The histology of vascular terminations in the rabbit's spleen

Snook, Theodore

doi:10.1002/ar.1091300407

Cited by 44 publications

(16 citation statements)

References 17 publications

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“…The AN was apparent around the lymph follicles. The PALS abruptly decreased in thickness a t the peripheral segment of the central artery, forming a tapering conus as described in the rabbit spleen (Snook, 1958). A thin rim of lymphatic tissue was observed around this segment; however, both the AN and IZ became less distinct.…”

Section: Splenic Arterymentioning

confidence: 59%

“Intermediate zone” of mammalian spleens: Light and electron microscopic study of three primitive mammalian species (platypus, shrew, and mole) with special reference to intrasplenic arteriovenous communication

Tanaka

1990

Am. J. Anat.

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The intermediate zone (IZ) of nonperfused and perfused spleens in three species of primitive mammals (shrew, mole, platypus) was studied morphologically. The IZ is a tissue zone consisting of plexiform vessels, probably venous capillaries, and is located transitionally between the white and red pulp. The IZ is separated from the white pulp by the arterial net (AN), in which the white pulp arteries terminate. Development of the IZ differs between the three species examined being distinctive in the platypus and shrew. The IZ is thin in the mole spleen. A closed type of arteriovenous (A-V) anastomosis was demonstrated in or around the IZ in the two Insectivora species examined. In the shrew spleen, peripheral arterial branches running within the IZ anastomose with the AN around the follicle. The AN anastomoses eventually with venous plexiform vessels of the IZ around the nonfollicular area of the white pulp to form a closed system. In the mole spleen, A-V anastomoses were noted between white pulp arteries (follicular and AN) and veins of the red pulp, either by direct communication or through fenestrated IZ vessels compatible with the plexiform vessels of the shrew spleen. A-V anastomosis in the IZ is probable, but not confirmed, in the platypus spleen, as analysis was limited to a nonperfused specimen. Well-developed ellipsoids were noted around arterial terminals of the IZ in the shrew spleen. Ellipsoids were also noted around all arterial terminals of the mole spleen directed to the red pulp. Most ellipsoids of the mole spleen appeared located within the IZ. No ellipsoids were present around arterial terminals of the IZ in the platypus spleen. Closed circulation was noted in terminals of the pulp artery in spleens of all three species. All pulp arteries of the mole spleen are postellipsoid segments of white pulp (AN and follicle) arteries. No ellipsoids were found around terminals of the pulp artery (penicillar artery) in shrew and platypus spleens. The IZ is probably homologous to the perilymphatic sinusoid (vein) of the lungfish spleen and may be regarded as part of the red pulp. The IZ may be representative of primitive mammalian spleens that have closed circulation. The marginal zone (MZ) of common mammalian spleens is probably a modified IZ by differentiation (remodelling) of the intrasplenic vein. In this process, withdrawal of venous vessels from the IZ occurred, leaving a lymphoreticular zone with open circulation (MZ). The marginal sinus reported in some mammalian spleens is probably a modified AN formed during this process. Possible morphological alterations of the spleen in vertebrate phylogeny are discussed.

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Section: Splenic Arterymentioning

confidence: 59%

“Intermediate zone” of mammalian spleens: Light and electron microscopic study of three primitive mammalian species (platypus, shrew, and mole) with special reference to intrasplenic arteriovenous communication

Tanaka

1990

Am. J. Anat.

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“…The investigators used different species and ages which might have contributed to the controversy (Snook, 1958). The lymphomyeloid tissue is a flexible and variable system in vertebrates.…”

mentioning

confidence: 99%

Splenic white pulp and associated vascular channels in chicken spleen

Oláh

Glick

1982

Am. J. Anat.

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We have studied the chicken spleen by light and transmission electron microscopy. Germinal centers are located at the beginning of the central artery which is surrounded by the periarterial lymphatic sheath (PALS). The central artery has no branch crossing the PALS, and there is no histologically identifiable marginal zone in the chicken spleen. The central artery continues as penicilliform capillaries.The mid-portion of the penicilliform capillary is surrounded by the ellipsoid or Schweigger-Seidel sheath. The endothelial lining of this part of the pencilliform capillary contains small channels, formed between neighboring endothelial cells, which enter the ellipsoid. These channels allow circulating substances to accumulate in the ellipsoid.The cells of the ellipsoid are reticular cells, round or ovoid in shape, exhibiting a limited number of cell junctions. At the surface of the ellipsoid are ellipsoidassociated cells (EAC) which have an affinity for toluidine blue. After perfusion fixation, the majority of the cells in the ellipsoid are lost; this suggests weak cellular connections between the ellipsoid cells. The ellipsoid-associated cells remain in loco. On the basis of their shape and cytological features, two stages of EACs can be distinguished. The round or ovoid EACs elaborate active Golgi zones surrounded by numerous small vesicles containing an electron-dense substance. Occasionally, mitotic figures can be seen among them which may suggest that they are immature forms. In the second or more mature stage, the EACs assume an elongated spindle shape. The spindle-shaped EACs reveal inactive Golgi cisternae and fewer but larger granules than the round or immature EACs. Unmyelinated nerve fibers and nerve ending were observed in the ellipsoid.Perfusion fixation reveals that the distal portions of the penicilliform capillaries extend into the red pulp and become the sinuses. Therefore, the circulation of the chicken spleen is anatomically closed except for the channels in the mid-portion of the penicilliform capillary.The periellipsoid white pulp (PWP) possesses a few small lymphocytes, macrophages, and plasma cells with the majority of cells being young blastlike cells which may replenish the EACs and ellipsoidal cells.Carbon, injected intravenously, appears on the EAC membrane by 30 minutes, while Brucella abortus is completely phagocytized at this time. Binding the carbon triggers the EAC to detach from the ellipsoid and migrate to the periellipsoidal white pulp (PWP). The EACs phagocytize carbon by 2 hours, and by 5 and 8 days are present in the red pulp and surround the germinal centers at the border of the periarterial lymphatic sheath, respectively. Secretory cells which have been identified in germinal centers might originate from EACs.

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“…They are not as rare as suggested in the literature based on two-dimensional microscopy (7,8,14,(19)(20)(21). They are more numerous than we appreciated in our preliminary work when we were inadvertently breaking connections by our handling of the brittle casts (15).…”

Section: Discussionmentioning

confidence: 72%

“…He then suggested a "closed" type circulation with direct continuity between terminal arterial capillaries and sinuses in human spleen (3). Subsequently, other students of the spleen were also equivocal, although generally agreeing that the open-type circulation was the more important, while direct vessel continuities, if they existed in the intermediate zone, had an insignificant functional role (7,8,14,(19)(20)(21). It is not the purpose of this communication to consider fully the evidence for or against the opposing views.…”

Section: Discussionmentioning

confidence: 93%

Arteriovenous shunts in the human spleen

Barnhart¹,

Baechler²,

Lusher³

1976

American J Hematol

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The mission of this study was to determine whether or not arteriovenous connections, indicative of a "closed" type of circulation, existed in the human spleen. Spleens from four patients requiring therapeutic splenectomy were the basis for this report. Scanning electron microscopy of plastic corrosion casts, prepared from these four spleens, revealed direct vascular conduits between splenic pulp arteries or arterial capillaries and the venous sinuses in the red pulp. Also demonstrated were a few arteriovenous shunts between pulp arteries or arterial capillaries and pulp or trabecular veins. Inclusion of sized microspheres in low-viscosity perfusion plastic illustrated that some diameters of the connecting shunts were 7-10 mum, with other shunts even smaller. Not only do arteriovenous connections exist in human spleens, but their frequency, as revealed by methods accentuating three-dimensional aspects of the splenic microcirculation, justify future reconsiderations of the functional significance of this closed type of circulation. Examination of samples of the same intact spleens, prepared by freeze-fracture and conventional critical-point drying, also revealed an "open" type circulation structure, namely, pore-patterned sinus walls that could facilitate blood cell movement from pulp cords into venous sinuses. Scanning electron microscopy thus has provided direct evidence that human spleens have both "open" and "closed" circulatory pathways in their microvasculature.

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The histology of vascular terminations in the rabbit's spleen

Cited by 44 publications

References 17 publications

“Intermediate zone” of mammalian spleens: Light and electron microscopic study of three primitive mammalian species (platypus, shrew, and mole) with special reference to intrasplenic arteriovenous communication

“Intermediate zone” of mammalian spleens: Light and electron microscopic study of three primitive mammalian species (platypus, shrew, and mole) with special reference to intrasplenic arteriovenous communication

Splenic white pulp and associated vascular channels in chicken spleen

Arteriovenous shunts in the human spleen

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