Pooja Godiyal, Assistant Professor

1. PRESENTEDBY
MRS. POOJA GODIYAL

2. Introduction
• The lymphatic system is part of the vascular
system and an important part of the immune
system
• It comprised of a network of lymphatic vessels
that carry a clear fluid called lymph
• The lymphatic system is a network of very
small tubes (or vessels) that drains lymph fluid
from all over the body
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4. Introduction
Lymphatic system consists of:
• Lymph
• Lymph vessels
• Lymph nodes
• Lymph organs, e.g. spleen and thymus
• Diffuse lymphoid tissue, e.g. tonsils
• Bone marrow
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5. Functions
Tissue drainage
• Everyday around 21 litres of plasma fluid,
carrying dissolved substances and some plasma
protein
• About 3 – 4 litres fluid are drained away by the
lymphatic vessels
• If this did not happen, the tissues would rapidly
become waterlogged and
• The cardiovascular system would begin to fail as
the blood volume falls
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6. Functions
Absorption in the small intestine
• Breakdown products of fat and fat soluble
materials, e.g. the fat soluble vitamins, are
absorbed into the central lacteals (lymphatic
vessels) of the villi
Immunity
• The lymphatic organs are concerned with the
production and maturation of lymphocytes
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7. Lymph and Lymph vessels
Lymph
• Latin word, lympha meaning water
• A fluid that circulates throughout the lymphatic system
• Like the venous system, its function is to return fluid from
the tissues to the central circulation
• Interstitial fluid – the fluid which is between the cells in all
body tissues – enters the lymph capillaries
• This lymphatic fluid is then transported via progressively
larger lymphatic vessels through lymph nodes, where
substances are removed by tissue lymphocytes and
circulating lymphocytes are added to the fluid before
emptying ultimately into right and left subclavian vein,
where it mixes with central venous blood
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8. Lymph
Functions
• Returns proteins and excess interstitial fluid to the blood
stream
• It also carries away larger particles, e.g. bacteria and cell
debris from damaged tissues, which can then be filtered out
and destroyed by the lymph nodes
• Lymph contains lymphocytes, which circulate in the
lymphatic system allowing them to patrol the different
regions of the body
• Lymph also transport fats from the digestive system
(beginning in the lacteals) to the blood via chylomicrons
(lipoprotein particles that enable fats and cholesterol to
move within the water –based solution of the blood stream)
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9. Lymph capillaries
• These originate as
blind – ended tubes in
the interstitial spaces
• They have the same
structure as blood
capillaries
• A single layer of
endothelial cells, but
their walls are more
permeable to all
interstitial fluid
constituents
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10. Lymphatic pathway
Lymphatic capillary
Lymphatic vessel
Lymph node
Lymphatic vessels merge to
form
Lymphatic trunk
Collecting duct
Mixed into subclavian veins
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11. Large lymph vessels
• Lymph vessels are often found running along
side of the arteries and veins
• A fibrous covering, a middle layer of smooth
muscle and elastic tissue and an inner lining of
endothelium
• Lymph vessels become larger a they join
together
• Forming two larger ducts that empty lymph
into the subclavian vein
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12. Thoracic duct
• Begins at cysterna chyli
(a dialated lymph
channel situated in front
of the first two lumbar
vertebrae)
• The duct is about 40cm
long
• It drains lymph from
both legs, the pubic and
abdominal cavities, the
left half of the thorax,
head, neck and the left
arm
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14. Right lymphatic duct
• This is a dilated lymph vessel about 1cm long
• It lies in the root of the neck and opens into the
right subclavian vein
• It drains lymph from the right half of the
thorax, head and neck and the right arm
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15. Lymphatic organs and tissues
LYMPH NODES
• Lymph nodes are oval or bean shaped organs
• They lie often in groups, along the length of
lymph vessels
• Lymph drains through a number of nodes
before returning to venous circulation
• These nodes vary considerably in size, some
are as small as a pin head and the largest are
about the size of an almond
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17. Structure of lymph nodes
• Lymph nodes have an outer capsule of fibrous
tissue which dips down into the node
substance forming partition, or trabeculae
• The main substance of the node consists of
reticular and lymphatic tissue containing many
lymphocytes and macrophages
• Four or five afferent lymph vessels may enter a
lymph node while only one efferent vessel
carries lymph away from the node
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18. Structure of lymph nodes
• Every lymph node has a concave surface
called the hilum
Functions
Filtering and phagocytosis:
• Lymph is filtered by the reticular and
lymphoid tissue as it passes through lymph
nodes
Maturation and proliferation of lymphocytes
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19. Spleen
• Largest lymph organ
• Formed by reticular and lymphatic tissue
Location:
• Lies in the left hypochondriac region of the
abdominal cavity between the fundus of the
stomach and the diaphragm
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20. Spleen
• It is purplish in colour
• It s usually about 12cm long, 7cm wide and
2.5cm thick
• It weighs about 200gm
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21. Structure
• Slightly oval in shape with the
hilum on the lower medial border
• The anterior surface is covered
with peritoneum
• It is enclosed with fibrous capsule
that dips into the organ forming
trabeculae
• The cellular material, consisting of
lymphocytes and macrophages, is
called splenic pulp, and it lies
between the trabeculae
• Red pulp is the part suffused with
blood
• White pulp consists of areas of
lymphatic tissue where there are
sleeves of lymphocytes and
macrophages and blood vessels
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22. Spleen
The structures entering and leaving the spleen at
hilum are:
• Splenic artery
• Splenic vein
• Lymphatic vessels (efferent only)
• Nerves
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23. Functions of spleen
Phagocytosis:
• Old and abnormal erythrocytes are destroyed in the
spleen and the breakdown products, bilirubin and iron
are passed to the liver, via the splenic and portal vein
• Other cellular material, e.g. leukocyte, platlets and
microbes are phagocytosed in the spleen
• Unlike lymph nodes, the pleen has no afferent
lymphatics entering in it, o it I not exposed to
diseases spread by lymph
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24. Functions of spleen
Storage of blood:
• Spleen contains up to 350ml of blood
• In response to sympathetic stimulation can rapidly
return a large part of this volume to the circulation,
e.g. in haemorrhage
Immune response
• Spleen contains T and B lymphocyte, which are
activated by the presence of antigens
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25. Functions of spleen
Erythropoiesis:
• The spleen and the liver are important sites of fetal
blood cell production, and the spleen can also fulfill
this function in adults in times of great need
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26. Thymus gland
• Lies in the upper part of the mediastinum
behind the sternum and extend upwards into
the root of the neck
• Weighs about 10 to 15 gm at birth and grows
until the individual reaches puberty, when it
begins to atrophy
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27. Thymus gland
Structure
• The thymus consists of two lobe joined by
areolar tissue
• The lobes are enclosed by a fibrous capsule
• Dividing them into lobules that consists of an
irregular branching framework of epithelial
cells and lymphocytes
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29. Thymus gland
Functions
• The lymphocyte originate from pluripotent
stem cells in red bone marrow. Those that enter
the thymus develop into T lymphocyte
• Thymus gland secretes hormone - thymosine
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30. Mucosa associated lymphoid tissue
• Throughout the body, at some locations there
are collections of lymphoid tissue which are
not enclosed in a capsule
• They contain B and T lymphocytes
• MALT is found throughout the gastrointestinal
tract, in the respiratory tract and in the urinary
tract
• The main groups of MALT are the tonsils and
the Peyer’s patches
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31. Mucosa associated lymphoid tissue
Tonsils
• These are located in
the mouth and
throat, and will
therefore destroy
swallowed and
inhaled antigens
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32. Mucosa associated lymphoid tissue
Peyer’s patches
• These are large collections of lymphoid tissue
are found in the small intestine, and intercept
swallowed antigens
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