dr karim

1. LYMPHOID
ORGANS
Assoc. Prof. Dr. Karim Al-Jashamy
MSU/IMS 2010

2. Lymphoid Tissue
 Lymphoid tissue is CT with rich supply of
lymphocytes
 Exists free within regular CT or is surrounded
by capsules.
 Very little cytoplasm so stain dark blue with
H&E.
 Rich network of reticular fibrils produced by
fibroblast whose many processes rest on fibrils.

3. Lymphatic System

4. Lymphatic Capillaries

5. Lymph Node

6. Structure of Lymph Node

8. Lymph Nodes
 Functions include:
 Filtration of particles and microorganisms to keep
them out of general circulation.
 Interaction of circulating antigens in lymph with
lymphocytes to initiate immune response.
 Activation, proliferation of B lymphocytes and
antibody production.
 Activation, proliferation of T lymphocytes.

9. Cells of Lymph Node
 Lymphoid cells
 Macrophages and other phagocytic antigen processing
cells
 Lymphatic and vascular endothelial cells and
fibroblasts responsible for lymph node supporting
framework.

10. Lymph Node

12. Section of a lymph node showing
the cortex and the medulla
1 Capsule; 2 lymphoid nodule
with germinative center, Trabecula
subcapsular sinus; (4) intermediate sinus; (5) medullary cords; (6) medullary
sinus; (7) trabecula.
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13. Medulla of Lymph Node
Lymphocytes predominate
Medullary sinuses
Medullary cords

14. LYMPH NODE
Stained with H&E
1 - cortex
2 - paracortical zone
3 - medulla
4 - medullary cords
5 - lymphoid follicle of the
cortex
6 - capsule
7 - subcapsular sinus
8 - cortical sinus
9 - medullary sinus

16. Medullary sinus of a lymph node containing reticular cells with long
processes and elongated nuclei, macrophages, and many lymphocytes. (1)
Macrophage; (2) reticular cell; (3) trabecula. H&E stain. High
magnification.

17. Spleen
 Largest accumulation of lymphoid tissue
 Abundant phagocytic cells—defense against
antigens in blood
 Site of destruction of aged erythrocytes.
 Production site of activated lymphocytes which
are delivered to the blood.
 THUS, an important blood filter and antibody-
forming organ.

18. Spleen

22. Spleen

23. Spleen

24. Lymphoid Nodule
1. Germinative Center
2. Central artery

26. Tonsil

28. Tonsils are lymphoid structures located in the mucosa
of the tongue, palate, and pharynx which provide sites
where immune surveillance cells (lymphocytes) can
encounter foreign antigens enter the body through the
mouth or nose.
Each tonsil consists of an epithelial crypt (invaginated
pocket) surrounded by dense clusters of lymph nodules,
each with a germinal center where lymphocytes
proliferate.
 The nodules are embedded in a mass of diffuse
lymphoid tissue that consists of lymphocytes migrating
to and from the germinal centers.

29. The epithelium lining the
crypt corresponds with that
on the adjacent surface --
stratified squamous in the
tongue and palate, or
Pseudostratified Columnar in
the pharynx.
In either case, the epithelium may be heavily
infiltrated with lymphocytes, and the crypt may be filled
with lymphocytes and other debris

33. PALATINE TONSIL
1 - lymphoid follicle
2 - diffuse lymphoid tissue
3 - crypt
4 - epithelium of the oral cavity musosa
6 - submucosa of the inner cover of oral cavity forms
hemi-capsule of the tonsil

34. Thymus

36. THYMUS (lobule)
H&E
1 - cortex
2 - medulla
3 - Hassal's corpuscle
4 - interlobular connective tissue
(septa)