Histology of Tonsil and Splenic Circulation by Dr. Roomi

8/2/2019 Histology of Tonsil and Splenic Circulation by Dr. Roomi

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HISTOLOGY OF TONSILS

ANDSPLENIC CIRCULATION

BY

DR. MUDASSAR ALI ROOMI (MBBS, M.PHIL)


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SPLENIC CIRCULATION

Splenic artery : its 4-5 ramienter the Hilum.

Along trabeculae Finestarterioles pass

Adventitia of the arteries isreplaced by periartereolarLymphoid sheath (PALS)

Lymphatic aggregations isenlarged at certain places to

form splenic lymphaticnodule (Malpighian bodies0.25 1 mm)

Splenic arteriole iseccentrically placed inlymphatic nodule

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Blood Circulation in Spleen

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Splenic Artery

5 or 4 branches

Enter trabelulae

Small arteriole branches

(Periart Lymphatic sheath surrounds it)

Central Arterioles in Splenic NoduleEccentric position

Branches to Splenic Nodule

Arterioles lose thin Lymph Sheath

divide in Red Pulp

Straight Vs (Penicilli)

Thick wall due to condensation of Ret. Lymphocytes)

Lumen of B.Vs. Narrow ellipsoid

One or more Capillaries


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spleen

1. Closed Theory It states that the terminal

arterial capillaries open directlyinto the venous sinuses.

2. Open Theory It states that terminal arterialcapillaries release their bloodinto pulp reticulum, from wherethe blood gradually filters intothe venous sinuses.

3. CompromiseTheory both open and closed

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Lymphoid organs and MALT

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Mucosa-Associated Lymphoid tissue(MALT)

The digestive, respiratory, andgenitourinary tracts are common sites ofinvasion by pathogens because theirlumens are open to the externalenvironment.

To protect the organism, the mucosal

connective tissue of these tracts containslarge and diffuse collections of dendriticcells, lymphocytes, IgA-secreting plasmacells, APCs, and lymphoid nodules.

Lymphocytes and dendritic cells are alsopresent within the epithelia lining thelumens. Most of the lymphocytes are Bcells; among T cells, CD4 helper cellspredominate.

In some places, these aggregates formlarge, conspicuous structures such as thetonsils and the Peyer patches in theileum.

Similar aggregates with lymphoid follicles

are found in the appendix. Collectively the mucosa-associated

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tonsils

Definition: Tonsils arepartially encapsulatedlymphoid tissue lyingbeneath and in contact

with the epithelium of theoral cavity and pharynx.

According to theirlocation they are called

palatine, pharyngeal,or lingual tonsils .

Waldyers ring

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Palatine tonsils

Palatine tonsils islocated in theposterior parts of the

soft palate.

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Palatine tonsils

These are covered by stratifiedsquamous epithelium.

Each has 1020 epithelialinvaginations that penetrate the tonsildeeply, forming crypts .

The lymphoid tissue in these tonsilsforms a band that contains freelymphocytes and lymphoid nodules,generally with germinal centers.

The epithelium is densely infiltrated bydendritic cells and lymphocytes

Separating the lymphoid tissue fromsubjacent structures is a band ofdense connective tissue that acts as acapsule or barrier against spreadingtonsil infections.

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Palatine tonsils

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The pharyngeal tonsil

The pharyngeal tonsil issituatedin the posteriorwall of the nasopharynx

usually covered byciliated pseudostratifiedcolumnar epithelium.

The pharyngeal tonsil iscomposed of pleated

mucosa containingdiffuse lymphoid tissueand lymphoid nodulesand a capsule thinnerthan that of the palatinetonsils.

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lingual tonsils

The lingual tonsils are situated along the posterior surface of thetongue

and are covered by stratified squamous epithelium with crypts.

The lymphoid tissue of these tonsils has many of the same basic

features as that of palatine tonsils. All these epithelia contain intraepithelial lymphocytes and dendritic

cells.

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COMPARISON

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Adenoid hypertrophy

Adenoidhypertrophy (orenlarged adenoids)is the unusualgrowth("hypertrophy") ofthe adenoid tonsil.

Treatment: Surgicalremoval of theadenoids is aprocedure called

adenoidectomy April 30, 2012

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Tonsillitis

Tonsillitis isinflammation of thetonsils most

commonly causedby a viral orbacterial infection.

Symptoms oftonsillitis includesore throat andfever.

Tonsillitis

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Gut-Associated Lymphoid Tissue(GALT)

The appendix and Peyer patches in theileum of the digestive system are maincomponents of GALT.

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Gut-Associated Lymphoid Tissue(GALT)

MALT extends along the entire gastrointestinaltract, but in the wall of the ileum are particularlylarge aggregates of lymphoid follicles calledPeyer patches, each consisting of 10200nodules and bulging into the gut lumen with noconnective tissue capsule.

The simple follicle-associated epithelium (FAE)

covering these nodules contains specialized Mcells with apical microfolds rather than the brushborder and glycocalyx typical of enterocytes.

M cells continuously sample antigens andmicroorganisms in the intestinal lumen. Eachis characterized by a large basal intraepithelialpocket open to the underlying lymphoid tissuethrough a porous basement membrane.

Antigenic material bound to the apical surface ofM cells is rapidly translocated via transcytosisfrom the intestinal lumen to APCs andlymphocytes located in the pocket.

T helper cells and B cells derived from theselymphocytes move away from the FAE and initiateadaptive responses to the antigens.

These B cells give rise to plasma cells secreting

IgA, which is transported by enterocytes into theintestinal lumen to bind and neutralize potentially

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Clinical problem

Appendicitis is acommon disease, whichmay be triggered bybacterial and viral

infections resulting inhyperplasia of lymphaticnodules and obstructionof the lumen of the

appendix. Clinical features?

Complications?

Treatment?April 30, 2012

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en ca on po n s pa a ne


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en ca on po n s: pa a netonsil

Tonsillar cryptslined byStratifiedsquamous non-keratinizedepithelium

No lymph

sinuses No cortex and

medulla

Lymph nodules

are arranged in April 30, 2012

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COMPARISON

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Histology of Tonsil and Splenic Circulation by Dr. Roomi

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