The lymphatic system is a drainage system that works alongside the venous system to remove tissue fluid from interstitial spaces. Lymph capillaries absorb excess tissue fluid and transport it through lymphatic vessels to lymph nodes, where it is filtered. The filtered lymph then drains into either the thoracic duct or right lymphatic duct and returns to the bloodstream. The lymphatic system removes larger particles from tissues and transports mature lymphocytes throughout the body. Key components include lymph vessels, central lymphoid tissues like bone marrow and thymus, peripheral lymphoid organs like lymph nodes and spleen, and circulating lymphocytes in the bloodstream.

1. Lymphatic System
Dr.Rikki Deogade
Department of Anatomy
DMMC
Nagpur

2. Defn
• Lymphatic system is essentially a drainage
system which is accessory to the venous
system.

3. Subclavian
veins
Lymphatic
Ducts
Lymphatic
vessels
Lymphatic
capillaries
-
Interstitial
spaces
Blood
capillaries
Formation
& flow
of lymph

4.  Most of the tissue fluid
formed at the arterial end
of capillaries is absorbed
back into the blood by the
venous ends of the
capillaries and the
postcapillary venules.
 The rest of the tissue fluid (10-20%) is absorbed by the
lymphatics which begin blindly in the tissue spaces.

5. • Larger particles (proteins and particulate
matter) can be removed from the tissue fluid
only by the lymphatics.
• Therefore, the lymphatic system may be
regarded as 'drainage system of coarse type'
&
the venous system as 'drainage system of fine
type'.

6. • The tissue fluid flowing in the lymphatics is
called lymph.
It passes through filters (lymph nodes)
placed in the course of lymphatics
finally drains into
Venous blood

7. • Lymph from most of the tissues is clear and
colourless,
but
Lymph from small intestine is milky-white due to
absorption of fat.
(The intestinal milky lymph is called chyle, and
lymph vessels, the lacteals )

8. Components of Lymphatic system
(1) Lymph vessels
(2) Central lymphoid tissues
(3) Peripheral lymphoid organs
(4) Circulating lymphocytes

9. (1) Lymph Vessels
lymph capillaries begin blindly in the tissue
spaces and form intricate networks.
Their calibre is greater and less regular than that
of blood capillaries, and their endothelial wall is
permeable to substances of much greater
molecular size.
Lymph capillaries are absent from the cellular
structures like brain, spinal cord, splenic pulp, and
bone marrow

12. • Lymph capillaries join to form lymphatics,
which are superficial and deep lymphatics.
• The superficial lymphatics accompany veins,
&
Deep lymphatics accompany arteries.

13. Lymph
passes through
filters or barriers of the regional lymph nodes
which trap
particulate matter.

14. Filtered lymph
passes through
larger lymphatics
eventually collected into
2 large trunks, the thoracic duct and right
lymphatic duct.
which pour their lymph into
brachiocephalic veins.

15. • Thoracic duct
drains
both lower limbs, abdomen, left halves of
thorax,head and neck and left upper limb.
• Right lymphatic duct
drains
right halves of thorax, head and neck and right
upper limb

16. Lymphatics
anastomose freely with
their neighbours of the same side as well as
of the opposite side.

17. Larger lymphatics
supplied with
their vasa vasorum &
accompanied by
a plexus of fine blood vessels
which form
red streaks seen in lymphangitis

18. 2. Central Lymphoid Tissues
• It comprise bone marrow & thymus.
• All 'pluripotent' lymphoid stem cells are
initially produced by bone marrow,
except
during early fetal life when these are
produced by liver and spleen.

19. Stem cells
undergo differentiation
in the central lymphoid tissues,
so that the lymphocytes become
competent defensive elements of the immune
system.

20. Bone marrow
helps differentiation of
the committed B-lymphocytes
which are capable of
synthesizing antibodies
after getting transformed into plasma cells.

21. • In birds, B-cells
are differentiated in
wall of the bursa of Fabricius
a hindgut diverticulum

23. 3. Peripheral Lymphoid Organs
• It comprise lymph nodes, spleen, and
epithelio-lymphoid tissues.
• The mature lymphocytes join the circulating
pool of lymphocytes.

24. 4. Circulating Pool of Lymphocytes
Pool
contains
mature progenies of B- and T-lymphocytes
which may be called upon
during antigenic emergencies

25. Lymphatic Follicle (Nodule)
• Collections of lymphocytes occur at many places in the
body.
• Everywhere there is a basic pattern, the lymphatic
follicle. The follicle
• is a spherical collection of lymphocytes with a pale
centre known as
• germinal centre, where the lymphocytes are more
loosely packed.
• The central cells are larger in size, stain less deeply, and
divide more
• rapidly, than the peripheral cells.

26. LYMPH NODES

28. • Nodes are oval or reniform in shape, 1-25 mm
long, and light brown, black (pulmonary), or
creamy white (intestinal) in colour.
• Usually they occur in groups (cervical, axillary,
inguinal, mesenteric,mediastinal, etc.), but at
times there may be a solitary lymph node.
• Superficial nodes are arranged along the
veins, and the deep nodes along the arteries.

29. • Structurally, a lymph node is made up of the
following parts :-
1. Fibrous and reticular framework
2. Lymphatic channels
3. Cortex
4. Medulla
5. Blood channels

30. Functions of lymph nodes
1. Center of lymphocytes production
:- By multification of preexisting lymphocytes
2. Plasma cells produced antibody
3. T lymphocytes attack foreign cell
4. Filter lymph
:- Foreign substances trapped by reticular
fibers
:-Microphages  phagocytosis
:- Lymphocytes  by immune response

31. Applied
Lymphadenitis :- enlargement & inflammation of
lymph nodes, draining infected area.
Lymph nodes :- not firm, movable, very tender
Metastasis:- spread of disease from one part to
another
All malignant tumour exhibit metastasis
Secondary tumour sites can be predicated
According to direction of lymph flow.
Cancerous lymph node are from non tender and
fixed to underlying structures.

32. Primary lymphoid organs :-
Produce lymphocytes independent of
Antigenic Stimulus.
Eg- Thymus , Bone Marrow
Secondary lymphoid organs :-
Produce lymphocytes only in
response to an Antigenic Stimulus.
Eg- Spleen, Tonsil, Lymph Node

33. Tonsil
Only Lymphoid organ with
Epithelial lining (Stratified
Squamous Non-Keratinized Epithelium).
Numerous Crypts present on Medial side
Lymphocytes arranged as lymphatic nodules
Seen in
Lymph Node, Spleen ,Tonsil

34. Spleen

35. White Pulp

37. Thymus
• Capsule is Present
• Lymphocytes arranged as lobules