Download The Lymphatic System

LymphaticSystem
Lymphatic System
The Lymphatic System
By Scott Ford, M.Ed.
•Composed of:
•Lymph
•Lymphatic vessels
•Lymphatic tissue
•Lymphatic organs
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Basic Functions
What is Lymph
• Brings materials back to the blood system
• Carries fluid from tissue spaces back to the blood
• Blood capillaries absorb around 85% of fluid that is filtered out of them
• The lymphatic system catches the rest
• Carries away proteins and large particulate matter from tissue spaces
• Immunity
• Because the lymphatic system brings back large molecules and fluids from the body there
are check points through the lymphatic system designed to identify and destroy bad stuff
• Lipid Absorption
• Lacteals found in the small intestine absorbed dietary lipids that cannot be absorbed by
the blood capillaries
• Typically a clear, colorless fluid
• Similar to blood plasma
Composition of Lymph
Edema
• As lymph first flows from tissues it is almost the same as interstitial fluid
• When the system fails proteins and fluid
accumulate in the interstitium
• Protein concentration is around 2g/dL, in some tissue like it can be as
high as 6g/dL
• A major route for the absorption of nutrients from the gastrointestinal
tract
• Some others things that can be found:
• Hormones
• Bacteria
• Viruses, Cellular debris, macrophages
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• As blood moves through the circulatory systems fluids and small
molecules pass from the plasma into the surrounding tissues
• Much of this fluid is reabsorbed by the blood vessels, lymph is a
collection of the fluid that does not make it back
• 85% is reabsorbed
• Also found within lymph are larger molecules that can not pass into the
blood capillaries, like large proteins, fats and other substance
• Proteins need the lymphatic system to get
back into the circulatory system
• Accumulation of proteins in the interstitial
space increase colloid osmotic pressure
of the interstitial fluid, allows more fluid
filtration into interstitium
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The Path
Lymphatic Capillaries
• Lymphatic systems primary job is to bring fluids
back into the circulatory system
• Because it brings fluids back from the
interstitial spaces, it makes sense to start
there
• Microscopic tubes that are found
within the interstitial spaces
• Not found in: CNS, cartilage,
cornea, bone and bone marrow
Lymphatic
capillaries
Lymphatic
vessels
Lymph
node
Lymphatic
vessel
Lymphatic Vessels
• Like veins but thinner
• Three layers:
• Tunica Intima
• Tunica Media
• Tunica Adventitia
• Semilunar valves
prevent lymph from
flowing backwards
Lymphatic
trunk
Collecting
duct
Subclavian
vein
• Walls are like blood capillaries
• Single layer endothelium
• Special lymphatic capillaries in the
small intestine absorb digested fats
TunicaIntima
• Innerendotheliallining
TunicaMedia
• Middlelayerofsmoothmuscleandelasticfibers
TunicaAdventitia
• Outerlayerofconnectivetissue
Lymphatic Nodes
Lymphatic trunk
• Vary in size and shape
• Typically bean shaped
• Lymphatic vessels drain into trunks
• Filter lymph for
microorganism, infected
cells and other materials
that do not belong
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• Trunks are named for the regions
they serve
• Lumbar trunk
• Intestinal
• Intercostal
• Bronchomediastinal trunks
• Subclavian
• Jugular
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Collecting duct
Collecting duct
• Lymphatic trunks drain into one
of two collecting ducts
• Thoracic Duct
• Right Lymphatic Duct
• Lymph from left side of head, left
arm, parts of chest enter
thoracic duct
• Most of lymph from lower part of
body flows up thoracic duct and
empties into venous system at
junction of left interior jugular
vein and subclavian vein
• Lymph from right side of neck,
head, right arm, parts of thoracic
enter right lymph duct, enters
the venous system at junction of
right subclavian vein and
internal jugular veins
Thoracic Duct
Right Lymphatic Duct
• Largest and longer of
the two
• Starts in the abdomen
• Passes up through the
diaphragm next to aorta
• Comes up anterior to
vertebral column
• Empties into left
subclavian
• Drains from following
trunks:
• Intestinal
• Lumbar
• Intercostal trunks
• Left subclavian
• Left jugular
• Left bronchomediastinal
trunks
• Starts at the right thorax at the merger of the right jugular,
right subclavian and right bronchomediastinal trunk
• Receives the drainage from:
• Right arm
• Right side of thorax
• Right side of head
• Empties into the right subclavian vein
Lymph Movement
Lymph Movement
• Flow of lymph is similar to
movement of venous blood
• Valves preventing lymph from
flowing backwards
• Total rate of lymph flow is around 120 mL/hr
• 2-3L/day
• Rate of lymph flow is determined by
• Interstitial fluid hydrostatic pressure
• Lymph flow is very low in normal situations
• If the pressure rises lymph flow can increase
• If pressure increases too much the flow remains constant
• Lymphatic pump
• Squeezing of the vessels that move lymph along the vessels
• External factors like exercise the lymphatic pump may dramatically
increase movement of lymph
• Like venous blood, the movement
of lymph is a very low pressure
system
• Under even less pressure then
venous blood
• Basically lymph moves when the
lymph vessels are squished
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LymphaticSystem
The Lymph Nodes
Garbage Pick Up
• Located along the lymphatic pathways
• The most numerous of the lymphatic organs (covered later)
• Bacterial and other small materials can easily
pass into the lymph
• Contain large numbers of lymphocytes and macrophages
• Primary Jobs
• Filter possible bad stuff before it returns to the bloodstream
• Monitor body fluids
• Site of T and B cell activation
• Lymph passes through series of check points,
nodes, on its way to the blood
• In these nodes the bacteria and other junk is
filters out, or phagocytized by macrophages
Anatomy of Lymph Nodes
Anatomy of Lymph Nodes
• Vary in size and shape
• Typically bean shaped
• Materials entering the node
attach to the convex
surface
• Leaving node at hilum
• An indented area
• Nodes are encapsulated by
connective tissue
Location of Nodes
Lymphatic Organs
• There are around 450-600 lymph nodes
found throughout the body
• Depends on source
• There is lymphatic tissue, which is basically a collection of lymphocytes in
connective tissue
• The major collection of lymph nodes are:
• Cervical region
• Axillary region
• Supratrochlear region
• Inguinal region
• Pelvic cavity
• Abdominal cavity
• Thoracic cavity
• Primary Lymphatic Organs (produce mature lymphocytes)
• Red bone marrow
• Thymus
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• The capsule extends into the
node and compartmentalized
the node into the structural
units known as lymph nodules
• Lymphatic organs are more defined
• Secondary Lymphatic Organs (mature lymphocytes migrate to)
• Lymph nodes
• Tonsils
• Spleen
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Red Bone Marrow
Thymus
• Two types of bone marrow:
• Yellow
• Adipose tissue, not worries
about it for the lymphatic system
• Red
• Discussed in the endocrine system
• Red Bone Marrow produces blood
(hemopoiesis)
• Supplies lymphocytes to the immune
system
• A soft structure enclosed in a capsule
• Located in the mediastinum posterior to the sternum
• Active in children
• After puberty starts to shrink and fill with fat
• As a child it plays a part in production of T lymphocytes
Tonsils
Spleen
• Patches of lymphatic tissue found at the entrance to the pharynx
• Protect the body against pathogens that can enter through the
mouth or nose
• Largest of the lymphatic organs
• Found in the upper left portion of abdominal cavity
• Posterior and lateral to stomach
• Three sets of tonsils
• Pharyngeal tonsil (adenoids)
• Palatine tonsils
• The biggest of the three
• Most common site of infection
• The tonsils remove din a tonsillectomy
• Lingual tonsils
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• Allows for cells of the immune system to proliferate
• Monitors blood for foreign or damaged cells
• Removes old blood cells
• White Pulp
• Deals with immune response
• Red pulp
• Mechanical filtration of red blood cells
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