Anatomy & Physiology - LYMPHATIC SYSTEM PPT By wincy Thirumurugan

ANATOMY AND PHYSIOLOGY OF LYMPHATIC SYSTEM
BY.MRS.WINCY THIRUMURUGAN
PROFESSOR.

OVERVEIW:
Lymphatic system is considered as a part of both
the circulatory and immune systems.
The lymphatic system begins with the lymphatic
capillary meshwork that collects the excessive fluid
from the tissues..
The lymphatic system involves many organs,
including the tonsils, adenoids, spleen, and
thymus. Lymph nodes filter out bacteria and cancer
cells and create white blood cells to fight infection.
These nodes are found throughout the body (neck,
armpits, groin, chest, and abdomen).

DEFINITION:
The lymphatic system is a network of vessels
and organs that regulates the amount of fluid
in the human body and defends it against
infections.
OR
The lymphatic system consists of lymphatic
vessels, a fluid called lymph, lymph nodes,
the thymus, and the spleen.
The lymphatic system is a system of
specialized vessels and organs whose main
function is to return the lymph from
the tissues back into the bloodstream.

Lymph
Lymph is a transudative fluid that is transparent and
yellow. It is formed when fluid leaves the capillary bed in
tissues due to hydrostatic pressure.
Roughly 10% of blood volume becomes lymph.It is created
as a result of the filtration of the plasma.
The plasma from the blood diffuses through the porous
capillary wall into the tissues to deliver nutrients.
After feeding the hungry cells on the periphery, the
majority of fluid gets reabsorbed back into the blood
vessels, while around 10% of the fluid stays in the tissue.
That amount of residual fluid in the tissues is
called the interstitial fluid. When the interstitial fluid gets
absorbed into the lymphatic capillaries it becomes the
lymph.

LYMPHATIC VESSELS :
THE TUBAL STRUCTURES CARRY THE LYMPH FLUID
FROM THE TISSUE TO THE BLOOD STREAM.
The lymph travels from the tissues through larger lymph
vessels until it reaches its destination point; the bloodstream.
On the way, it traverses lymphoid organs filled with
immune cells that monitor if there are any pathogens in the
incoming lymph.
TYPES OF VESSELS :
AFFERENT VS EFFERENT LYMPH VESSELS:
Lymphatic vessels that carry lymph towards the lymph
node are known as afferent, whereas the vessels that carry
lymph away from the lymph node are
called efferent lymphatic vessels.

Lymphatic capillaries
Lymphatic capillaries are the smallest
lymphatic vessels that collect the interstitial
fluid from the tissues. They are organized in
networks called lymphatic plexuses.
Plexuses converge to make larger lymphatic
vessels that carry the lymph away from the
tissues and into the bloodstream.
There are also special types of lymphatic
capillaries called lacteals. These capillaries
absorb nutrients from the small intestine.

COMPOSITION OF THE LYMPH FLUID:
The composition of lymph is fairly similar to that of blood
plasma, with the majority of the volume (around 95%)
comprised of water.
The remaining 5% is composed of proteins, lipids,
carbohydrates (mainly glucose), various ions and some cells
(mainly lymphocytes), although this can vary depending on
where in the body the lymph is produced.
For example, chyle (lymph that is produced in the
gastrointestinal system) is particularly rich in fats.
VOLUME OF LYMPH :
The average adult produces between 3-4 litres of lymphatic
fluid each day, although this can vary in illness.

Lymphatic pathway/circulation:
The lymphatic system (also called the
lymphoid system) is part of the immune
system.
The system moves lymph, a clear fluid
containing white blood cells from the
tissue through afferent lymphatic
vessel,lymph nodes,efferent lymphatic
vessels,lymphatic trunk,lymphatic duct
and the right subclavian vein into the
superior venacava and mix with the
venous blood.

Lymphatic pathway/circulation:
lymph from the
tissue through
afferent
lymphatic
vessel,
lymph nodes
efferent
lymphatic
vessels,
lymphatic
trunk
lymphatic duct
the right
subclavian vein the right
subclavian vein
superior
venacava
mix with the
venous blood.

TYPES OF LYMPHATIC VESSELS
SUPERFICIAL AND DEEP LYMPHATIC VESSELS.
The superficial vessels are located in the subcutaneous layer
of the skin where they collect the lymph from
the superficial structures of the body. They tend to follow the
drainage of the venous system and in the end, drain into deep
lymphatic vessels.
The deep lymphatic vessels carry lymph from internal
organs. In contrast to the superficial vessels, the deep vessels
are accompanied by the arteries. These arteries lean onto the
walls of the deep lymphatic vessels, putting pressure upon
them and helping the flow of the lymph.
Along the way, both superficial and deep lymphatic vessels go
through lymph nodes that monitor the content of the lymph.

LYMPHATIC TRUNKS:
The efferent vessels empty into the lymphatic trunks. The
lymphatic trunks are named according to the region of the
body that they drain the lymph from.
There are four pairs of trunks:
1. Lumbar,
2. Bronchomediastinal,
3. Subclavian and
4. Jugular.
There is also one unpaired intestinal lymph trunk, that
drains lymph from the majority of organs of the
gastrointestinal tract. The duct opens in the cisterna
chyli which is the dilated origin of the thoracic duct.

LYMPHATIC DUCT:
The lymphatic trunks then converge into the two
lymphatic ducts; the right lymph duct and thoracic
duct.
 The RIGHT LYMPHATIC DUCT collects lymph
from the right upper limb and the right side of
the head and chest.
 The THORACIC DUCT is a larger vessel and
collects lymph from the rest of the body.
The lymphatic ducts take the lymph into the right
and left subclavian veins, which flow into
the superior vena cava.

Lymphatic vessels vs. blood vessels
The lymphatic vessels should not be confused with blood
vessels.
First of all, the lymphatic system is a one-way street starting
blindly in the tissues and opening into the circulatory system
on the other end.
On the other hand, the venous and arterial vessels of
the circulatory system vessels are connected by capillary
networks and thus the blood flows in circles.
The lymphatic system doesn’t have a pump that can regulate
the pressure of the flow of the lymph like the circulatory
system has (the heart). Instead, the lymph flows thanks to
the movements of the body, pulsation of the arteries and
contractions of skeletal muscles.

Lymphatic vessels vs. blood vessels
The lymphatic vessels have valves that prevent the
lymph flowing backwards.
Lymphatic vessels are located throughout the whole
body but note that some tissues and organs are
lacking the lymphatic
vessels(e.g. epidermis, cartilage, bone marrow, the
structures of the eye).
For a long time, it has been believed that the central
nervous system doesn't contain lymph vessels. Now
there is convincing evidence that the lymphatics do
exist in some parts of the central nervous system.

Lymphoid organs :
The Lymphoid organs are the sites where the
maturation and proliferation of lymphocytes occur
and help carry out various immune functions.
OR
the Lymphoid organs are specialized tissues that
provide the typical anatomic location and
microenvironment, which helps in attaining maturity
of lymphocytes and thus, activates them.

Types of Lymphoid Organs
The lymphatic system is
composed of three types of
lymphoid organs which are as
follows:
1. Primary lymphoid Organs
2. Secondary lymphoid Organs
3. Tertiary lymphoid Organs

1. Primary Lymphoid Organs
I. Primary lymphoid organs are those organs
where B and T-lymphocytes mature and acquire
antigen-specific receptors.
II. These organs are the sites of origin and
proliferation of lymphocytes. Thus, they are also
called central lymphoid organs.
III. After the maturation of lymphocytes, they
migrate to the secondary lymphoid organs.
IV. These organs include bone marrow and
thymus (and the bursa of Fabricius in birds).

a) Bone Marrow
1) It is a sponge-like tissue found inside the long bones.
2) The red bone marrow is involved in the immune system working.
3) It is the main lymphoid organ where all blood cells, including
lymphocytes, are produced and multiply.
4) At the time of birth, many bones contain red bone marrow, which
actively creates immune system cells. In adulthood, only a few of our
bones contain red bone marrow, including the ribs, breastbone, and
pelvis.
5) Bone marrow is primarily responsible for both the creation of T-cell
precursors and the production and maturation of B cells.
6) Maturation of B-lymphocytes completes in the bone marrow only.
On the contrary, T-cells travel from the bone marrow to the thymus,
where they develop further and mature.
7) From the bone marrow, B cells immediately join the circulatory
system and travel to secondary lymphoid organs in search of
pathogen

b) Thymus
1) The thymus is a bi-lobed, pinkish-grey organ located
behind the breastbone and above the heart.
2) It is quite large in size at the time of birth but keeps
reducing with age. It reaches full maturity only in children
and then slowly transforms into fatty tissue.
3) It is the site where T-lymphocytes mature. T-cells begin
as hematopoietic precursors from the bone marrow and
eventually migrate to the thymus, where they are referred to
as thymocytes.
4) T-cells mediate the cell-mediated immune response
(CMIR).
5) Thymus also secretes a family of hormones collectively
known as thymosin which is essential for the normal
functioning of the immune system.

2. Secondary Lymphoid Organs
I. Secondary lymphoid organs are the sites where B
and T-lymphocytes undergo proliferation and
differentiation.
II. They interact with the antigens and become
effector cells. They are also called the peripheral
lymphoid organs.
III. They are associated with the initiation of the
adaptive immune response.
IV. In the secondary lymphoid tissues, the
lymphocytes move from one lymphoid organ to
another through blood and lymph.
V. These organs include lymph nodes, spleen,
tonsils, Peyer’s patches of the small intestine,
and Mucosal associated lymphoid tissues

a) Lymph Nodes
1) These are small bean-shaped tissues found at intervals
along the lymphatic system composed of lymphoid tissue.
2) These are an organized collection of lymphoid tissue,
through which the lymph passes on its way back to the
blood.
3) These are the first organized lymphoid structures that
encounter the antigens entering the tissue spaces.
4) In the germinal centre of these lymph nodes, the selection
of B lymphocytes occurs.
5) They act as filters for the lymph, preventing foreign
particles or germs from entering the bloodstream and also
activate the production of special antibodies in the blood. It
also produces lymphocytes and plasma cells.
6) Swollen or painful lymph nodes indicate that the immune
system is active, i.e., fighting against an infection.

LYMPH NODES
Lymph nodes are kidney shaped structures which act to
filter foreign particles from the blood, and play an
important role in the immune response to infection.
On average, an adult has around 400 to 450 different lymph
nodes spread throughout the body – with the majority
located within the abdomen.
Each node contains immune cells they are exposed to the
fluid as it passes through the node, and can mount
an immune response if they detect the presence of a
pathogen.
This immune response often recruits more inflammatory
cells into the node – which is why lymph nodes
are palpable during infection.
Lymph fluid enters the node through afferent lymphatic

b) Spleen
1) It is a large bean-shaped organ located in the left upper
abdomen and beneath the diaphragm. It is the largest
lymphoid organ. This appears due to more blood flow through
it.
2) In the foetus, the spleen produces all types of blood cells,
but in adults, it only produces lymphocytes and phagocytes.
3) It is a large reservoir of erythrocytes (or RBCs). At maturity,
it removes particulate matter and aged blood cells, mainly red
blood cells.
4) The spleen is involved in the synthesis of antibodies in its
white pulp. By way of blood and lymph node circulation, the
spleen is also involved in the removal of antibody-coated
bacteria and antibody-coated blood cells.
5) If the spleen is removed completely, then the other immune
systems can carry out their functions.

The lymph nodes are secondary lymphoid organs
distributed throughout the whole body, grouped
according to the body regions they are in
(e.g. axillary, pelvic, mediastinal lymph nodes).
The lymph nodes house lymphocytes and other immune
cells (e.g. macrophages, plasmocytes, dendrocytes).
Macrophages located within the sinuses of the lymph
node act to filter foreign particles out of the fluid as it
travels through and the lymph nodes serve as a filtration
point for the lymph that travels towards the venous
system.
In case the immunocytes detect a foreign particle in the
lymph (e.g. microorganism), they will start the immune
response to prevent the harming particle from

c) Tonsils
1) The tonsils (also called palatine tonsils) are a pair
of soft tissue masses located at the rear of the throat
(pharynx).
2) Since they are located at the throat and the palate
regions, they can stop the germs from entering the
body through the mouth or the nose. 3) There are
different types of tonsils like palatine tonsils,
adenoids, and the lingual tonsil, which are
sometimes together called Waldeyer’s ring because
they form a ring around the opening to the throat
from the mouth and nose.
4) They act as filters to protect the body from
bacteria and viruses and also contain white blood
cells, which are responsible for killing germs.

d) Peyer’s Patches
1) Peyer’s patches are small clusters of lymphoid follicles found
throughout the mucus membrane of the small intestine,
especially along the ileum. They are also called aggregated
lymphoid nodules.
2) These are an important part of gut associated lymphoid
tissue (GALT). They are located within both the small and large
intestines of many mammalian species.
3) Pathogenic microorganisms, any form of antigens, etc. which
enter the intestinal tract come across the macrophages,
dendritic cells, B-lymphocytes, and T-lymphocytes found in
Peyer’s patches.
4) T cells, B-cells and memory cells are stimulated when
antigens come in contact with Peyer’s patches.
5) They play an important role in the immune system by
monitoring the intestinal bacteria populations and thus
preventing the growth of pathogenic bacteria in the intestines.

e) Mucosal-Associated Lymphoid Tissues (MALT)
1) MALT is a significant aggregate of lymphoid tissues
located in the mucosal lining of the major tracts like
respiratory, digestive, and urinogenital tracts.
2) MALTs are concentrations of many lymphoid tissues
found in the various submucosal membrane sites of the
body, like the gastrointestinal tract, nasopharynx, thyroid,
breast, lung, salivary glands, eye, and skin.
3) It constitutes about 50%50% of the lymphoid tissues in
the human body.
4) They do not serve as the filters of lymph but are the
centres of lymphocyte production.
5) Apart from B-lymphocytes and T-lymphocytes,
phagocytic macrophages and dendritic cells are also
present.

3. Tertiary Lymphoid Organs
I. Tertiary lymphoid organs are generally found at the sites of
chronic inflammation in autoimmune diseases (like rheumatoid
arthritis).
II. These organized accumulations of T and B cells basically
resemble secondary lymphoid organs and generate
autoreactive effector cells.
III. Tertiary lymphoid organs usually contain very few
lymphocytes that assume their role when they encounter the
antigens that cause inflammation.
IV. These organs also play a prominent role in the immune
response to cancer.

The Lymphoid Organs Functions
The functions of lymphoid organs are as follows:
1. The main function of lymphoid organs is developing and
providing immunity to the body.
2. The primary lymphoid organs, i.e., the bone marrow and
thymus, are the sites where the proliferation and maturation of
B-lymphocytes and T-lymphocytes take place.
3. Bone marrow is involved in the production of blood cells,
i.e., RBCs (or erythrocytes), WBCs (or leucocytes), and
Platelets (or thrombocytes).
4. The spleen helps in the removal of damaged red blood
cells. In foetal conditions, this is also a haematopoietic organ.
5. Lymph nodes and spleen helps in filtering out and
destroying the unwanted lymphocytes. They also help in
maintaining the population of mature lymphocytes to enable
the adaptive immune response to begin.
6. The tonsils prevent foreign materials and pathogens from
entering the body.

Lymphocytes
 Lymphocytes are a type of WBC (leucocytes) that are the main
components of our immune system. There are two types of
lymphocytes, T-lymphocytes, and B-lymphocytes.
 The lymphocytes are one of the body's main immune cells. They arise
from the stem cells in the primary lymphoid organs and belong to the
part of the immune system called the acquired immunity.
 After maturation, the lymphocytes are distributed mainly in the
secondary lymphoid organs.
 According to their histology and functional characteristics, the
lymphocytes are divided into three major groups; B lymphocytes, T
lymphocytes and natural killer (NK) cells. Their main role is to
establish a specific immune response to foreign particles (antigens).
 B lymphocytes destroy the antigens indirectly, by producing antigen-
specific antibodies that attach to antigens and mark them for
destruction.
 On the other hand, T lymphocytes and NK cells directly kill cells that
are infected by viruses or become cancerous.

• Lymphocytes are white blood cells that help the body
fight infection and disease. The normal range for an
adults is between 1,000 and 4,800 lymphocytes in 1
microliter (µL) of blood.
• In children, the normal range is between 3,000 and
9,500 lymphocytes in 1 µL of blood.
• The immune system is a complex network of cells known
as immune cells that include lymphocytes. These cells
work together to defend the body against foreign
substances, such as bacteria, viruses, and cancer cells
that can threaten its functioning.

TYPES OF B -LYMPHOCYTE:
There are different types of B cells and T cells that have specific roles in the body
and the immune system.
B cells
There are also several types of B cells:
Memory B cells
Memory B cells circulate in the body to start a fast antibody response when they
find a foreign substance. They remain in the body for decades and become
memory cells, which remember antigens and help the immune system respond
faster to future attacks.
Regulatory B cells
Regulatory B cells, or Bregs, only account for a small number of B cells in healthy
people. Although few in number, they have a vital role to play.
Bregs have protective anti-inflammatory effects in the body and stop lymphocytes
that cause inflammation. They also interact with several other immune cells and
promote the production of regulatory T cells, or Tregs.
Plasma cells
Plasma cells are terminally differentiated B cells that produce antibodies and are
responsible for antibody-mediated immunity. Terminally differentiated cells are
cells that become specialized to a point after which they can no longer divide.

TYPES OF T- LYMPHOCYTE:
There are several types of T cells:
Killer T cells
Killer, or cytotoxic, T cells scan the surface of cells in the body to see if they have
become infected with germs or turned cancerous. If so, they kill these cells.
Helper T cells
Helper T cells “help” other cells in the immune system to start and control the
immune response against foreign substances.
There are different types of helper T cells, and some are more effective than
others against different types of germs.
Regulatory T cells, or Tregs
Tregs control or suppress other cells in the immune system. They have both
helpful and harmful effects.
They maintain tolerance to germs, prevent autoimmune diseases, and limit
inflammatory diseases. But they can also suppress the immune system from doing
its job against certain antigens and tumors.
Memory T cells
Memory T cells protect the body against antigens that they have previously
identified. They live for a long time after an infection is over, helping the immune
system remember previous infections.
If the same germ enters the body a second time, memory T cells remember it and
quickly multiply, helping the body fight it more quickly.

FUNCTIONS /PHYSIOLOGY OF LYMPHATIC SYSTEM
 The lymphatic system has several crucial functions for maintaining
body homeostasis which include: maintaining the body's fluid
balance, transportation of large molecules and immune surveillance.
 The fluid balance is maintained by draining the extra fluid that
remains after the exchange of blood and nutrients between the tissues
and capillaries. If not regularly drained, this amount of fluid can
accumulate and cause swelling (edemas).
 The lymphatic organs house numerous immune system cells which
surveil the content of the lymph as it flows toward the venous system.
If a foreign particle is detected, the immune cells start an immune
response to destroy the pathogen and prevent the infection and
damage. The lymphatic system filters the lymph by destroying
pathogens, inactivating toxins, and removing particulate matter.
 Lymph nodes, small bodies interspersed along lymphatic vessels, act
as cleaning filters and as immune response centers that defend against
infection.

CONTI……
 This system supplements and extends the
cardiovascular system in the following ways:The
lymphatic system collects excess fluids and plasma
proteins from surrounding tissues (interstitial fluids) and
returns them to the blood circulation. Because lymphatic
capillaries are more porous than blood capillaries, they
are able to collect fluids, plasma proteins, and blood cells
that have escaped from the blood.
 The lymphatic system absorbs lipids and fat‐soluble
materials from the digestive tract. Lymph also carries
the molecules that are too large to diffuse through the
capillary wall (e.g. proteins or lipids). This is why the
small intestine has a vast lymphatic drainage, as it is the
site where the lipids and proteins are absorbed from

Clinical Relevance
 lymphoma is one of a group of tumours developing
from lymphatic cells. Lymphedema: This is an
accumulation of lymph fluid in the body. It most commonly
occurs in the arms and legs. It ranges from mild to very
painful. It is common in people who have received cancer
treatment.
 Lymphatic filariasis: Also called elephantiasis, this infection
is caused by a parasite that infects the body through a
mosquito bite. The worms invade the lymphatic system,
resulting in a blocked lymphatic system and swelling, pain,
and disfigurement.
 Lymphadenopathy: This is the medical term for swollen
lymph nodes. Lymph nodes, themselves, can become
infected, but swollen lymph nodes also indicate an infection
within the body.

CONTI……
 Lymphadenitis: This term refers to an infection of the lymph node(s).
This infection often occurs due to germs that spread through the
lymphatic system from one part of the body to the lymph nodes.
 Lymphangitis: Inflammation of the lymph vessels, which may result
from some bacterial infections.
 Lymphocytosis: This condition is a higher than normal amount of
lymphocytes, often a result of your body dealing with infection or
inflammation.
 Castleman disease: This condition is an overgrowth of cells in the
lymphatic system. An infection causes it. It may result in a full feeling
in the abdomen, lumps in the armpits, groin, neck, and weight loss.
 Mesenteric lymphadenitis: This is inflammation of lymph nodes in the
abdomen. An infection causes it, and it usually affects children and
teenagers.
 Tonsillitis: An infection of the tonsils, resulting in a very sore throat.

REFERENCE :
1. Available From :https://www.khanacademy.org/science/in-in-class-12-
biology-india/xc09ed98f7a9e671b:in-in-human-health-and-disease/xc09ed
2. Available From :Lymphoid Organs: Definition, Types, Functions, Examples –
Embibe
3. Available
From:https://www.bing.com/images/search?view=detailV2&ccid=ATNqHuiN
&id=377A360442C1E23C9DC6140D786AB2579E53D701&th
4. Available From
:https://www.bing.com/images/search?view=detailV2&ccid=ATNqHuiN&id=3
77A360442C1E23C9DC6140D786AB2579E53D701&th

Anatomy & Physiology - LYMPHATIC SYSTEM PPT By wincy Thirumurugan

Anatomy & Physiology - LYMPHATIC SYSTEM PPT By wincy Thirumurugan

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