Placenta

Last updated
Placenta
Healthy Placenta.jpg
Human placenta from just after birth with the umbilical cord in place
Placenta.svg
Human placenta shown in uterus connected to fetus with umbilical cord
Details
Precursor decidua basalis, chorion frondosum
Identifiers
Latin placenta
MeSH D010920
TE E5.11.3.1.1.0.5
Anatomical terminology

The placenta (pl.: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate maternal and fetal circulations, and is an important endocrine organ, producing hormones that regulate both maternal and fetal physiology during pregnancy. [1] The placenta connects to the fetus via the umbilical cord, and on the opposite aspect to the maternal uterus in a species-dependent manner. In humans, a thin layer of maternal decidual (endometrial) tissue comes away with the placenta when it is expelled from the uterus following birth (sometimes incorrectly referred to as the 'maternal part' of the placenta). Placentas are a defining characteristic of placental mammals, but are also found in marsupials and some non-mammals with varying levels of development. [2]

Contents

Mammalian placentas probably first evolved about 150 million to 200 million years ago. The protein syncytin, found in the outer barrier of the placenta (the syncytiotrophoblast) between mother and fetus, has a certain RNA signature in its genome that has led to the hypothesis that it originated from an ancient retrovirus: essentially a virus that helped pave the transition from egg-laying to live-birth. [3] [4] [5]

The word placenta comes from the Latin word for a type of cake, from Greek πλακόεντα/πλακοῦντα plakóenta/plakoúnta, accusative of πλακόεις/πλακούς plakóeis/plakoús, "flat, slab-like", [6] [7] with reference to its round, flat appearance in humans. The classical plural is placentae, but the form placentas is more common in modern English.

Evolution and phylogenetic diversity

The placenta has evolved independently multiple times, probably starting in fish, where it originated multiple times, including the genus Poeciliopsis. [8] Placentation has also evolved in some reptiles. [9]

The mammalian placenta evolved more than 100 million years ago and was a critical factor in the explosive diversification of placental mammals. [10] Although all mammalian placentas have the same functions, there are important differences in structure and function in different groups of mammals. For example, human, bovine, equine and canine placentas are very different at both the gross and the microscopic levels. Placentas of these species also differ in their ability to provide maternal immunoglobulins to the fetus. [11]

Structure

Placental mammals, including humans, have a chorioallantoic placenta that forms from the chorion and allantois. In humans, the placenta averages 22 cm (9 inch) in length and 2–2.5 cm (0.8–1 inch) in thickness, with the center being the thickest, and the edges being the thinnest. It typically weighs approximately 500 grams (just over 1 lb). It has a dark reddish-blue or crimson color. It connects to the fetus by an umbilical cord of approximately 55–60 cm (22–24 inch) in length, which contains two umbilical arteries and one umbilical vein. [12] The umbilical cord inserts into the chorionic plate (has an eccentric attachment). Vessels branch out over the surface of the placenta and further divide to form a network covered by a thin layer of cells. This results in the formation of villous tree structures. On the maternal side, these villous tree structures are grouped into lobules called cotyledons. In humans, the placenta usually has a disc shape, but size varies vastly between different mammalian species. [13]

The placenta occasionally takes a form in which it comprises several distinct parts connected by blood vessels. [14] The parts, called lobes, may number two, three, four, or more. Such placentas are described as bilobed/bilobular/bipartite, trilobed/trilobular/tripartite, and so on. If there is a clearly discernible main lobe and auxiliary lobe, the latter is called a succenturiate placenta. Sometimes the blood vessels connecting the lobes get in the way of fetal presentation during labor, which is called vasa previa .[ citation needed ]

Gene and protein expression

About 20,000 protein coding genes are expressed in human cells and 70% of these genes are expressed in the normal mature placenta. [15] [16] Some 350 of these genes are more specifically expressed in the placenta and fewer than 100 genes are highly placenta specific. The corresponding specific proteins are mainly expressed in trophoblasts and have functions related to pregnancy. Examples of proteins with elevated expression in placenta compared to other organs and tissues are PEG10 and the cancer testis antigen PAGE4 and expressed in cytotrophoblasts, CSH1 and KISS1 expressed in syncytiotrophoblasts, and PAPPA2 and PRG2 expressed in extravillous trophoblasts.

Physiology

Development

Placenta Placenta.png
Placenta
The initial stages of human embryogenesis HumanEmbryogenesis.svg
The initial stages of human embryogenesis

The placenta begins to develop upon implantation of the blastocyst into the maternal endometrium, very early on in pregnancy at about week 4. [17]

The outer layer of the late blastocyst, is formed of trophoblasts, cells that form the outer layer of the placenta. This outer layer is divided into two further layers: the underlying cytotrophoblast layer and the overlying syncytiotrophoblast layer. The syncytiotrophoblast is a multinucleated continuous cell layer that covers the surface of the placenta. It forms as a result of differentiation and fusion of the underlying cytotrophoblasts, a process that continues throughout placental development. The syncytiotrophoblast contributes to the barrier function of the placenta. [18]

The placenta grows throughout pregnancy. Development of the maternal blood supply to the placenta is complete by the end of the first trimester of pregnancy week 14 (DM). [17]

Placental circulation

Maternal blood fills the intervillous space, nutrients, water, and gases are actively and passively exchanged, then deoxygenated blood is displaced by the next maternal pulse. Gray39.png
Maternal blood fills the intervillous space, nutrients, water, and gases are actively and passively exchanged, then deoxygenated blood is displaced by the next maternal pulse.

Maternal placental circulation

In preparation for implantation of the blastocyst, the endometrium undergoes decidualization. Spiral arteries in the decidua are remodeled so that they become less convoluted and their diameter is increased. The increased diameter and straighter flow path both act to increase maternal blood flow to the placenta. There is relatively high pressure as the maternal blood fills intervillous space through these spiral arteries which bathe the fetal villi in blood, allowing an exchange of gases to take place. In humans and other hemochorial placentals, the maternal blood comes into direct contact with the fetal chorion, though no fluid is exchanged. As the pressure decreases between pulses, the deoxygenated blood flows back through the endometrial veins.[ citation needed ]

Maternal blood flow begins between days 5–12, [19] and is approximately 600–700 ml/min at term.

Fetoplacental circulation

Deoxygenated fetal blood passes through umbilical arteries to the placenta. At the junction of umbilical cord and placenta, the umbilical arteries branch radially to form chorionic arteries. Chorionic arteries, in turn, branch into cotyledon arteries. In the villi, these vessels eventually branch to form an extensive arterio-capillary-venous system, bringing the fetal blood extremely close to the maternal blood; but no intermingling of fetal and maternal blood occurs ("placental barrier"). [20]

Endothelin and prostanoids cause vasoconstriction in placental arteries, while nitric oxide causes vasodilation. [21] On the other hand, there is no neural vascular regulation, and catecholamines have only little effect. [21]

The fetoplacental circulation is vulnerable to persistent hypoxia or intermittent hypoxia and reoxygenation, which can lead to generation of excessive free radicals. This may contribute to pre-eclampsia and other pregnancy complications. [22] It is proposed that melatonin plays a role as an antioxidant in the placenta. [22]

This begins at day 17–22. [23]

Birth

Placental expulsion begins as a physiological separation from the wall of the uterus. The period from just after the child is born until just after the placenta is expelled is called the "third stage of labor". The placenta is usually expelled within 15–30 minutes of birth.[ citation needed ]

Placental expulsion can be managed actively, for example by giving oxytocin via intramuscular injection followed by cord traction to assist in delivering the placenta. Alternatively, it can be managed expectantly, allowing the placenta to be expelled without medical assistance. Blood loss and the risk of postpartum bleeding may be reduced in women offered active management of the third stage of labour, however there may be adverse effects and more research is necessary. [24]

The habit is to cut the cord immediately after birth, but it is theorised that there is no medical reason to do this; on the contrary, it is theorised that not cutting the cord helps the baby in its adaptation to extrauterine life, especially in preterm infants. [25]

Microbiome

The placenta is traditionally thought to be sterile, but recent research suggests that a resident, non-pathogenic, and diverse population of microorganisms may be present in healthy tissue. However, whether these microbes exist or are clinically important is highly controversial and is the subject of active research. [26] [27] [28] [29]

Functions

Nutrition and gas exchange

The placenta intermediates the transfer of nutrients between mother and fetus. The perfusion of the intervillous spaces of the placenta with maternal blood allows the transfer of nutrients and oxygen from the mother to the fetus and the transfer of waste products and carbon dioxide back from the fetus to the maternal blood. Nutrient transfer to the fetus can occur via both active and passive transport. [30] Placental nutrient metabolism was found to play a key role in limiting the transfer of some nutrients. [31] Adverse pregnancy situations, such as those involving maternal diabetes or obesity, can increase or decrease levels of nutrient transporters in the placenta potentially resulting in overgrowth or restricted growth of the fetus. [32]

Excretion

Waste products excreted from the fetus such as urea, uric acid, and creatinine are transferred to the maternal blood by diffusion across the placenta.[ citation needed ]

Immunity

The placenta functions as a selective barrier between maternal and fetal cells, preventing maternal blood, proteins and microbes (including bacteria and most viruses) from crossing the maternal-fetal barrier. [33] Deterioration in placental functioning, referred to as placental insufficiency, may be related to mother-to-child transmission of some infectious diseases. [34] A very small number of viruses including rubella virus , Zika virus and cytomegalovirus (CMV) can travel across the placental barrier, generally taking advantage of conditions at certain gestational periods as the placenta develops. CMV and Zika travel from the maternal bloodstream via placental cells to the fetal bloodstream. [33] [35] [36] [37]

Beginning as early as 13 weeks of gestation, and increasing linearly, with the largest transfer occurring in the third trimester, IgG antibodies can pass through the human placenta, providing protection to the fetus in utero. [38] [39] This passive immunity lingers for several months after birth, providing the newborn with a carbon copy of the mother's long-term humoral immunity to see the infant through the crucial first months of extrauterine life. IgM antibodies, because of their larger size, cannot cross the placenta, [40] one reason why infections acquired during pregnancy can be particularly hazardous for the fetus. [41]

Endocrine function

Immunological barrier

The placenta and fetus may be regarded as a foreign body inside the mother and must be protected from the normal immune response of the mother that would cause it to be rejected. The placenta and fetus are thus treated as sites of immune privilege, with immune tolerance.

For this purpose, the placenta uses several mechanisms :

However, the placental barrier is not the sole means of evading the immune system, as foreign fetal cells also persist in the maternal circulation, on the other side of the placental barrier. [46]

DNA methylation

The trophoblast is the outer layer of cells of the blastocyst (see day 9 in Figure, above, showing the initial stages of human embryogenesis). Placental trophoblast cells have a unique genome-wide DNA methylation pattern determined by de novo methyltransferases during embryogenesis. [47] This methylation pattern is principally required to regulate placental development and function, which in turn is critical for embryo survival. [47]

Other

The placenta also provides a reservoir of blood for the fetus, delivering blood to it in case of hypotension and vice versa, comparable to a capacitor. [48]

Ultrasound image of human placenta and umbilical cord (color Doppler rendering) with central cord insertion and three umbilical vessels, at 20 weeks of pregnancy Human placenta umbilical cord Ultrasound by Dr. W. Moroder.jpg
Ultrasound image of human placenta and umbilical cord (color Doppler rendering) with central cord insertion and three umbilical vessels, at 20 weeks of pregnancy

Clinical significance

Micrograph of a cytomegalovirus (CMV) infection of the placenta (CMV placentitis). The characteristic large nucleus of a CMV-infected cell is seen off-centre at the bottom-right of the image. H&E stain. CMV placentitis1 mini.jpg
Micrograph of a cytomegalovirus (CMV) infection of the placenta (CMV placentitis). The characteristic large nucleus of a CMV-infected cell is seen off-centre at the bottom-right of the image. H&E stain.

Numerous pathologies can affect the placenta.[ citation needed ]

Society and culture

The placenta often plays an important role in various cultures, with many societies conducting rituals regarding its disposal. In the Western world, the placenta is most often incinerated. [49]

Some cultures bury the placenta for various reasons. The Māori of New Zealand traditionally bury the placenta from a newborn child to emphasize the relationship between humans and the earth. [50] Likewise, the Navajo bury the placenta and umbilical cord at a specially chosen site, [51] particularly if the baby dies during birth. [52] In Cambodia and Costa Rica, burial of the placenta is believed to protect and ensure the health of the baby and the mother. [53] If a mother dies in childbirth, the Aymara of Bolivia bury the placenta in a secret place so that the mother's spirit will not return to claim her baby's life. [54]

The placenta is believed by some communities to have power over the lives of the baby or its parents. The Kwakiutl of British Columbia bury girls' placentas to give the girl skill in digging clams, and expose boys' placentas to ravens to encourage future prophetic visions. In Turkey, the proper disposal of the placenta and umbilical cord is believed to promote devoutness in the child later in life. In Transylvania and Japan, interaction with a disposed placenta is thought to influence the parents' future fertility.[ citation needed ]

Several cultures believe the placenta to be or have been alive, often a relative of the baby. Nepalese think of the placenta as a friend of the baby; the orang Asli and Malay populations in Malay Peninsula regard it as the baby's older sibling. [53] [55] Native Hawaiians believe that the placenta is a part of the baby, and traditionally plant it with a tree that can then grow alongside the child. [49] Various cultures in Indonesia, such as Javanese and Malay, believe that the placenta has a spirit and needs to be buried outside the family house. Some Malays would bury the baby's placenta with a pencil (if it is a boy) or a needle and thread (if it is a girl). [55]

In some cultures, the placenta is eaten, a practice known as placentophagy. In some eastern cultures, such as China, the dried placenta (ziheche 紫 河 车, literally "purple river car") is thought to be a healthful restorative and is sometimes used in preparations of traditional Chinese medicine and various health products. [56] The practice of human placentophagy has become a more recent trend in western cultures and is not without controversy; its practice being considered cannibalism is debated.

Some cultures have alternative uses for placenta that include the manufacturing of cosmetics, pharmaceuticals and food. [57]

Additional images

See also

Related Research Articles

The amniotic sac, also called the bag of waters or the membranes, is the sac in which the embryo and later fetus develops in amniotes. It is a thin but tough transparent pair of membranes that hold a developing embryo until shortly before birth. The inner of these membranes, the amnion, encloses the amniotic cavity, containing the amniotic fluid and the embryo. The outer membrane, the chorion, contains the amnion and is part of the placenta. On the outer side, the amniotic sac is connected to the yolk sac, the allantois, and via the umbilical cord, the placenta.

<span class="mw-page-title-main">Amnion</span> Innermost membranous sac that surrounds and protects the developing embryo

The amnion is a membrane that closely covers the human and various other embryos when first formed. It fills with amniotic fluid, which causes the amnion to expand and become the amniotic sac that provides a protective environment for the developing embryo. The amnion, along with the chorion, the yolk sac and the allantois protect the embryo. In birds, reptiles and monotremes, the protective sac is enclosed in a shell. In marsupials and placental mammals, it is enclosed in a uterus.

<span class="mw-page-title-main">Chorion</span> Outermost fetal membrane around the embryo in amniotes

The chorion is the outermost fetal membrane around the embryo in mammals, birds and reptiles (amniotes). It develops from an outer fold on the surface of the yolk sac, which lies outside the zona pellucida, known as the vitelline membrane in other animals. In insects, it is developed by the follicle cells while the egg is in the ovary. Some mollusks also have chorions as part of their eggs. For example, fragile octopus eggs have only a chorion as their envelope.

<span class="mw-page-title-main">Blastocyst</span> Structure formed around day 5 of mammalian embryonic development

The blastocyst is a structure formed in the early embryonic development of mammals. It possesses an inner cell mass (ICM) also known as the embryoblast which subsequently forms the embryo, and an outer layer of trophoblast cells called the trophectoderm. This layer surrounds the inner cell mass and a fluid-filled cavity known as the blastocoel. In the late blastocyst, the trophectoderm is known as the trophoblast. The trophoblast gives rise to the chorion and amnion, the two fetal membranes that surround the embryo. The placenta derives from the embryonic chorion and the underlying uterine tissue of the mother.

<span class="mw-page-title-main">Gestational hypertension</span> Medical condition

Gestational hypertension or pregnancy-induced hypertension (PIH) is the development of new hypertension in a pregnant woman after 20 weeks' gestation without the presence of protein in the urine or other signs of pre-eclampsia. Gestational hypertension is defined as having a blood pressure greater than 140/90 on two occasions at least 6 hours apart.

<span class="mw-page-title-main">Trophoblast</span> Early embryonic structure that gives rise to the placenta

The trophoblast is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the placenta. They form during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg to become extraembryonic structures that do not directly contribute to the embryo. After blastulation, the trophoblast is contiguous with the ectoderm of the embryo and is referred to as the trophectoderm. After the first differentiation, the cells in the human embryo lose their totipotency because they can no longer form a trophoblast. They become pluripotent stem cells.

<span class="mw-page-title-main">Syncytiotrophoblast</span> Embryonic cell of the placental surface

Syncytiotrophoblast is the epithelial covering of the highly vascular embryonic placental villi, which invades the wall of the uterus to establish nutrient circulation between the embryo and the mother. It is a multinucleate, terminally differentiated syncytium, extending to 13 cm.

<span class="mw-page-title-main">Cytotrophoblast</span>

"Cytotrophoblast" is the name given to both the inner layer of the trophoblast or the cells that live there. It is interior to the syncytiotrophoblast and external to the wall of the blastocyst in a developing embryo.

Placental insufficiency or utero-placental insufficiency is the failure of the placenta to deliver sufficient nutrients to the fetus during pregnancy, and is often a result of insufficient blood flow to the placenta. The term is also sometimes used to designate late decelerations of fetal heart rate as measured by cardiotocography or an NST, even if there is no other evidence of reduced blood flow to the placenta, normal uterine blood flow rate being 600mL/min.

<span class="mw-page-title-main">Implantation (embryology)</span> First stage of pregnancy

Implantation, also known as nidation, is the stage in the embryonic development of mammals in which the blastocyst hatches, attaches, adheres, and invades into the wall of the female's uterus. Implantation is the first stage of gestation, and, when successful, the female is considered to be pregnant. An implanted embryo is detected by the presence of increased levels of human chorionic gonadotropin (hCG) in a pregnancy test. The implanted embryo will receive oxygen and nutrients in order to grow.

<span class="mw-page-title-main">Decidualization</span> Physiological process in the endometrium

Decidualization is a process that results in significant changes to cells of the endometrium in preparation for, and during, pregnancy. This includes morphological and functional changes to endometrial stromal cells (ESCs), the presence of decidual white blood cells (leukocytes), and vascular changes to maternal arteries. The sum of these changes results in the endometrium changing into a structure called the decidua. In humans, the decidua is shed during childbirth.

<span class="mw-page-title-main">Human embryonic development</span> Development and formation of the human embryo

Human embryonic development or human embryogenesis is the development and formation of the human embryo. It is characterised by the processes of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, the development of the human body entails growth from a one-celled zygote to an adult human being. Fertilization occurs when the sperm cell successfully enters and fuses with an egg cell (ovum). The genetic material of the sperm and egg then combine to form the single cell zygote and the germinal stage of development commences. Embryonic development in the human, covers the first eight weeks of development; at the beginning of the ninth week the embryo is termed a fetus. The eight weeks has 23 stages.

<span class="mw-page-title-main">Percutaneous umbilical cord blood sampling</span>

Percutaneous umbilical cord blood sampling (PUBS), also called cordocentesis, fetal blood sampling, or umbilical vein sampling is a diagnostic genetic test that examines blood from the fetal umbilical cord to detect fetal abnormalities. Fetal and maternal blood supply are typically connected in utero with one vein and two arteries to the fetus. The umbilical vein is responsible for delivering oxygen rich blood to the fetus from the mother; the umbilical arteries are responsible for removing oxygen poor blood from the fetus. This allows for the fetus’ tissues to properly perfuse. PUBS provides a means of rapid chromosome analysis and is useful when information cannot be obtained through amniocentesis, chorionic villus sampling, or ultrasound ; this test carries a significant risk of complication and is typically reserved for pregnancies determined to be at high risk for genetic defect. It has been used with mothers with immune thrombocytopenic purpura.

<span class="mw-page-title-main">Velamentous cord insertion</span> Velamentous placenta

Velamentous cord insertion is a complication of pregnancy where the umbilical cord is inserted in the fetal membranes. It is a major cause of antepartum hemorrhage that leads to loss of fetal blood and associated with high perinatal mortality. In normal pregnancies, the umbilical cord inserts into the middle of the placental mass and is completely encased by the amniotic sac. The vessels are hence normally protected by Wharton's jelly, which prevents rupture during pregnancy and labor. In velamentous cord insertion, the vessels of the umbilical cord are improperly inserted in the chorioamniotic membrane, and hence the vessels traverse between the amnion and the chorion towards the placenta. Without Wharton's jelly protecting the vessels, the exposed vessels are susceptible to compression and rupture.

Immune tolerance in pregnancy or maternal immune tolerance is the immune tolerance shown towards the fetus and placenta during pregnancy. This tolerance counters the immune response that would normally result in the rejection of something foreign in the body, as can happen in cases of spontaneous abortion. It is studied within the field of reproductive immunology.

<span class="mw-page-title-main">Fetal membranes</span> Amnion and chorion which surround and protect a developing fetus

The fetal membranes are the four extraembryonic membranes, associated with the developing embryo, and fetus in humans and other mammals. They are the amnion, chorion, allantois, and yolk sac. The amnion and the chorion are the chorioamniotic membranes that make up the amniotic sac which surrounds and protects the embryo. The fetal membranes are four of six accessory organs developed by the conceptus that are not part of the embryo itself, the other two are the placenta, and the umbilical cord.

<span class="mw-page-title-main">Placental expulsion</span>

Placental expulsion occurs when the placenta comes out of the birth canal after childbirth. The period from just after the baby is expelled until just after the placenta is expelled is called the third stage of labor.

<span class="mw-page-title-main">Villitis of unknown etiology</span> Medical condition

Villitis of unknown etiology (VUE), also known as chronic villitis, is a placental injury. VUE is an inflammatory condition involving the chorionic villi. VUE is a recurrent condition and can be associated with intrauterine growth restriction (IUGR). IUGR involves the poor growth of the foetus, stillbirth, miscarriage, and premature delivery. VUE recurs in about 1/3 of subsequent pregnancies.

<span class="mw-page-title-main">Chorionic gonadotropin beta</span> Protein-coding gene in the species Homo sapiens

Choriogonadotropin subunit beta (CG-beta) also known as chorionic gonadotrophin chain beta is a protein that in humans is encoded by the CGB gene.

Extravillous trophoblasts(EVTs), are one form of differentiated trophoblast cells of the placenta. They are invasive mesenchymal cells which function to establish critical tissue connection in the developing placental-uterine interface. EVTs derive from progenitor cytotrophoblasts (CYTs), as does the other main trophoblast subtype, syncytiotrophoblast (SYN). They are sometimes called intermediate trophoblast.

References

  1. ↑ Jin M, Xu Q, Li J, Xu S, Tang C (September 2022). "Micro-RNAs in Human Placenta: Tiny Molecules, Immense Power". Molecules. 27 (18): 5943. doi: 10.3390/molecules27185943 . PMC   9501247 . PMID   36144676.
  2. ↑ Pough FH, Andrews RM, Cadle JE, Crump ML, Savitsky AH, Wells KD (2004). Herpetology (3rd ed.). Pearson. ISBN   978-0-13-100849-6.[ page needed ]
  3. ↑ Mitra A (31 January 2020). "How the placenta evolved from an ancient virus". WHYY . Retrieved 9 March 2020.
  4. ↑ Chuong EB (October 2018). "The placenta goes viral: Retroviruses control gene expression in pregnancy". PLOS Biology. 16 (10): e3000028. doi: 10.1371/journal.pbio.3000028 . PMC   6177113 . PMID   30300353.
  5. ↑ Villarreal LP (January 2016). "Viruses and the placenta: the essential virus first view". APMIS. 124 (1–2): 20–30. doi: 10.1111/apm.12485 . PMID   26818259. S2CID   12042851.
  6. ↑ Henry George Liddell, Robert Scott, "A Greek-English Lexicon", at Perseus Archived 2012-04-05 at the Wayback Machine .
  7. ↑ "placenta" Archived 2016-01-30 at the Wayback Machine . Online Etymology Dictionary .
  8. ↑ Reznick DN, Mateos M, Springer MS (November 2002). "Independent origins and rapid evolution of the placenta in the fish genus Poeciliopsis". Science. 298 (5595): 1018–1020. Bibcode:2002Sci...298.1018R. doi:10.1126/science.1076018. PMID   12411703. S2CID   2372572.
  9. ↑ Blackburn DG, Avanzati AM, Paulesu L (November 2015). "Classics revisited. History of reptile placentology: Studiati's early account of placentation in a viviparous lizard". Placenta. 36 (11): 1207–1211. doi:10.1016/j.placenta.2015.09.013. PMID   26474917.
  10. ↑ Ayala FJ (May 2007). "Darwin's greatest discovery: design without designer". Proceedings of the National Academy of Sciences of the United States of America. 104 (Suppl 1): 8567–8573. doi: 10.1073/pnas.0701072104 . PMC   1876431 . PMID   17494753.
  11. ↑ Bowen R. "Implantation and Development of the Placenta: Introduction and Index". Pathophysiology of the Reproductive System. Colorado State. Retrieved 7 July 2019.
  12. ↑ Yetter JF (March 1998). "Examination of the placenta". American Family Physician. 57 (5): 1045–54. PMID   9518951. Archived from the original on 2011-10-16.
  13. ↑ "Placental Structure and Classification". Colorado State. Archived from the original on 2016-02-11.
  14. ↑ Fujikura T, Benson RC, Driscoll SG (August 1970). "The bipartite placenta and its clinical features". American Journal of Obstetrics and Gynecology. 107 (7): 1013–1017. doi:10.1016/0002-9378(70)90621-6. PMID   5429965. Bipartite placenta represented 4.2 per cent (366 of 8,505) of placentas of white women at the Boston Hospital for Women who were enrolled in the Collaborative Project.
  15. ↑ "The human proteome in placenta - The Human Protein Atlas". www.proteinatlas.org. Archived from the original on 2017-09-26. Retrieved 2017-09-26.
  16. ↑ Uhlén M, Fagerberg L, Hallström BM, Lindskog C, Oksvold P, Mardinoglu A, et al. (January 2015). "Proteomics. Tissue-based map of the human proteome". Science. 347 (6220): 1260419. doi:10.1126/science.1260419. PMID   25613900. S2CID   802377.
  17. 1 2 "Stages of Development of the Fetus - Women's Health Issues". Merck Manuals Consumer Version. Retrieved 2022-06-12.
  18. ↑ "How Your Fetus Grows During Pregnancy". www.acog.org. Retrieved 2022-06-12.
  19. ↑ Dashe JS, Bloom SL, Spong CY, Hoffman BL (2018). Williams Obstetrics. McGraw Hill Professional. ISBN   978-1-259-64433-7.[ page needed ]
  20. ↑ "Placental blood circulation". Online course in embryology for medical students. Universities of Fribourg, Lausanne and Bern (Switzerland). Archived from the original on 2011-09-28.
  21. 1 2 Kiserud T, Acharya G (December 2004). "The fetal circulation". Prenatal Diagnosis. 24 (13): 1049–1059. doi:10.1002/pd.1062. PMID   15614842. S2CID   25040285.
  22. 1 2 Reiter RJ, Tan DX, Korkmaz A, Rosales-Corral SA (2013). "Melatonin and stable circadian rhythms optimize maternal, placental and fetal physiology". Human Reproduction Update. 20 (2): 293–307. doi: 10.1093/humupd/dmt054 . PMID   24132226.
  23. ↑ Williams book of obsteritcis.
  24. ↑ Begley CM, Gyte GM, Devane D, McGuire W, Weeks A, Biesty LM (February 2019). "Active versus expectant management for women in the third stage of labour". The Cochrane Database of Systematic Reviews. 2019 (2): CD007412. doi:10.1002/14651858.CD007412.pub5. PMC   6372362 . PMID   30754073.
  25. ↑ Mercer JS, Vohr BR, Erickson-Owens DA, Padbury JF, Oh W (January 2010). "Seven-month developmental outcomes of very low birth weight infants enrolled in a randomized controlled trial of delayed versus immediate cord clamping". Journal of Perinatology. 30 (1): 11–16. doi:10.1038/jp.2009.170. PMC   2799542 . PMID   19847185.
  26. ↑ Perez-Muñoz ME, Arrieta MC, Ramer-Tait AE, Walter J (April 2017). "A critical assessment of the "sterile womb" and "in utero colonization" hypotheses: implications for research on the pioneer infant microbiome". Microbiome. 5 (1): 48. doi: 10.1186/s40168-017-0268-4 . PMC   5410102 . PMID   28454555.
  27. ↑ Mor G, Kwon JY (October 2015). "Trophoblast-microbiome interaction: a new paradigm on immune regulation". American Journal of Obstetrics and Gynecology. 213 (4 Suppl): S131–S137. doi:10.1016/j.ajog.2015.06.039. PMC   6800181 . PMID   26428492.
  28. ↑ Prince AL, Antony KM, Chu DM, Aagaard KM (October 2014). "The microbiome, parturition, and timing of birth: more questions than answers". Journal of Reproductive Immunology. 104–105: 12–19. doi:10.1016/j.jri.2014.03.006. PMC   4157949 . PMID   24793619.
  29. ↑ Hornef M, Penders J (May 2017). "Does a prenatal bacterial microbiota exist?". Mucosal Immunology. 10 (3): 598–601. doi: 10.1038/mi.2016.141 . PMID   28120852.
  30. ↑ Wright C, Sibley CP (2011). "Placental Transfer in Health and Disease". In Kay H, Nelson M, Yuping W (eds.). The Placenta: From Development to Disease . John Wiley and Sons. pp.  66. ISBN   978-1-4443-3366-4.
  31. ↑ Perazzolo S, Hirschmugl B, Wadsack C, Desoye G, Lewis RM, Sengers BG (February 2017). "The influence of placental metabolism on fatty acid transfer to the fetus". Journal of Lipid Research. 58 (2): 443–454. doi: 10.1194/jlr.P072355 . PMC   5282960 . PMID   27913585.
  32. ↑ Kappen C, Kruger C, MacGowan J, Salbaum JM (2012). "Maternal diet modulates placenta growth and gene expression in a mouse model of diabetic pregnancy". PLOS ONE. 7 (6): e38445. Bibcode:2012PLoSO...738445K. doi: 10.1371/journal.pone.0038445 . PMC   3372526 . PMID   22701643.
  33. 1 2 Madhusoodanan J (October 10, 2018). "Break on through: How some viruses infect the placenta". Knowable Magazine. doi: 10.1146/knowable-101018-1 .
  34. ↑ Erlebacher A (2013-03-21). "Immunology of the maternal-fetal interface". Annual Review of Immunology. 31 (1): 387–411. doi:10.1146/annurev-immunol-032712-100003. PMID   23298207.
  35. ↑ Pereira L (September 2018). "Congenital Viral Infection: Traversing the Uterine-Placental Interface". Annual Review of Virology. 5 (1): 273–299. doi:10.1146/annurev-virology-092917-043236. PMID   30048217. S2CID   51724379.
  36. ↑ Arora N, Sadovsky Y, Dermody TS, Coyne CB (May 2017). "Microbial Vertical Transmission during Human Pregnancy". Cell Host & Microbe. 21 (5): 561–567. doi:10.1016/j.chom.2017.04.007. PMC   6148370 . PMID   28494237.
  37. ↑ Robbins JR, Bakardjiev AI (February 2012). "Pathogens and the placental fortress". Current Opinion in Microbiology. 15 (1): 36–43. doi:10.1016/j.mib.2011.11.006. PMC   3265690 . PMID   22169833.
  38. ↑ Palmeira P, Quinello C, Silveira-Lessa AL, Zago CA, Carneiro-Sampaio M (2012). "IgG placental transfer in healthy and pathological pregnancies". Clinical & Developmental Immunology. 2012: 985646. doi: 10.1155/2012/985646 . PMC   3251916 . PMID   22235228.
  39. ↑ Simister NE, Story CM (December 1997). "Human placental Fc receptors and the transmission of antibodies from mother to fetus". Journal of Reproductive Immunology. 37 (1): 1–23. doi:10.1016/s0165-0378(97)00068-5. PMID   9501287.
  40. ↑ Pillitteri A (2009). Maternal and Child Health Nursing: Care of the Childbearing and Childrearing Family. Hagerstwon, MD: Lippincott Williams & Wilkins. p. 202. ISBN   978-1-58255-999-5.
  41. ↑ "What infections can affect pregnancy?". National Institute of Child Health and Human Development. 27 April 2021. Retrieved 25 June 2021.
  42. ↑ Handwerger S, Freemark M (April 2000). "The roles of placental growth hormone and placental lactogen in the regulation of human fetal growth and development". Journal of Pediatric Endocrinology & Metabolism. 13 (4): 343–356. doi:10.1515/jpem.2000.13.4.343. PMID   10776988. S2CID   28778529.
  43. ↑ "Human Placental Lactogen". www.ucsfhealth.org. May 17, 2009. Archived from the original on April 29, 2017. Retrieved July 21, 2017.
  44. ↑ "Placenta 'fools body's defences'". BBC News. 10 November 2007. Archived from the original on 29 April 2012.
  45. ↑ Clark DA, Chaput A, Tutton D (March 1986). "Active suppression of host-vs-graft reaction in pregnant mice. VII. Spontaneous abortion of allogeneic CBA/J x DBA/2 fetuses in the uterus of CBA/J mice correlates with deficient non-T suppressor cell activity". Journal of Immunology. 136 (5): 1668–1675. doi: 10.4049/jimmunol.136.5.1668 . PMID   2936806. S2CID   22815679.
  46. ↑ Williams Z, Zepf D, Longtine J, Anchan R, Broadman B, Missmer SA, Hornstein MD (June 2009). "Foreign fetal cells persist in the maternal circulation". Fertility and Sterility. 91 (6): 2593–2595. doi: 10.1016/j.fertnstert.2008.02.008 . PMID   18384774.
  47. 1 2 Andrews S, Krueger C, Mellado-Lopez M, Hemberger M, Dean W, Perez-Garcia V, Hanna CW. Mechanisms and function of de novo DNA methylation in placental development reveals an essential role for DNMT3B. Nat Commun. 2023 Jan 23;14(1):371. doi: 10.1038/s41467-023-36019-9. PMID: 36690623; PMCID: PMC9870994
  48. ↑ Assad RS, Lee FY, Hanley FL (May 2001). "Placental compliance during fetal extracorporeal circulation". Journal of Applied Physiology. 90 (5): 1882–1886. doi:10.1152/jappl.2001.90.5.1882. PMID   11299282. S2CID   8785947.
  49. 1 2 "Why eat a placenta?". BBC News. 18 April 2006.
  50. ↑ Metge J (2005). "Working In/Playing With Three Languages". Sites: A Journal of Social Anthropology and Cultural Studies. 2 (2): 83–90. doi: 10.11157/sites-vol2iss2id65 .
  51. ↑ Francisco E (3 December 2004). "Bridging the Cultural Divide in Medicine". Science.
  52. ↑ Shepardson M (1978). "Changes in Navajo mortuary practices and beliefs". American Indian Quarterly. 4 (4): 383–396. doi:10.2307/1184564. JSTOR   1184564. PMID   11614175.
  53. 1 2 Buckley SJ. "Placenta Rituals and Folklore from around the World". Mothering. Archived from the original on 6 January 2008. Retrieved 7 January 2008.
  54. ↑ Davenport A (June 2005). "The Love Offer". Johns Hopkins Magazine. 57 (3).
  55. 1 2 Barakbah A (2017). Ensiklopedia Perbidanan Melayu. Universiti Islam Malaysia Press. pp. 236–237. ISBN   978-967-13305-9-3.
  56. ↑ Falcao R. "Medicinal Uses of the Placenta". Archived from the original on 5 December 2008. Retrieved 25 November 2008.
  57. ↑ Kroløkke C, Dickinson E, Foss KA (May 2018). "The placenta economy: From trashed to treasured bio-products". European Journal of Women's Studies. 25 (2): 138–153. doi:10.1177/1350506816679004. ISSN   1350-5068. S2CID   151874106.
  58. ↑ "Placental Weights: Means, Standard Deviations, and Percentiles by Gestational Age". Placental and Gestational Pathology. 2017. p. 336. doi:10.1017/9781316848616.039. ISBN   978-1-316-84861-6.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.