The lymphatic system is a network of tissues, vessels and organs that work together to move a colorless, watery fluid called lymph back into your circulatory system (your bloodstream). Some 20 liters of plasma flow through your body’s arteries and smaller arteriole blood vessels and capillaries every day. After delivering nutrients to the body’s cells and tissues and receiving their waste products, about 17 liters are returned to the circulation by way of veins. The remaining three liters seep through the capillaries and into your body’s tissues. The lymphatic system collects this excess fluid, now called lymph, from tissues in your body and moves it along until it's ultimately returned to your bloodstream. Your lymphatic system has many functions. Its key functions include: Maintains fluid levels in your body: As just described, the lymphatic system collects excess fluid that drains from cells and tissue throughout your body and returns it to your bloodstream, which is then recirculated through your body. Absorbs fats from the digestive tract: Lymph includes fluids from your intestines that contain fats and proteins and transports it back to your bloodstream. Protects your body against foreign invaders: The lymphatic system is part of the immune system. It produces and releases lymphocytes (white blood cells) and other immune cells that monitor and then destroy the foreign invaders — such as bacteria, viruses, parasites and fungi — that may enter your body. Transports and removes waste products and abnormal cells from the lymph.

1. LYMPHATIC SYSTEM
Pawan Kumar Sahu
Lecturer at
Rudauli College of Pharmacy,
Ayodhya (U.P.)

2. LYMPHATIC SYSTEM DIAGRAM

3. INTRODUCTION
Lymph is a tissue fluid which is formed by the passage of substances from blood
capillaries into tissue spaces.
It flows in a closed system called Lymphatic System.
This system consists of lymph vessels, lymph capillaries, lymph nodes etc.
Composition of lymph:-
Lymph is a colorless fluid which consists of blood plasma and lymphocytes but not
platelets.
It is alkaline in reaction.
It contains low proteins and nutrients. Lymph from intestine contains a high amount of
fat. Fluid from the intestines called chyle, which contains proteins and fats.

4. FUNCTION OF LYMPHATIC SYSTEM
Lymph nodes perfect the body against infection by filtering and destroying
bacteria.
Also, lymph nodes are the sites where lymphocytes are produced.
The lymphatic's drain the excess fluid from tissues back to circulation.
The lymphatic carry waste products from tissues to blood.
Function of Lymph:-
Lymph is formed by filtration of tissue fluid into lymphatic capillaries.

5. LYMPHATIC SYSTEM
It is a closed system through which lymph flows. The system consists of lymph
capillaries, lymph vessels and lymph nodes etc.
The lymphatic system initially start with lymphatic capillaries. They are thin walled
capillaries similar to blood capillaries. These capillaries are composed of a single
layer of cells.
From the lymphatic capillaries, lymph flows into collecting trunks.
The collecting trunks end up in lymphatic vessels. In the course of these vessels,
there are some lymph nodes.
The lymphatic vessels unite to form larger trunks. These trunks open into the right
lymphatic duct and thoracic duct.

6. LYMPHATIC SYSTEM
These ducts open into subclavian vein.
Villi of the small intestine contain small lymphatic vessels called lacteals. The
digested fat is absorbed through these lacteals. The lymph that flows through these
vessels is called chyle. Chyle contains a high amount of fat.

7. LYMPH NODES
These are small, oval or bean shaped glands present in the course of lymphatic
vessels.
Lymph nodes are clustered throughout the body, including the neck (cervical lymph
nodes), groin (inguinal lymph nodes), and armpits (axillary lymph nodes). There
are internal lymph nodes in the abdomen (mesenteric and retroperitoneal), chest
cavity (mediastinal), and lower abdomen (pelvic).
Swollen lymph nodes (lymphadenopathy) can occur in response to an infection or
disease in any part of the body. When a lymph node is infected and becomes
swollen, it is referred to as lymphadenitis.
Cancer can also affect lymph nodes either as it spreads from a tumor or starts in
the lymph nodes themselves (lymphoma).

8. THE LYMPH GLAND CONTAINS:-
A concave border called hilum.
An outer dense fibrous tissue called capsule.
The capsule gives rise to fibrous bands called trabaculae. The trabaculae divide the
substance of the nodes into irregular spaces.
The spaces between the trabaculae contain lymphoid tissues (which produces
lymphocytes).
Through the hilum pass:
An afferent lymphatic vessel (for entry)
An efferent lymphatic vessel (for exit)
Arteries and veins.

9. SECTION OF LYMPH NODES

10. FUNCTION OF LYMPH NODES
They filter out solid particles including bacteria.
They produce lymphocytes.
Production of plasma proteins like globulin. (This is done by dissolution and
disintegration of lymphocytes)
Lymph nodes support the immune system by trapping foreign agents and killing
them.
They do so by filtering bacteria, viruses, and other disease-causing agents
circulating in the lymphatic system. White blood cells, called lymphocytes, are then
recruited to control infection.

11. TERMINOLOGY
Lymphatic ducts:-
The two main lymphatic ducts are thoracic ducts and right lymphatic ducts.
After filtration by the lymph nodes, the lymph is emptied by lymphatic vessels into
these two lymphatic ducts.
Thoracic duct:-
It is the larger lymphatic duct.
It drains lymph from the pelvis, abdomen, left half of throax, left arm, head and
neck.
It pours its contents into the left subclavian vein.

12. TERMINOLOGY
Right lymphatic duct:-
It is small dilated lymph vessel about 1 cm long.
It drains lymph from the right half of thorax, right arm and also head and neck.
It empties into the veins at the right side of the root of the neck.
Other Lymphatic Tissues:-
In addition to lymph node, lymphatic tissues are present in the following sites:
1. Spleen
1. Spleen
2. Thymus
2. Thymus
3. Tonsils
3. Tonsils
4. Appendix
4. Appendix
5. Peyer’s Patches in intestine
5. Peyer’s Patches in intestine

13. SPLEEN
It is a dark purple colored lymphoid structure.
It is highly vascular and bean shaped and measures about 12 cm in length.
It is present in the left side of the abdominal cavity below the diaphragm.

14. STRUCTURE OF SPLEEN
Spleen contains the following structures:-
An outer covering of fibro-elastic tissue called Capsule.
Trabaculae arises from the capsule and pass into the substance of the gland.
The spaces between trabaculae contain the splenic tissue. These tissues contain the
lymphoid tissues called as Malphigian Corpuscles.
Spleen is supplied by splenic artery and drained by splenic vein.

15. FUNCTION OF SPLEEN
Spleen produces all types of blood cells during foetal life.
Red Blood Cells are destroyed in spleen.
Histocytes of spleen ingest and destroy foreign particles including bacteria.
Spleen serves as a reservoir of blood.
It also produces antibodies.

16. THYMUS
The thymus gland contains lymphoid tissue.
It lies in the thorax behind the sternum but in front of the heart and arch of aorta.
It weighs about 10 to 15 grams at birth and it grows until puberty.
Later it gradually decreases in size and shrinks.

17. STRUCTURE OF THYMUS
The thymus consists of two lobes which are joined by areolar tissue.
Each lobe is enclosed by a fibrous capsule which dips into the substance of
thymus and divides it into lobules.
The lobules contain epithelial cells and lymphocytes.
Functions:-
The thymus mostly contain lymphoid tissue.
It takes part in the production of T-Lymphocytes.
Notes:- T-lymphocytes are part of the immune system and develop from stem
cells in the bone marrow. They help protect the body from infection and may help
fight cancer. Also called T cell and thymocyte.

18. TONSILS
They are two collections of lymphoid tissues lying one on each side of the
pharynx between the pillars of fauces.
Tonsils contains masses of lymphoid tissue.
Also they are supplied with blood and lymphatic vessels.
The surface of tonsils is covered with mucous membrane which is studied by crypts.
Lymphocytes are present in these crypts also.
Notes:- The fauces is the narrow passage from the
mouth to the pharynx, situated between the soft
palate and the base of the tongue.

19. VILLI
They are minute projections which are present in the mucous coat of small
intestines.
They have a central lymphatic vessel called lacteal.
The lacteal communicates with lymphatic vessels in the submucous coat.
Through these vessels it communicates with cysterna chyli and then to thoracic duct.

20. PEYER’S PATCHES
Peyer’s patches resemble the look of the tonsils.
Location:- Peyer’s patches are found in the wall of the small intestine.
Function:- The macrophages of Peyer’s patches are in an ideal position to capture
and destroy bacteria (always present in tremendous numbers in the intestine),
thereby preventing them from penetrating the intestinal wall.
Mucosa-associated lymphatic tissue:- Peyer’s patches and the tonsils are part of
the collection of small lymphoid tissues referred to as mucosa-associated
lymphatic tissue (MALT); MALT acts as a sentinel to protect the upper respiratory
and digestive tracts from the never-ending attacks of foreign matter entering those
cavities.

21. PEYER’S PATCHES DIAGRAM