The placenta is a temporary
embryonic and later
fetal organ
Organ may refer to:
Biology
* Organ (biology), a part of an organism
Musical instruments
* Organ (music), a family of keyboard musical instruments characterized by sustained tone
** Electronic organ, an electronic keyboard instrument
** Hammond ...
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
Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemic ...
during
pregnancy
Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins.
Pregnancy usually occurs by sexual intercourse, but ...
.
The placenta connects to the fetus via the
umbilical cord, and on the opposite aspect to the maternal
uterus
The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...
in a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
-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.
Mammalian
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fu ...
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
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsk ...
that helped pave the transition from
egg-laying to
live-birth.
The word ''placenta'' comes from the
Latin
Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
word for
a type of cake, from
Greek πλακόεντα/πλακοῦντα ''plakóenta/plakoúnta'', accusative of πλακόεις/πλακούς ''plakóeis/plakoús'', "flat, slab-like", with reference to its round, flat appearance in humans. The classical plural is ''placentae'', but the form ''placentas'' is more common in modern English.
Phylogenetic diversity
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.
Structure
Placental mammals, including humans, have a chorioallantoic placenta that forms from the
chorion and
allantois
The allantois (plural ''allantoides'' or ''allantoises'') is a hollow sac-like structure filled with clear fluid that forms part of a developing amniote's conceptus (which consists of all embryonic and extraembryonic tissues). It helps the embryo ...
. 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. 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
cotyledon
A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germinating seed." The numb ...
s. In humans, the placenta usually has a disc shape, but size varies vastly between different mammalian species.
The placenta occasionally takes a form in which it comprises several distinct parts connected by blood vessels.
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''.
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. 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
Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins.
Pregnancy usually occurs by sexual intercourse, but ...
. 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
Human placental lactogen (hPL), also called human chorionic somatomammotropin (HCS), is a polypeptide placental hormone, the human form of placental lactogen ( chorionic somatomammotropin). Its structure and function are similar to those of hum ...
and
KISS1
Kisspeptins (including kisspeptin-54 (KP-54), formerly known as metastin) are proteins encoded by the ''KISS1'' gene in humans. Kisspeptins are ligands of the G-protein coupled receptor, GPR54. ''Kiss1'' was originally identified as a human met ...
expressed in
syncytiotrophoblasts, and
PAPPA2
Pappalysin-2 also known as pregnancy-associated plasma protein A2 (PAPP-A2) is a protein that in humans is encoded by the ''PAPPA2'' gene.
References
Further reading
*
*
*
*
*
*
{{gene-1-stub ...
and
PRG2 expressed in extravillous trophoblasts.
Physiology
Development
The placenta begins to develop upon
implantation of the
blastocyst into the maternal
endometrium, very early on in pregnancy at about week 4.
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.
The placenta grows throughout
pregnancy
Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins.
Pregnancy usually occurs by sexual intercourse, but ...
. Development of the maternal blood supply to the placenta is complete by the end of the first trimester of pregnancy week 14 (DM).
Placental circulation
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
In the placenta, the intervillous space is the space between chorionic villi
Chorionic villi are villi that sprout from the chorion to provide maximal contact area with maternal blood.
They are an essential element in pregnancy from a histo ...
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.
Maternal blood flow begins between days 5–12, 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 (plate) vessels, also fetal surface vessels are blood vessels, including both arteries and veins, that carry blood through the chorion in the fetoplacental circulation.
Chorionic arteries branch off the umbilical artery, and supply the ...
. Chorionic arteries, in turn, branch into
cotyledon arteries
The placenta of humans, and certain other mammals contains structures known as cotyledons, which transmit fetal blood and allow exchange of oxygen and nutrients with the maternal blood.
Ruminants
The Artiodactyla have a cotyledonary placenta. I ...
. 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 and
prostanoid
Prostanoids are active lipid mediators that regulate inflammatory response. Prostanoids are a subclass of eicosanoids consisting of the prostaglandins (mediators of inflammatory and anaphylactic reactions), the thromboxanes (mediators of vasocons ...
s cause
vasoconstriction in placental arteries, while
nitric oxide causes
vasodilation.
[ On the other hand, there is no neural vascular regulation, and catecholamines have only little effect.]
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
Complications of pregnancy are health problems that are related to pregnancy. Complications that occur primarily during childbirth are termed obstetric labor complications, and problems that occur primarily after childbirth are termed puerperal ...
. It is proposed that melatonin plays a role as an antioxidant in the placenta.
This begins at day 17–22.
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.
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.
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
At the end of pregnancy, the fetus must take the journey of childbirth to leave the reproductive mother. Upon its entry to the air-breathing world, the newborn must begin to adjust to life outside the uterus. This is true for all viviparous a ...
, especially in preterm infants.
Microbiome
The placenta is traditionally thought to be sterile
Sterile or sterility may refer to:
*Asepsis
Asepsis is the state of being free from disease-causing micro-organisms (such as pathogenic bacteria, viruses, pathogenic fungi, and parasites). There are two categories of asepsis: medical and surgi ...
, 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.
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
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
back from the fetus to the maternal blood. Nutrient transfer to the fetus can occur via both active and passive transport. Placental nutrient metabolism was found to play a key role in limiting the transfer of some nutrients. Adverse pregnancy situations, such as those involving maternal diabetes
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...
or obesity
Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's ...
, can increase or decrease levels of nutrient transporters in the placenta potentially resulting in overgrowth or restricted growth of the fetus.
Excretion
Waste products excreted from the fetus such as urea, uric acid, and creatinine are transferred to the maternal blood by diffusion
Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical ...
across the placenta.
Immunity
The placenta functions as a selective barrier between maternal and fetal cells, preventing maternal blood, proteins and microbes (including bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
and most viruses) from crossing the maternal-fetal barrier.
Deterioration in placental functioning, referred to as placental insufficiency
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 u ...
, may be related to mother-to-child transmission of some infectious diseases.
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.
Beginning as early as 13 weeks of gestation, and increasing linearly, with the largest transfer occurring in the third trimester, IgG antibodies
Immunoglobulin G (Ig G) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG a ...
can pass through the human placenta, providing protection to the fetus ''in utero''.
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, one reason why infections acquired during pregnancy can be particularly hazardous for the fetus.
Endocrine function
* The first hormone released by the placenta is called the human chorionic gonadotropin (hCG) hormone. This is responsible for stopping the process at the end of menses when the corpus luteum ceases activity and atrophies. If hCG did not interrupt this process, it would lead to spontaneous abortion of the fetus. The corpus luteum also produces and releases progesterone and estrogen
Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal ac ...
, and hCG stimulates it to increase the amount that it releases. hCG is the indicator of pregnancy that pregnancy tests look for. These tests will work when menses has not occurred or after implantation has happened on days seven to ten. hCG may also have an anti-antibody effect, protecting it from being rejected by the mother's body. hCG also assists the male fetus by stimulating the testes to produce testosterone, which is the hormone needed to allow the sex organs of the male to grow.
* Progesterone helps the embryo implant by assisting passage through the fallopian tubes. It also affects the fallopian tubes and the uterus
The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...
by stimulating an increase in secretions necessary for fetal nutrition. Progesterone, like hCG, is necessary to prevent spontaneous abortion because it prevents contractions of the uterus and is necessary for implantation.
* Estrogen
Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal ac ...
is a crucial hormone in the process of proliferation. This involves the enlargement of the breasts and uterus, allowing for growth of the fetus and production of milk. Estrogen is also responsible for increased blood supply towards the end of pregnancy through vasodilation. The levels of estrogen during pregnancy can increase so that they are thirty times what a non-pregnant woman mid-cycles estrogen level would be.
* Human placental lactogen (hPL) is a hormone used in pregnancy to develop fetal metabolism and general growth and development. Human placental lactogen works with growth hormone
Growth hormone (GH) or somatotropin, also known as human growth hormone (hGH or HGH) in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in ...
to stimulate Insulin-like growth factor production and regulating intermediary metabolism. In the fetus, hPL acts on lactogenic receptors to modulate embryonic development, metabolism and stimulate production of IGF, insulin, surfactant and adrenocortical hormones. hPL values increase with multiple pregnancies, intact molar pregnancy, diabetes
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...
and Rh incompatibility
Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis foetalis, is an alloimmune condition that develops in a fetus at or around birth, when the IgG molecules (one of the five ...
. They are decreased with toxemia, choriocarcinoma
Choriocarcinoma is a malignant, trophoblastic cancer, usually of the placenta. It is characterized by early hematogenous spread to the lungs. It belongs to the malignant end of the spectrum in gestational trophoblastic disease (GTD). It is also c ...
, and Placental insufficiency
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 u ...
.
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
An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of different microorganisms including viruses, bacteria, parasites, and fungi which coul ...
of the mother that would cause it to be rejected
''Rejected'' is an animated film directed by Don Hertzfeldt that was released in 2000. It was nominated for an Academy Award for Best Animated Short Film the following year at the 73rd Academy Awards, and received 27 awards from film festivals ...
. The placenta and fetus are thus treated as sites of immune privilege, with immune tolerance.
For this purpose, the placenta uses several mechanisms :
*It secretes neurokinin B-containing phosphocholine molecules. This is the same mechanism used by parasitic nematodes to avoid detection by the immune system of their host.
*There is presence of small lymphocytic suppressor cells in the fetus that inhibit maternal cytotoxic T cells by inhibiting the response to interleukin 2.
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.
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
A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals.
The effect of ...
.
Clinical significance
Numerous pathologies can affect the placenta.
* Placenta accreta, when the placenta implants too deeply, all the way to the actual muscle of uterine wall (without penetrating it)
* Placenta praevia, when the placement of the placenta is too close to or blocks the cervix
* Placental abruption
Placental abruption is when the placenta separates early from the uterus, in other words separates before childbirth. It occurs most commonly around 25 weeks of pregnancy. Symptoms may include vaginal bleeding, lower abdominal pain, and dang ...
, premature detachment of the placenta
* Placentitis
Placentitis is an inflammation of the placenta. The main forms of placentitis are:
*Villitis, inflammation of chorionic villi.
*Intervillositis, inflammation of the intervillous space.
It may be caused by vertically transmitted infections.
...
, inflammation of the placenta, such as by TORCH infections
A vertically transmitted infection is an infection caused by pathogenic bacteria or viruses that use mother-to-child transmission, that is, transmission directly from the mother to an embryo, fetus, or baby during pregnancy or childbirth. It ca ...
.
Society and culture
The placenta often plays an important role in various culture
Culture () is an umbrella term which encompasses the social behavior, institutions, and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities, and habits of the individuals in these groups ...
s, with many societies conducting rituals regarding its disposal. In the Western world
The Western world, also known as the West, primarily refers to the various nations and states in the regions of Europe, North America, and Oceania. , the placenta is most often incinerated.
Some cultures bury the placenta for various reasons. The Māori
Māori or Maori can refer to:
Relating to the Māori people
* Māori people of New Zealand, or members of that group
* Māori language, the language of the Māori people of New Zealand
* Māori culture
* Cook Islanders, the Māori people of the Co ...
of New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...
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
Cambodia (; also Kampuchea ; km, កម្ពុជា, UNGEGN: ), officially the Kingdom of Cambodia, is a country located in the southern portion of the Indochinese Peninsula in Southeast Asia, spanning an area of , bordered by Thailand ...
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
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, for ...
bury girls' placentas to give the girl skill in digging clams, and expose boys' placentas to ravens to encourage future prophet
In religion, a prophet or prophetess is an individual who is regarded as being in contact with a divine being and is said to speak on behalf of that being, serving as an intermediary with humanity by delivering messages or teachings from the ...
ic visions. In Turkey
Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a transcontinental country located mainly on the Anatolian Peninsula in Western Asia, with a small portion on the Balkan Peninsula ...
, the proper disposal of the placenta and umbilical cord is believed to promote devoutness in the child later in life. In Transylvania
Transylvania ( ro, Ardeal or ; hu, Erdély; german: Siebenbürgen) is a historical and cultural region in Central Europe, encompassing central Romania. To the east and south its natural border is the Carpathian Mountains, and to the west the A ...
, and Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
, 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 (; ne, नेपाल ), formerly the Federal Democratic Republic of Nepal ( ne,
सङ्घीय लोकतान्त्रिक गणतन्त्र नेपाल ), is a landlocked country in South Asia. It is ma ...
ese 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. 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
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Gui ...
, 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
A pencil () is a writing or drawing implement with a solid pigment core in a protective casing that reduces the risk of core breakage, and keeps it from marking the user's hand.
Pencils create marks by physical abrasion, leaving a tra ...
(if it is a boy) or a needle and thread (if it is a girl).
In some cultures, the placenta is eaten, a practice known as placentophagy. In some eastern cultures, such as China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
, the dried placenta (''ziheche'' , 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. The practice of human placentophagy
Human placentophagy, or consumption of the placenta, is defined as "the ingestion of a human placenta postpartum, at any time, by any person, either in raw or altered (e.g., cooked, dried, steeped in liquid) form". While there are several anecdotes ...
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
The placenta is an organ which links the fetus to the mother in mammals for the transfer of oxygen and nutrients to the fetus and fetal waste products to the mother. Many species of mammals consume their placentas. Placentas are consumed in some ...
that include the manufacturing of cosmetics, pharmaceuticals and food.
Additional images
File:Gray30.png, Fetus of about 8 weeks, enclosed in the amnion. Magnified a little over two diameters.
File:Placenta with fetal membranes.jpg, Placenta with attached fetal membranes, ruptured at the margin at the left in the image
File:CMV placentitis1.jpg, Micrograph
A micrograph or photomicrograph is a photograph or digital image taken through a microscope or similar device to show a magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken on a m ...
of a placental infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...
( CMV placentitis)
File:CMV placentitis2.jpg, Micrograph of CMV placentitis
File:Placenta vasculature 3D power doppler 00001.gif, A 3D Power Doppler image of vasculature in 20-week placenta
File:2910 The Placenta-02.jpg, Schematic view of the placenta
File:Human placenta 01.JPG, Maternal side of a whole human placenta, just after birth
File:Human placenta 02.JPG, Fetal side of same placenta
File:Fetal side close-up of freshly delivered placenta.jpeg, Close-up of umbilical attachment to fetal side of freshly delivered placenta
File:Placenta weight by gestational age.svg, Placenta weight by gestational age
File:Ziheche.jpg, ''Ziheche'' (紫河车), dried human placenta used in traditional Chinese medicine
See also
*Choriovitelline placenta A choriovitelline placenta is a placenta formed by the yolk sac and chorion. In a choriovitelline placenta, the yolk sac fuses with the chorion and, subsequently, wrinkles develop that hold the embryo to the uterine wall, thus forming the choriovite ...
* Caul
*Zygote
A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism.
In multicell ...
*Pregnancy in fish
Pregnancy has been traditionally defined as the period of time eggs are incubated in the body after egg-sperm union. Although the term often refers to placental mammals, it has also been used in the titles of many international, peer-reviewed, sc ...
References
External links
The placenta-specific proteome
a
the Human Protein Atlas
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.
{{Authority control
Vertebrate developmental biology
Embryology of cardiovascular system
Organs (anatomy)
Reproductive system
Microbiomes
Human female endocrine system