The placenta is a temporary

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...

nic and later fetal organ that begins

developing Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking, development phase, including finance and budgeting *Development (music), the process thematic material is reshaped * Photograph ...

from the

blastocyst 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 th ...

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 ] A mother is the female parent of a child. A woman may be considered a mother by virtue of having given birth, by raising a child who may or may not be her biological offspring, or by supplying her ovum for fertilisation in the case of ges ...

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 Taxonomy (biology), 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 ...

-dependent manner. In humans, a thin layer of maternal decidual (

endometrial The endometrium is the inner epithelial layer, along with its mucous membrane, of the mammalian uterus. It has a basal layer and a functional layer: the basal layer contains stem cells which regenerate the functional layer. The functional layer ...

) 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 mammal Placental mammals ( infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguish ...

s, but are also found in

marsupials Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a ...

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), fur or ...

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 Syncytiotrophoblast (from the Greek 'syn'- "together"; 'cytio'- "of cells"; 'tropho'- "nutrition"; 'blast'- "bud") is the epithelial covering of the highly vascular embryonic placental villi, which invades the wall of the uterus to establish nu ...

) 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 A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptase ...

: essentially a

virus A virus is a wikt:submicroscopic, submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and ...

that helped pave the transition from

egg-laying Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...

to live-birth. The word ''placenta'' comes from the

Latin Latin (, or , ) is a classical language belonging to the 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 the power ...

word for a type of cake, from

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

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. 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 The umbilical artery is a paired artery (with one for each half of the body) that is found in the abdominal and pelvic regions. In the fetus, it extends into the umbilical cord. Structure Development The umbilical arteries supply deoxygenated ...

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 num ...

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

. 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

s, and PAPPA2 and

PRG2 Eosinophil major basic protein, often shortened to major basic protein (MBP; also called Proteoglycan 2 (PRG2)) is encoded in humans by the ''PRG2'' gene. Function The protein encoded by this gene is the predominant constituent of the crystall ...

expressed in extravillous trophoblasts.

Physiology

Development

The placenta begins to develop upon implantation of the

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

layer. The syncytiotrophoblast is a

multinucleate Multinucleate cells (also known as multinucleated or polynuclear cells) are eukaryotic cells that have more than one nucleus per cell, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coord ...

d 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

. 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 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 (the decidual reaction) to endometrial stromal cells (ESCs) ...

. 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

pulse In medicine, a pulse represents the tactile arterial palpation of the cardiac cycle (heartbeat) by trained fingertips. The pulse may be palpated in any place that allows an artery to be compressed near the surface of the body, such as at the ...

s, 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

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 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 prostanoids cause

vasoconstriction Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood ve ...

in placental arteries, while

nitric oxide Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its ...

causes

vasodilation Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstricti ...

. 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 radical A daughter category of ''Ageing'', this category deals only with the biological aspects of ageing. Ageing Ailments of unknown cause Biogerontology Biological processes Causes of death Cellular processes Gerontology Life extension Metabo ...

s. This may contribute to

pre-eclampsia Pre-eclampsia is a disorder of pregnancy characterized by the onset of high blood pressure and often a significant amount of protein in the urine. When it arises, the condition begins after 20 weeks of pregnancy. In severe cases of the disease ...

and other pregnancy complications. It is proposed that

melatonin Melatonin is a natural product found in plants and animals. It is primarily known in animals as a hormone released by the pineal gland in the brain at night, and has long been associated with control of the sleep–wake cycle. In vertebrat ...

plays a role as an

antioxidant Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricants ...

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 Oxytocin (Oxt or OT) is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. It plays a role in social bonding, reproduction, childbirth, and the period after childbirth. Oxytoci ...

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 an ...

, especially in preterm infants.

Microbiome

The placenta is traditionally thought to be sterile, but recent research suggests that a resident, non-pathogenic, and diverse population of

microorganisms A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

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 Passive transport is a type of membrane transport that does not require energy to move substances across cell membranes. Instead of using cellular energy, like active transport, passive transport relies on the second law of thermodynamics to d ...

. 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 ...

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. circulatory_system_fetus_SMIL

Excretion

Waste products excreted from the fetus such as urea,

uric acid Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates, such as ammonium acid urate. Uric acid is a product of the metabolic breakdown ...

, 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 p ...

across the placenta.

Immunity

The placenta functions as a selective barrier between maternal and fetal cells, preventing maternal blood, proteins and

microbe A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s (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 A virus is a submicroscopic infectious agent that replicates only inside the living cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room ...

) 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 ''Zika virus'' (ZIKV; pronounced or ) is a member of the virus family '' Flaviviridae''. It is spread by daytime-active '' Aedes'' mosquitoes, such as ''A. aegypti'' and ''A. albopictus''. Its name comes from the Ziika Forest of Uganda, wh ...

'' and ''

cytomegalovirus ''Cytomegalovirus'' (''CMV'') (from ''cyto-'' 'cell' via Greek - 'container' + 'big, megalo-' + -''virus'' via Latin 'poison') is a genus of viruses in the order '' Herpesvirales'', in the family '' Herpesviridae'', in the subfamily '' Betahe ...

'' (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 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 Humoral immunity is the aspect of immunity that is mediated by macromolecules - including secreted antibodies, complement proteins, and certain antimicrobial peptides - located in extracellular fluids. Humoral immunity is named so because it ...

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 Human chorionic gonadotropin (hCG) is a hormone for the maternal recognition of pregnancy produced by trophoblast cells that are surrounding a growing embryo (syncytiotrophoblast initially), which eventually forms the placenta after implantati ...

(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 Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the ma ...

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 a ...

, 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 Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the ma ...

helps the

implant by assisting passage through the fallopian tubes. It also affects the fallopian tubes and 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 a ...

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

. 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 The insulin-like growth factors (IGFs) are proteins with high sequence similarity to insulin. IGFs are part of a complex system that cells use to communicate with their physiologic environment. This complex system (often referred to as the IGF ...

production and regulating intermediary metabolism. In the fetus, hPL acts on lactogenic receptors to modulate embryonic development, metabolism and stimulate production of IGF,

insulin Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the ''INS'' gene. It is considered to be the main anabolic hormone of the body. It regulates the metabol ...

, surfactant and adrenocortical hormones. hPL values increase with multiple pregnancies, intact molar pregnancy,

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, 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 could ...

of the mother that would cause it to be rejected. The placenta and fetus are thus treated as sites of

immune privilege Certain sites of the mammalian body have immune privilege, meaning they are able to tolerate the introduction of antigens without eliciting an inflammatory immune response. Tissue grafts are normally recognised as foreign antigen by the body and ...

, 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 Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

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 a ...

Human placenta umbilical cord Ultrasound by Dr

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 The cervix or cervix uteri (Latin, 'neck of the uterus') is the lower part of the uterus (womb) in the human female reproductive system. The cervix is usually 2 to 3 cm long (~1 inch) and roughly cylindrical in shape, which changes durin ...

* Placental abruption, 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 can ...

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 grou ...

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 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 List of islands of New Zealand, smaller islands. It is the ...

traditionally bury the placenta from a newborn child to emphasize the relationship between humans and the earth. Likewise, the

Navajo The Navajo (; British English: Navaho; nv, Diné or ') are a Native Americans in the United States, Native American people of the Southwestern United States. With more than 399,494 enrolled tribal members , the Navajo Nation is the largest fe ...

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 Thailan ...

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 , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

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 Provinces and territories of Canada, province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include ...

bury girls' placentas to give the girl skill in digging clams, and expose boys' placentas to

raven A raven is any of several larger-bodied bird species of the genus ''Corvus''. These species do not form a single taxonomic group within the genus. There is no consistent distinction between "crows" and "ravens", common names which are assigned ...

s 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 s ...

ic visions. In

Turkey Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a list of transcontinental countries, transcontinental country located mainly on the Anatolia, Anatolian Peninsula in Western Asia, with ...

, 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 ...

, 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 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 The Malay Peninsula ( Malay: ''Semenanjung Tanah Melayu'') is a peninsula in Mainland Southeast Asia. The landmass runs approximately north–south, and at its terminus, it is the southernmost point of the Asian continental mainland. The are ...

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 Guine ...

, 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 (mechanical), abra ...

(if it is a boy) or a

needle Needle may refer to: Crafting * Crochet needle, a tool for making loops in thread or yarn * Knitting needle, a tool for knitting, not as sharp as a sewing needle * Sewing needle, a long slender tool with a pointed tip * Trussing needle, a long sl ...

and

thread Thread may refer to: Objects * Thread (yarn), a kind of thin yarn used for sewing ** Thread (unit of measurement), a cotton yarn measure * Screw thread, a helical ridge on a cylindrical fastener Arts and entertainment * ''Thread'' (film), 2016 ...

(if it is a girl). In some cultures, the placenta is eaten, a practice known as placentophagy. In some eastern cultures, such as China, 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 Traditional Chinese medicine (TCM) is an alternative medicine, alternative medical practice drawn from traditional medicine in China. It has been described as "fraught with pseudoscience", with the majority of its treatments having no logica ...

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 Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, b ...

is debated. Some cultures have alternative uses for placenta 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 magnify, magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken ...

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 d ...

( 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

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