LYMPH NODES

LYMPH NODES
JAI NARAIN VYAS UNIVERSITY, JODHPUR
ASSISTANT PROFESSOR:- ASHWIN SINGH
CHOUHAN
DEPARTMENT:- PHARMACOLOGY
E-mail:- anshukavya1993@gmail.com

LYMPH
A clear fluid composed mainly of water, electrolytes, and
some small plasma proteins.
Transported in the lymphatic pathway form the
lymphatic capillaries to the collecting ducts, and at the
end disposed into the venous blood.
Reabsorbed by lymphatic capillaries in all body tissues
(especially in extremities) where excessive tissue fluids
occur.
Because of the lack of a pumping organ in the lymphatic
pathway, lymph movement is largely dependent on
skeletal muscle activity (similar to blood flow in the
veins).
Lymph movement is normally constant and smooth,
except when obstruction (small blood clot, tumor) occurs
which tend to back up the lymph, and results in edema
(fluid accumulation in tissues).
JNVU PHARMACY, JODHPUR

Lymph nodes are small solid structures placed at varying
points along the lymphatic system such as the groin, armpit
and mesentery.
They contain both T and B lymphocytes as well as accessory
cells and are primarily responsible for mounting immune
responses against foreign antigens entering the tissues.
Lymph nodes are situated at strategic positions throughout
the body and serve to filter the lymph.

The lymph nodes are small bean shaped glands or bulbs
that tend to occur in clusters much like grapes.
Along the lymph channels reside approximately 600
lymph nodes. These act as filters that sieve off the
harmful substances brought by the lymphatic channels.
The lymphatic channels of the fingers, hand and arm for
example comes to be filtered at the lymph nodes that lie
at the elbow and the arm pit.
Similarly, those of the legs, toes and thighs drain and
nodes behind the knees and the groin.
Lymph channels from the face, head and scalp drain at
the nodes present at the back of the head, behind the
ears and sides of the neck.

Some lymph nodes are located deeper within the body
at the chest (between the two lobes of the lungs), around
the coils of the intestines, in the pelvis etc.
The lymph nodes contain 2 regions within them – these
include the cortex and the medulla.
The cortex contains collections of lymphocytes. These
contain predominantly B-lymphocytes and some T-
lymphocytes.
The B lymphocytes mature completely within the bone
marrow while the T lymphocytes exit the bone marrow
immature and attain maturity within the thymus.
The lymphatic vessels entering the lymph nodes are
called afferent lymphatic vessels and those exiting are
called efferent lymphatic vessels.

They range in size from 2 to 10 mm, are spherical in
shape and are encapsulated.
Lymph node is surrounded by a fibrous capsule which
dips down into the node substance forming partition or
trabeculae.
The node is made by reticular and lymphatic tissues
containing mainly lymphocytes and macrophages.
Beneath the capsule is the subcapsular sinus, the
cortex, a paracortical region and a medulla.
The cortex contains many follicles and on antigenic
stimulation becomes enlarged with germinal centers.
The follicles are comprised mainly of B cells and
follicular dendritic cells.
The paracortical (thymus-dependent) region contains
large numbers of T cells interspersed with interdigitating
cells.
STRUCTURE OF LYMPH NODES

Each lymph node has 4-5 afferent vessels that bring
lymph to the node while only one efferent vessel draining
lymph away from the node.
It also has a concave surface called the hilum where an
artery enters, a vein and the efferent lymph vessel leave.
Depending upon the position, the lymph nodes may be
superficial or deep lymph nodes. Groups of lymph nodes
are present in the neck, collarbone, under the arms
(armpit), and groin.

FUNCTION OF LYMPH NODES
Filter lymph before returned to blood stream.
99 percent of pathogens (bacteria, toxins etc.) are
removed.
Located in ideal spots to protect vital organs of body.
The primary role of the lymph node is to filter the lymph
and then produce an immune response against trapped
microbes/antigens.
Filtering of the lymph helps in removal of particles not
normally found in the serum.
The lymphoide tissues in the nodes break down
materials which have been filtered off such as
microorganisms, tumor cells and cells damaged by
inflammation.
Lymphocyte develops from the reticular and lymphoid
tissue in the nodes.
Antibodies and antitoxins are also formed by the cells of
lymph nodes. JNVU PHARMACY, JODHPUR

Lymph arriving from the tissues or from a preceding
lymph node in the chain, passes via the afferent
lymphatics into the subcapsular sinus and then into the
cortex, around the follicles, into the paracortical area and
then into the medulla.
Lymph in the medullary sinuses then drains into efferent
lymphatics and hence through larger lymphatic vessels
back into the bloodstream.
LYMPH CIRCULATION IN LYMPH NODES

THE LYMPHATIC SYSTEM
The lymphatic system also consists of other organs like
the spleen that lies on the above left sided part of the
abdomen.
It acts like a large filter to remove worn out and
damaged red blood cells from the blood and recycle
them.
The spleen also contains B lymphocytes and T
lymphocytes. When blood passes through the organ these
cells pick up the infections.
The lymphatic system also contains the thymus that lies
behind the chest bone.
The thymus is a maturation site for T lymphocytes.
Tonsils and adenoids are also part of the lymphatic
system. The lie at the back of the throat. These are
sentinels that protect the digestive system and the lungs
from bacteria and viruses.

FUNCTIONS OF THE LYMPHATIC SYSTEM
Drainage of fluid from blood stream into the tissues – The
circulating blood through narrow vessels leads to leakage of
fluid or plasma into the tissues carrying oxygen and nutrients
to the tissues and carrying waste materials from the tissues
into the lymph channels.The leaked fluid drains into the
lymph vessels. This forms a circulatory system of fluids within
the body.
Filtration of the lymph at the lymph nodes – The nodes
contain white blood cells that can attack any bacteria or
viruses they find in the lymph as it flows through the lymph
nodes.The cancer cells may also get trapped similarly at the
lymph nodes and thus lymph nodes act as indicators of how
far the cancer has already spread.
Filtering blood – This is done by the spleen. The spleen
filters out bacteria, viruses and other foreign particles.
Raise an immune reaction and fight infections – The
lymphatic system especially the lymph nodes are over active
in case of an infection the lymph nodes or glands often swell
up in case of a local infection.

Lymphoid tissues are collections of lymphocytes
strategically located at potential sites of infection. They
can be classified as either primary lymphoid organs (bone
marrow and thymus) where de novo synthesis and
maturation of lymphocytes occur; or secondary lymphoid
organs where activation of lymphocytes occur. Lymph
nodes are secondary lymphoid organs widely distributed
throughout the body.
They are strategically located at areas that are open to
foreign microorganisms (e.g. the oral cavity). For the
sake of completeness, other secondary lymphoid
organs include (but are not limited to) the spleen,
mucosa-associated lymphoid tissue (MALT), tonsils, and
Peyer’s patches. The average young adult has about 450
lymph nodes throughout the body; most of which are in
the abdominopelvic region, then the thorax and the
remainder in the head and neck.

LYMPHOID
TISSUES
Primary: bone marrow, thymus
Secondary: lymph nodes, spleen, MALT, Peyer's patches
STRUCTURE
OF A LYMPH
NODE
Hilum - passage for the artery, vein, afferent and efferent lymph vessels
Capsule - surrounding dense connective tissue
Cortex - lymphatic nodules
- primary nodule - dormant B-lymphocites
- secondary nodule - activated B-lymphocites form germinative center with dark
zone (centroblasts), light zone (centrocytes) and mantle zone (small quiescent
cells)
Paracortex - CD4 and CD8-T cells, migrating dendritic cells
Medulla:
- medullary cords - plasma cells, small lymphocytes and macrophages
- medullary sinuses - drain lymph to the efferent lymph vessel
REGIONAL
NODES
Cervical - superficial (parotid, mastoid, occipital) and deep nodes
Waldeyer's ring - pharyngeal tonsils, tubal tonsils of Gerlach, palatine tonsils,
lingual tonsils, MALT at the oropharyngeal wall
Axillary - apical, central, posterior (subscapular), anterior (pectoral), lateral
nodes
Supratrochlear - superficial to the deep fascia of the arm and medial to the
basillic vein
Mediastinal - hilum of the lungs, juxta-oesophageal, superior and inferior
tracheobronchial nodes
Abdominal - para-aortic, mesenteric, common iliac, external iliac, internal
iliac, superior and middle rectal nodes
Inguinal - superficial (inferior, superolateral, superomedial), deep nodes
VASCULATURE Lymphatic vessels (afferent, efferent), lymphatic capillaries
CLINICAL Lymphadenopathy, lymphedema, sentinel lymph nodes

GROSS ANATOMY
Lymph nodes are bean-shaped structures about 0.1 –
2.5 cm in length.
The node is enclosed in a capsule and has an
indentation on one surface (along one of its long axes)
known as the hilum.
The hilum is the point at which arteries carrying
nutrients and lymphocytes enter the lymph node and
veins leave it.
Afferent lymphatic vessels enter the lymph node
through the capsule peripherally and efferent lymphatic
vessels leave the node via the hilum.
The former takes lymph from peripheral sites to the
node, while the latter takes processed lymph from the
nodes back to the venous circulation.

HISTOLOGY
A horizontal section through the lymph node reveals
that the dense connective tissue capsule (composed of
elastin, collagen and fibroblasts) projects trabeculae
interiorly; giving the lymph node a lobular appearance,
while carrying major blood vessels of the lymph node.
Additionally, there is a pericapsular adipose tissue
layer that surrounds the connective tissue capsule. This
layer contains arterioles and venules that supply the
lymph node.
The lymph node is divided into an outer cortex and
an inner medulla.
Histological staining of the node reveals that the cortex
stains darker than the medulla with hematoxylin and
eosin (H&E) due to its higher cell content.
The cortex contains lymphoid nodules, which are non-
encapsulated, spherical collections of lymphocytes.

Beneath the fibrous capsule is the subcapsular sinus.
The subcapsular sinus receives afferent lymphatic ducts
at intervals that deposit lymphatic fluid in the space.
The subcapsular sinus communicates with the cortical
sinuses that travel parallel to the capsular trabeculation.
They carry lymph to the medullary sinus.

CORTEX
Within the cortex are regions of lymphocyte aggregation
(primarily B-cells and some supporting T-cells) and
specialized follicular dendritic cells that form the lymphoid
follicles or lymphatic nodules.
These can either be primary or secondary follicles
depending on their cellular population. Primary lymphoid
follicles contain small, dormant lymphocytes, while
secondary lymphoid follicles contain a lighter staining
area of active lymphocyte proliferation known as
a germinal centre.
The germinal centre supports affinity maturation (high
affinity antibody production) of B-cells. It is subdivided
into a dark zone, light zone and a mantle zone. The B-
cells of the dark zone are known as centroblasts. They
rapidly replicate, resulting in hypermutation of their
antibody molecules. germinal centre.

Centroblasts migrate to the light zone, where they are
referred to as centrocytes. Here they compete for binding
with the unprocessed antigens presented on the surface
of follicular dendritic cells. Those centrocytes that
successfully bind to the follicular dendritic cells will
survive, while the others will die. Small, quiescent cells
are peripherally marginalized due to the rapid
proliferation of the central cells. These cells form
the mantle zone of the germinal centre.

PARACORTEX
Deep to the cortical layer and superficial to the medulla
is the paracortex.
This region contains mostly T-cells of the CD4 (cluster
of differentiation) and CD8 subsets.
Migrating dendritic cell lines (such as Langerhans cells)
found in this area present processed antigen to the T-
cells.
MEDULLA
The lymphocytes of the medulla are less organized and
form irregular medullary cords.
The cords also contain plasma cells, small lymphocytes
and macrophages.
The medullary sinuses drain the lymph coming from the
cortical sinuses to the efferent lymphatic vessel via the
hilum.

BLOOD SUPPLY
The hilum of the lymph nodes is the primary point of
entry for arteries and exit for veins. Once they enter the
hilum, they give off straight branches that pass through
the medulla. The arteries form bundles of anastomosing
arterioles and capillaries in the cortex that return to
similarly branched venules and veins. In the paracortical
zone, there are large numbers of postcapillary high
endothelial veins that act as a point where blood-borne
lymphocytes leave the blood vessels and enter the lymph
nodes.

FLOW OF LYMPH IN NODES
In the nodes the lymph get enter by afferent lymphatic
vessels and out by the efferent lymphatic vessels.
The afferent lymphatic vessels consist valve at the
opening part and the valve is open in such a direction
that once lymph can enter in to the afferent vessels in
not go back from that also efferent lymphatic vessels
consist valve at the end of their part and the here also
the valve is located in same manner of afferent vessels.
The efferent lymphatic vessels have wider diameters
than the afferent lymphatic vessels.
The main function of lymph nodes is filtration of lymph.
It filters the foreign substances which are harmful for us
because the macrophages, T-lymphocytes and B-
lymphocytes of nodes destroy them.

LYMPHATIC VESSELS
The lymphatic vasculature is comprised of lymphatic
capillaries and lymphatic vessels. They are valvular
channels responsible for taking lymph to and from the
lymph nodes and back to the main systemic circulation.
The valves of the lymphatic vessels ensure that lymph
flows in a unidirectional manner: from afferent lymphatic
vessels to efferent lymphatic vessels. They have very thin
walls and their valves can be appreciated histologically
when the vessel is cut along its longitudinal axis. Unlike
arteries and veins, which are open at both ends,
lymphatic vessels begin as blind-ended (closed at one
end) channels in the interstitium of specific organs. Their
thin endothelial walls permit passive movement of excess
interstitial fluid into the lumen of the vessels, which is
subsequently returned to the venous circulation.

REGIONAL LYMPH NODES
As stated above, lymph nodes are strategically located
throughout the body at points susceptible to foreign
microorganisms. The following is an overview of these
lymph node regions and their subdivisions.
Brain
It is a long held concept that the brain is the only region
of the body devoid of a lymphatic system. The idea was
that resident microglia were totally responsible for
maintaining immunity within the region. However, the
method by which these macrophages entered the central
nervous system was still unclear. It has been recently
proposed by Louveau et al. (2015) that lymphatic
channels line the dural sinuses located between the two
layers of dura and drain their contents to the deep group
of cervical lymph nodes.

CERVICAL
The cervical lymph nodes can be subdivided into two
major groups.
Those superficial to the sternocleidomastoid muscle are
known as the superficial cervical nodes, while those deep
to the same muscle are the deep cervical nodes.
The superficial cervical nodes are further subdivided
into the pre-auricular or parotid nodes (anterior to
the external ear), mastoid nodes (posterior to the
external ear), and the occipital nodes.
The deep cervical nodes are located in relation to
the internal jugular vein.
The superior deep cervical nodes are adjacent to the
upper part of the internal jugular vein, while the inferior
deep cervical nodes are adjacent to the lower part of the
same vein.

WALDEYER'S RING
The nasal and oral passages are two of the major ports
of entry that pathogens use to access the human body.
The region is guarded by a collection of lymphatic tissue
known as Waldeyer’s ring.
This circular collection of lymphoid tissue is formed by
the pharyngeal tonsils (adenoids) located in the fossa of
Rosenmüller, the tubal tonsils of Gerlach in the torus
tubaris, the palatine tonsils between the palatoglossal
and palatopharyngeal folds, the lingual tonsils at the
posterior region of the tongue and mucosa-associated
lymphatic tissue lining the oropharyngeal wall.

AXILLARY
The axillary lymph nodes were previously divided into
three groups by pectoralis minor. Level one nodes are
inferior to the muscle, level two nodes are posterior to
the muscle and level three nodes are superior to the
muscle. Subsequently, axillary nodes have been divided
into five groups:
apical
central (in the fat of the axilla)
posterior (subscapular)
anterior (pectoral)
lateral (medial to the axillary vein) nodes.

EPITROCHLEAR
Epitrochlear or supratrochlear nodes are located
superficial to the deep fascia of the arm and medial to
the basilic vein and proximal to the medial epicondyle.
MEDIASTINAL
Bronchopulmonary lymph nodes (Nodi lymphoidei
bronchopulmonales)Mediastinal lymph nodes are divided
into nine stations.
They include those found in the hilum of the lungs, the
juxta-oesophageal nodes, and superior and inferior
tracheobronchial nodes.
There are also posterior mediastinal nodes.
The thymus, which is a primary lymphatic organ, is also
found in the anterior mediastinum.

ABDOMINAL
Throughout the abdominopelvic region there are
numerous groups of nodes associated with specific
viscera and adjacent to the main vascular structures
within the region.
Those associated with the vascular structures include
the para-aortic and mesenteric (superior and inferior)
nodes, common, internal and external iliac nodes, and
the superior and middle rectal nodes

INGUINAL
The inguinal lymph nodes are defined as superficial or
deep based on their relationship to the fascia lata of the
thigh.
The group of nodes superficial to the fascia lata are
the superficial inguinal nodes. They are further
subdivided into inferior, superolateral and superomedial
nodes.
Those nodes deep to the fascia are the deep inguinal
nodes. The largest and most superior of the deep nodes
is the deep inguinal node of Cloquet. It is located in the
femoral ring.

DISEASE OF LYMPH NODES

CANCER DIAGNOSIS
Although cancerous lesions are the product of
unregulated cell proliferation, the metastatic process
usually follows a particular pattern. For carcinomas that
disseminate by way of the lymphatic system, they most
often come in contact with regional nodes (i.e. those
nodes that are closest to the origin of the tumor) before
moving on to the next tier of nodes in the series.
Therefore, these immediate regional nodes are referred
to as sentinel lymph nodes.

While classically the word sentinel referred to a soldier
who stands guard at a post, from a medical perspective,
sentinels are one of the first concrete indicators of
disease. This concept contributes to the notion that if
cancer is indeed present, then it is more likely to be first
found in a sentinel node than other lymph nodes. As a
result, clinicians are more inclined to perform a sentinel
lymph node biopsy in order to help diagnose and stage
individuals suspected to have cancer.
If a sentinel node is biopsied and no evidence of cancer
is observed, then it is unlikely that the patient has cancer.
On the other hand, if there is evidence of cancer cells
found on a sentinel lymph node biopsy, then the patient
has cancer and it is also likely that the cancer has spread
to nearby nodes. This information will assist with staging
of the cancer and the mode of therapy that will be
employed.

Lymphedema
Lymphedema is where Edema, or fluid collection, leads to
swelling of limbs and other regions drained by the
affected lymphatic channel.
The primary function of the lymph channels are to drain
the fluids of the body. When this is impaired there may
be swelling.
For example, if there is a blockage of the channels
draining the legs, there may be excessive swelling of the
leg.
It may be either primary or secondary. A primary
condition is inherited and may be because of impaired or
missing lymphatic vessels. This may appear at birth or
may develop later in life with no palpable reasons or
cause.

Secondary lymphedema usually occurs due to some
acquired condition that has led to the lymphatic channel
blockage or malfunctioning.
This could be after a surgery, injury or an infection. There
may be damage to the channels or to the lymph nodes.
For therapy compression bandages may be tried to allow
for adequate drainage of the accumulated lymph.

Lymphadenopathy
Lymphadenopathy occurs when the lymph nodes swell
due to infections.
For example, an infection of the leg such as an abscess or
cellulitis may lead to swelling of lymph nodes at the
groin. These lymph nodes may be painful, red, warm and
tender to touch.
Viral infections like measles, German measles (rubella),
glandular fever, HIV AIDS etc. may also cause
lymphadenopathy of all the lymph nodes.
Some conditions like rheumatoid arthritis affect the
immunity and may lead to swollen lymph nodes.

Lymphadenitis
Lymphadenitis is inflammation of the lymph nodes usually
caused due to infections
Lymphoma
Lymphoma is cancer of the lymphatic system. This cancer
may be of various forms.
The major classes are Hodgkin’s and Non-Hodgkin’s
lymphomas. These start as the lymphocytes in lymph
nodes turn cancerous.
The lymphomas can begin in the stomach or intestinal
lymph nodes as well.
Symptoms of lymphoma include fatigue or tiredness,
fever, propensity for infections, unexplained weight loss
and excessive sweating at night.
Other cancers like breast cancer (affects lymph nodes of
the arm pit) may also spread to the nearest lymph nodes.

Filariasis
Filariasis is infection of the lymphatic channels by a worm
or parasite.
Splenomegaly
This is where the spleen is swollen due to a viral infection
like infectious mononucleosis.
Tonsilitis
Tonsilitis is where the tonsils become infected, inflamed
and swollen.
The tonsils normally protect the entrance of the
gastrointestinal tract and the respiratory tract. The
infection may lead to sore throat, fever, and severe
difficulty and pain while swallowing.

LYMPH NODES

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LYMPH NODES