Unit-III, chapter-2- Lymphatic System, Functions of Lymphatic System, Major Parts of Lymphatic System, Composition of Lymph, Lymph and Lymphatic Capillaries, Structure of lymph node, Mechanisms of Lymph Flow, Functions of Lymph Node, Mucosa-Associated Lymphoid Tissue (MALT), As per PCI syllabus, B. Pharm. First Year, Human Anatomy and Physiology-I.

1. BP101T. Human Anatomy And Physiology-I (Theory)
Unit-III
2. Lymphatic system
Represented By,
Mr. Audumbar Mali.
(Assistant Professor)
Sahyadri College of Pharmacy Methwade

2. INTRODUCTION
• The lymphatic system is an accessory system for the flow of fluid from the
tissue space into the circulation
• Lymph is a fluid which is obtained at the interstitial space between the cell.
• The lymph contains old debris of dead tissue, protein molecule and dead
bacteria etc.
The lymphatic system is a network of tissues and organs that
help to the body free from toxins, waste and other unwanted
materials. The primary function of the lymphatic system is to
transport lymph, a fluid containing infection-fighting white
blood cells, throughout the body.

3. Functions of Lymphatic System: -
1.Tissue Drainage,
2.Absorption in the Small intestine,
3.Immunity.

4. Major Parts of Lymphatic System

5. Lymphatic System Consists of:-
 Lymph,
 Lymph Vessels
 Lymph Nodes
 Lymph Organs, eg. Spleen and Thymus,
 Diffuse Lymphoid tissue, eg. Tonsils,
 Bone Marrow.

6. Sr.n
o.
Constituents Blood/ 100 ml Lymph/100
ml
1 Urea 21.7 mg 23.5 mg
2 Non-protein
nitrogenous
substances
32.6 mg 34.8 mg
3 Creatine 1.37 mg 1.4 mg
4 Chlorides 678 mg 111 mg
5 Phosphorous 22 mg 11.8 mg
6 Calcium 11.7 mg 9.8 mg
1. Lymph:-
Composition of Lymph :
It contains large number of lymphocytes i.e. from 500-75000 cells/ cubic mm of
lymph
The Non- cellular part of lymph is as follows.
Water- 94%
Solids- 6%
Solids are
•Proteins 2-10%, the presence of protein varies from part to
part of body.
I] lymph from liver, contains 6% of proteins.
II] lymph from upper limb, contains 2% of proteins.
III] lymph from intenstine, contains 4% of proteins.
•During fasting the fat content is low but after fatty diet it will increases.
•Carbohydrate- sugar 132.2 mg/ 100 ml of lymph.
•Other constituents
Rate of flow of lymph
1 to 1. 5 ml/ minute from thoracic duct or left lymphatic duct.

7. Formation of Lymph
The formation of lymph is increases depend upon the tissue
fluid.
Factors responsible for lymph formation :
•Blood capillary Pressure
If the permeability of blood capillary increases due to any reason,
more tissue fluid will be formed, and recently there is more lymph formation.
•Rise in Temperature
If the temperature increases at a particular area, which increases the permeability of
blood capillary.
•The substances like peptones, foreign protein, histamine, extract of strawberry etc.
causes injuries to the blood capillary which increases permeability.
•Lack of oxygen increases the permeability of blood capillary.
•The substances which alter the osmotic pressure of blood will increases the formation
of lymph.
Ex. Hypo and hypertonic solution.

8. 21-8
Lymph and Lymphatic Capillaries
• Lymph
• clear, colorless fluid, similar to plasma but much less protein
• Lymphatic capillaries
• closed at one end
• It is surrounding tissue by protein filaments
• endothelial cells loosely overlapped
• allow bacteria and cells entrance to lymphatic capillary
• creates valve-like flaps that open when interstitial fluid pressure is high, and close
when it is low

9. Lymphatic Capillaries

10. Lymphatic Capillaries
•Lymphatic capillaries are tiny vessel lies besides the blood capillaries and found
in the intracellular spaces.
•The capillary walls are formed by endothelial cells and capillaries are
supported by fibrous connective tissue.
•These capillaries repeatedly join together to form a bigger vessel known as
lymphatic vessel, which passes through 8-10 lymph node and finally all the
lymph concluded into lymphatic duct.

12. 21-12
Lymphatic Vessels
• Larger and composed of 3 layers
• tunica interna: endothelium and valves
• tunica media: elastic fibers, smooth muscle
• tunica externa: thin outer layer

13. Lymphatic Collecting Vessels
• From the lymph capillaries, lymph flows to collecting
vessels
• Collecting vessels (lymphatics) in the skin travel with
superficial veins

14. Lymph Nodes
• Oval structures located along lymphatics
• Enclosed by a fibrous capsule
• Cortex = outer portion
• Germinal centers produce lymphocytes
• Medulla = inner portion
• Medullary cords
• Lymph enters nodes through afferent lymphatics, flows through sinuses, exits through
efferent lymhpatic

15. Lymph nodes are beanshaped structures about 0.1 – 2.5 cm in length.
The node is enclosed in a capsule and has an present 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.

16. Structure of lymph node:
•A concave border called as hilum or
hylus.
•An outer fibrous dense tissue called
capsule.
•The capsule give rise to partition
known as trabecules.
•The space between trabecules contain
reticular tissue, lymphatic tissue which
contain lymphocytes and macrophages.
•Through hylum afferent( entry) and
efferent (exit) blood vessels comes and
goes out.

17. Types of lymph node
The lymph nodes are arranged in deep and superficial group
•The lymph from head and neck passes through deep and
superficial cervical node.
•The lymph from organ and tissue in the thoracic cases passes
through many nodes such as parasternal, midsternal,
intercoastal node etc.
•The lymph from breast passes through axillary node.
•The lymph from pelvic and abdominal cavity passes
through many node before entering into cisternia chyli.
•The lymph from lower limb passes through deep and
superficial popleteal and inguinal node.

18. 21-18
Mechanisms of Lymph Flow
• Lymph flows at low pressure and speed
• Moved along by rhythmic contractions of lymphatic vessels
• stretching of vessels stimulates contraction
• Flow aided by skeletal muscle pump
• Thoracic pump aids flow from abdominal to thoracic cavity
• Valves prevent backward flow
• Rapidly flowing blood in subclavian veins, draws lymph into
it
• Exercise significantly increases lymphatic return

19. Functions of Lymph Node: -
• Filtering and Phagocytosis and
• Proliferation of Lymphocytes.
• Lymph nodes serve two major functions in the body. They filter lymph and
assist the immune system in building an immune response. Lymph is a clear
fluid that comes from blood plasma that exits blood vessels at capillary beds.
This fluid becomes the interstitial fluid that surrounds cells. Lymph vessels
collect and direct interstitial fluid toward lymph nodes. Lymph nodes house
lymphocytes which are immune system cells that originate from bone
marrow stem cells. B-cells and T-cells are lymphocytes found in lymph nodes
and lymph tissues. When B-cell lymphocytes become activated due to the
presence of a particular antigen, they create antibodies that are specific to
that specific antigen.

20. • The antigen is tagged as an intruder and labeled for destruction by other
immune cells. T-cell lymphocytes are responsible for cell-mediated immunity
and participate in the destruction of pathogens as well.
• Lymph nodes filter lymph of harmful pathogens such as bacteria and
viruses. The nodes also filter out cellular waste, dead cells, and cancerous cell.
The filtered lymph from all areas of the body is eventually returned to the
blood through a blood vessel near the heart. Returning this fluid to the blood
prevents edema or the excess accumulation of fluid around tissues. In cases
of infection, lymph nodes release lymphocytes into the bloodstream to aid in
the identification and destruction of pathogens.

21. Spleen :
•It is situated in the left hypochondric area of abdomen.
•It is dark, purple coloured lymphoid structure, bean shaped, highly vascular haemopoietic organ
situated in left hypochondriac region directly beneath the diaphragm above the left kidney and
descending colon behind the fundus of stomach.
• It about 12 cm in length, 7 cm wide, 2.5 cm thick present in the left side of abdominal cavity,
below the diaphragm and weight about 150- 200 gms.
Structure
Parts:
1] Capsule with outer covering layer peritoneum
2] Trabeculae with or without blood
vessels.
3] Hilus ( hilum)
4] White pulp scattered throughout
the red pulp.
5] Red pulp
6] Reticular network
7] Blood vessels

22. •A concave border called as hylus.
•It contains an outer covering of fibro elastic tissue called as capsule.
•The capsule give rise to partition known as trabaculae, which contain lymphoid tissue
known as Malpighian capsule.
•Spleen is supplied by spllenic artery and drain by spllenic vein they enter and exit
through hylus.
•Splenic Pulp: The Parenchymal tissue is enclosed within the capsule is the splenic
pulp.
A] White Pulp- Typical lymphatic tissue
B] Red Pulp- Atypical lymphatic tissue
White Pulp:
•The white pulps are seen scattered all throughout the red pulp as grey patches.
•These gray patches at early periods were described as Malpighian bodies.
•It is the accumulation of lymphatic tissue surrounding a major arterial vessel of spleen
(lymphatic tissue contains lymphocyte, plasma cells, macrophages)
•Infilteration lymphocytes are greater in the course of vessels forms spherical or ovoid
nodules which are called as splenic nodules.

23. Red Pulp:
•It is modified lymphatic tissue and mainly infiltrated with cells of the circulating blood, it
contains two components,
•Splenic Sinuses or Sinusoids :
- These are long vascular channels having 35 to 40µ in diameter.
- They may have an irregular course and may vary in diameter
•Splenic Cords:
- It appears continues partition between sinuses.
- These cords form a spongy network of modified lymphatic tissue that gradually merges into the
white pulp.
Marginal Zone :
It is the junctional region in between the white pulp and red pulp,
consists of meshwork of branched reticular cells in association with extracellular reticulum
(arterial vessels open)
Functions of Spleen: -
1. Phagocytosis,
2. Storage of Blood:- 350 ml
3. Immune Response,
4. Erythropoiesis:- Production of blood cells

24. Thymus Gland: -

25. The thymus gland is a secretory gland that has an important role in immune function. One of its main
secretions is the hormone thymosin. Thymosin stimulates the maturation of T cells, which are
derivatives of white blood cells that circulate our system.
Function of Thymus Gland: -
The main function of the thymus gland is to release thymosin hormone that will stimulate the maturation
of T cells. All of our childhood, white blood cells or lymphocytes will come in contact with the thymus
gland. This contact will transform them into T cells. Once the T cells have matured, they will migrate
to the lymph nodes which are the stores of immune cells in the body.
So, the thymus gland can be understood to be a recipient of immature T cells that were created in the bone
marrow but have yet to reach full maturation. Once the thymus receives the cells, they will be trained to
only attack foreign agents. The way this happens is through positive selection. Only the T cells that have
properly responded to foreign antigens will be selected to survive and eventually migrate to the medulla.
The T cells that do not make the cut will die by apoptosis in a healthy patient.

26. Once the surviving T cells have reached the medulla, the T cells will proceed to
mature. The remaining T cells will go on to kill pathogens, will activate helper B cells
that make antibodies against specific antigens, and will store the memories of previous
infections and viruses so that the body can be better prepared to fight them off if they
ever return.

27. Mucosa-Associated Lymphoid Tissue (MALT): -
MALT is also called mucosa-associated lymphatic tissue, is a diffuse system of
small concentrations of lymphoid tissue found in various submucosal membrane sites
of the body, such as the gastrointestinal tract, oral passage, nasopharyngeal
tract, thyroid, breast, lung, salivary glands, eye, and skin. MALT is populated by
lymphocytes such as T cells and B cells, as well as plasma cells and macrophages,
each of which is well situated to encounter antigens passing through the mucosal
epithelium. In the case of intestinal MALT, M cells are also present, which sample
antigen from the lumen and deliver it to the lymphoid tissue.
There are three types of situations in which MALT is present-
Tonsils, Appendix, Small Intestinal area
MALT constitute about 50% of the lymphoid tissue in human body.

28. References:
1. Human Anatomy and Physiology-I,
By Dr. Mahesh Prasad, Dr. Antesh Kumar Jha,
Mr. Ritesh Kumar Srivastav, Nirali Prakashan,
As per PCI Syllabus.
Page No. 3.21 to 2.28.
2. www.google.com.

29. Thank you