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Encyclopedia > Placenta
Placenta
Placenta
Precursor decidua basalis, chorion frondosum
Dorlands/Elsevier p_22/12643330

The placenta (Latin for cake, referencing its appearance in humans) is an ephemeral organ present in placental vertebrates, such as eutherial mammals and sharks during gestation (pregnancy). Protherial (egg-laying) and metatherial (marsupial) mammals do not produce a placenta. The placenta develops from the same sperm and egg cells that form the fetus, and functions as a foetomaternal organ with two components, the foetal part (Chorion frondosum), and the maternal part (Decidua basailis). Image File history File links Broom_icon. ... Image File history File links No higher resolution available. ... This article or section is in need of attention from an expert on the subject. ... Decidua is the term for the uterine lining (endometrium) during a pregnancy that forms the maternal part of the placenta. ... For the entertainment company see Chorion (company). ... Elseviers logo. ... For other uses, see Latin (disambiguation). ... For the kind of film, see ephemeral film. ... This article is about the biological unit. ... Orders Superorder Xenarthra: Pilosa Cingulata Infraclass Epitheria: Superorder Afrotheria: Afrosoricida (Golden mole and tenrec) Macroscelidea (Elephant shrew) Tubulidentata (Aardvark) Hyracoidea (Hyrax) Proboscidea (Elephant) Sirenia (Manatee, Dugong) Superorder Laurasiatheria: Chiroptera (Bats) Insectivora (Shrews, Moles) Cetacea (Whale, dolphin) Artiodactyla (Ruminants et al) Perissodactyla(Horse et al. ... Typical classes Petromyzontidae (lampreys) Placodermi - extinct Chondrichthyes (cartilaginous fish) Acanthodii - extinct Actinopterygii (ray-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Amphibia (amphibians) Reptilia (reptiles) Aves (birds) Mammalia (mammals) Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Orders[1] Bobolestes Eomaia Maelestes Montanalestes Murtoilestes Prokennalestes Placentalia Superorder Xenarthra: Cingulata (Armadillos) Pilosa (Sloths, True Anteaters) Superorder Afrotheria: Afrosoricida (Tenrecs, etc. ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the presence of sweat glands, including milk producing sweat glands, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex... For other uses, see Shark (disambiguation). ... Gestation is the carrying of an embryo or fetus inside a female viviparous animal. ... This article is about human pregnancy in biological females. ... Metatheria is a grouping within the animal class Mammalia. ...

Contents

Structure

Functions

For nine months the placenta feeds and nourishes the fetus while also disposing of toxic waste. Without it the baby could not survive. After the baby is born, the placenta no longer serves a function.


Among organs, it is unique. It is the only organ in the human body that serves a vital function and then becomes obsolete.


Filtration and transfer

The placenta receives nutrients, oxygen, antibodies, and hormones from the mother's blood, and passes out waste. It forms a barrier (called the "placental barrier"), which filters out some substances that could harm the fetus. The placental barrier does not allow the blood from the mother and the blood from the embryo to mix, in order to avoid the possible transfusion of different blood types. However, many substances are not filtered out, including alcohol, all anesthesiatic drugs used in medical childbirth (opioids and cocaine derivatives), and some chemicals associated with smoking cigarettes. Several types of viruses, such as Human Cytomegalovirus, may also cross this barrier; this often leads to various degrees of birth defects in the infant. For other uses, see Blood (disambiguation). ... This article does not cite any references or sources. ... Anesthesia or anaesthesia (see spelling differences) has traditionally meant the condition of having the perception of pain and other sensations blocked. ... A cigarette will burn to ash on one end. ... This article is about biological infectious particles. ... Species see text Cytomegalovirus (CMV) (from the Greek cyto-, cell, and -mega-, large) is a viral genus of the Herpesviruses group: in humans it is commonly known as human herpesvirus 5 (HHV-5). ... A congenital disorder is a medical condition or defect that is present at or before birth (for example, congenital heart disease). ...


Placental circulation

Maternal placental circulation

The Maternal blood enters the intervillous space through endometrial arteries (spiral arteries), 80 to 100 in number. They pierce the decidual plate and then pass through the gaps in cytotrophoblastic shell. As the artery enters, it is under high pressure because it enters through the small gap; this pressure forces the blood deep into intervillous spaces and bathes the villi. Exchange of gases takes place. As the pressure decreases, the deoxygenated blood flows backwards to the decidua and enters the endometrial veins. The trophoblast proliferates rapidly and forms a network of branching processes which cover the entire ovum and invade and destroy the maternal tissues and open into the maternal bloodvessels, with the result that the spaces in the trophoblastic network are filled with maternal blood; these spaces communicate freely with one... Endometrial arteries are those arteries that enter the endometrium to supply nutrition and oxygen to the fetus Category: ...


Fetoplacental circulation

Deoxygenated fetal blood passes through umbilical arteries to placenta. At the junction of umbilical cord and placenta, the umbilical arteries branch radially to form chorionic arteries. Chorionic arteries also branch before they enter into the villi. In the villi, they form an extensive arteriocapillary venous system, bringing the fetal blood extremely close to the maternal blood; but normally no intermingling of fetal and maternal blood occurs.


Metabolic and endocrine activity

In addition to the transfer of gases and nutrients, the placenta also has metabolic and endocrine activity. It produces, among other hormones, progesterone, which is important in maintaining the pregnancy; somatomammotropin (also known as placental lactogen), which acts to increase the amount of glucose and lipids in the maternal blood; estrogen; relaxin, and human chorionic gonadotrophin (hCG). This results in increased transfer of these nutrients to the fetus and is also the main cause of the increased blood sugar levels seen in pregnancy. The hormone HCG (human chorionic gonadotrophin) ensures that progesterone and oestrogen is still being secreted as these hormones make sure the uterus lining is developing and is a good environment for the foetus. However after about 2 months the placenta takes on the role of producing progesterone and therefore HCG is no longer needed. HCG is excreted in urine and this is how pregnancy tests work. Major endocrine glands. ... Hormone is also the NATO reporting name for the Soviet/Russian Kamov Ka-25 military helicopter. ... Progesterone is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species. ... Also called human placental lactogen, somatomammotropin is an important hormone of pregnancy. ... Estriol. ... Categories: Possible copyright violations ... Human chorionic gonadotropin (hCG) is a peptide hormone produced in pregnancy, that is made by the embryo soon after conception and later by the trophoblast (part of the placenta). ...


Materno-foetal circulation passes through the duct of Smith-Bessant before crossing the laura-brain barrier.


Parasitic cloaking from immune system of mother

To hide itself from the mother's immune system the placenta secretes Neurokinin B containing phosphocholine molecules. This is the same mechanism used by the parasitic nematode to avoid detection by the immune system of its host.[1] Neurokinin B is a tachykinin peptide. ... Phosphocholine (PC) is an intermediate in the synthesis of phosphatidylcholine in tissues. ... A parasite is an organism that lives in or on the living tissue of a host organism at the expense of it. ... Classes Adenophorea    Subclass Enoplia    Subclass Chromadoria Secernentea    Subclass Rhabditia    Subclass Spiruria    Subclass Diplogasteria    Subclass Tylenchia The nematodes or roundworms (Phylum nematoda from Greek (nema): thread + -ode like) are one of the most common phyla of animals, with over 80,000 different described species (over 15,000 are parasitic). ...


Birth

When the fetus is born, its placenta begins a physiological separation for spontaneous expulsion afterwards (and for this reason is often called the afterbirth). The umbilical cord is routinely clamped and severed prior to the delivery of the placenta, often within seconds or minutes of birth, a medical protocol known as 'active management of third stage' which has been called into question by advocates of natural birth and 'passive management of third stage'[2] The site of the former umbilical cord attachment in the center of the front of the abdomen is known as the umbilicus, navel, or belly-button. In placental mammals, the umbilical cord is a tube that connects a developing embryo or fetus to the placenta. ... For the human abdomen, see human abdomen. ... This article or section does not cite its references or sources. ...


Modern obstetric practice has decreased maternal death rates enormously. The addition of active management of the third stage of labor is a major contributor towards this. It involves giving oxytocin via IM injection, followed by cord traction to assist in delivering the placenta. Premature cord traction can pull the placenta before it has naturally detached from the uterine wall, resulting in hemorrhage. The BMJ summarized the Cochrane group metanalysis (2000) of the benefits of active third stage as follows: Oxytocin (Greek: quick birth) is a mammalian hormone that also acts as a neurotransmitter in the brain. ... The British Medical Journal (BMJ) is a medical journal published weekly in the United Kingdom by the British Medical Association (BMA)which published its first issue in 1845. ...

"One systematic review found that active management of the third stage of labour, consisting of controlled cord traction, early cord clamping plus drainage, and a prophylactic oxytocic agent, reduced postpartum haemorrhage of 500 or 1000 mL or greater and related morbidities including mean blood loss, postpartum haemoglobin less than 9 g/dL, blood transfusion, need for supplemental iron postpartum, and length of third stage of labour. Although active management increased adverse effects such as nausea, vomiting, and headache, one RCT identified by the review found that women were less likely to be dissatisfied when their third stage of labour was actively managed."[1]

Risks of retained placenta include hemorrhage and infection. If the placenta fails to deliver in 30 minutes in a hospital environment, manual extraction may be required if heavy ongoing bleeding occurs, and very rarely a curettage is necessary to ensure that no remnants of the placenta remain (in rare conditions with very adherent placenta (placenta accreta)). However, in birth centers and attended home birth environments, it is common for licensed care providers to wait for the placenta's birth up to 2 hours in some instances. In surgery, the use of a curette to remove tissue by scraping or scooping. ...


Non-humans

In most mammalian species, the mother bites through the cord and consumes the placenta, primarily for the benefit of prostaglandin on the uterus after birth. This is known as placentophagy. However, it has been observed in zoology that chimpanzees, with which humans share 99% of genetic material, apply themselves to nurturing their offspring, and keep the fetus, cord, and placenta intact until the cord dries and detaches the next day. E1 - Alprostadil I2 - Prostacyclin A prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body. ... Mother goat eating placenta Rat eating its offsprings placenta after birth Placentophagy (from placenta + Greek φαγειν, to eat) is the act of mammals eating the placenta of their young after childbirth. ...

Top: Human placenta shown a few minutes after birth. The side shown faces the baby with the umbilical cord top right. The white fringe surrounding the bottom is the remnants of the amniotic sac. Bottom: A different placenta displays side that connects to the uterine wall.

Image File history File linksMetadata Size of this preview: 397 × 600 pixelsFull resolution (1200 × 1813 pixel, file size: 365 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File linksMetadata Size of this preview: 397 × 600 pixelsFull resolution (1200 × 1813 pixel, file size: 365 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... In placental mammals, the umbilical cord is a tube that connects a developing embryo or fetus to the placenta. ... A drawing of the amniotic sac from Grays Anatomy. ... This article is about female reproductive anatomy. ...

Pathology

See:

Placenta accreta is a severe obstetric complication involving an abnormal attachment of the placenta to the myometrium (the middle layer of the uterine wall). ... Placental abruption (Also known as abruptio placentae) is a complication of pregnancy, wherein the placental lining has separated from the uterus of the mother. ...

Cultural practices and beliefs

The placenta often plays an important role in various human cultures, with many societies conducting rituals regarding its disposal. In the Western world, the placenta is most often incinerated.[3] For other uses, see Culture (disambiguation). ... Occident redirects here. ... Incineration is the process of burning waste streams under controlled industrial conditions. ...


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.[4] Similarly, the Navajo bury the placenta and umbilical cord at a specially-chosen site,[5] particularly if the baby dies during birth.[6] In Cambodia and Costa Rica, burial of the placenta protects and ensures the health of the baby and the mother.[7] 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.[8] This article needs additional references or sources for verification. ... This article is about the Māori people of New Zealand. ... For other uses, see Navajo (disambiguation). ... The Aymara are a native ethnic group in the Andes region of South America; about 2. ...


The placenta is believed by some communities to have power over the lives of the baby or its parents. The Kwakiutl of British Columbia bury girls' placentas to give the girl skill in digging clams, and expose boys' placentas to ravens to encourage future prophetic visions. In Turkey, the proper disposal of the placenta and umbilical cord is believed to promote devoutness in the child later in life. In Ukraine, Transylvania, and Japan, interaction with a disposed placenta is thought to influence the parents' future fertility. The ancient Egyptians believed that the placenta was imbued with magical powers.[7] bye Until the 1980s the term Kwakiutl was usually applied to all of the various First Nations peoples of northern Vancouver Island, Queen Charlotte Strait and the Johnstone Strait whose traditional Wakashan language was Kwakwala and also a group of peoples erroneously called for many years the Northern Kwakiutl... Motto: Splendor sine occasu (Latin: Splendour without diminishment) Capital Victoria Largest city Vancouver Official languages English (de facto) Government Lieutenant-Governor Steven Point Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament House seats 36 Senate seats 6 Confederation July 20, 1871 (6th province) Area  Ranked 5th Total 944... For other uses, see Raven (disambiguation). ... For other senses of this word, see Prophet (disambiguation). ... This article is about the region in Romania. ... Khafres Pyramid and the Great Sphinx of Giza, built about 2550 BC during the Fourth Dynasty of the Old Kingdom,[1] are enduring symbols of the civilization of ancient Egypt Ancient Egypt was a civilization in Northeastern Africa concentrated along the middle to lower reaches of the Nile River...


Several cultures believe the placenta to be or have been alive, often a relative of the baby. Nepalese think of the placenta as a friend of the baby's; Malaysians regard it as the baby's older sibling. The Ibo of Nigeria and Ghana consider the placenta the deceased twin of the baby, and conduct full funeral rites for it.[7] Native Hawaiians believe that the placenta is a part of the baby, and traditionally plant it with a tree which can then grow alongside the child.[3] IBO can stand for: Independent Business Owner - an owner of a franchise, especially in a multi-level marketing business. ... Hawaiian could refer to the Hawaiian language the native Hawaiian people within Hawaii. ...


In some cultures, the placenta is eaten, a practice known as placentophagy. Placenta can be eaten fried, grilled or even microwaved. Mother goat eating placenta Rat eating its offsprings placenta after birth Placentophagy (from placenta + Greek φαγειν, to eat) is the act of mammals eating the placenta of their young after childbirth. ...


Additional images

See also

For other uses, see Embryo (disambiguation). ... Parturition redirects here. ... This article is about female reproductive anatomy. ...

References

  1. ^ Placenta 'fools body's defences'. BBC News (2007-11-10).
  2. ^ http:www.sarahjbuckley.com/articles/leaving-well-alone.htm
  3. ^ a b "Why eat a placenta?", BBC, 2006-04-18. Retrieved on 2008-01-08. 
  4. ^ Metge, Joan. 2005. "Working in/Playing with three languages: English, Te Reo Maori, and Maori Bod Language." In Sites N.S vol. 2, No 2:83-90.
  5. ^ Francisco, Edna (2004-12-03). Bridging the Cultural Divide in Medicine. Minority Scientists Network. Retrieved on 2008-01-07.
  6. ^ Shepardson, Mary (1978). Changes in Navajo Mortuary Practices and Beliefs. American Indian Quarterly. University of Nebraska Press. Retrieved on 2008-01-07.
  7. ^ a b c Buckley, Sarah J.. Placenta Rituals and Folklore from around the World. Mothering. Retrieved on 2008-01-07.
  8. ^ Davenport, Ann (June 2005). The Love Offer. Johns Hopkins Magazine. Retrieved on 2008-01-07.

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 314th day of the year (315th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 108th day of the year (109th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) will be a leap year starting on Tuesday of the Anno Domini (common) era, in accordance with the Gregorian calendar. ... is the 8th day of the year in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... is the 337th day of the year (338th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) will be a leap year starting on Tuesday of the Anno Domini (common) era, in accordance with the Gregorian calendar. ... is the 7th day of the year in the Gregorian calendar. ... 2008 (MMVIII) will be a leap year starting on Tuesday of the Anno Domini (common) era, in accordance with the Gregorian calendar. ... is the 7th day of the year in the Gregorian calendar. ... 2008 (MMVIII) will be a leap year starting on Tuesday of the Anno Domini (common) era, in accordance with the Gregorian calendar. ... is the 7th day of the year in the Gregorian calendar. ... 2008 (MMVIII) will be a leap year starting on Tuesday of the Anno Domini (common) era, in accordance with the Gregorian calendar. ... is the 7th day of the year in the Gregorian calendar. ...

External links

Wikimedia Commons has media related to:
Placenta
  • Additional Human placenta photography [2]

[[zh:胎 The hypothalamic-pituitary-gonadal axis (also HPTA) is a way of referring to the combined effects of the hypothalamus, pituitary gland, and gonads as if these individual endocrine glands were a single entity. ... Look up testes in Wiktionary, the free dictionary. ... // For ovary as part of plants see ovary (plants) An ovary is an egg-producing reproductive organ found in female organisms. ... The corpus luteum (Latin for yellow body) is a small, temporary endocrine structure in animals. ... The pineal gland (also called the pineal body or epiphysis) is a small endocrine gland in the brain. ... A porcine islet of Langerhans. ...


  Results from FactBites:
 
Understanding Placenta Previa -- the Basics (502 words)
The placenta is the organ created during pregnancy to nourish the fetus, remove its waste and produce hormones to sustain the pregnancy.
The fetus is attached to the placenta by the umbilical cord.
In placenta accreta, the placenta is firmly attached to the uterus; in placenta increta, the placenta has grown into the uterus; and in placenta percreta, it has grown through the uterus.
  More results at FactBites »

 
 

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