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Immunology Jul 2015The microanatomical structure of the spleen has been primarily described in mice and rats. This leads to terminological problems with respect to humans and their... (Review)
Review
The microanatomical structure of the spleen has been primarily described in mice and rats. This leads to terminological problems with respect to humans and their species-specific splenic microstructure. In mice, rats and humans the spleen consists of the white pulp embedded in the red pulp. In the white pulp, T and B lymphocytes form accumulations, the periarteriolar lymphatic sheaths and the follicles, located around intermediate-sized arterial vessels, the central arteries. The red pulp is a reticular connective tissue containing all types of blood cells. The spleen of mice and rats exhibits an additional well-delineated B-cell compartment, the marginal zone, between white and red pulp. This area is, however, absent in human spleen. Human splenic secondary follicles comprise three zones: a germinal centre, a mantle zone and a superficial zone. In humans, arterioles and sheathed capillaries in the red pulp are surrounded by lymphocytes, especially by B cells. Human sheathed capillaries are related to the splenic ellipsoids of most other vertebrates. Such vessels are lacking in rats or mice, which form an evolutionary exception. Capillary sheaths are composed of endothelial cells, pericytes, special stromal sheath cells, macrophages and B lymphocytes. Human spleens most probably host a totally open circulation system, as connections from capillaries to sinuses were not found in the red pulp. Three stromal cell types of different phenotype and location occur in the human white pulp. Splenic white and red pulp structure is reviewed in rats, mice and humans to encourage further investigations on lymphocyte recirculation through the spleen.
Topics: Anatomy, Comparative; Animals; B-Lymphocytes; Capillaries; Cell Movement; Humans; Mice; Models, Anatomic; Rats; Spleen
PubMed: 25827019
DOI: 10.1111/imm.12469 -
Internal and Emergency Medicine Aug 2019The spleen is a lymphoid organ that has been poorly studied compared to other solid organs, probably because it has been considered a useless and unnecessary part of the... (Review)
Review
The spleen is a lymphoid organ that has been poorly studied compared to other solid organs, probably because it has been considered a useless and unnecessary part of the body. For many centuries it has been considered a mysterious organ with uncertain functions. The first descriptions of the spleen date back to ancient ages. The spleen has been considered as a reservoir of liquids, strictly linked to stomach digestion, and in different cultures, it has been linked to melancholy and sadness due to the accumulation of black bile (humoral doctrine). A detailed anatomic description was first made by Vesalius during the Renaissance, and further implemented with the description of its microscopic structure by Marcello Malpighi in the seventeenth century. The first case reports regarding spleen functions and pathology regarded common causes of splenomegaly, such as malaria infection, and traumatic rupture. At the beginning of the last century, the pivotal concepts of hypo- and hypersplenism were introduced, along with the cumulating evidence of the relation between spleen removal and increased susceptibility to infections and thromboembolism. The study of hyposplenic states, which occur much more commonly than originally thought in many immune-mediated disorders, has rapidly increased after the validation of a simple method for assessing spleen function, namely pitted red cell count. In recent years, spleen morphology, in particular spleen stiffness, has been proposed as a marker of portal hypertension. In this paper, we retrace the fundamental steps of the discovery of the functions of the spleen.
Topics: History, 15th Century; History, 16th Century; History, 17th Century; History, 18th Century; History, 19th Century; History, Ancient; History, Medieval; Humans; Medicine, Traditional; Spleen; Splenectomy
PubMed: 31152307
DOI: 10.1007/s11739-019-02115-2 -
Journal of Applied Physiology... Jan 2019The spleen contains a reservoir of red blood cells that are mobilized into circulation when under physiological stress. Despite the spleen having an established role in...
The spleen contains a reservoir of red blood cells that are mobilized into circulation when under physiological stress. Despite the spleen having an established role in compensation to acute hypoxia, no previous work has assessed the role of the spleen during ascent to high altitude. Twelve participants completed 2 min of handgrip exercise at 30% of maximal voluntary contraction at 1,045, 3,440, and 4,240 m. In a subset of eight participants, an infusion of phenylephrine hydrochloride was administered at a dosage of 30 µg/l of predicted blood volume at each altitude. The spleen was imaged by ultrasound via a 2- to 5.5-MHz curvilinear probe. Spleen volume was calculated by the prolate ellipsoid formula. Finger capillary blood samples were taken to measure hematocrit. Spleen images and hematocrit were taken both before and at the end of both handgrip and phenylephrine infusion. No changes in resting spleen volume were observed between altitudes. At low altitude, the spleen contracted in response to handgrip [272.8 ml (SD 102.3) vs. 249.6 ml (SD 105.7), P = 0.009], leading to an increase in hematocrit (42.6% (SD 3.3) vs. 44.3% (SD 3.3), P = 0.023] but did not contract or increase hematocrit at the high-altitude locations. Infusion of phenylephrine led to spleen contraction at all altitudes, but only lead to an increase in hematocrit at low altitude. These data reveal that the human spleen may not contribute to acclimatization to chronic hypoxia, contrary to its response to acute sympathoexcitation. These results are explained by alterations in spleen reactivity to increased sympathetic activation at altitude. NEW & NOTEWORTHY The present study demonstrated that, despite the known role of the human spleen in increasing oxygen delivery to tissues during acute hypoxia scenarios, the spleen does not mobilize red blood cells during ascent to high altitude. Furthermore, the spleen's response to acute stressors at altitude depends on the nature of the stressor; the spleen's sensitivity to neurotransmitter is maintained, while its reflex response to stress is dampened.
Topics: Acclimatization; Adult; Altitude; Female; Hand Strength; Hemodynamics; Humans; Male; Phenylephrine; Spleen; Young Adult
PubMed: 30462566
DOI: 10.1152/japplphysiol.00753.2018 -
Surgical and Radiologic Anatomy : SRA Jan 2018A thorough understanding of the anatomy, physiology, and development of the spleen is essential for determining the pathophysiological mechanisms underpinning splenic... (Review)
Review
A thorough understanding of the anatomy, physiology, and development of the spleen is essential for determining the pathophysiological mechanisms underpinning splenic diseases and congenital variations. The aim of this review is to briefly summarize current knowledge regarding the normal development of the spleen, and to provide an overview of clinically relevant congenital splenic variations. These include such variations as asplenia, polysplenia, hyposplenia, lobulation of spleen, accessory spleens, accessory splenic nodules, wandering spleen, splenogonadal and splenopancreatic fusion, splenic cysts, and cavernous haemangioma of the spleen. All of these congenital variations are also mentioned in internationally accepted embryological nomenclature, known as the Terminologia Embryologica. Interestingly, most patients who have these diseases are asymptomatic, and are often diagnosed only after an injury or during unrelated medical procedures. Using examples from published case reports, we highlight how an understanding of the embryology of the spleen and the etiology of its disease states would improve clinical practice.
Topics: Anatomic Variation; Humans; Lymphatic Abnormalities; Spleen; Terminology as Topic
PubMed: 28631052
DOI: 10.1007/s00276-017-1893-0 -
Lymphology Jun 1983Embryogenesis and later development of the spleen's hematologic and immune functions involves ingrowth of vascular channels, influx of reticular cells and related... (Review)
Review
Embryogenesis and later development of the spleen's hematologic and immune functions involves ingrowth of vascular channels, influx of reticular cells and related byproducts to form a filtering network, migration of cells from other organs such as bone marrow and thymus, and final maturation of transient and resident cell populations.
Topics: Animals; Erythrocytes; Humans; Immunity, Cellular; Lymphocytes; Spleen
PubMed: 6350736
DOI: No ID Found -
Anatomia, Histologia, Embryologia Jul 2019Spleen is one of the important lymphoid organs with wide variations of morphological and physiological functions according to species. Morphology and function of the...
Spleen is one of the important lymphoid organs with wide variations of morphological and physiological functions according to species. Morphology and function of the spleen in bats, which are hosts to several viral strains without exhibiting clinical symptoms, remain to be fully elucidated. This study aims to examine the spleen morphology of fruit bats associated with their physiological functions. Spleen histological observations were performed in three fruit bats species: Cynopterus titthaecheilus (n = 9), Rousettus leschenaultii (n = 3) and Pteropus vampyrus (n = 3). The spleens of these fruit bats were surrounded by a thin capsule. Red pulp consisted of splenic cord and wide vascular space filled with blood. Ellipsoids in all three studied species were found numerously and adjacent to one another forming macrophages aggregates. White pulp consisted of periarteriolar lymphoid sheaths (PALS), lymphoid follicles and marginal zone. The lymphoid follicle contained a germinal centre and a tingible body macrophage that might reflect an active immune system. The marginal zone was prominent and well developed. This study reports some differences in spleen structure of fruit bats compared to other bat species previously reported and discusses possible physiological implications of the spleen based on its morphology.
Topics: Animals; Chiroptera; Spleen
PubMed: 30968443
DOI: 10.1111/ahe.12442 -
Transplant Immunology Feb 2008While graft rejection has been studied for many years, recent investigations have focused on the generation and maintenance of transplantation tolerance. This review... (Review)
Review
While graft rejection has been studied for many years, recent investigations have focused on the generation and maintenance of transplantation tolerance. This review examines the role of secondary lymphoid organs, especially the spleen, characterizes the maintenance mechanism that is key to the development of tolerance and explores the implications of new strategies for inducing tolerance in transplantation.
Topics: Animals; Graft Rejection; Humans; Spleen; Transplantation Immunology; Transplantation Tolerance
PubMed: 18158118
DOI: 10.1016/j.trim.2007.09.003 -
Seminars in Nuclear Medicine Jul 1985Despite the fact that the spleen has multiple functions, only one has been widely used for evaluation of the organ by imaging techniques (phagocytosis of 99mTc sulfur... (Review)
Review
Despite the fact that the spleen has multiple functions, only one has been widely used for evaluation of the organ by imaging techniques (phagocytosis of 99mTc sulfur colloid). The usual splenic uptake of this radiocolloid can by used to determine the size, location, and integrity of the organ. A major use of splenic radiocolloid imaging has been in the study of congenital defects. Thus, eventration of the diaphragm, accessory spleens, splenogonadal fusion, the asplenia and polysplenia syndromes, and the wandering spleen are amenable to study by means of intravenously administered radiocolloid. Interference with the splenic uptake of radiocolloid can be either focal or generalized (as in functional asplenia). Imaging of the spleen has a major role in evaluating suspected trauma of the organ and in following its clinical course. The return of splenic function after splenectomy (splenosis or accessory spleens) can be documented by radionuclide imaging, and likely by hematologic techniques when the volume of tissue is sufficiently large. The detection of intrasplenic lesions is important in tumor staging and as an alerting sign to an ongoing process.
Topics: Abscess; Adult; Child; Child, Preschool; Cysts; Diaphragmatic Eventration; Humans; Hypersplenism; Phagocytosis; Postoperative Complications; Radiation Dosage; Radionuclide Imaging; Spleen; Splenic Diseases; Splenic Neoplasms; Splenic Rupture; Splenomegaly; Technetium Tc 99m Sulfur Colloid
PubMed: 3898381
DOI: 10.1016/s0001-2998(85)80005-2 -
BioEssays : News and Reviews in... Feb 2007The vertebrate spleen has important functions in immunity and haematopoiesis, many of which have been well studied. In contrast, we know much less about the mechanisms... (Review)
Review
The vertebrate spleen has important functions in immunity and haematopoiesis, many of which have been well studied. In contrast, we know much less about the mechanisms governing its early embryonic development. However, as a result of work over the past decade-mostly using knockout mice--significant progress has been made in unravelling the genetic processes governing the spleen's early development. Key genetic regulators, such as Tlx1 and Pbx1, have been identified, and we know some of the early transcriptional hierarchies that control the early patterning and proliferation of the splenic primordium. In mouse and humans, asplenia can arise as a result of laterality defects, or the spleen can be absent with no other discernible abnormalities. Surprisingly, given the spleen's diverse functions, asplenic individuals suffer no major haematopoietic or immune defects apart from a susceptibility to infection with encapsulated bacteria. Recent evidence has shed light on a previously unknown role of the spleen in the development and maintenance of specific B cell populations that are involved in the initial response to infection caused by encapsulated bacteria. The lack of these populations in asplenic mice and humans may go some way to explaining this susceptibility.
Topics: Animals; Embryonic Development; Hematopoiesis, Extramedullary; Humans; Immunity; Species Specificity; Spleen
PubMed: 17226804
DOI: 10.1002/bies.20528 -
Nuclear Medicine Communications Mar 2017Splenic pathophysiology has been relatively unstudied, but recently, the spleen has received more attention as a result of the discovery of the 'cardiosplenic axis'.... (Review)
Review
Splenic pathophysiology has been relatively unstudied, but recently, the spleen has received more attention as a result of the discovery of the 'cardiosplenic axis'. This term describes a role that the spleen plays in the progression of atherosclerosis following acute myocardial infarction. Human studies of this axis have largely used fluorine-18-fluorodeoxyglucose (F-FDG) PET/CT to quantify peri-infarction inflammation, arterial wall inflammation and splenic metabolic activity. Most of these studies have quantified arterial wall inflammation and splenic metabolic activity using the standardized uptake value, but this is a semiquantitative measurement with several drawbacks, including overestimation of metabolic activity in overweight individuals and a dependence on blood glucose levels. A better approach to the measurement of metabolic activity using F-FDG is to measure tissue F-FDG clearance from dynamic imaging and Patlak-Rutland graphical analysis. This is the preferred approach for future human studies of the cardiosplenic axis that will be required to better define the nature of the spleen's role.
Topics: Heart; Heart Diseases; Humans; Molecular Imaging; Spleen
PubMed: 28009777
DOI: 10.1097/MNM.0000000000000635