Placenta
Encyclopedia
The placenta is an organ
that connects the developing fetus
to the uterine
wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals
, but are also found in some snakes and lizards
with varying levels of development up to mammalian levels. Note, however, that the homology
of such structures in various viviparous organisms
is debatable at best and, in invertebrates such as Arthropoda, is definitely analogous
at best. However, a recent publication describes what amounts to a phylogenetically
analogous, but physiologically and functionally almost identical structure in a skink
. In some senses it is not particularly surprising, because many species are ovoviviparous
and some are known as examples of various degrees of viviparous matrotrophy. However, the latest example is the most extreme to date, of a purely reptilian placenta directly comparable to a eutheria
n placenta.
The word placenta comes from the Latin
for cake, from Greek
plakóenta/plakoúnta, accusative of plakóeis/plakoús – πλακόεις, πλακούς, "flat, slab-like", in reference to its round, flat appearance in humans. The classical plural is placentae, but the form placentas is common in modern English and probably has the wider currency at present.
Prototheria
l (egg-laying) and metatheria
l (marsupial) mammals produce a choriovitelline placenta that, while connected to the uterine wall, provides nutrients mainly derived from the egg sac.
The placenta functions as a fetomaternal organ with two components: the fetal placenta , or (Chorion frondosum), which develops from the same sperm and egg cells that form the fetus; and the maternal placenta, or (Decidua basalis), which develops from the maternal uterine tissue.
of approximately 55–60 cm (22–24 inch) in length that contains two arteries and one vein. 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.
into the maternal endometrium
. The outer layer of the blastocyst becomes the trophoblast
, which forms 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 cytotrophoblast cells, a process that continues throughout placental development. The syncytiotrophoblast (otherwise known as syncytium), thereby contributes to the barrier function of the placenta.
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 (approximately 12–13 weeks).
through these spiral arteries bathes 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 pulse
s, the deoxygenated blood flows back through the endometrial veins.
Maternal blood flow is approx 600–700 ml/min at term.
Endothelin
and prostanoid
s cause vasoconstriction
in placental arteries, while nitric oxide
vasodilation
. On the other hand, there is no neural vascular regulation, and catecholamines have only little effect.
Adverse pregnancy situations, such as those involving maternal diabetes or obesity, can increase or decrease levels of nutrient transporters in the placenta resulting in overgrowth or restricted growth of the fetus.
Furthermore, the placenta functions as a selective maternal-fetal barrier against transmission of microbes to the fetus. However, insufficiency in this function may still cause mother-to-child transmission of infectious diseases.
Hormones:
Human Chorionic Gonadotropin (hCG): The first placental hormone produced is hCG, which can be found in maternal blood and urine as early as the first missed menstrual period (shortly after implantation has occurred) through about the 100th day of pregnancy. This is the hormone analyzed by pregnancy test; a false-negative result from a pregnancy test may be obtained before or after this period. Women's blood serum will be completely negative for hCG by one to two weeks after birth. hCG testing is proof that all placental tissue is delivered. hCG is present only during pregnancy because it is secreted by the placenta, which is present only during pregnancy.
hCG also ensures that the corpus luteum continues to secrete progesterone and estrogen. Progesterone is very important during pregnancy because, when its secretion decreases, the endometrial lining will slough off and pregnancy will be lost. hCG suppresses the maternal immunologic response so that placenta is not rejected.
Human Placental Lactogen (hPL [Human Chorionic Somatomammotropin]): This hormone is lactogenic and growth-promoting properties. It promotes mammary gland growth in preparation for lactation in the mother. It also regulates maternal glucose, protein, and fat levels so that this is always available to the fetus.
Estrogen is referred to as the "hormone of women" because it stimulates the development of secondary female sex characteristics. It contributes to the woman's mammary gland development in preparation for lactation and stimulates uterine growth to accommodate growing fetus.
Progesterone is necessary to maintain endometrial lining of the uterus during pregnancy. This hormone prevents preterm labor by reducing myometrial contraction. Levels of progesterone are high during pregnancy.
inside the mother, and thus must evade from attack by the mother's immune system
.
For this purpose, the placenta uses several mechanisms:
However, the placental barrier is not the sole means to evade the immune system, as foreign foetal cells also persist in the maternal circulation, on the other side of the placental barrier.
.
begins as a physiological separation from the wall of the uterus. The period from just after the fetus is expelled until just after the placenta is expelled is called the third stage of labor. The placenta is usually expelled within 15–30 minutes of the baby's being born.
Placental expulsion can be managed actively, for example by giving oxytocin
via intramuscular injection followed by cord traction to assist in delivering the placenta. As an alternative, it can be managed expectantly, allowing the placenta to be expelled without medical assistance. A Cochrane database study suggests that blood loss and the risk of postpartum bleeding will be reduced in women offered active management of the third stage of labour (needs updating).
Numerous pathologies can affect the placenta.
Infections involving the placenta:
s, with many societies conducting rituals regarding its disposal. In the Western world
, the placenta is most often incinerated.
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. Likewise, the Navajo
bury the placenta and umbilical cord at a specially chosen site, particularly if the baby dies during birth. In Cambodia
and Costa Rica
, burial of the placenta is believed to protect and ensure the health of the baby and the mother. 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.
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 raven
s to encourage future prophet
ic visions. In Turkey
, the proper disposal of the placenta and umbilical cord is believed to promote devoutness in the child later in life. In Ukraine
, Transylvania
, and Japan
, interaction with a disposed placenta is thought to influence the parents' future fertility.
Several cultures believe the placenta to be or have been alive, often a relative of the baby. Nepal
ese think of the placenta as a friend of the baby; Malaysian Orang Asli
regard it as the baby's older sibling. The Ibo
of Nigeria
consider the placenta the deceased twin of the baby, and conduct full funeral rites for it. 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. Various cultures in Indonesia
, such as Javanese, believe that the placenta has a spirit and needs to be buried outside the family house.
In some cultures, the placenta is eaten, a practice known as placentophagy
. In some eastern cultures, such as China
and Hong Kong
, the dried placenta (紫河車) is thought to be a healthful restorative and is sometimes used in preparations of traditional Chinese medicine
and various health products.
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
that connects the developing fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
to the uterine
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals
Eutheria
Eutheria is a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials . They are distinguished from noneutherians by various features of the feet, ankles, jaws and teeth...
, but are also found in some snakes and lizards
Squamata
Squamata, or the scaled reptiles, is the largest recent order of reptiles, including lizards and snakes. Members of the order are distinguished by their skins, which bear horny scales or shields. They also possess movable quadrate bones, making it possible to move the upper jaw relative to the...
with varying levels of development up to mammalian levels. Note, however, that the homology
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
of such structures in various viviparous organisms
Vivipary
Vivipary has two different meanings. In animals, it means development of the embryo inside the body of the mother, eventually leading to live birth, as opposed to laying eggs...
is debatable at best and, in invertebrates such as Arthropoda, is definitely analogous
Analogy (biology)
An analogy is a trait or an organ that appears similar in two unrelated organisms. The cladistic term for the same phenomenon is homoplasy, from Greek for same form. Biological anologies are often the result of convergent evolution....
at best. However, a recent publication describes what amounts to a phylogenetically
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
analogous, but physiologically and functionally almost identical structure in a skink
Skink
Skinks are lizards belonging to the family Scincidae. Together with several other lizard families, including Lacertidae , they comprise the superfamily or infraorder Scincomorpha...
. In some senses it is not particularly surprising, because many species are ovoviviparous
Ovoviviparity
Ovoviviparity, ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch...
and some are known as examples of various degrees of viviparous matrotrophy. However, the latest example is the most extreme to date, of a purely reptilian placenta directly comparable to a eutheria
Eutheria
Eutheria is a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials . They are distinguished from noneutherians by various features of the feet, ankles, jaws and teeth...
n placenta.
The word placenta comes from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for cake, from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
plakóenta/plakoúnta, accusative of plakóeis/plakoús – πλακόεις, πλακούς, "flat, slab-like", in reference to its round, flat appearance in humans. The classical plural is placentae, but the form placentas is common in modern English and probably has the wider currency at present.
Prototheria
Prototheria
Prototheria is a taxonomic group, or taxon, to which the order Monotremata belongs. It is conventionally ranked as a subclass within the mammals.Most of the animals in this group are extinct...
l (egg-laying) and metatheria
Metatheria
Metatheria is a grouping within the animal class Mammalia. First proposed by Thomas Henry Huxley in 1880, it is nearly synonymous with the earlier taxon Marsupialia though it is slightly wider since it also contains the nearest fossil relatives of marsupial mammals.The earliest known...
l (marsupial) mammals produce a choriovitelline placenta that, while connected to the uterine wall, provides nutrients mainly derived from the egg sac.
The placenta functions as a fetomaternal organ with two components: the fetal placenta , or (Chorion frondosum), which develops from the same sperm and egg cells that form the fetus; and the maternal placenta, or (Decidua basalis), which develops from the maternal uterine tissue.
Structure
In humans, the placenta averages 22 cm (9 inch) in length and 2–2.5 cm (0.8–1 inch) in thickness (greatest thickness at the center and become thinner peripherally). It typically weighs approximately 500 grams (1 lb). It has a dark reddish-blue or maroon color. It connects to the fetus by an umbilical cordUmbilical cord
In placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta...
of approximately 55–60 cm (22–24 inch) in length that contains two arteries and one vein. 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.
Development
The placenta begins to develop upon implantation of the blastocystBlastocyst
The blastocyst is a structure formed in the early embryogenesis of mammals, after the formation of the morula. It is a specifically mammalian example of a blastula. It possesses an inner cell mass , or embryoblast, which subsequently forms the embryo, and an outer layer of cells, or trophoblast,...
into the maternal endometrium
Endometrium
-Function:The endometrium is the innermost glandular layer and functions as a lining for the uterus, preventing adhesions between the opposed walls of the myometrium, thereby maintaining the patency of the uterine cavity. During the menstrual cycle or estrous cycle, the endometrium grows to a...
. The outer layer of the blastocyst becomes the trophoblast
Trophoblast
Trophoblasts are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta. They are formed during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg...
, which forms 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 cytotrophoblast cells, a process that continues throughout placental development. The syncytiotrophoblast (otherwise known as syncytium), thereby contributes to the barrier function of the placenta.
The placenta grows throughout pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
. Development of the maternal blood supply to the placenta is complete by the end of the first trimester of pregnancy (approximately 12–13 weeks).
Placental circulation
Maternal placental circulation
In preparation for implantation, the uterine endometrium undergoes 'decidualisation'. Spiral arteries in 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. The relatively high pressure as the maternal blood fills intervillous spaceIntervillous space
As a brief introduction, "inter" means between, and "villous" means "pertaining to a villus ", which in this case contains blood vessels, so the intervillous space is the "space between the villi containing the vessels" of the mother and the embryo.The trophoblast, which is a collection of cells...
through these spiral arteries bathes the fetal villi
Chorionic villi
Chorionic villi are villi that sprout from the chorion in order to give a maximum area of contact with the maternal blood.Embryonic blood is carried to the villi by the branches of the umbilical arteries, and after circulating through the capillaries of the villi, is returned to the embryo by the...
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 pulse
Pulse
In medicine, one's pulse represents the tactile arterial palpation of the heartbeat by trained fingertips. The pulse may be palpated in any place that allows an artery to be compressed against a bone, such as at the neck , at the wrist , behind the knee , on the inside of the elbow , and near the...
s, the deoxygenated blood flows back through the endometrial veins.
Maternal blood flow is approx 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").Endothelin
Endothelin
Endothelins are proteins that constrict blood vessels and raise blood pressure. They are normally kept in balance by other mechanisms, but when they are over-expressed, they contribute to high blood pressure and heart disease....
and prostanoid
Prostanoid
Prostanoid is the term used to describe a subclass of eicosanoids consisting of: the prostaglandins , the thromboxanes and the prostacyclins - Biosynthesis : Cyclooxygenase catalyzes the conversion of the free essential fatty acids to...
s cause vasoconstriction
Vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
in placental arteries, while nitric oxide
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
vasodilation
Vasodilation
Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins. The process is essentially the opposite of vasoconstriction, or the narrowing of blood vessels. When...
. On the other hand, there is no neural vascular regulation, and catecholamines have only little effect.
Nutrition
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 supply. Nutrient transfer to the fetus occurs via both active and passive transport. Active transport systems allow significantly different plasma concentrations of various large molecules to be maintained on the maternal and fetal sides of the placental barrier.Adverse pregnancy situations, such as those involving maternal diabetes or obesity, can increase or decrease levels of nutrient transporters in the placenta resulting in overgrowth or restricted growth of the fetus.
Immunity
IgG antibodies can pass through the human placenta, thereby providing protection to the fetus in utero.Furthermore, the placenta functions as a selective maternal-fetal barrier against transmission of microbes to the fetus. However, insufficiency in this function may still cause mother-to-child transmission of infectious diseases.
Endocrine function
In humans, aside from serving as the conduit for oxygen and nutrients for fetus, the placenta secretes hormones (secreted by syncytial layer/syncytiotrophoblast of chorionic villi) that are important during pregnancy.Hormones:
Human Chorionic Gonadotropin (hCG): The first placental hormone produced is hCG, which can be found in maternal blood and urine as early as the first missed menstrual period (shortly after implantation has occurred) through about the 100th day of pregnancy. This is the hormone analyzed by pregnancy test; a false-negative result from a pregnancy test may be obtained before or after this period. Women's blood serum will be completely negative for hCG by one to two weeks after birth. hCG testing is proof that all placental tissue is delivered. hCG is present only during pregnancy because it is secreted by the placenta, which is present only during pregnancy.
hCG also ensures that the corpus luteum continues to secrete progesterone and estrogen. Progesterone is very important during pregnancy because, when its secretion decreases, the endometrial lining will slough off and pregnancy will be lost. hCG suppresses the maternal immunologic response so that placenta is not rejected.
Human Placental Lactogen (hPL [Human Chorionic Somatomammotropin]): This hormone is lactogenic and growth-promoting properties. It promotes mammary gland growth in preparation for lactation in the mother. It also regulates maternal glucose, protein, and fat levels so that this is always available to the fetus.
Estrogen is referred to as the "hormone of women" because it stimulates the development of secondary female sex characteristics. It contributes to the woman's mammary gland development in preparation for lactation and stimulates uterine growth to accommodate growing fetus.
Progesterone is necessary to maintain endometrial lining of the uterus during pregnancy. This hormone prevents preterm labor by reducing myometrial contraction. Levels of progesterone are high during pregnancy.
Cloaking from immune system of mother
The placenta and fetus may be regarded as a foreign allograftAllotransplantation
Allotransplantation is the transplantation of cells, tissues, or organs, sourced from a genetically non-identical member of the same species as the recipient. The transplant is called an allograft or allogeneic transplant or homograft...
inside the mother, and thus must evade from attack by the mother's immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
.
For this purpose, the placenta uses several mechanisms:
- It secretes Neurokinin BNeurokinin BNeurokinin B is a tachykinin peptide.It is found in higher concentration in pregnant women suffering pre-eclampsia and can bind the immune-cloaking molecule phosphocholine....
-containing phosphocholinePhosphocholinePhosphocholine is an intermediate in the synthesis of phosphatidylcholine in tissues. Phosphocholine is made in a reaction, catalyzed by choline kinase, that converts ATP + Choline into Phosphocholine and ADP...
molecules. This is the same mechanism used by parasitic nematodeNematodeThe nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
s to avoid detection by the immune system of their hostHost (biology)In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...
. - There is presence of small lymphocytic suppressor cells in the fetus that inhibit maternal cytotoxic T cellCytotoxic T cellA cytotoxic T cell belongs to a sub-group of T lymphocytes that are capable of inducing the death of infected somatic or tumor cells; they kill cells that are infected with viruses , or are otherwise damaged or...
s by inhibiting the response to interleukin 2Interleukin 2Interleukin-2 is an interleukin, a type of cytokine immune system signaling molecule, which is a leukocytotrophic hormone that is instrumental in the body's natural response to microbial infection and in discriminating between foreign and self...
.
However, the placental barrier is not the sole means to evade the immune system, as foreign foetal cells also persist in the maternal circulation, on the other side of the placental barrier.
Other functions
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 capacitorCapacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
.
Birth
Placental expulsionPlacental expulsion
Placental expulsion occurs when the placenta comes out of the birth canal after childbirth. The period from just after the fetus is expelled until just after the placenta is expelled is called the third stage of labor....
begins as a physiological separation from the wall of the uterus. The period from just after the fetus is expelled until just after the placenta is expelled is called the third stage of labor. The placenta is usually expelled within 15–30 minutes of the baby's being born.
Placental expulsion can be managed actively, for example by giving oxytocin
Oxytocin
Oxytocin is a mammalian hormone that acts primarily as a neuromodulator in the brain.Oxytocin is best known for its roles in sexual reproduction, in particular during and after childbirth...
via intramuscular injection followed by cord traction to assist in delivering the placenta. As an alternative, it can be managed expectantly, allowing the placenta to be expelled without medical assistance. A Cochrane database study suggests that blood loss and the risk of postpartum bleeding will be reduced in women offered active management of the third stage of labour (needs updating).
Pathology
- Placenta accretaPlacenta accretaPlacenta accreta is a severe obstetric complication involving an abnormally deep attachment of the placenta, through the endometrium and into the myometrium...
(when the placenta implants too deeply, into actual muscle of uterine wall) - Placenta praeviaPlacenta praeviaPlacenta praevia is an obstetric complication in which the placenta is attached to the uterine wall close to or covering the cervix. It can sometimes occur in the later part of the first trimester, but usually during the second or third. It is a leading cause of antepartum haemorrhage...
- Placental abruptionPlacental abruptionPlacental abruption is a complication of pregnancy, wherein the placental lining has separated from the uterus of the mother. It is the most common pathological cause of late pregnancy bleeding. In humans, it refers to the abnormal separation after 20 weeks of gestation and prior to birth...
/abruptio placentae
Infections involving the placenta:
- Placentitis, such as the TORCH infections.
- ChorioamnionitisChorioamnionitisChorioamnionitis is an inflammation of the fetal membranes due to a bacterial infection. It typically results from bacteria ascending into the uterus from the vagina and is most often associated with prolonged labour...
.
Cultural practices and beliefs
The placenta often plays an important role in various cultureCulture
Culture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...
s, with many societies conducting rituals regarding its disposal. In the Western world
Western world
The Western world, also known as the West and the Occident , is a term referring to the countries of Western Europe , the countries of the Americas, as well all countries of Northern and Central Europe, Australia and New Zealand...
, the placenta is most often incinerated.
Some cultures bury
Burial
Burial is the act of placing a person or object into the ground. This is accomplished by excavating a pit or trench, placing an object in it, and covering it over.-History:...
the placenta for various reasons. The Māori of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
traditionally bury the placenta from a newborn child to emphasize the relationship between humans and the earth. Likewise, the Navajo
Navajo people
The Navajo of the Southwestern United States are the largest single federally recognized tribe of the United States of America. The Navajo Nation has 300,048 enrolled tribal members. The Navajo Nation constitutes an independent governmental body which manages the Navajo Indian reservation in the...
bury the placenta and umbilical cord at a specially chosen site, particularly if the baby dies during birth. In Cambodia
Cambodia
Cambodia , officially known as the Kingdom of Cambodia, is a country located in the southern portion of the Indochina Peninsula in Southeast Asia...
and Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
, burial of the placenta is believed to protect and ensure the health of the baby and the mother. If a mother dies in childbirth, the Aymara of Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
bury the placenta in a secret place so that the mother's spirit will not return to claim her baby's life.
Kwakiutl
The term Kwakiutl, historically applied to the entire Kwakwaka'wakw ethno-linguistic group of originally 28 tribes, comes from one of the Kwakwaka'wakw tribes, the Kwagu'ł or Kwagyeulth, at Fort Rupert, with whom Franz Boas did most of his anthropological work and whose Indian Act Band government...
of British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
bury girls' placentas to give the girl skill in digging clams, and expose boys' placentas to raven
Raven
Raven is the common name given to several larger-bodied members of the genus Corvus—but in Europe and North America the Common Raven is normally implied...
s to encourage future prophet
Prophet
In religion, a prophet, from the Greek word προφήτης profitis meaning "foreteller", is an individual who is claimed to have been contacted by the supernatural or the divine, and serves as an intermediary with humanity, delivering this newfound knowledge from the supernatural entity to other people...
ic visions. In Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
, the proper disposal of the placenta and umbilical cord is believed to promote devoutness in the child later in life. In Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
, Transylvania
Transylvania
Transylvania is a historical region in the central part of Romania. Bounded on the east and south by the Carpathian mountain range, historical Transylvania extended in the west to the Apuseni Mountains; however, the term sometimes encompasses not only Transylvania proper, but also the historical...
, and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, interaction with a disposed placenta is thought to influence the parents' future fertility.
Several cultures believe the placenta to be or have been alive, often a relative of the baby. Nepal
Nepal
Nepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
ese think of the placenta as a friend of the baby; Malaysian Orang Asli
Orang Asli
Orang Asli , is a generic Malaysian term used for people indigenous to Peninsular Malaysia...
regard it as the baby's older sibling. The Ibo
Igbo people
Igbo people, also referred to as the Ibo, Ebo, Eboans or Heebo are an ethnic group living chiefly in southeastern Nigeria. They speak Igbo, which includes various Igboid languages and dialects; today, a majority of them speak English alongside Igbo as a result of British colonialism...
of Nigeria
Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...
consider the placenta the deceased twin of the baby, and conduct full funeral rites for it. Native Hawaiians
Native Hawaiians
Native Hawaiians refers to the indigenous Polynesian people of the Hawaiian Islands or their descendants. Native Hawaiians trace their ancestry back to the original Polynesian settlers of Hawaii.According to the U.S...
believe that the placenta is a part of the baby, and traditionally plant it with a tree that can then grow alongside the child. Various cultures in Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
, such as Javanese, believe that the placenta has a spirit and needs to be buried outside the family house.
In some cultures, the placenta is eaten, a practice known as placentophagy
Placentophagy
Placentophagy is the act of mammals eating the placenta of their young after childbirth.The placenta contains high levels of prostaglandin which stimulates involution of the uterus, in effect cleaning the uterus out...
. In some eastern cultures, such as China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
and Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
, the dried placenta (紫河車) is thought to be a healthful restorative and is sometimes used in preparations of traditional Chinese medicine
Traditional Chinese medicine
Traditional Chinese Medicine refers to a broad range of medicine practices sharing common theoretical concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage , exercise , and dietary therapy...
and various health products.
External links
- Additional Human placenta photography
- The Placenta, gynob.com, with quotes from Williams Obstetrics, 18th Edition, F. Gary Cunningham, M.D., Paul C. MacDonald, M.D., Norman F. Grant, M.D., Appleton & Lange, Publishers.