Assoc. Prof. Dr. Karim Al-Jashamy
Lymphoid tissue is CT with rich supply of
Exists free within regular CT or is surrounded
Very little cytoplasm so stain dark blue with
Rich network of reticular fibrils produced by
fibroblast whose many processes rest on fibrils.
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
Activation, proliferation of T lymphocytes.
Cells of Lymph Node
Macrophages and other phagocytic antigen processing
Lymphatic and vascular endothelial cells and
fibroblasts responsible for lymph node supporting
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.
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
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-
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
The nodules are embedded in a mass of diffuse
lymphoid tissue that consists of lymphocytes migrating
to and from the germinal centers.
The epithelium lining the
crypt corresponds with that
on the adjacent surface --
stratified squamous in the
tongue and palate, or
Pseudostratified Columnar in
In either case, the epithelium may be heavily
infiltrated with lymphocytes, and the crypt may be filled
with lymphocytes and other debris
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