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The Spleen
Presented by
Prof. Dr. Maha Wagdy
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Spleen
Largest lymphoid organin the body located inleft upper quadrant ofthe abdominal cavity
Primary function is tofilter blood from antigen.
has no afferentlymphatic so it does notfilter lymph.
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Spleen
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CapsuleTrabecula
V
no cortex or medulla
A
Structure of spleen
Stroma peritoneum
SMF
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Fine stroma
Formed of reticularcells and fibers
More condensed inthe white pulp thanthe red pulp.
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Centralartery
PALS
Nodule
V
Red pulp
White pulp
no cortex or medulla
A
Structure of spleen
parenchyma
Sinusoids
Splenic Cords
Nodule
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White pulp
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White pulp
Primary lymphatic nodule formed ofBlymphocyte, macrophages.
1.Lymphatic nodule
Secondary lymphaticnodule has germinalcenterformed of
lymphoblast, plasmacell.
Central
artery
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2- Periarterial lymphatic sheath
Thymus dependantarea
Formed ofTlymphocytes
area around centralrtery
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WP = PALS + SNsWhite Pulp = PeriArteriolar Lymphoid
Sheath + Splenic Nodules
RP = Ss + SCs
Red Pulp = Sinusoids + Splenic Cords
Central artery
White to the nakedeye in fresh spleenviolet in H&E
Red to the naked eye infresh spleen, & in H&E
Cords are Swiss cheeseto the holes sinusoidsOr cords are spongetisuue and the sinusoidsthe spaces
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Central artery
Reticular fibers
Spleen stained by Silver
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Marginal Zone
Area betweenwhite pulp and redpulp.
composed of:1. marginal sinuses
2. interdigitatingdendritic cells
3. T & B
lymphocytes4. macrophages
5. plasma cells
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Importance of marginal zone
1. Site where blood born cells and antigens have theirfirst free access to the parenchyma of the spleen
2. Site ofentry ofT & B cell to the spleen.
3. Macrophages attack micro-organism in blood4. Interdigitating cell presents antigen to Lymphocyte
which initiate immune response.
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Red pulp
Formed of:1. blood sinusoids.
2. Splenic cords orBillroths cords:cellular massessupported by reticular
fibers and cells
Plasma cells
macrophages
blood cells T & B
lymphocytes
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WP = PALS + SNsWhite Pulp = PeriArteriolar Lymphoid
Sheath + Splenic Nodules
RP = Ss + SCs
Red Pulp = Sinusoids + Splenic Cords
Central artery
White to the nakedeye in fresh spleenviolet in H&E
Red to the naked eye infresh spleen, & in H&E
Cords are Swiss cheeseto the holes sinusoidsOr cords are spongetisuue and the sinusoidsthe spaces
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- The venoussinuses are similar
to tall woodenbarrels with bothends open.- The endothelialcells represented bythe wooden staves- The basal laminarepresented by thehoops around thebarrel
Endothelial cell
Endothelial cells are tall elongated with itslongitudinal axes parallel to longitudinal
axes of sinusoid
Basal lamina
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Blood sinusoid
Large, dilated irregularlumen
Endothelial cells are tallelongated in shape
Narrow intercelular cleft Associated macrophages
Discontinuous rings ofbasal lamina
Reticular fibersarranged in a transversedirection
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Blood circulation of the spleen
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Splenic circulation
Closed theory Open theory Combined theory
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Closed theory Open theory Combined theory
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SPLEEN Blood flow
Trabecular artery
Pulp veinSinusoids
Sheathed capillary (M&R)
Splenic V
Trabecular vein
Splenic Artery
Central artery[ ]
Simple arterial capillary
Penicillar arterioleArterial capillary
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Function of spleen
Site of activation of both T- and B-lymphocytes. These cell types interact withdendritic cells & macrophages that presentantigen to these lymphocytes.
Production of Ig Production of blood cells duringembryogenesis
Destruction of erythrocytes; old RBCs arerigid & are severely damaged when theypass through the slits (spaces) between thethe endothelial cells of splenic sinuses andphagocytosed by macrophages.
Temporary reservoir of blood
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PeritoneumCapsule SMFTrabeculae irregular
mainly from the hilumParenchyma red pulpand white pulp
N0 peritoneum
Capsule no SMFTrabeculae regularFrom the convex surfaceof the capsuleParenchyma cortex andmedulla
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SpleenLymph nodeDifferences
ySize of clenched fist.yKidney shaped of variable in sizeGeneralconsideration
yIn the left hypochondriumyScattered everywhere
ySingleySingle or multiple in groups
yCovered by peritoneumyNot covered by peritoneumCapsule
yThin capsule of collagenous and
elastic fibers with some smoothmuscle fibers
yThick capsule of collagenous and
elastic fibers
yNo lymphatic penetrate the capsuleyPenetrated by afferent lymphatics
yIrregular trabeculae arise mainly
from the hilum
yRegular thick trabeculae arise from
the capsule
Trabeculae
ySmooth muscle fibers are presentyDont contain smooth muscle fibers
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yLie in between the red and white pulp
divide the spleen into incomplete
compartments
yDivide the outer cortex into
regular compartments, while in
medulla, trabeculae are thin and
irregular
yDivided into white and red pulpyDivided into cortex and medullaParenchyma
yScattered all over the splenic tissueyConfined to cortical
compartments
Lymph nodules
yEither primary or secondary noduleyEither primary (formed mainly of
small B lymphocytes) or secondary
nodule (peripheral small B
lymphocytes and central pale
lymphoblasts that are termed
germinal center)
yPossess a central artery surrounded
by Periarterial lymphatic sheath (PALS)
formed of mainly T lymphocytes
yHave no central artery
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SpleenLymph nodeDifferences
yWhite pulp (lymphoid nodules)y splenic cords
yIn the form of cortical nodules, inner cortex
consists mainly of T lymphocytes never
arranged in nodules and medullary cords
formed of plasma cells, macrophages and Blymphocytes)
Dense lymphoidtissue
yRed pulp: modified loose lymphoid tissue in
the form of splenic cord containing
lymphocyte, plasma cell, macrophages and
blood cells
yIn between the nodules and the medullary
cords, containing lymphocytes, plasma cells
and macrophages
Loose lymphoidtissue
yContain blood sinusoidsyContain lymph sinuse
yPeriarterial lymphatic sheath areas around
the central arteries in lymphatic nodules
y inner cortex or paracortexThymic
dependent area( mainly T lymphocyte)
yOnly efferent lymphaticsyHas afferent and efferent lymphaticsLymphaticvessels
ymarginal sinuses present in marginal zones
between white and red pulp
ypost- capillary venules present in paracortexSite of entry of
T&B lymphocytes
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y Filtration of bloody Filtration of lymphFunctions
yImmunological responseyHumoral and cell mediated immunological
response
yDestruction of old RBCs
yTemporary reservoir for blood cells and platelets
yHaemopoietic organ during foetal life
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Histological organization of thymus and palatine tonsil
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QUIZ
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SPLEEN
1 - lymphoidfollicle (whitepulp)
2 - red pulp
3 capsule
4 - trabeculae(connectivetissue)
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The histological features of the spleen
include:
a. periarterial lymphatic sheaths.
b. cortex and medulla.c. Hassals corpuscles.
d. presence of crypts.
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