
• Tonsils – three pairs of enlarged lymph nodes in the
pharynx
• Pharyngeal tonsils (adenoids) – back of the sinuses
• Palatine tonsils – in palate that separates the nasal
and oral cavities
• Lingual tonsils – base of tongue
Lymphatic tissue
• Appendix - function appears to expose white blood
cells to a variety of antigens, or foreign substances,
present in the gastrointestinal tract, helps to
suppress potentially destructive antibody responses
while promoting local immunity.
http://www.scientificamerican.com/article.cfm?id=what-is-the-function-of-t
Lymph organs
• Thymus gland-located above the heart in the
mediastinum and produces T lymphocytes
• Thymus is largest in childhood and shrinks with
age
• Spleen is the largest lymphatic organ and filters
blood to protect against infections
• White pulp in spleen contains many lymphocytes
• Red pulp in spleen contains red blood cells and
lymphocytes and macrophages
Body Defenses
• 1st Line of Defense – Non-Specific Barriers
• Prevention of pathogens entering the body
• Skin and mucus membranes (includes skin, tears, saliva, gastric
juices and mucus membranes)
• 2nd Line of Defense - Non-Specific -Leukocytes
• Killing the pathogen that enters body by phagocytic action
• Inflammatory response – phagocytes move to infected area, due
to stimulation by chemicals released by damage cells.
Phagocytes engulf pathogen and digest it
• P. 359 text
• 3rd Line of Defense – Specific Immune Response
• Killing the pathogen by antibody action
• Immune response system – lymphocytes release antibody in
response to presence of antigen
Nonspecific Immune Responses
• 1 - Inflammation - response to tissue injury
serving to defend against foreign invader;
redness, heat, swelling, pain
• 2 - Interferon - group of proteins that defend
against viral infection; prevents replication of
virus in other host cells
• 3 - Natural killer cells - lymphocyte-like cells that
rather nonspecifically lyse & destroy virusinfected cells & cancer cells
• 4 - The complement system - inactive plasma
proteins that, when activated, destroy foreign
cells; “complement” the work of antibodies
Nonspecific Immune Responses:
Inflammatory Response
Specific Immune Responses
• Often more effective than nonspecific response
• Specific response begins due to presence of an
antigen
• Selective attack aimed at "target" following prior
exposure
• Two classes of responses:
• Cell-mediated immunity - activated T
lymphocytes
• Humoral immunity - antibodies produced by B
lymphocytes
Cell Mediated vs. Humoral Immunity
Two separate but overlapping arms of immunity
Cell Mediated
Humoral
(antibody-mediated system)
• The lymphocytes –
Cytotoxic T-Cells (killer T- • Protection provided by antibodies
cells) themselves defend
present in “humors” – fluids
the body by injecting or • binding activates lymphocytes to
destroying infected cell
undergo clonal selection to produce
• Killer T-cells also produce
plasma cells or memory cell
T memory cells which
• plasma cells manufacture quantities of
"remember" a specific
antibodies (Immunoglobulins - Ig) that
bind to the foreign invader (the antigen)
protein or antigen.
A response to an agent against
which the body has already
formed memory cells is called a
secondary response. All other
responses are primary responses.
and prime it for destruction.
• B memory cells retain a "memory" of the
specific antigen that can be used to
mobilize the immune system faster if the
body encounters the antigen later in life.
These cells generally persist for years.
Antibodies/Immunoglobulins
• Antibodies/Immunoglobulins are proteins that bind to
specific antigens. B cells, located in lymphoid tissue,
release the antibodies, which then circulate in the blood
plasma, lymph, or extracellular fluids.
• Some antibodies migrate to other areas of the body, such
as the respiratory tract or the placenta, or enter various
body secretions, such as saliva, sweat, and milk
• There are five classes of antibodies (or
immunoglobulins): IgA, IgD, IgE, IgG, and IgM.
• Antibodies bind to antigens, thus forming an antigenantibody complex. This complex attracts macrophages,
which will phagocytize any foreign substance that has
that specific antigen-antibody complex.
Immunoglobulins (Ig) (MADGE)
• IgG-80% of antibody, activates complement,
crosses placenta to protect fetus, active against
bacteria and viruses
• IgA-13%, found in breast milk, tears, and other
fluids, most common in mucosa
• IgM-6 %, develops in plasma (anti-A and anti-B
antibodies), also activates complement, reacts
usually on first exposures
• IgD, found on most B cells, important in
activating B cells
• IgE, associated with allergic reactions (hay fever,
asthma, hives)
Lymphocytes
Types of Immunity
• Natural Acquired Immunity
• Active – immunity acquired by exposure to disease
(antibodies) , last for years and sometimes for life
• Passive – acquired naturally by fetus through
passage of antibodies form mother through
placenta or breast milk, temporary
• Artificial Acquired Immunity
• Active - vaccines, immunizations, dead or weaken
pathogen injected into body to produce antibodies
• Passive– injection of antibodies from another
person or animal, short term
Self vs. Nonself cells
• Key to a healthy immune system is its ability to
distinguish between the body’s own cells,
recognized as “self,” and foreign cells, or “nonself.”
• Body’s immune defenses normally coexist
peacefully with cells that carry distinctive “self”
marker molecules.
• When immune defenders encounter foreign
cells or organisms carrying markers that say
“nonself,” they quickly launch an attack.
Self vs. Nonself cells
• Major Histocompatibility Complex (MHC) (also
called human leukocyte antigens, HLAs) is the
mechanism by which the immune system is able
to differentiate between self and nonself cells.
MCH generates markers on the plasma
membrane.
• MHC is a collection of glycoproteins (proteins with a
carbohydrate) that exist on the plasma membranes
of nearly all body cells
• proteins of a single individual are unique, its
extremely unlikely two people will possess cells
with the same set of MHC molecules (except for
identical twins)
Self vs. Nonself cells
• Immunocompetence – the ability of body’s
immune cells to recognize (by binding) specific
antigens
• Lymphocytes develop tolerance for self-antigens
• Lymphocytes once immunocompetent only react to
one distinct antigen
• Lymphocytes become immunocompetent before
meeting antigens they may later attack
• It is our genes that determine what specific foreign
substance our immune system will be able to
recognize and resist
• P. 363-364 text
Self vs. Nonself cells
• In abnormal situations, the immune system can
mistake self for nonself and launch an attack
against the body’s own cells or tissues. The result
is called an autoimmune disease (MS,
Rheumatoid arthritis, Type I Diabetes,
Autoimmune thyroid disorders, Crohn’s, Lupus)
Immune System Protection
• Immune system protects against infection,
but also against other antigens
• Blood group antigens
• Tissue antigens (i.e., graft rejection)
• For successful organ graft, immune system
must be suppressed
• Transplanted tissue must be cleared of
immune cells, too
• Treatment usually requires some form of
immunosuppression therapy.
Four major types of grafts
• Autograft – tissue grafts transplanted from one site
to another in the same person
• Isograft – tissue grafts donated be a genetically
identical person, twin
• Allograft – tissue grafts are taken from an in related
person
• Xenograft – tissue grafts harvested from a different
animal species, such as transplanting a baboon heart
into a human heart.
Summary
• The lymphatic system helps maintain homeostasis of
fluids, and also helps remove antigens from the body
• The immune system consists of barriers (physical
and chemical) and specific and nonspecific
mechanisms to eliminate antigens
• “Immune cells” are blood cells. Some circulate in the
blood and can then migrate into tissues at site of
injury. These include neutrophils and macrophages.
Summary
• All blood cells arise in the bone marrow. B
lymphocytes initially develop in the bone marrow
and then migrate to lymphoid tissues (esp. lymph
nodes and spleen) T lymphocytes develop in the
thymus
• B cells produce antibodies, which interact with
antigen to help eliminate it.
• Helper T cells regulate the immune response;
cytotoxic T cells kill virus-infected cells and probably
tumor cells. (They also are responsible for transplant
rejection.)
Summary
• B and T cell response is antigen-specific and has
“memory” (second response is faster and stronger
than the first)
• Immune system can be overly responsive to antigens
(hypersensitivity/allergy) or can mistakenly be
directed against self antigen (autoimmunity)
• Immune deficiencies leave people vulnerable to
infection
Review Questions:
• 1. All of the following belong to the lymphatic system EXCEPT
A. lymph.
B. lymphatic vessels.
C. red bone marrow.
D. yellow bone marrow.
• 2. Which of the following cells produce antibodies?
A. T-lymphocytes
B. B-lymphocytes
C. monocytes
D. Phagocytes
• 3. Lymph nodes
A. are bean-shaped organs.
B. are located along lymphatic vessels.
C. are scattered throughout the body.
D. All of the above.
Review Questions:
• 4. Worn-out and damaged red blood cells are destroyed in the
A. thymus gland.
B. tonsils.
C. spleen.
D. lymph nodes
• 5. The first line of defense against disease-causing organisms is
A. cell-based immunity.
B. production of antibodies.
C. inflammation.
D. the intact skin.
• 6. Complement proteins
A. are found in blood plasma.
B. are present in infected cells.
C. are produced by T-cells.
D. are produced by B-cells
Review Questions:
• 7. All of the following are symptoms of inflammation EXCEPT
A. pain
B. redness
C. fever
D. Swelling
• 8. Which of the following can act as an antigen?
A. bacteria
B. viruses
C. food
D. All of the above.
• 9. Vaccination is an example of
A. naturally acquired active immunity.
B. naturally acquired passive immunity.
C. artificially acquired active immunity.
D. artificially acquired passive immunity
Review Questions:
• 10. Cell-mediated immunity is provided by
A. macrophages.
B. basophils.
C. T-cells.
D. B-cells.
• 11. One of the functions that the lymphatic system performs is
to return excess __________fluid to the blood.
A. Clear
B. Interstitial
C. Red-colored
D. thoracic
Review Questions:
• 12. Lymph nodes are widely distributed throughout the body
along the lymphatic pathways where they filter
_______before it is returned to the ________.
A. lymph, blood
B. lymph, heart
C. blood, heart
D. blood, lymph
• 13. Lymph enters a lymph node through __________, filters
through ________, and leaves through ________.
A. efferent vessels, afferent vessels, sinuses
B. sinuses, afferent vessels, efferent vessels
C. afferent vessels, sinuses, efferent vessels
D. afferent vessels, efferent vessels, sinuses
Review Questions:
• 14. The tonsils that are located near the opening of the oral
cavity that separates the nasal and oral cavities
•
A. lingual
B. pharyngeal
C. palatine
D. Oral
• 15. The thymus also produces a hormone,___________ , that
stimulates the maturation of lymphocytes in other lymphatic
organs.
A. oxytocin
B. thymosin
C. calcitonin
D. estrogen
Review Questions:
• 16. The lymphatic system absorbs __________ from the
digestive system.
A. lipids
B. lymph
C. nutrients
D. Proteins
• 16 A. What is the name of the specialize lymph capillaries in
the digestive system?
• 17. All the lymph that is collected returns to venous circulation
by entering into the __________.
A. Capilliaries
B. lacteals
C. right and left subclavian veins
d. lymphatic ducts
Review Questions:
• 18. Which is the only cell that does not mature in the bone
marrow?
A. T cells
B. B cells
C. macrophages
D. neutrophils
• 19. Fluid that passes through the lymphatic vessels?
A. Flows toward the lungs
B. Passes from the lymphatic vessels into the arteries
C. Enters the left ventricle of the heart through the right
thoracic duct
D. Moves in a single direction toward the heart
Review Questions:
• 20. Peyer's patches are aggregates (collections) of lymphatic
nodules found in the area of the __________.
A. tonsils
B. appendix
C. ileum of the small intestine
D. thymus gland
• 20A. Peyer’s patch is an example of what type of tissue and
where is another location it can be found?
• 21. Which of the following would be considered a nonspecific
barrier?
A. skin
B. fever
C. NK cells
D. T cells
Review Questions:
• 22. Vasodilatation is part of the second line of defense
because it results in greater flow of WBCs to the infected site.
What chemical causes the vessels to dilate?
A. histamine
B. postaglandin
C. complement proteins
D. interferons
• 23. A fever is considered to be a __________ defense.
A. specific
B. nonspecific
C. nonspecific barrier
Review Questions:
• 24. Where are the major histocompatibility complex
molecules located?
A. in the plasma of blood
B. on the cell membrane
C. in the interstitial fluid
D. in the cell nucleolus
• 25. Which of the following types of immune responses
involves antigens binding directly to the B cells causing the
production of antibodies?
A. APC immunity
B. humoral immunity
C. cell-mediated immunity
D. Nonspecific immunity
Review Questions:
• 26. Which of the following antibodies are involved in causing
basophils to release histamine ( as in the case of an allergic
reation)?
A. IgA
B. IgG
C. IgE
D. IgM
• 27. The process of transferring antibodies from mom to baby
is known as __________ immunity.
A. active
B. passive
C. antibiotic
D. immunizations
Review Questions:
• 28. Vaccines work to prevent a person from getting a specific
virus during the flu season because the vaccine stimulates the
__________.
A. first line of the body’s defenses
B. activity of T cells
C. production of memory B cells
D. Production of NK cells
• 29. The immune system’s loss of its ability to distinguish “self”
from “nonself” results in :
A. Autoimmune diseases
B. Immune response diseases
C. Immunodeficiency diseases
D. Cell-mediated immune deficiency diseases
Review Questions:
• 30. All the following are important functions of the lymph
nodes except:
A. They serve as sites for production of antibodies
B. They remove foreign material phagocytized by macrophages
C. They are the sites where antigens stimulate the immune
system
D. They function in the production of neutophils, eosinophils
and basophils
• 31. Lymphocytes that develop immunocompetence in the
thymus are:
A. B lymphocytes
B. T lymphocytes
C. Macrophages
D. Plasma cells
Review Questions:
32. The movement of fluid through the lymphatic vessels is
assisted by:
A. Pressure from the right ventricle
B. Pressure of contracting skeletal muscles
C. Movement of phagocytes such as macrophages
D. Movement of red blood cells