The spleen is a single intra-abdominal lymphatic organ that filters blood. It is composed of stroma including a capsule, trabeculae, and reticular connective tissue, as well as parenchyma consisting of white pulp and red pulp. The white pulp contains lymphocytes arranged in Malpighian corpuscles around arterioles. The red pulp is made up of splenic cords and blood sinusoids containing blood cells, macrophages, and platelets. The spleen functions to filter blood, form and store blood cells, and play an immunological role in trapping antigens.

2. The lymphatic organs
Dr. Samar Asker

3. The spleen
Single intra abdominal hemo
lymphatic organ.
To filter the blood from any
organism formed of
stroma & parenchyma.

4. Stroma
Trabecula
e
Capsule
Reticular CT

5. a- Capsule:
Thick C. T. formed of cells
fibroblast ---- collagen &
elastic fibers containing
smooth muscle fibres.
Is covered by peritoneum.

6. b-Trabeculae:
They arise from
the hilum of
spleen may be
from the capsule .
Formed of Thick
C. T. containing
smooth muscle
fibres.
Divide the spleen
into irregular
compartments

7. Reticular
CT : formed
of cells &
fibres in the
bacheground
stained only
with
silver{Ag}
stain.

8. Parenchyma:
IN fresh sections it
shows white spots
on red background
i.e devided into:
White pulp &
red Pulp

9. White pulp =
(Malpighian corpuscle):
Rounded or oval scattered
follicles with an arteriole on
one side called central
arteriole or follecular arteriole.
Formed of reticular CT in which
cells are arranged around the
arteriole into 4 concentric
zones:

10. B,T, p &
M
1. Thymus dependent zone:
periarteriolalr lymphatic
sheath (PALS) contain Tlymphocytes around the
arteriole
2. Germinal center: pale area
contain activated large B
lymphocytes, plasma
blasts, plasma cells &
macrophages.
3. Follicular zone= corona:
dark contain B
lymphocytes
4. Marginal zone : at the
periphery contain T& B
lymphocytes plasma cells
& macrophages.
B
B
p&M
T

11. B
B
,T
,p
M
&

13. B- red Pulp:red In fresh
Formed of :
Spleniccords +
Blood sinusoids.
Splenic cords: Billroth
cords the areas
between the white pulp
& bl. Sinusoids contain
blood cells (RBCs+
lymphocytes +
monocyts)+plasma
cells +Macrophage.

14. Blood sinusoids.
irregular blood
spaces lined with
fenestrated
endothelial cells with
non-continuous
basement membrane
for easy passage of
blood cells to the
blood. Macrophages
appear in the wall of
the sinusoids to
engulf any foreign
bodies

15. Functions
Formation
Filtration
Storage
Blood
Immuonological
Destruction

16. Functions
1. Filtration of blood from any organism by
macrophages
2. Formation of blood cells : in embryo &
lymphocytes in germinal center
3. Storage of blood cells & platelets.
4. Destruction of RBCs& storage of iron.
5. Immuonological function the reticular
cells trap the antigen & present it to
lymphocytes---- humeral & cell
mediated immunity.

17. Lymph
node
spleen
number multiple
Single
Function Filterati
on of
lymph
Immunit
y
Filtration
& stores of
blood
Immunity

18. Lymph node
Capsule
Thin, covered with fat
Smooth ms only at
,.hilum
Trabeculae Thin arise from the
capsule
spleen
Thick covered with
peritoneum
rich in smooth muscle
Thick arise from the hilum

19. Lymph node
Parenchy
ma
Cells
Cortex & medulla
Cortex = lymph follicle &
lymph sinus
The follicles have no
.arteriol
Medulla = Medullary
cords & Medullary
. sinuses
lymphocytes +
.macrophages + plasma
spleen
White pulp & red pulp
White pulp = lymph follicle
. no sinuses
.The follicle contain arteriole
Red pulp = splenic cords &
. blood sinusoids
macrophages + plasma cells +
WBCs +RBCs

20. Tonsils
Partially
capsulated
lymphatic tissue
3 sites:

21. Palatine tonsils
Two oval masses of
lymphatic tissue under the
mucous membrane of oropharynx.

22. Lymphatic tissue of
two kinds:
Lymph follicle with or
without germinal
center
Diffuse lymphatic
tissue: lymphocytes
and plasma cells &
macrophage.

23.  Each
tonsils is
covered with
stratified
squamous
epithelium which
dips into the
underlying
lymphatic tissue
to crypts.

24. mucous glands
deep to the follicle
their ducts open to
the surface & not in
the base of the
crypt so inflamatin
is common

25. Incomplete capsule:
separates the tonsils
from the underlying
structure.
Salivary corpuscle:
Lymphocyte which
pentrate the epith. To
appear in the saliva.

26. Lingual tonsil:
At the base of the tongue .
Secondary follicle & diffuse
lymphatic.
 Non keratinised str.
Sqam.epth which form crypt.
mucous glands open
into the base of the crypt.

27. Pharyngeal Tonsil
Single mass of lymphoid
tissue under nasopharynex.
Covered with pseudo
stratified columnar ciliated
epith. with goblet cells
Folded with no crypt
Function :at the beginning
of the respiratory &digestive
systems so protect from
bacteria & produce Ab