Dedicated to my students

1. Mr. Johny Kutty
Joseph
Asstt. Professor
SMVDCoN

2. •The lymphatic system is part
of the circulatory system and
a vital part of the immune
system, comprising a
network of lymphatic vessels
that carry a clear fluid called
lymph directionally towards
the heart.
•Unlike the cardiovascular
system, the lymphatic system
is not a closed system.
•One of the main functions of
the lymph system is to
provide an accessory return

3. The four parts of lymphatic system are
1. LYMPH
2. LYMPH VESSEL
3. LYMPHOID TISSUE/ LYMPHOID
ORGAN
4. LYMPHOCYTES and PHAGOCYTES

4.  A clear fluid composed mainly of water,
electrolytes and some plasma proteins
 Transported in lymphatic pathway from
lymphatic vessels to collecting ducts and
end disposed into venous blood
 When blood circulates in high pressure, the
fluid (plasma) portion seeps through thin
capillary walls into surrounding tissue.
 This interstitial fluid bathes the cells and is
returned to blood through walls of venules.
 The remainder enters a network of thin
walled tubes called lymphatic vessels and
now is called lymph

5.  In average adult, seepage 2.9l/day
 Reabsorbed by lymphatic capillaries in all
body tissues where excessive tissue fluids
occur.
 Because of lack of pumping organ, lymph
movement is largely dependent on skeletal
muscle activity.
 Movement normally constant and smooth,
except when obstruction (small clot, tumor)
occurs which tend to back up the lymph,
and result in edema (fluid accumulation in
tissues)

6.  Lymphatic capillary run parallel to blood
capillaries in all body tissues and allow diffusion
of fluid from interstitial spaces into lymphatic
pathway.
 Capillaries also responsible for absorbing short
chain fatty acids in the small intestine using
specialized capillaries called lacteals.
 Structurally identical to veins- vessel wall
composed of 3 thin layers of tissue, and contain
valves to prevent backflow.
 They form specialized lymphatic organs called
lymph nodes which store macrophages and
lymphocytes to eliminate foreign substance in
the lymph.

7.  Thoracic duct returns lymph from left side of
the body to left subclavian vein, and Right
lymphatic duct returns lymph from right part
of the body to right subclavian vein

8.  Lymphatic capillary has high degree of
permeability.
 It permits large molecules to enter lymph
vessels and it is removed from interstitial
space. It cannot be performed by blood
vessels as it cannot absorb large molecules.
Eg. Proteins
 It also helps in absorbing large molecules
from intestine thus supporting the
metabolism.

9. A number of morphologically and functionally
diverse organs and tissues contribute to the
development of immune responses. These
organs can be distinguished by function as
primary lymphatic organs and secondary
lymphatic organs.
1. Primary Lymphatic Organs are red bone
marrow and thymus gland. The red bone
marrow produce (hematopoiesis) T-cells in
response to an antigen and they get matured
in thymus gland.
2. Secondary Lymphatic Organs are lymph
nodes, spleen, lymphatic nodules. These are
the sites of immune responses.

10.  Flat, bi-lobed organ located in the
mediastinum between the sternum and the
aorta.
 Each lobe surrounded by a capsule and
divided into lobules, which are separated from
each other by strans of connective tissue
called trabeculae.
 Each lobule organized into 2 compartments:
the outer compartment cortex, and the inner
compartment medulla.
 The maturation of T cells and monocytes takes
place in the medulla which is supported by
epithelial cells and macrophages present in the

11.  Thymic function is known to decline with age.
Thymus reaches maximal size at puberty and
atrophies, with a significant decrease in both
cortical and medullary cells and an increase in
total fat content of the organ.
 Average weight of thymus in human infants is
30g, and age dependent involution leaves the
organ with a weight of 3g in elderly.

12.  Complex tissue
which is the site of
haematopoesis
and fat deposition.
 Haematopoetic
cells generated in
bone marrow
move through
walls of blood
vessel and enter
blood stream,
which carries them
out of the marrow
and distributes

13.  Around 600 bean shaped lymph nodes are
located throughout the body.
 It contains a reticular network packed with
lymphocytes, macrophages and dendritic
cells.
 As lymph percolates through, antigen is
trapped by cellular network of phagocytic
cells and dendritic cells.
 Ideal environment for lymphocyte to
effectively encounter and respond to trapped
antigen.
 Lymph node can be divided into 3 centric
regions: the Cortex, the Paracortex and the

14.  Beneath cortex,
paracortex:
largely populated
by T
lymphocytes and
dendritic cells
that migrated
from tissues to
the node.
 Medulla is more
sparsely
populated with
lymphoid lineage
cells, and many
are plasma cells
actively
secreting
antibodies.

15.  Defense Functions: it includes filtration and
phagocytosis. The structure of Lymph Node
is appropriate for it.
 Haematopoesis: The lymph nodes serve as
the final area of maturation of lymphocytes
and monocytes that have migrated from bone
marrow.
 Breast cancer spreads all over the breast
from primary tumor to other areas through
lymphatic system. Hence removal of large
area is required as treatment.

16.  Situated high in the left abdominal cavity, an
ovoid organ.
 Filter blood and trap blood borne antigen: thus
respond to systemic infections.
 Not supplied by lymphatic vessels. Instead
blood borne antigen is carried to spleen by
splenic artery.
 Surrounded by a capsule from which a number
of projections (trabeculae) extend into interior
to form compartments.
 Compartments are of two types: the RED pulp
and the WHITE pulp, separated by a diffuse
marginal zone.

17.  Blood from the splenic artery enters white pulp
where immune function same as lymph node
take place.
 Within the red pulp the following functions
such as removal of defective blood cells and
platelets, storage of platelets for emergency
use, and production of blood cells during fetal
life, destruction of blood cells (after maturity)

18.  Defense: as the blood pass through spleen it
filters all the microorganisms and destroy by
phagocytosis.
 Tissue Repair: The monocytes in association
with WBC helps in tissue repair and healing
especially in case of MI and CVA.
 Haematopoesis: The lymph nodes serve as
the final area of maturation of lymphocytes
and monocytes that have migrated from bone
marrow.
 Destruction of RBC and Platelets. This is done
with the help of macrophages and Phagocytes.
 Blood reservoir: Around 350ml of blood is

19.  They are egg shaped masses of lymphatic
tissues different from lymph nodes since they
do not have capsules.
 They are located at the mucosal lining of GI,
urinary, respiratory and reproductive tracts
and also referred as MALT (mucosa-
associated lymphatic tissue)
 They also occur in aggregations such as
tonsils.
 There are 5 tonsils in the oral cavity. They are
positioned to provide immunity to inhaled or
ingested antigens. They are Pharyngeal tonsils
(1nos), Palatine tonsils (2nos) and lingual

20.  T CELLS
 B CELLS
 MONOCYTES AND
MACROPHAGES/PHAGOCYTES
 MAST CELLS
 DENDRITIC CELLS: derived from
monocytes and have long branched
projections similar to neurons.
 GRANULOCYTIC CELLS: Neutrophil.
Eosinophil, Basophil

21.  Water and solutes continually filter out from
capillary into interstitial space.
 To balance this outflow fluid continually
reenters blood through lymphatic system.
 Fluid that is forced out of the bloodstream
during normal circulation is filtered through
lymph nodes to remove bacteria, abnormal
cells and other matter.
 This fluid is then transported back into the
bloodstream via the lymph vessels.
 Lymph only moves in one direction, toward the
heart.

23.  It is responsible for the removal of interstitial
fluid from tissues
 Absorption of Fat: Lymph
vessels called lacteals are present in the
lining of the small intestine. While most
other nutrients absorbed and passed on to
the portal vein into the liver for processing,
fats (lipids) are passed on to the lymphatic
system and reaches liver for processing
 Transportation of WBC to and fro
 Immune function: Cells in the lymphatic
system react to antigens presented or found

24. Lymphedema: is a condition of
localized fluid retention and tissue swelling
caused by a compromised/improper lymphatic
system. The condition can be inherited or can
be caused by an injury to lymph vessel or
nodes as a result of treatment of cancer such as
radiation, surgery or a parasitic infection called
filariasis. Lymphedema
Filariasis