Lymph node -basic introduction ,anatomy , histology ,and physiology

1. LYMPH NODE
Department of Oral diagnostic medicine and radiology
PRESENTED BY – ZAREESH.S.AKHTAR
1 year MDS

2. CONTENT
◦ Introduction
◦ Components of Lymph nodes
◦ Anatomy of Lymph Node
◦ Physiology of Lymph Node
◦ Function Of Lymph Nodes
◦ Reference

3. Introduction
◦ Lymphoid system is a part of the hematopoietic system
represented by thymus, lymph nodes and spleen.
◦ Lymph nodes form a part of the immune system as well as the
circulatory system.
◦ It collects and drains lymph and are distributed along the course
of the larger lymphatic vessels.

4. ◦ Lymph originates as blood plasma
,in tissue capillary bed ,plasma
leaves the circulatory system to
become interstitial fluid.
10%
100%
90%

5. Components of Lymph nodes
◦ Afferent Lymphatic (entry of lymph )
◦ Capsule - Lymphoid Follicles
◦ Outer Cortex-
1. Macrophages ,
2. Reticular cells ,
3. Follicular dendritic cell
◦ Germinal Centre-
1. B-Lymphocytes cell

6. ◦ Inner Cortex –
1. Macrophages ,
2. Dendritic cell
3. Plasma cell
◦ Medullary sinuses
◦ Hilum
◦ Efferent Lymphatic (lymph goes out )

7. ANATOMY OF LYMPH NODE

8. ◦ Humans have about 450 lymph nodes.
◦ Lymph nodes are small oval ,bean
shaped structures scattered throughout
body along lymph vessels.
◦ Usually of 0.1-2.5 cm length.
◦ May be deep or superficial.
◦ Filter lymph fluid to trap foreign
organisms , cell debris , and tumor cells.

9. ◦ Lymph node has 2 surfaces
◦ 1-Convex surface
◦ Receives Afferent Lymphatics through
which Lymph comes into Lymph node.
◦ These have specialised one way valve.
Afferent
lymph
node
Convex surface

10. • 2-Concave Surface
Also called hilum have 3 important
structure
• -artery
• -vein
• -efferent lymphatics
Concave Surface

11. THE LYMPHOID LOBULE
◦ The lymphoid lobule is the basic anatomical and
functional unit of the lymph node.
◦ Lobules are described in lymph nodes as
physiological compartments.
◦ These compartments contain specific lobular
structures so changes in these compartments
reflect alterations in the lobules.

12. ◦ The (superficial) cortex contains spherical
follicles that are surrounded and separated by
interfollicular (or diffuse) cortex.
◦ The paracortex consists of deep cortical units
(DCUs).
◦ Each lobule has a single DCU that can be
anatomically and functionally divided into a
central DCU and a surrounding peripheral
DCU

13. ◦ Lymph spreads through the subcapsular
sinus over the lobule’s apex, flows down
the sides of the lobule through transverse
sinuses and then flows into the medullary
sinuses.
◦ Lymph from all the lobules drains into a
single efferent lymphatic vessel that exits
the node at the hilus .

14. Lymph nodes –Capsule ,Cortex and Medulla
• The cortex, paracortex and
medulla are each composed of
specific areas of the lymph
node’s lobules and sinuses.
• The lobules lie together within
the sinus system .

15. • The body of lymphoid
islands is united by its
lymphocytes which move
back and forth between the
lobules for antigens.

16. Capsule of the lymph node
◦ Lymph nodes are surrounded by a fibrous
connective tissue capsule that enters the
organ as trabeculae that defines a cortex
and medulla.
◦ The capsule and trabeculae are the source
of reticulin fibers that are found through
the node and form the main supporting
network of the organ

17. ◦ Beneath the capsule is a
subcapsular sinus into
which lymph flow from
the afferent lymphatic
vessels

18. Reticulin Framework
◦ The reticular fibers are delicate ,black –staining
strand supporting the parenchyma and contributing
to the perivascular connective tissue
◦ The reticular meshwork is a, porous, sponge-like
tissue composed of stellate, spindle shaped or
elongated fibroblastic reticular cells (FRCs) and their
reticular fibers
◦ Reticular Fibers i.e. Type III Collagen

19. ◦ Macrophages known as sinus histiocytes cling to the reticular meshwork .
◦ They occur in clusters, especially in transverse sinuses near the capsule,
and are relatively infrequent in the subcapsular sinus.
◦ Sinus histiocytes increase in response to the need for particle clearance and
may completely fill the sinuses (sinus histiocytosis)
◦ Some sinus histiocytes originate in the tissues and migrate to the sinuses
after antigenic stimulation .

20. ◦ Lymphatic sinuses
◦ Subcapsular sinuses
◦ Trabecular sinuses / cortical sinuses

21. CORTEX
◦ Cortex is divided into
◦ 1-Outer cortex
◦ Filled with lymphoid follicles.
◦ Outer edge of follicle contains
more T-cells.
◦ Inner Germinal center is the site
of B-cells proliferation.

22. Cellular Zones Of Lymph Nodes
◦ A Primary follicle is
uniformly populated
by small ,quiescent
lymphocytes
◦ A Secondary follicle
has a germinal center.

23. Zones of Germinal Centre
• In the ‘dark zone’ the B cells [centroblast]undergo rapid proliferation.
• ‘Light zone’ B cells occur as centrocytes.
• The mantle zone is produced as surrounding cells are marginalized by the rapidly
growing center.

24. ◦ 2-Inner cortex or paracortex
◦ Contain T-cells randomly
arranged ,
◦ Macrophages and dendritic
cells

25. Medulla
◦ Medulla is the inner collecting area of sinuses
◦ The medulla consist of anastomosing cords of lymphatic tissue .
◦ The medullary cords interspersed with the medullary sinuses that
drain the lymph from the node into the efferent lymphatics vessels
that are located at the hilus

26. Hilum
◦ The hilum has numerous arteries and
veins .
◦ The lymph leaves the lymph node via
the efferent lymphatics vessels with
valves at the hilum

27. PHYSIOLOGY OF
LYMPH NODE

30. Function Of Lymph Nodes
◦ Lymph nodes play an important role in the defense mechanism of the body.
◦ They filter out micro-organism (such as bacteria ) and foreign substance
such as toxins , etc.
◦ Filter lymph ,thereby promoting lymphocyte contact with antigen
◦ Provides necessary microenvironment for antigen – dependent
differentiation.
◦ New lymphocytes are manufactured in the lymph nodes.

31. ◦ Inderbir singh’s textbook of human histology
◦ Grey’s Anatomy
◦ Medical Physiology by K Sembulingam
◦ Textbook of Physiology by A K Jain
◦ Lymph Nodes go with the flow –JEM journal of experimental Medicine
◦ Normal Structure ,Function , and Histology of Lymph Nodes.-Toxicologic
Pathology ;Cynthia L. Willard – Mack
◦ Lymph Nodes: The Unrecognized Barrier against Pathogens
Ania Bogoslowski and Paul Kubes
ACS Infectious Diseases 2018 4 (8), 1158-1161
DOI: 10.1021/acsinfecdis.8b00111
Reference