The lymphatic system includes tissues and organs that produce, store, and carry white blood cells to fight infections. It develops beginning in the fifth week of embryonic life from lymph sacs that become lymph vessels and organs. The main components are lymph, lymph organs like lymph nodes and the spleen and thymus, lymph vessels, and lymphoid tissues. The lymphatic system works to drain fluid into the bloodstream, filter lymph and blood, and help the body fight infections by producing lymphocytes and macrophages.

2. Definition
The tissues and organs that produce, store, and carry
white blood cells that fight infections and other
diseases.
This system includes the
Bone Marrow
Spleen
Thymus

3. Development
Development starts by the end of the fifth week of
embryonic life.
The lymphatic system begins as a series of sacs 108 at
the points of junction of certain of the embryonic
veins.
The lining walls of its vessels are always endothelial.
These lymph-sacs are developed by the confluence
of numerous venous capillaries, which at first lose
their connections with the venous system, but
subsequently, on the formation of the sacs, regain
them.

4. Development in Human Embryo
In human embryo the lymph sacs from which the
lymphatic vessels are derived are six in number.
Two paired Jugular Lymph sac
At the junction of the internal jugular and subclavian veins.
Retroperitoneal Lymph sac
At the root of the mesentery of the intestine. develops from
the primitive vena cava and mesonephric veins

Posterior Lymph sacs
Develop from the iliac veins

5. Lymphatic System Components
Lymphatic system components includes :
Lymph
Lymph Organs
Lymph Vessels
Lymph Tissues

6. Lymph
Lymph means clear water and it is basically the
colorless fluid and protein that has been squeezed out
of the blood.
Lymph is a fluid similar in composition to blood
plasma.
Changes in plasma composition will change lymph
composition.
 Protein concentration of lymph is lower than in
plasma and varies inversely proportional to rate of
formation that varies from tissue to tissue.

7. Lymph flow rate
 Lymph flow rate is usually low. It is influenced
primarily by the rate of lymph formation.
The flow rate is affected by compression of
lymphatics by negative intrathoracic pressure
(breathing).
Valves in the lymph vessels prevent retrograde flow
similar to those in veins.

9. Formation of lymph
 ISF forms at the arterial (coming from the heart) end
of the capillaries because of higher pressure of blood,
Most of it returns to its venous ends and venules; the
rest (10—20%) enters the lymph capillaries as lymph.
Thus lymph formed is a watery clear liquid with the
same composition as the ISF.
 As it flows through the lymph nodes, however, it
comes in contact with blood and tends to accumulate
more cells (particularly lymphocytes) and proteins.

11. Lymphatic Organs
An organ that is characterized by clusters of
lymphocytes and other cells, such as macrophages,
enmeshed in a framework of short, branching
connective tissue fibers.
Formation:
The lymphocytes originate in the red bone marrow
with other types of blood cells and are carried in the
blood from the bone marrow to the lymphatic organs.

12. Types of Lymphatic organs
Primary lymphatic organs
Thymus gland
 Bone marrow
Secondary lymphatic organs
 Encapsulated diffuse lymphoid tissue
includes the spleen and lymph nodes.
 Unencapsulated diffuse lymphoid tissue
includes gut-associated lymphoid tissues and
the tonsils.


13. Lymph nodes
One of a number of small swellings found at intervals
along the lymphatic system.
They are widely distributed throughout the body
along the lymphatic pathways.
 Lymph nodes are not present in the central nervous
system.
Composed of lymphoid tissue.

14. Structure of lymph nodes
Small bean-shaped structures
Usually less than 2.5 cm (1 inch) in length.
Three superficial regions where lymph nodes tend to
cluster
1.
2.
3.
Inguinal nodes in the groin
Axillary nodes in the armpit
Cervical nodes in the neck

16. Function of Lymph nodes
Filter the lymph before it is returned to the blood
Preventing foreign particles from entering the
bloodstream
They also produce lymphocytes

17. Waxing, Waning of Lymph Nodes
Waxing and waning terms used to describe transient or
short-term fluctuations in the size of lymph nodes
that could be accounted
Response to treatment
Immune activation against lymphoma
Collapsing of necrotic areas in lymph nodes may
explain a sudden decrease in a large lymph node.
Lymph nodes may enlarge when immune cells react
to pathogen such as virus or bacteria.

18. Swollen
Lymph
Glands

19. Tonsils
Cluster of lymphatic tissue just under the mucous
membranes that line the nose, mouth, and pharynx
(throat) called tonsils.
There are three groups of tonsils.
1. Pharyngeal tonsils
2. Palatine tonsils
3. Lingual tonsils
Provide protection against harmful substances and
pathogens that may enter the body through the nose
or mouth.

21. Enlarge
Tonsil

22. Spleen

23. Function of Spleen
Filters blood
Stores blood

24. Thymus
Primary lymphatic organ in the body; it is located
over the heart and/or in the neck area, anterior to the
ascending aorta and posterior to the sternum.
The thymus consists of two lobes enclosed in a
capsule and is further divided internally
Function of the thymus is the processing and
maturation of special lymphocytes (white blood cells)
called T-lymphocytes or T-cells, which are associated
with antibody production.

27. Lymphatics
Tubular vessels transport back lymph to the blood
ultimately replacing the volume lost from the blood
during the formation of the interstitial fluid.
Lymph capillaries
Lymph vessels
Lymphatic trunks
Lymphatic ducts

28. The two main lymph ducts are:
 Right
lymphatic duct
 Thoracic duct
Structure of lymphatics is based on that of blood
vessels.
 Inner lining of single flattened endothelial cells
 Smooth muscles arranged in a circular fashion
around endothelial cells
 Outermost layer consists of fibrous tissue

30. Lymphoid Tissues
Specialized form of reticular connective tissue that
contains various types of white blood cells enmeshed
In it, most numerous being the lymphocytes.
Lymphoid tissue can be of three types depending
upon the stage of lymphocyte development and
maturation.
 Primary(central) lymphoid tissue
 Secondary(peripheral) lymphoid tissue
 Tertiary lymphoid tissue

31. Function of Lymphoid Tissues
Makes up the spleen, the thymus, and the tonsils, as
well as visceral nodes, and lacteals which are all
associated with mucous membranes of the gastrointestinal tract.
Concerned with immune functions in defending the
body against the infections and spread of tumors.

32. Functions of Lymphatic System
Draining fluid into the bloodstream
Filtering lymph
Filtering the blood
helps fight infection in many ways such as
Helping to make special white blood cells
(lymphocytes) that produce antibodies

Having other blood cells called macrophages
inside the lymph nodes which swallow up and kill any
foreign particles,


33. Draining
Fluid
into
Bloodstream