Transcript Lymphatic System - Downey Unified School District

Lymphatic System
Definition
● the system which
transports lymph,
which carries white
blood cells, toxins,
waste, and unwanted
material.
Lymphatic System Functions
● removes interstitial
fluid
● transports white
blood cells to and
from lymph nodes in
bone
● antigen presenting
cells are present
Lymphatic pathways
begin as lymphatic
capillaries that merge to
form larger lymphatic
vessels
Lymphatic Vessels
● carry lymph; formed by merging of lymphatic capillaries
● walls similar to veins, only thinner, and possess valves
prevent backflow of lymph
● larger lymphatic vessels lead to lymph nodes and then
merge into lymphatic trunks
*empty into the thoracic duct and the right lymphatic duct
Lymph
● colorless fluid containing white blood
cells
● 90% water and 10% solutes
(proteins, cellular waste products,
dissolved gases, and hormones)
● bathes the tissues and drains
through the lymphatic system into
the bloodstream
Lymph Continued...
● similar to plasma; has lower
concentration of proteins
F(x):
1. returns smaller protein
molecules and fluid to blood
2. transports foreign particles
to lymph nodes
Lymphatic Capillaries
● Characteristics: microscopic
closed-ended tubes
● Location: everywhere in the body
except in non-vascular tissue (ex.
bone)
● F(x): receive tissue fluid through their
thin walls; drain and process
extracellular fluid
Lymphatic Capillaries Continued...
● Lacteals are lymphatic
capillaries in the villi of
the small intestine
● F(x): absorb
fats/transport fat to
venous circulation
*chyle special lymph
containing proteins and
fats
Lymphatic vs. Blood Capillaries
Difference:
1.originate as blind pockets
2.larger diameter
3.thinner walls
4.have flattened/irregular
outline
Major Lymph-Collecting Vessels
● Superficial lymphatics and deep
lymphatics collect lymph from
lymphatic capillaries
● Deep lymphatics are larger lymphatic
vessels; found in deep arteries/veins
● Converge to form even larger vessels
called lymphatic trunks
Lymphatic Trunks
● drain lymph from
the lymphatic
vessels
● named for
regions they
serve
Principle Lymphatic Trunks
a. lumbar
b. intestinal
c. bronchomediastinal
d. subclavian
e. jugular
f.
intercostal
● pass their lymph into venous blood
by joining one of two collecting
ducts
Lymphatic Ducts
● trunks lead to two collecting ducts-the thoracic duct and the right
lymphatic duct
● collecting ducts join the subclavian
veins
● after leaving two collecting ducts,
lymph enters the venous system and
becomes part of plasma
Thoracic Duct
● larger and longer of the two collecting
ducts
● collects almost all of the lymph that
circulates throughout the body
● drains lymph from intestinal lumbar,
and intercostal trunks, as well as from
the left subclavian vein near junction
of right jugular vein
Right Lymphatic Duct
● originates in right thorax at union of
right jugular, right subclavian, and
right bronchomediastinal trunks
● about 1.25 cm long
● drains lymphatic fluid from the right
thoracic cavity, the right arm, and from
the right side of the neck and the head
Lymph Flow
● under low pressure
● may not flow readily
without external aid
● moved by the
contractions of skeletal
● muscles and low pressure
in the thorax created
breathing movements
Factors Affecting Lymph Flow
● hydrostatic pressure of tissue fluid
drives lymphs into lymphatic
capillaries
● muscular activity influences
movement
● Physical exercise
Obstruction of Lymph Movement
● obstruction of lymph flow
results in edema
● surgical removal of lymph
nodes causes edema in the
affected area
*Edema is the swelling of the lymph
nodes
Lymphocytes
● Three classes of lymphocytes
o
o
o
T Cells (thymus-dependent)
B Cells (bone marrow-derived)
NK cells (natural killer)
T Cells
● approximate 80% of lymphocytes are
classified as T Cells
● T Cells include:
o
o
o
Cytotoxic T cells
Helper T cells
Suppressor T cells
T Cells- Cytotoxic T Cells
● destroy target cell on contact
● attack foreign cells or body cells infected by
virus
● direct contact
● primarily involved in production of cellmediated immunity
T Cells- Helper T Cells
● stimulate activation and function of both T
cells and B cells
● Helper T (TH1) cell: activates cell-mediated
immunity: macrophages, CD8 T cells, and
natural killer cells
● Helper T (TH2) cell: stimulates production of
eosinophils, IgM and IgE
T Cells- Suppressor T cells
● inhibit activation and function of both T cells
and B cells
● close down the immune response after
invading organisms are destroyed
● release their own lymphokines after an
immune response has achieved its goal,
signaling all other participants to cease their
attack
B Cells
● account for 10-15% of circulating
lymphocytes
● B cells can differentiate in to
plasma cells
● produce antibodies (proteins)
necessary to fight off infections
while other B cells mature into
memory B cells
Plasma Cells
● production and secretion of of antibodies
(soluble proteins; aka immunoglobulins)
● antibody: chemical that attaches to the
antigen in order to sterilize or kill the cell.
● Proteins bind to specific chemical targets
called antigens
Antigens
● chemical target
● can be pathogens or foreign compounds
● mostly proteins, but some lipids,
polysaccharides, and nucleic acids can also
stimulate antibody production
● antibody+antigen=destruction of target
compound or organism
NK Cells
● 5-10% of lymphocytes
● aka large granular lymphocytes
● attack:
o
o
o
foreign cells
normal cells infected with viruses
cancer cells that appear in normal tissues
● immunological surveillance
Macrophage “King of Phagocytes”
● Macrophages engulf and
digest debris (like dead cells)
and foreign particles
● phagocytosis
● cannot identify specific targets
● considered part of the innate
immune response
Memory Cells
● some T-cells and Bcells turn into Memory
T-cells and Memory Bcells
● remember the virus or
bacteria they just
fought
● help make antibodies
Lymphoid Tissue
Identify
 cells and organs make up the
lymphatic system, ex: white blood
cells (leukocytes), bone marrow,
thymus, spleen, and lymph nodes.
 connective tissue dominated by
lymphocytes
 lymphoid nodule densely packed in
an area of areolar tissue
 germinal center contains
lymphocytes
Lymphoid Tissue Continued

MALT: mucosa-associated lymphoid tissue;
collection of lymphoid tissues linked with the
digestive system
 Large nodules in the walls of the pharynx called
tonsils; pharyngeal, palatine, lingual
Location
 throughout body
Function
 helps protect it from bacteria and other foreign
entities.
Lymphoid Organs



Afferent lymphatics cary
lymph node from peripheral
tissues
Efferent lymphatics are
attached to the lymph node
at the hilus
deep cortex dominated by Tcells; outer cortex medulla
contain B Cell
Lymphoid Organs Continued...

Reticular epithelial cells scattered
among the lymphocytes produce
thymic hormones

red pulp contains large numbers of
red blood cells/ white pulp
resembles lymphoid nodules
Lymph Nodes
● oval-shaped organ of the
lymphatic system
● distributed widely
throughout the body
including the armpit and
stomach and linked by
lymphatic vessels
● Lymph nodes are major
sites of B, T, and other
immune cells
Lymph Nodes Cont.
● proper functioning of the
immune system, act as filters
for foreign particles and
cancer cells.
● lymph nodes are small
ranging in diameter from 1 to
25mm
● Blood vessels and nerves
attack to the lymph node at
the hilus
Primary Lymph Nodes
Examples of Lymph Nodes
● Cervical Region
● Axillary region
● Supraclavicular
● Pelvic
● Submandibular
● occipital
Thymus
●
●
●
●
stores immature lymphocytes
mature into T-cells
located in chest above heart
pink and grainy consistency; thymic
lobes; septae fibrous partitions that
originate at the capsule, divide
lobes into lobule
● Hassall’s corpuscles
● thymosin in thymus controls
immunological defenses
Tonsils
● large clusters of
lymphatic cells
● swell when
fighting infection
● rear of pharynx
Spleen
● contains largest lymphoid tissue
● removes abnormal cells via
phagocytosis
● stores iron and recycles blood
cells
● begins process of immune
response by B and T cells in
response of circulating antigens
lymphopoiesis
● the formation
of
lymphocytes
is different for
each cell
T cell
● formed in bone
marrow
● migrate to cortex of
thymus to mature
B cell
● forms in bone marrow
● matures in bone marrow
then migrates to
lymphoid tissue
● introduced to antigen and
is then activated
NK cell
● lack antigen receptor
● developed in bone marrow
● after maturation migrate to blood
● kill abnormal cells
dendritic cell
● antigen present
● produced throughout the body but mainly
bone marrow
● released into blood
Fluid Formation
● originates from plasma
● includes water and dissolved substances
that have passed through capillary wall
● lacks proteins
● as protein concentration of tissue fluid
increases, colloid osmotic pressure
increases
Fluid Formation Continued...
● formed when interstitial fluid is
present
● collected from lymph
capillaries
● interstitial fluid secreted from
all body organs
● diffusion allows water and
solutes to pass from fluid to
blood
● transported to lymph
vessels/nodes
Fluid Formation Continued...
● lymph emptied out into subclavian vein
● enter blood stream and carry out functions
Lymph Formation
● increasing hydrostatic pressure within
interstitial spaces forces some tissue fluid
into lymphatic capillaries
● lymph formation prevents accumulation of
excess tissue fluid (edema)
Properties of Immunity
● lymphocytes provide immunity through:
specificity
versatility
memory
tolerance
*memory cells allow immune system to remember previous
target antigens
o
o
o
o
Tolerance: ability to ignore some antigens
Specific Immune Response
● involves innate immunity or acquired
immunity
o
genetically determined and present at birth
● Active immunity
o
appears after exposure to antigen
● Passive immunity
o
produced by the transfer of antibodies from another
source
Specific Immune Response
Continued...
● Called when nonspecific
immune response is not
enough
● Macrophages
a. Eat foreign invaders.
b. Inform T
Lymphocytes when a specific
antigen is present
Specific Immune Response
Continued...
● Helper T Cells - produce and secrete Chemicals
a. promote large numbers of effector and memory cells
● Cytotoxic T cells - t lymphocytes that eliminate infected
body and tumor cell
● B Cells - produce antibodies
B Cells and Antibody-Mediated
Immunity
● The humoral response (or
antibody‐mediated response)
● involves B cells that recognize antigens or
pathogens that are circulating in the lymph
or blood (“humor” is a medieval term for
body fluid).
T Cells and Cell Mediated Immunity
● The cell‐mediated response involves mostly
T cells and responds to any cell that displays
aberrant MHC markers, including cells
invaded by pathogens, tumor cells, or
transplanted cells.
Antibody- and Cell-Mediated Immunity
Allergies
● excessive immune responses to allergens
o
antigens that trigger allergic reactions
● four types of allergies are
(Type I) immediate hypersensitivity
o (Type II) cytotoxic reactions
o (Type III) immune complex disorders
o (Type IV) delayed hypersensitivity
o
● anaphylaxis: circulating allergen affects mast
cells throughout body
Hormones of the Immune System
● Interleukins
o
o
o
increase T cell sensitivity to antigens exposed on
macrophage membranes
stimulate B cell activity, plasma cell activity, plasma
cell formation, and antibody production
enhance nonspecific disease
● Interferons
o
o
slow spread of virus
synthesizing cell and neighbors resistant to viral
infection
Hormones of the Immune System
Continued
● tumor necrosis factors (TNFs)
o
slow tumor growth and kill tumor cells
● Several lymphokines adjust activities of
phagocytic cells to coordinate specific and
nonspecific defenses
Non-Specific Immune Responses
● prevent approach, deny the
entrance, or limit spread of living or
nonliving “hazards”
● Physical Barrier: hair, epithelia,
secretions
Non-Specific Responses Cont...
● Generalized responses; do not target a specific
cell
● Phagocytes - eat foreign material to destroy
them.
● Neutrophil - phagocytize bacteria
● Eosinophils - secrete enzymes to kill parasitic
worms among other pathogens
● Macrophage - “big eaters” phagocytize just
about anything
Primary Innate Defenses Overview
Interferons
● small proteins
● released by cells infected with viruses
● trigger production of antiviral proteins that
interfere with viral replication in cell
● cytokines-chemical messengers released by
tissue cells to coordinate local activities
Complement
● 11 proteins make up complement system
● interact in chain reactions to:
destroy target cell membranes
o stimulate inflammation
o attract phagocytes
o enhance phagocytosis
o
● Inflammation-coordinated nonspecific
response to tissue injury
Fever
● body temperature greater than 37.2 degrees
C
● can inhibit pathogens and accelerate
metabolic processes
What is the difference Between the
Cardiovascular and the Lymphatic System?
Lymphatic System
Cardiovascular
System
Similarities
●
●
●
Blood
Transportation
Blood flow is
continuous
Blood circulation
contains oxygen
●
●
●
Both
Systems
carry out
waste
removal
Both
contain
white blood
cell
Both have
vessels and
capillaries
●
●
●
●
Flows in an only
upward direction
Contains Drainage
areas
Contains more white
blood cells
tonsils is a clump of
lymphatic cells
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