Influencia de la anastomosis de las arterias umbilicales (Hyrtl's) en la morfometría y eficiencia placentaria / Influence of the anastomosis of the umbilical arteries (Hyrtl's) on the morphometry and efficiency of the placenta

La anastomosis de Hyrtl's (AH), vaso único con amplia variabilidad anatómica, comunica las arterias umbilicales cerca de la inserción del cordón umbilical en las placentas humanas. El objetivo del presente trabajo fue determinar si existe relación entre las características morfométricas de la placenta y la presencia de anastomosis y analizar si esta tiene influencia en la eficiencia placentaria. Estudio descriptivo. Se analizaron 60 placentas provenientes de madres que aceptaron participar en la investigación, embarazo único, a término (entre 37,0 y 41,6 semanas), con edades entre 18 y 37 años, con al menos cuatro visitas a control prenatal, sin comorbilidades. Las características placentarias de peso, diámetros y grosor se tomaron en fresco. Una vez fijadas con formaldehido al 10 %, mediante disección se ubicó, clasificó y fotografió la anastomosis. El peso de la placenta fue 494,4 ± 87,1 gramos, el grosor central correspondió a 1,7 ± 0,4 cm, DM 19,9 ± 2,0 cm y Dm 18,4 ± 1,7 cm. La inserción de cordón predominante fue excéntrica (65 %) y la forma discoidea u ovalada (60 %). En 51 placentas se ubicó la presencia de anastomosis (85 %). En el grupo de placentas con presencia AH se encontró un peso placentario más bajo al compararlo con el grupo que no presentó AH, el resto de las características morfométricas de la placenta, incluido el tipo de inserción de cordón umbilical no presentaron relación con la anastomosis. La eficiencia placentaria expresada con la relación entre peso neonato/peso placenta presentó diferencias significativas en el grupo con presencia de anastomosis, con mayores valores comparados con el grupo sin anastomosis. La presencia de AH contribuye positivamente a la eficiencia placentaria. Sin embargo, el incremento del peso placentario puede ser un efecto compensador de la placenta y no siempre indica una mayor eficiencia funcional del órgano.

SUMMARY: Hyrtl's anastomosis (HA), a single vessel, with wide anatomical variability, communicates the umbilical arteries, near the insertion of the umbilical cord in human placentas. The objective of this study was to determine if there is a relationship between the morphometric characteristics of the placenta and the presence of the anastomosis and to analyze if this influences the placental efficiency. Descriptive study. We analyzed 60 placentas from mothers who agreed to participate in the study, single pregnancy, term (between 37.0 and 41.6 weeks), aged between 18 and 37 years with at least four visits to prenatal control, without comorbidities. The placental characteristics of weight, diameters and thickness were taken fresh. Once fixed with 10 % formaldehyde, the anastomosis was located, classified, and photographed by dissection. The weight of the placenta was 494.4 ± 87.1 g, the central thickness corresponded to 1.7 ± 0.4 cm, the MD 19.9 ± 2.0 cm and Dm 18.4 ± 1.7 cm: The predominant cord insertion was eccentric, with 65 % and the discoid or oval shape with 60 %. In 51 placentas the presence of anastomosis was found (85 %). In the group of placentas with AH presence, a lower placental weight was found when compared to the group that did not present AH, the rest of the morphometric characteristics of the placenta, including the type of umbilical cord insertion, were not related to the anastomosis. Placental efficiency expressed as the neonatal weight/placental weight ratio showed significant differences in the group with presence of anastomosis, with higher values compared to the group without anastomosis. The presence of HA contributes positively to placental efficiency. However, the increase in placental weight may be a compensatory effect of the placenta and does not always indicate a greater functional efficiency of the organ.

Characteristics of the equine placenta at first trimester / Características de la placenta equina en el primer trimestre

The equine placenta is a simple apposition of fetal and maternal tissues, becoming more complex with the formation of microcotyledons around days 75 and 100 of gestation. The present study aimed to describe the gross and microscopic morphology of early equine placenta. Embryonic/fetal membranes from thirty-seven mares were submitted to macroscopic description, light, scanning and transmission microscopy. Overall the gross characteristics of membranes were similar with already described for older stages. However, transmission electron microscopy evidenced high metabolic rate in chorion and allantois, and high secretion profile in amnion and even higher in yolk sac. Gene ontologies enrichment, using published data, pointed several common ontologies in allantoic and amniotic fluids, related to oxygen and iron transport, extracellular space and high-density lipoprotein receptor binding. Overall, the morphological and ontology enrichment could indicate allantois and amnion crosstalk.

La placenta equina es una simple aposición de tejidos fetales y maternos, que se vuelve más compleja con la formación de microcotiledones alrededor de los días 75 y 100 de gestación. El presente estudio tuvo como objetivo describir la morfología macroscópica y microscópica de la placenta equina temprana. Las membranas embrionarias / fetales de treinta y siete yeguas fueron sometidas a descripción macroscópica, luz, escaneo y microscopía de transmisión. En general, las características generales de las membranas fueron similares a las ya descritas para las etapas más antiguas. Sin embargo, la microscopía electrónica de transmisión mostró una alta tasa metabólica en corion y alantoides, y un alto perfil de secreción en amnios e incluso mayor en el saco vitelino. El enriquecimiento de ontologías génicas, utilizando datos publicados, señaló varias ontologías comunes en fluidos alantoideos y amnióticos, relacionados con el transporte de oxígeno y hierro, espacio extracelular y unión a receptores de lipoproteínas de alta densidad. En general, el enriquecimiento morfológico y ontológico podría indicar alantoides y diafonía de amnios.

Placental measurements and their association with birth weight in a Brazilian cohort / Medidas placentárias e sua associação com o peso ao nascer em uma coorte brasileira

ABSTRACT: Introduction: Epidemiological studies have shown associations between placental measurements and perinatal and later life outcomes. Objectives: To report placental measurements and evaluate their association with birth weight in a Brazilian birth cohort. Methods: Retrospective cohort study with 958 mothers, placentas, and newborns delivered at the Ribeirão Preto Medical School Hospital, Universidade de São Paulo, Brazil, in 2010 and 2011. The information was collected from interviews, medical records, and pathology reports. The placental measurements were: weight, largest and smallest diameters, eccentricity, thickness, shape, area, and birth weight/placental weight and placental weight/birth weight ratios. We analyzed the associations between birth weight and placental measurements using multiple linear regression. Results: Placental weight alone accounted for 48% of birth weight variability (p < 0.001), whereas placental measurements combined (placental weight, largest and smallest diameters, and thickness) were responsible for 50% (p < 0.001). When adjusted for maternal and neonatal characteristics, placental measurements explained 74% of birth weight variability (p < 0.001). Conclusion: Placental measurements are powerful independent predictors of birth weight. Placental weight is the most predictive of them, followed by the smallest diameter.

RESUMO: Introdução: Estudos epidemiológicos demonstraram associações entre medidas placentárias, resultados perinatais e futuros. Objetivos: Descrever medidas placentárias e avaliar suas associações com peso ao nascer numa coorte de nascimentos brasileira. Metodologia: Estudo de coorte retrospectiva de 958 mães, placentas e recém-nascidos no Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo, Brasil, em 2010 e 2011. As informações foram coletadas por entrevistas, prontuários médicos e laudos de patologia. As medidas placentárias foram: peso, diâmetros maior e menor, excentricidade, espessura, forma, área, relações peso ao nascer/ peso da placenta e peso da placenta/ peso ao nascer. As associações entre peso ao nascer e medidas placentárias foram examinadas por meio de regressão linear múltipla. Resultados: O peso da placenta foi responsável por 48% da variabilidade do peso ao nascer (p < 0,001), enquanto o conjunto de medidas placentárias (peso, diâmetros maior e menor e espessura) foi responsável por 50% (p < 0,001). Quando ajustadas pelas características maternas e neonatais, as medidas placentárias explicaram 74% da variabilidade do peso ao nascer (p < 0,001). Conclusão: medidas placentárias são preditores independentes do peso ao nascer. O peso placentário é o mais forte preditor dentre elas, seguido pelo diâmetro menor.

Expresión de calreticulina en placenta canina / Calreticulin expression in canine placenta

La placenta es un anexo embrionario de los mamíferos que tiene por función principal el intercambio de nutrientes y gases y proteger al concepto de un potencial daño inmune provocado por diferencias alogénicas en los Complejos Principales de Histocompatibilidad paternos. Se han descrito diversas proteínas asociadas a su función, siendo Calreticulina una de ellas. Si bien existen estudios de la presencia de Calreticulina en placenta humana, no existen reportes de esta proteína en la placenta canina. Se obtuvieron muestras de placenta canina de las que se extrajo el contenido proteico total y se determinó la presencia de Calreticulina por western blot e inmunohistoquímica. Los resultados mostraron presencia de Calreticulina en placenta canina con un peso molecular aparente de 60 kDa, concordante con lo descrito para la molécula por otros autores. El análisis inmunohistoquímico mostró que Calreticulina canina está presente principalmente en el trofoblasto de las vellosidades, no existiendo diferencias en cuanto a su localización al compararla con placenta humana, pese a sus diferencias morfológicas e histológicas. Esta información permitirá establecer un protocolo estandarizado de extracción de Calreticulina desde placenta, así como orientar acerca de los posibles roles de esta molécula en la placenta.

The placenta is an embryonic organ present in mammals, whose main functions are the exchange of nutrients and gases and to protect the fetus from potential immune damage mediated by paternal and maternal allogeneic differences in the Major Histocompatibility Complex. Several proteins associated with its function have been described, being Calreticulin one of them. Although there are studies on the presence of Calreticulin in human placenta, there are no reports of this protein in canine placenta. Samples from canine placenta were obtained, proteins extracted and Calreticulin was subsequently detected by western blot and immunohistochemistry. The results showed the presence of Calreticulin in canine placenta with an apparent molecular weight of 60 kDa, in agreement with the results from other authors. The immunohistochemical analysis showed that canine Calreticulin is present mainly in the trophoblast of the villi, and there is no difference in its localization when compared with a blood-filled placenta such as human one, despite its morphological and histological differences. We also propose a standardized protocol for the extraction of Calreticulin from placenta, given its abundant expression in this organ. Future studies are aimed at elucidating possible roles of this protein in placenta.

Lección MOODLE de anatomía e histología de la placenta humana / MOODLE lesson of the anatomy and histology of the human placenta

RESUMEN: La falta de muestras biológicas humanas existentes, debido principalmente a las limitaciones ético-morales relacionadas con su obtención, ponen en relieve la necesidad de buscar otras alternativas de enseñanza y aprendizaje de las ciencias morfológicas. En este sentido, la implementación de lecciones a través de la plataforma MOODLE proporciona la oportunidad al estudiante de interactuar en un entorno que simula una situación de aprendizaje propio del laboratorio tradicional. El objetivo del presente trabajo fue generar una lección MOODLE sobre la anatomía e histología placentaria humana, como complemento a la clase teórica presencial, para estudiantes de la carrera de Obstetricia y Puericultura. Para tal cometido, se realizó búsqueda de información, imágenes y recursos TIC en bibliotecas e internet. Paralelamente, se llevó a cabo un proceso de captura fotográfica de muestras histológicas de placenta, así como también la grabación de un alumbramiento. Posteriormente, se procedió a la articulación y montaje de las actividades en la plataforma MOODLE con un enfoque constructivista. Además, se elaboró una encuesta de satisfacción, la cual fue validada por 3 expertos. La muestra estuvo constituida por 137 estudiantes de la carrera de Obstetricia. Se confeccionó un laboratorio virtual MOODLE de anatomía e histología de la placenta humana, el cual esta constituido por múltiples actividades con orientación clínica, las cuales permiten autoevaluarse. El laboratorio virtual nos ha ayudado ha subsanar la carencia de muestras humanas y los resultados de la encuesta de satisfacción aplicada a los estudiantes señalan una valoración positiva de la iniciativa.

SUMMARY: The lack of existing human biological samples, mainly due to the ethical-moral restrictions related to obtaining these, highlights the need to search for other teaching and learning alternatives in morphological science. In this sense, the implementation of lessons by means of the MOODLE platform provides the students with the opportunity to interact in a setting that simulates a learning situation that belongs to traditional laboratories. The purpose of this work was to generate a MOODLE lesson on the anatomy and histology of the human placenta, as a complement of the traditional theoretical classroom for students of Obstetrics. To that end, TIC information, images, and resources were sought in libraries and in the Internet, and at the same time a set of histological photographs of placenta samples was made, as well as a video recording of a placental delivery. Later, the coordination and set up of activities was made in the MOODLE platform with a constructivist approach. Furthermore, a satisfaction survey was prepared which was validated by three experts. The total sample consisted of 137 students in the 2th year of obstetrics. A virtual MOODLE laboratory of the anatomy and histology of the human placenta was made, which is constituted by multiple activities with a clinical orientation that allow self-evaluation. The virtual laboratory has helped overcome the lack of human samples, and results of the satisfaction survey applied to the students indicate a positive evaluation of this initiative.

Subplacental development in Galea spixii / Desenvolvimento subplacentário do preá (Galea spixii)

Animal models are essential to understand healthy human placentation. Guinea pig related rodents became on focus for such purposes. In particular, processes of trophoblast invasion are similar. The latter is associated with a specialized area, the subplacenta. Since previous results showed differences between the guinea pig and its close relative Galea spixii, we aimed to study subplacental development with more detail. We investigated 16 pregnant females of 14 to 55 days of gestation by means of histology, morphometrics, immunohistochemistry and electron microscopy. The overlap between the fetomaternal blood systems resulted as intimate, suggesting some exchange processes. Proliferation was revealed by three independent methods, being most active in early and mid-gestation, which was in accordance to former results. Though degeneration of tissues took place, the subplacenta was maintained towards term with access to the fetal vascularization, supporting a hypothesis about the release of substances to the fetal unit in advanced gestation. In contrast to other species, the extraplacental trophoblast showed a shift from syncytial streamers to giant cells during mid-gestation. Views on placentation in caviomorphs were influenced by the guinea pig, but our data supported recent studies that the subplacenta had a much greater placidity. In regard to subplacental grow, degeneration and likely also exchange processes, Galea and other species showed a more basal pattern of caviomorphs than the guinea pig. Such differences should be considered, when choosing most adequate animal models for special purposes in comparison to human placentation.(AU)

Modelos animais são essenciais para entender a placenta humana sadia. Neste sentido os roedores relacionados ao porquinho da índia tornaram-se foco para tal entendimento. Em particular, os processos de invasão trofoblástica são semelhantes. O último está associado a uma área especializada, a subplacenta. Uma vez que os resultados anteriores mostraram diferenças entre o porquinho da índia e seu relativo o preá, buscamos estudar o desenvolvimento subplacentário com mais detalhes. Pesquisamos 16 fêmeas gestantes de 14 a 55 dias de gestação por meio de histologia, morfometria, imuno-histoquímica e microscopia eletrônica. A sobreposição entre os sistemas sanguíneos materno e fetal apresentou-se com íntima relação, sugerindo alguns processos de troca. A proliferação foi revelada por três métodos independentes, sendo mais ativos no início e metade da gestação, o que corroborou com os resultados anteriores. Embora a degeneração dos tecidos tenha ocorrido, a subplacenta foi mantida até o termo gestacional com acesso à vascularização fetal, apoiando uma hipótese sobre a liberação de substâncias para a unidade fetal em gestação avançada. Em contraste com outras espécies, o trofoblasto extraplacentário mostrou uma mudança de flâmulas sinciciais para células gigantes durante a metade da gestação. As visualizações sobre a placentação em caviomorfos foram influenciadas pelo porquinho da índia, mas nossos dados apoiaram estudos recentes de que a subplacenta apresentava uma plasticidade muito maior. Em relação ao crescimento subplacentário, a degeneração e provavelmente também os processos de troca, o preá e outras espécies apresentaram um padrão mais basal de caviomorfos do que o porquinho da índia. Tais diferenças devem ser consideradas, ao escolher os modelos animais mais adequados para fins especiais em comparação com a placentação humana.(AU)

Histological characterization of reproductive tract and fetal annexes of the West Indian Manatee (Trichechus manatus) from Brazil / Caracterização histológica do trato reprodutor e anexos fetais do peixe-boi marinho (Trichechus manatus) do Brasil

The West Indian manatee (Trichechus manatus) is one of the most threatened aquatic mammals in Brazil, and is currently classified as "endangered" (MMA). The objective of this study was to characterize histologically the reproductive tract and fetal annexes of stranded manatees in northeastern Brazil. Tissue samples were collected from the reproductive tract of 23 manatees, which were fixed in 10% buffered formalin, processed using standard histological protocols and stained with hematoxylin eosin. We qualitatively described the histological and histomorphometric characteristics of each structure. Six ovaries were analyzed. In four ovaries, we found a large number of primordial and primary follicles. Two ovaries were different from the others: one had inflammatory infiltration and the other had a thickening in the cortex and absence of follicles. We also analyzed seven uteri (of which four were in the proliferative phase, two in the secretory phase, and one in the recovery phase), four placentas, one vagina, six testes (four were in the immature phase, one in the pubertal phase, and one in the mature phase), two epididymides, two penises, and one umbilical cord. The histological and morphometric findings in our work will support future analyses of the reproductive tract of T. manatus from Brazil.(AU)

O peixe-boi marinho (Trichechus manatus) é um dos mamíferos aquáticos mais ameaçados do Brasil e, atualmente é classificado como "em perigo" (MMA). O objetivo deste estudo foi caracterizar histologicamente o trato reprodutor e os anexos fetais de peixes-bois marinhos encalhados no Nordeste do Brasil. Foram coletadas amostras de tecidos do trato reprodutor de 23 peixes-bois marinhos (T. manatus), que foram fixadas em formol tamponado a 10%, processados usando protocolos histológicos padrão e corados com hematoxilina eosina. Foi realizada a descrição qualitativa das características histológicas e histomorfométricas de cada estrutura. Foram analisados seis ovários. Em quatro ovários, foi encontrado um grande número de folículos primordiais e primários. Dois ovários eram diferentes dos outros: um tinha infiltração inflamatória e o outro tinha um espessamento no córtex e ausência de folículos. Também foram analisadas sete amostras uterinas (das quais quatro estavam na fase proliferativa, duas na fase secretória e uma na fase de recuperação), quatro placentas, uma vagina, seis testículos (quatro na fase imatura, um na fase puberal e um na fase madura), dois epidídimos, dois pênis e um cordão umbilical. Os achados histológicos e morfométricos em nosso trabalho apoiarão futuras análises do trato reprodutivo de T. manatus do Brasil.(AU)

Terminologia embryologica y placenta: propuesta de términos embriológicos en español / Terminologia embryologica and placenta: proposal of embryological terms in Spanish

RESUMEN: En el área de la embriología, y en relación al uso de Terminologia Embryologica (TE), existen términos que son utilizados y que no se corresponden con ésta última. Pero a esta situación clásica, desde el origen de Nomina Anatomica de Basilea en 1895, se suma la ausencia de términos embriológicos en TE y que son diariamente reconocidos y nombrados en la práctica clínica. Además, no existe aún traducción oficial al español de TE. El objetivo de este trabajo consistió en realizar una propuesta de términos en español correspondientes a los términos incluídos en Paraplacenta [E6.0.2.4.0.1.], Placenta [E5.11.3.1.1.0.5] y Anomaliae placentae [E6.0.2.5.1.0.1], a partir de Terminologia Embryologica (TE) publicada por el Federal International Programme on Anatomical Terminologies en 2013, y en la cual sólo se encuentra la traducción al idioma inglés. La importancia de todos los trabajos relacionados con el buen uso de las terminologías y su correcta traducción al idioma vernáculo, radica en que la aplicación de un lenguaje único y común permitirá una mejor y mayor difusión de las investigaciones en el área de las ciencias morfológicas.

SUMMARY: In embryology, and in reference to the use of Terminologia Embryologica (TE), a number of terms used do not apply to TE., Since the origins of the Nomina Anatomica of Basel in 1895, the absence of embryological terms in TE is noted, even though these terms are commonly used in clinical practice. Furthermore, to date there is no official Spanish translation of TE. The aim of this work was to present a proposal of terms in Spanish, for the structures of the chapter Adnexa embryonica et fetalia; Membranae extraembryonicae et fetales corresponding to the terms included in Paraplacenta [E6.0.2.4.0.1.], Placenta [E5.11.3.1.1.0.5] and Anomaliae placentae [E6.0.2.5.1.0.1], from Terminologia Embryologica (TE) published by the Federal International Program on Anatomical Terminologies in 2013, wherein only the English translation can be found. The importance of all the articles related to the good use of terminologies and their correct translation into the vernacular language, is that the application of a unique and common language will allow a better and greater diffusion of the research in the area of the morphological sciences.

Placental weight and birth weight to placental weight ratio in monochorionic and dichorionic growth-restricted and non-growth-restricted twins

OBJECTIVE: The aim of the present study was to compare the placental weight and birth weight/placental weight ratio for intrauterine growth-restricted and non-intrauterine growth-restricted monochorionic and dichorionic twins. METHODS: This was a retrospective analysis of placentas from twin pregnancies. Placental weight and the birth weight/placental weight ratio were compared in intrauterine growth-restricted and non-intrauterine growth-restricted monochorionic and dichorionic twins. The association between cord insertion type and placental lesions in intrauterine growth-restricted and non-intrauterine growth-restricted monochorionic and dichorionic twins was also investigated. RESULTS: A total of 105 monochorionic (intrauterine growth restriction=40; non-intrauterine growth restriction=65) and 219 dichorionic (intrauterine growth restriction=57; non-intrauterine growth restriction=162) placentas were analyzed. A significantly lower placental weight was observed in intrauterine growth-restricted monochorionic (p=0.022) and dichorionic (p<0.001) twins compared to non-intrauterine growth-restricted twins. There was no difference in the birth weight/placental weight ratio between the intrauterine growth restriction and non-intrauterine growth restriction groups for either monochorionic (p=0.36) or dichorionic (p=0.68) twins. Placental weight and the birth weight/placental weight ratio were not associated with cord insertion type or with placental lesions. CONCLUSION: Low placental weight, and consequently reduced functional mass, appears to be involved in fetal growth restriction in monochorionic and dichorionic twins. The mechanism by which low placental weight influences the birth weight/placental weight ratio in intrauterine growth-restricted monochorionic and dichorionic twins needs to be determined in larger prospective studies.

Immunophenotyping of leukocytes in bovine placenta / Imunofenotipagem de leucócitos na placenta bovina

Lymphocytes and macrophages are the main white cells involved in fetal-maternal tolerance. Little is known about these leukocytes in bovine placenta, such as the quantity and location of these cells. Thus, the objective of this study was to identify lymphocyte and macrophage populations in bovine placenta using specific markers and flow cytometry. This study analyzed samples of placentomes and intercaruncular regions of cows in the three quarters of pregnancy. In the placentomes, during the first quarter of pregnancy, mean percentage of labeled CD3+ cells was 2.34%; CD8+, 1.28%; CD14+, 1.66%; and CD335+, 0.96%. For the intercaruncular region, percentage of CD3+ cells was 0.71%; CD8+, 1.63%; CD14+, 2.81%; and CD335+, 2.81%. In the second quarter, placentomes showed 0.94% CD3+ cells; 0.77% CD8+; 0.72% CD14+; and 0.51% CD335+. In the intercaruncular region, percentage of labeled CD3+ cells was 0.50%; CD8+, 1.81%; CD14+, 2.64%; and CD335+, 0.51%. In the third quarter, placentomes showed labeling of 0.88% CD3+; 0.66% CD8+; 1.06% CD14+; and 0.74% CD335+ cells. In the intercaruncular region, percentage of labeled CD3+ cells was 0.19%; CD8+, 2.23%; CD14+, 2.43%; and CD335+, 0.16%. The results showed that there was a greater immunomarking of leukocytes CD3+ and CD335+ in the placentome when compared to the intercaruncular region during the third trimester. It can be concluded that leukocytes populations in bovine placenta is reduced, probably because of the syndesmochorial characteristic of bovine placenta. This represents a significant barrier for the immunological system of the mother, sharply decreasing the exposure of the conceptus to the mother's immune system.(AU)

Linfócitos e macrófagos são os principais leucócitos envolvidos na tolerância materno-fetal. Pouco se sabe sobre esses leucócitos na placenta bovina, como por exemplo, a quantidade e localização dessas células. Assim, o objetivo desse estudo foi identificar populações de linfócitos e macrófagos na placenta bovina utilizando marcadores específicos e citometria de fluxo. Este estudo analisou amostras de placentônios da região intercaruncular de bovinos nos três trimestres da gestação. No primeiro trimestre, nos placentônios, a porcentagem média de células CD3+ foi 2,34%; CD8+, 1,28%; CD14+, 1,66%; e CD335+, 0,96%. Na região intercaruncular, a porcentagem de células CD3+ foi 0,71%; CD8+, 1,63%; CD14+, 2,81%; e CD335+, 2,81%. No segundo trimestre, os placentônios apresentaram 0,94% de células CD3+; 0,77% de CD8+; 0,72% de CD14+e 0,51% de CD335+. Na região intercaruncular, a porcentagem de células CD3+ foi 0,50%; CD8+, 1,81%; CD14+, 2,64%; e CD335+, 0,51%. No terceiro trimestre, os placentônios apresentaram 0,88% de células marcadas CD3+; 0,66% de CD8+; 1,06% de CD14+ e 0,74% de CD335+. Na região intercaruncular, a porcentagem de células CD3+ foi 0,19%; CD8+, 2,23%; CD14+, 2,43% e CD335+, 0,16%. Os resultados mostraram que a imunomarcação de leucócitos na região do placentônio foi maior do que na região intercaruncular no terceiro trimestre. Concluiu-se que a população de leucócitos CD3+ e CD335+ na placenta bovina está reduzida, provavelmente devido à sua característica sindesmocorial. Essa característica representa uma barreira significante para o sistema imunológico da mãe, o que diminui drasticamente a exposição do concepto ao sistema de defesa da mãe.(AU)

Placental Growth Measures in Relation to Birth Weight in a Latin American Population / Medidas de crescimento placentário em relação ao peso de nascimento em uma população latino-americana

Abstract Introduction The placenta, translates how the fetus experiences the maternal environment and is a principal influence on birth weight (BW). Objective To explore the relationship between placental growth measures (PGMs) and BW in a public maternity hospital. Methods Observational retrospective study of 870 singleton live born infants at Hospital Maternidad Sardá, Universidad de Buenos Aires, Argentina, between January 2011 and August 2012 with complete data of PGMs. Details of history, clinical and obstetrical maternal data, labor and delivery and neonatal outcome data, including placental measures derived from the records, were evaluated. The following manual measurements of the placenta according to standard methods were performed: placental weight (PW, g), larger and smaller diameters (cm), eccentricity, width (cm), shape, area (cm2), BW/PW ratio (BPR) and PW/BW ratio (PBR), and efficiency. Associations between BW and PGMs were examined using multiple linear regression. Results Birth weight was correlated with placental weight (R2 =0.49, p < 0.001), whereas gestational age was moderately correlated with placental weight (R2 =0.64, p < 0.001). By gestational age, there was a positive trend for PW and BPR, but an inverse relationship with PBR (p < 0.001). Placental weight alone accounted for 49% of birth weight variability (p < 0,001), whereas all PGMs accounted for 52% (p < 0,001). Combined, PGMs, maternal characteristics (parity, pre-eclampsia, tobacco use), gestational age and gender explained 77.8% of BW variations (p < 0,001). Among preterm births, 59% of BW variances were accounted for by PGMs, compared with 44% at term. All placental measures except BPR were consistently higher in females than in males, which was also not significant. Indices of placental efficiency showed weakly clinical relevance. Conclusions Reliable measures of placental growth estimate 53.6% of BW variances and project this outcome to a greater degree in preterm births than at term. These findings would contribute to the understanding of the maternal-placental programming of chronic diseases.

Resumo Introdução Aplacenta traduz como o feto experimenta o ambientematerno, alémde ser a principal influência sobre o peso ao nascer (PN). Objetivo Explorar a relação entre medidas de crescimento da placenta (MCPs) e PN em uma maternidade pública. Métodos Estudo retrospectivo observacional de 870 recém-nascidos vivos únicos na Maternidade Sardá, Universidade de Buenos Aires, Argentina, entre janeiro de 2011 e agosto de 2012 com os dados completos das MCPs. Foram avaliados dados da história clínica e obstétricamaterna, trabalho de parto e resultados neonatais, incluindomedidas da placenta derivadas dos registrosmédicos. Foramrealizadas as seguintesmediçõesmanuais da placenta: peso da placenta (PP, g), diâmetros maior e menor (cm), excentricidade, espessura (cm), forma, área (cm2), razões PN/PP e PP/PN e eficiência. Associações entre PN e MCPs foram examinadas por meio de regressão linear múltipla. Resultados Peso ao nascer foi correlacionado com peso placentário (R2 = 0,49, p < 0,001), enquanto idade gestacional foi moderadamente correlacionada com peso placentário (R2 = 0,64, p < 0,001). Por idade gestacional, houve uma tendência positiva para a relação PP e PN/PP, mas uma relação inversa com a razão PP/PN (p < 0,001). Somente peso da placenta respondeu por 49% da variabilidade do peso ao nascer (p < 0,001), ao passo que todas as MCPs foram responsáveis por 52% (p < 0,001). Combinados, MCPs, características maternas (paridade, pré-eclâmpsia, fumo), idade gestacional e sexo explicaram 77,8% da variação do peso ao nascer (p < 0,001). Entre nascimentos pré-termo, 59% da variância do PN foi contabilizada pelas MCPs, emcomparação com44% a termo. Todas asmedidas placentárias, exceto a razão PN/PP, foram consistentemente maiores em mulheres do que em homens, mas não significativas. Índices de eficiência placentária mostraram fraca relevância clínica. Conclusões medidas confiáveis de crescimento placentário estimam 53,6% da variância do peso ao nascer, e projetamesse resultado a ummaior grau emnascimentos pré-termo do que a termo. Estes resultados contribuiriam para a compreensão da programação materno-placentária de doenças crónicas.

Histological features of the placenta and their relation to the gross and data from Thoroughbred mares / Achados histológicos da placenta e sua relação com seus aspectos macroscópicas e dados de éguas Puro Sangue Inglês

The placenta is a transitory organ that originates from maternal and fetal tissues, the function of which is transporting nutrients from the mother to the fetus. The aim of this study was describe the histological features of placentas in healthy Thoroughbred mares at foaling and evaluate their relation with the gross placental and data of these mares. For this study 188 Thoroughbred mares were used. It was performed clinical observation for signs of placentitis during daily health checks and ultrasonic examination monthly to assess the fetus and placenta. All of the mares that exhibited clinical signs of placentitis were treated during gestation. The parturition was assisted, the placentas were grossly evaluated and samples were collected immediately after expulsion. The following data were considered for each mare: age, gestational age, number of parturition, time for placental expulsion, umbilical-cord length, placental weight and clinical signs of placentitis. Histological evaluation of the placentas revealed extensive cytoplasmic vacuolization of the epithelial areolar cells, presence of inflammatory infiltrates and hypoplasia-atrophy of the microcotyledons. Most of the gross placental findings were consistent with the histological results. In conclusion the mares with a vacuolated placental chorionic epithelium were older and had experienced a larger number of births. Great part of the mares with inflammatory infiltrates did not showed any clinical signs of placentitis during gestation.(AU)

A placenta é um órgão transitório originado do tecido fetal e materno, com função de transportar nutrientes da mãe para o feto. O objetivo deste estudo foi descrever os achados histológicos das placentas de éguas Puro Sangue Inglês (PSI) a termo e avaliar sua relação com a macroscopia da placenta e dados dessas éguas. O estudo utilizou 188 éguas PSI. Foram realizadas observações clinicas diárias para presença de sinais clínicos de placentite e ultrassonografia mensal para avaliar saúde do feto e placenta. As éguas que apresentaram sinais clínicos de placentite durante a gestação foram tratadas. Os partos foram assistidos, as placentas avaliadas macroscopicamente e coletadas imediatamente após sua expulsão. Como dados das éguas foram considerados: idade, tempo de gestação, número de partos, tempo de eliminação da placenta, comprimento de cordão umbilical, peso da placenta e sinais clínicos de placentite. A avaliação histológica das placentas demonstrou extensiva vacuolização citoplasmática das células do epitélio coriônico das regiões areolares, presença de infiltrados inflamatórios e hipoplasia-atrofia de microcotilédones. A maior parte dos achados macroscópicos da placenta foram condizentes com os resultados de histologia. Como conclusão, a vacuolização do epitélio coriônico foi característica de éguas mais velhas e com maior número de partos. Grande parte das éguas com infiltrados inflamatórios não demonstraram sinais clínicos de placentite.(AU)

Reduced placental volume and flow in severe growth restricted fetuses

OBJECTIVES: To evaluate placental volume and vascular indices in pregnancies with severe fetal growth restriction and determine their correlations to normal reference ranges and Doppler velocimetry results of uterine and umbilical arteries. METHODS: Twenty-seven fetuses with estimated weights below the 3rd percentile for gestational age were evaluated. Placental volume and vascular indices, including vascularization, flow, and vascularization flow indices, were measured by three-dimensional ultrasound using a rotational technique and compared to a previously described nomogram. The observed-to-expected placental volume ratio for gestational age and observed-to-expected placental volume ratio for fetal weight were calculated. Placental parameters correlated with the Doppler velocimetry results of uterine and umbilical arteries. RESULTS: The mean uterine artery pulsatility index was negatively correlated with the observed-to-expected placental volume ratio for gestational age, vascularization index and vascularization flow index. The observed-to-expected placental volume ratio for gestational age and observed-to-expected placental volume ratio for fetal weight and vascularization index were significantly lower in the group with a bilateral protodiastolic notch. No placental parameter correlated with the umbilical artery pulsatility index. CONCLUSIONS: Pregnancies complicated by severe fetal growth restriction are associated with reduced placental volume and vascularization. These findings are related to changes in uterine artery Doppler velocimetry. Future studies on managing severe fetal growth restriction should focus on combined results of placental three-dimensional ultrasound and Doppler studies of uterine arteries.

Determinants of feto-placental ratio.

The dimension of delivered placentae mirrors the cumulative growth of the placenta from conception to parturition. Placental weight is the gross summary of fetal growth under the influence of many extrinsic and intrinsic factors. Hence, the present study evaluated the influence of gestation, sex of the newborn, and parity on feto-placental ratio. The study was conducted on 391 placentae of singleton newborn from a teaching hospital of North Karnataka, India. Data was collected from August 2012 to January 2013 by using standard operating procedures. The Mean and standard deviations of placental morphometry, weight and birth weight are 440 ± 100gm and 2700±500 gm respectively. In gestational age 28 to 32 weeks, the feto-placental ratio was 5.61:1; this increased consistently up to 6.19:1 with increasing gestation group 37 weeks and above. Feto-placental ratio increased with increasing groups of gestational age. Feto-placental ratio in <37 weeks of gestation was in favor of primipara (6.0:1) whereas, the similar figures in term babies was more in multipara (6.3:1). The paritywise feto-placental ratio direction changed from preterm to term babies, but the differences were not statistically significant. However, irrespective of gestation, multipara had higher feto-placental ratio (6.2:1) as compared to primipara (6.1:1). However, irrespective of gestation, males had higher feto-placental ratio (6.2:1) as compared to females (6.1:1). Feto-placental ratio is influenced by variates of pregnancy like gestation, sex of the newborn and parity. Hence, variations in any of these factors lead to adverse pregnancy outcome by deviation of feto-placental ratio.

Efeito da iluminação constante sobre a placenta de ratas: um estudo morfológico, morfométrico e histoquímico / The effect of constant illumination on the placenta in rats: a morphological, morphometric and immunohistochemical study

A presente pesquisa analisou o efeito da iluminação constante sobre a estrutura placentária de ratas, abordando parâmetros morfológicos, morfométricos e histoquímicos. Vinte ratas albinas foram submetidas aos seguintes tratamentos: 12hL/12hE por 60 dias, e acasaladas em seguida (GI); ausência de luz por 60 dias, e acasaladas em seguida (GII); iluminação constante por 60 dias, e acasaladas em seguida (GIII); iluminação constante por 60 dias, acasaladas em seguida e tratadas com melatonina (GIV). O estímulo luminoso foi em torno de 400 lux. A melatonina foi administrada na água (400mg/mL de etanol). Os resultados mostraram que histologicamente o GII apresentou vacuolização das células do trofospongio. Morfometricamente, o GIII apresentou camada do labirinto com redução no número de trofoblastos sinciciais e maior vascularização materno-fetal, hiperplasia e hipertrofia das células trofoblásticas gigantes, uma maior média da área total do disco placentário; porém, na camada de trofospongio, as células trofoblásticas e trofoblastos sinciciais não diferiram nos grupos experimentais. As placentas do GIV foram semelhantes às do GI. Histoquimicamente não houve alterações nas fibras colágenas, elásticas, reticulares e glicosaminoglicanas ácidas. Em conclusão, a iluminação constante promove alterações morfológicas e morfométricas na placenta de ratas, podendo acarretar redução funcional e restrições ao crescimento fetal. Essas alterações são abolidas pela reposição de melatonina.

This study examined the effect of constant illumination on the placental structure of rats, addressing morphological, morphometric and immunohistochemical parameters. 20 albino rats were subjected to the following treatments: GI-12hL/12hE for 60 days and then mated; GII- dark for 60 days and then mated; GIII- constant illumination for 60 days and then mated and GIV- constant light for 60 days, mated and then treated with melatonin. The light stimulus was around 400 lux. Melatonin was administered in water (400 mg / ml ethanol). The results showed that GII had histologically trofospongio vacuolization of cells. Morphometrically, GIII presented a labyrinth layer reduction in the number of syncytial trophoblasts and greater maternal-fetal vasculature, hyperplasia and hypertrophy of trophoblast giant cells, a higher average of the total area of the placenta disk, but in the trofospongio layer, the trophoblast cells and syncytial trophoblasts did not differ between experimental groups. The placentas in GIV were similar to GI. Histochemically there were no changes in the collagen and elastic fibers, reticular and acidic glycosaminoglycans. In conclusion, the constant lighting promotes morphological and morphometric changes in the placenta in rats and may lead to functional reduction and restrictions on fetal growth. These changes are abolished by the melatonin replacement.

Morphology of Pêga jennies term placenta and its fetal-maternal interface / Morfologia da placenta a termo e da interface materno-fetal da jumenta Pêga

This study describes the placental morphology and fetal-maternal interface regarding macroscopic and microscopic aspects from Pêga Jennies at end of pregnancy. Eleven placentas were evaluated after delivery, and four fragments from each placenta were taken in duplicate corresponding to the pregnant uterine horn and non-pregnant horn. Fragments from fetal-maternal interface were obtained from one Jennie at C- section. All fragments were submitted to light microscopy and scanning electron microscopy. Regarding the macroscopic aspect of the placenta, microcotyledons were observed at the endometrial interface, characterized by the diffuse aspect of the placenta. Light microscopy revealed villous type chorion at the chorioallantoic membrane, which were organized in agglomeration villi, presenting a connective tissue stroma and trophoblastic cells. At the fetal-maternal interface, micro placentation, which were composed by inter digitations of agglomeration of villi, limited by maternal crypts, circled by arcades, composed by a fetal trophoblast and an internal portion. In addition, endometrial glands opening were observed. Scanning electron microscopy revealed that the chorioallantoic membranes were covered by villi agglomerations. At the top of those fetal villi we observed cell protrusions from trophoblast cells, which carried debris from maternal tissues. A transversal section from the fetal- maternal interface represented an intricate villi interdigitation with thin maternal caruncle structures, which consist in micro placentation. Macro and microscopic aspects of Jennies placenta, as well as the fetalmaternal interface presented similarities with the observed in mares.

O presente trabalho descreveu a morfologia placentária e a interface materno-fetal de jumentas da raça Pêga, quanto aos aspectos macroscópicos e microscópicos ao final da gestação. Foram avaliadas onze placentas, colhendo-se quatro fragmentos por placenta em duplicata, correspondentes ao corno uterino prenhe e ao corno uterino não prenhe. Fragmentos da interface materno-fetal, oriundos de uma jumenta com gestação a termo, foram obtidos durante o procedimento de cesariana. Os fragmentos foram examinados por microscopia de luz e microscopia eletrônica de varredura. Na macroscopia, foi observado microcotilédone na interface com o endométrio caracterizando placentação difusa. À microscopia de luz na membrana corioalantoide foi observado o córion do tipo viloso, com vilos organizados em tufos vilosos, estroma de tecido conjuntivo e células trofoblásticas. Na interface materno-fetal, microplacentônios, formados pela interdigitação dos tufos vilosos, limitados pelas criptas maternas, circundados pelas arcadas, compostos por uma parte fetal trofoblástica e uma parte interna, observando-se a abertura de glândulas endometriais. À microscopia eletrônica de varredura, foi constatado que a membrana corioalantoide se encontrava coberta por tufos vilosos. Nos ápices dos vilos fetais, foram observadas protrusões de células do trofoblasto, carreando debris de tecidos maternos. Em corte transversal da interface materno-fetal, foi verificada a intrincada interdigitação dos vilos com as finas estruturas das carúnculas maternas, formando os microplacentônios. Os aspectos macro e microscópicos da placenta da jumenta, assim como as descrições da interface materno-fetal apresentaram similaridades com os observados na égua.

Florfenicol associado ou não ao cloprostenol no tratamento de retenção de placenta em vacas leiteiras / Florfenicol and sodium cloprostenol for the treatment of retained placenta in dairy cows

The aim of this study was to compare the reproductive efficiency in dairy cows with retained placenta (RP), treated with Florfenicol associated or not with Cloprostenol. One hundred and eight cows with RP from dairy herds in southern Minas Gerais state and northern São Paulo state, were included for this purpose. The experiment was designed in factorial 2X2 . The four treatments encompassed two levels of each factor : 1 ) Florfenicol - 4 0mg/kg ( IM) divided in two injections or 40mg / kg ( SC) in one injection after calving; 2) Cloprostenol (0.530mg) - two injections associated with florfenicol treatment or without cloprostenol. The analysis of discrete variables used the Kruskal - Wallis (fou r groups) or Wilcoxon (two groups) statistic to compare groups. The Student "T" test was used to compare means of continuous variables. The overall occurrence of RP was 20.7%. The florfenicol groups had no effects on postpartum uterine health or subsequent reproductive efficiency of the cows. The cloprostenol injections of RP hastened the uterine involution and decreased the occurrence of uterine infection, and increased the percentage of animals with corpus luteum between 25 and 40 days after parturition. The intervals from parturition to first artificial insemination (AI) and to conception, as well as the number of AI per conception were reduced in the cloprostenol treatment.

Correlation between placental thickness in the second and third trimester and fetal weight / Correlação entre a espessura da placenta no segundo e terceiro trimester e peso fetal

PURPOSE: To investigate relationship between placental thickness during the second and third trimesters and placental and birth weights. METHODS: From January 2011 to June 2012, a total of 250 singleton pregnant women presented at our antenatal clinic were enrolled in this prospective study. All recruited women were assessed at the 1st trimester screening for baseline demographic and obstetric data. The placental thickness was measured trans-abdominally by placing the ultrasound transducer perpendicularly to the plane of the placenta, in the area of the cord insertion at second and third trimester. Pearson's correlation analysis was used to establish the degree of relationship between placental thickness and birth and placental weights. RESULTS: Of 250 recruited participants, 205 women were able to complete the study. The mean age of cases was 26.4±5.1. Values of mean birth and placental weights were 305.56±657.0 and 551.7±104.8 grams respectively. Ultrasonographic measures of placental thickness in second and third trimester and changes between them were 21.68±4.52, 36.26±6.46 and 14.67±5.67 mm respectively. There was a significant positive correlation between placental thickness and birth weight in the second and third trimesters (r=0.15, p=0.03; r=0.14, p=0.04 correspondingly). CONCLUSION: According to our study, birth weight has a positive relation with both second and third trimester placental thickness; however, placental thickness change could not predict low birth weight.

OBJETIVO: Investigar a relação entre espessura da placenta no segundo e terceiro trimestre e peso ao nascer e da placenta. MÉTODOS: Um total de 250 gestantes portadoras de um feto único que atenderam nossa clínica pré-natal de janeiro a junho de 2012 foram incluídas no estudo. Todas as mulheres recrutadas foram avaliadas na triagem do 1º trimestre a respeito dos dados demográficos e obstétricos basais. A espessura da placenta foi medida trans-abdominalmente colocando-se o transdutor do ultrassom perpendicular ao plano da placenta, na área de inserção do cordão, no segundo e terceiro trimestre. A análise de correlação de Pearson foi utilizada para estabelecer o grau de relação entre a espessura da placenta e o peso ao nascer e da placenta. RESULTADOS: Entre as 250 participantes recrutadas, 205 conseguiram completar o estudo. A média de idade das mulheres foi de 26,4±5,1 anos. O peso médio ao nascer e da placenta foram, respectivamente, de 305,56±657,0 e 551,7±104,8 gramas. As medidas ultrassonográficas da espessura da placenta no segundo e terceiro trimestre e as mudanças entre eles foram, respectivamente, de 21,68±4,52, 36,26±6,46 e 14,67±5,67 mm. Houve uma correlação positiva significativa entre a espessura da placenta no segundo e terceiro trimestre e o peso ao nascer (r=0.15, p=0.03; r=0.14, p=0.04). CONCLUSÃO: Com base em nosso estudo, o peso ao nascer tem correlação positiva com a espessura da placenta tanto no segundo como no terceiro semestre; entretanto, a espessura da placenta não pode predizer baixo peso ao nascer.

Histomorphometry of preterm and term human placentas / Histomorfometría de placentas de pretérmino y término

The intra-uterine existence of foetus is dependent on placenta, a major organ of nutrition and homeostasis.The present study was carried out to compare morphometric and histological changes in preterm and term human placentas. Eighty placentas collected from Department of Obstetrics and Gynecology, JNMCH, AMU, Aligarh, were divided into group first of preterm placentas up to 36 weeks (n =30) and second group of full term placentas i.e. 37 to 40 weeks ( n = 50) respectively. The samples were fixed in 10 percent formol-saline solution. The gross morphological variables of placentas were studied. There was a significant increase in the placental weight, decidual area and umbilical cord diameter of term placenta as compared to that of the preterm ones. From each placenta whole thickness tissue blocks were taken and processed for paraffin sectioning. Five µ-thick sections were stained with Haematoxylin-eosin and Van Gieson stains and processed for light microscopy. A total of 200 villi were studied in each sample under high power field and occurrence of different features was expressed as percentages for each parameter. The appearance of microvilli and syncytial bud on the syncytium were almost absent in the villi of term placentas. It was concluded that with increasing gestational age there was a gradual increase in the number of capillaries in villi from preterm to term placenta.There was a significant increase in syncytial knot count, fibrinoid necrosis, vasculosyncytial membrane and decrease in the percentage of villi showing cytotrophoblastic cells and number of Hofbauer cells in term group as compared to preterm group.

La existencia intrauterina del feto depende de la placenta, el mayor órgano de nutrición y homeostasis. El estudio se llevó a cabo para comparar los cambios morfométricos e histológicos de la placenta humana de término y pretérmino. Ochenta placentas fueron obtenidas del Departamento de Obstetricia y Ginecología, JNMCH, AMU, Aligarh y se dividieron en grupos, el primer grupo de placentas de pretérmino hasta 36 semanas (n = 30) y el segundo grupo de placentas de término, de 37 a 40 semanas (n = 50 ). Las muestras fueron fijadas en solución de formol-salina al 10 por ciento. Se estudiaron las variables morfológicas macroscópicas de las placentas. Hubo un aumento significativo en el peso de la placenta, el área de decidua y el diámetro del cordón umbilical de la placenta a término en comparación con la de los prematuros. De cada placenta se tomaron y se procesaron bloques de tejido para incluirlos en parafina. Cortes de 5 µm fueron teñidos con HE y Van Gieson para microscopía óptica. De cada muestra fueron estudiadas 200 vellosidades, bajo campo de alta resolución y la aparición de diferentes características se expresó como porcentajes para cada parámetro. La aparición de las microvellosidades y brote sincitial en el sincitio estaban casi ausente en las vellosidades de las placentas de término. Se puede concluir que al aumentar la edad gestacional hubo un aumento gradual en el número de capilares en las vellosidades de la placenta de término. Existe un aumento significativo en el recuento de nudo sincitial, necrosis fibrinoide, membrana vasculosincisial y disminución en el porcentaje de las vellosidades que muestran células citotrofoblástica y número de células de Hofbauer en las placentas del término de grupo en comparación con el grupo de pretérmino.

Placenta: Anatomía e Histología Comparada / Placenta: Compared Anatomy and Histology

La placenta, anexo embrionario propio de los mamíferos placentados, imprescindible para la supervivencia embriofetal, está formada por la zona más superficial del endometrio y el corion, asociado con el saco vitelino o el alantoides, dependiendo de la especie. La placenta provee el intercambio gaseoso y nutricio entre la madre y el feto, secreta hormonas y posee propiedades inmunosupresoras. Existen diferentes criterios para clasificar la placenta; de acuerdo a la distribución de las vellosidades coriales de la placenta: difusa, cotiledonaria, zonaria y discoidal; de acuerdo a las características histológicas de la placenta: epiteliocorial, sindesmocorial, endoteliocorial y hemocorial.

The placenta is an extraembryonic membrane of placental mammals, essential for embryo survival. It is formed by the most superficial zone of the endometrium and the chorion, associated with the yolk sac or allantois, depending on the species. The placenta provides gas and nutrient exchange between mother and fetus, secretes hormones and has immunosuppressive properties. There are different criteria to classify the placenta; i. e. according to the distribution of the chorionic villi of the placenta: diffuse, cotyledonary, zonaria and discoidal; according to the histological characteristics of the placenta: epitheliochorial, syndesmochorial, endotheliochorial and hemocorial.