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77-615: There are several Pangool in Serer religion and each one is associated with a specific attribute, have their own sacred place of worship , means of worship, etc. The symbol of the Pangool is the serpent , represented by two coiled snakes. The etymology of fangool comes from the Serer phrase Fang Qool which means the sacred serpent the plural of which is pangool . Fangool means serpent. There are two main types of Pangool: non-human Pangool and human Pangool. Both are sacred and ancient, but

154-431: A Master of Pangool who knows how to evokes the ancestor. The earlier Pangool were not human beings, but superior beings created by Roog at the time human beings were created. They were believed to have been created by the divine in order to help human kind. It is for this reason why the terms Pangool and Nguus (Serer word for genie) are sometimes used interchangeably. Because some Pangool are linked to Serer lineages, only

231-454: A disagreement with his relative the king of Lambaye. After his migration, he founded Tukar, previously in the Serer pre-colonial Kingdom of Sine , now part of independent Senegal . Tukar is one of the Serer holy sites , and the Pangool affiliated with it are devotedly venerated in the Serer religious calendar, such as the ' Raan festival which takes place once a year on the second Thursday after

308-714: A family of giant, primitive, python-like snakes, was around until 50,000 years ago in Australia, represented by genera such as Wonambi . Recent molecular studies support the monophyly of the clades of modern snakes, scolecophidians, typhlopids + anomalepidids, alethinophidians, core alethinophidians, uropeltids ( Cylindrophis , Anomochilus , uropeltines), macrostomatans, booids, boids, pythonids and caenophidians. While snakes are limbless reptiles, evolved from (and grouped with) lizards, there are many other species of lizards that have lost their limbs independently but which superficially look similar to snakes. These include

385-399: 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

462-457: A link which transmits vital energies. Not every dead ancient ancestor is canonized as Pangool. Pangool can be subdivided further into: In addition to these, Pangool can be further categorized depending on their character and nature, such as: Blood is a sign of life in Serer cosmogony and these types of Pangool fulfill a vital role in Serer society, and are seen as one of the most ancient and powerful. The Fangool Ngolum Joof (var: Ngolum Diouf)

539-661: A minor component of the North American fauna, but during the Miocene, the number of species and their prevalence increased dramatically with the first appearances of vipers and elapids in North America and the significant diversification of Colubridae (including the origin of many modern genera such as Nerodia , Lampropeltis , Pituophis , and Pantherophis ). There is fossil evidence to suggest that snakes may have evolved from burrowing lizards, during

616-414: A positive cladistical correlation, although some of these features are shared with varanids. Genetic studies in recent years have indicated snakes are not as closely related to monitor lizards as was once believed—and therefore not to mosasaurs, the proposed ancestor in the aquatic scenario of their evolution. However, more evidence links mosasaurs to snakes than to varanids. Fragmented remains found from

693-529: A relative of the baby. Nepalese think of the placenta as a friend of the baby; the orang Asli and Malay populations in Malay Peninsula regard it as the baby's older sibling. Native Hawaiians believe that the placenta is a part of the baby, and traditionally plant it with a tree that can then grow alongside the child. Various cultures in Indonesia , such as Javanese and Malay, believe that

770-611: A sample of Pangool, their attributes and the part of Serer country they protect : Snake Snakes are elongated, limbless reptiles of the suborder Serpentes ( / s ɜːr ˈ p ɛ n t iː z / ). Like all other squamates , snakes are ectothermic , amniote vertebrates covered in overlapping scales . Many species of snakes have skulls with several more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads ( cranial kinesis ). To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear one in front of

847-520: A short tail remains of the caudal vertebrae. However, the tail is still long enough to be of important use in many species, and is modified in some aquatic and tree-dwelling species. Many modern snake groups originated during the Paleocene , alongside the adaptive radiation of mammals following the extinction of (non-avian) dinosaurs . The expansion of grasslands in North America also led to an explosive radiation among snakes. Previously, snakes were

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924-439: A vital role in the creation narrative , as they were the first things created on Earth by the divine, followed by animals (non- humans ). The exact date as to when the veneration of the Pangool became prevalent cannot be stated with a degree of accuracy. Lamane Jegan Joof founder of Tukar c. 11th century, is reported to have been accompanied by a group of Pangool when he migrated from Lambaye with his brother Ndik following

1001-473: Is placentae , but the form placentas is more common in modern English. The placenta has evolved independently multiple times, probably starting in fish , where it originated multiple times, including the genus Poeciliopsis . Placentation has also evolved in some reptiles . The mammalian placenta evolved more than 100 million years ago and was a critical factor in the explosive diversification of placental mammals. Although all mammalian placentas have

1078-420: Is a finer one, barely visible; the cavities are connected internally, separated only by a membrane with nerves that are extraordinarily attuned to detecting temperature changes between. As in the overlapping vision fields of human eyes, the forward-facing pit on either side of the face combined produces a field of vision: a pit viper can distinguish between objects and their environments, as well as accurately judge

1155-415: Is adapted for burrowing and its stomach indicates that it was preying on other animals. It is currently uncertain if Tetrapodophis is a snake or another species, in the squamate order, as a snake-like body has independently evolved at least 26 times. Tetrapodophis does not have distinctive snake features in its spine and skull. A study in 2021 places the animal in a group of extinct marine lizards from

1232-476: Is associated with DNA mutations in the Zone of Polarizing Activity Regulatory Sequence (ZRS), a regulatory region of the sonic hedgehog gene which is critically required for limb development. More advanced snakes have no remnants of limbs, but basal snakes such as pythons and boas do have traces of highly reduced, vestigial hind limbs. Python embryos even have fully developed hind limb buds, but their later development

1309-461: Is based on morphological characteristics and mitochondrial DNA sequence similarity. Alethinophidia is sometimes split into Henophidia and Caenophidia , with the latter consisting of "colubroid" snakes ( colubrids , vipers , elapids , hydrophiids , and atractaspids ) and acrochordids, while the other alethinophidian families comprise Henophidia. While not extant today, the Madtsoiidae ,

1386-461: Is critical for embryo survival. 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 . Numerous pathologies can affect the placenta. The placenta often plays an important role in various cultures , with many societies conducting rituals regarding its disposal. In the Western world , the placenta

1463-411: 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

1540-457: Is most often incinerated . Some cultures bury the placenta for various reasons. The Māori of New Zealand traditionally bury the placenta from a newborn child to emphasize the relationship between humans and the earth. Likewise, the Navajo bury the placenta and umbilical cord at a specially chosen site, particularly if the baby dies during birth. In Cambodia and Costa Rica , burial of

1617-459: Is not universal (see Amphisbaenia , Dibamidae , and Pygopodidae ). Living snakes are found on every continent except Antarctica, and on most smaller land masses; exceptions include some large islands, such as Ireland, Iceland, Greenland, and the islands of New Zealand, as well as many small islands of the Atlantic and central Pacific oceans. Additionally, sea snakes are widespread throughout

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1694-483: Is one of these blood Pangool . In many cases, offerings of alcohol rather than the sacrifice of domesticated animals are made to these blood Pangool . In contrast to the blood Pangool , the milk Pangool such as Moussa Sarr, Njemeh (var: Ndiémé) of Languème and Njoxona, etc., are those Pangool who are peaceful in nature and character. They even reject anything that symbolizes violence or things that may evoke destruction or death, i.e. iron, weapons, gunpowder, blood and

1771-624: Is potent enough to cause painful injury or death to humans. Nonvenomous snakes either swallow prey alive or kill by constriction . The English word snake comes from Old English snaca , itself from Proto-Germanic * snak-an- ( cf. Germanic Schnake 'ring snake', Swedish snok 'grass snake'), from Proto-Indo-European root * (s)nēg-o- 'to crawl to creep', which also gave sneak as well as Sanskrit nāgá 'snake'. The word ousted adder , as adder went on to narrow in meaning, though in Old English næddre

1848-585: Is relatively poor because snake skeletons are typically small and fragile making fossilization uncommon. Fossils readily identifiable as snakes (though often retaining hind limbs) first appear in the fossil record during the Cretaceous period. The earliest known true snake fossils (members of the crown group Serpentes) come from the marine simoliophiids , the oldest of which is the Late Cretaceous ( Cenomanian age) Haasiophis terrasanctus from

1925-816: Is stopped by the DNA mutations in the ZRS. There are about 3,900 species of snakes, ranging as far northward as the Arctic Circle in Scandinavia and southward through Australia. Snakes can be found on every continent except Antarctica, as well as in the sea, and as high as 16,000 feet (4,900 m) in the Himalayan Mountains of Asia. There are numerous islands from which snakes are absent, such as Ireland , Iceland , and New Zealand (although New Zealand's northern waters are infrequently visited by

2002-413: Is traditionally thought to be sterile , but recent research suggests that a resident, non-pathogenic , and diverse population of microorganisms may be present in healthy tissue. However, whether these microbes exist or are clinically important is highly controversial and is the subject of active research. The placenta intermediates the transfer of nutrients between mother and fetus. The perfusion of

2079-404: 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 . It is proposed that melatonin plays a role as an antioxidant in the placenta. This begins at day 17–22. Placental expulsion begins as a physiological separation from the wall of

2156-479: The Cretaceous Period . An early fossil snake relative, Najash rionegrina , was a two-legged burrowing animal with a sacrum , and was fully terrestrial . Najash , which lived 95 million years ago, also had a skull with several features typical for lizards, but had evolved some of the mobile skull joints that define the flexible skull in most modern snakes. The species did not show any resemblances to

2233-558: The Jurassic and Early Cretaceous indicate deeper fossil records for these groups, which may potentially refute either hypothesis. Both fossils and phylogenetic studies demonstrate that snakes evolved from lizards , hence the question became which genetic changes led to limb loss in the snake ancestor. Limb loss is actually very common in extant reptiles and has happened dozens of times within skinks , anguids , and other lizards. In 2016, two studies reported that limb loss in snakes

2310-632: The Jurassic period, with the earliest known fossils dating to between 143 and 167  Ma ago. The diversity of modern snakes appeared during the Paleocene epoch ( c.  66 to 56 Ma ago, after the Cretaceous–Paleogene extinction event ). The oldest preserved descriptions of snakes can be found in the Brooklyn Papyrus . Most species of snake are nonvenomous and those that have venom use it primarily to kill and subdue prey rather than for self-defense. Some possess venom that

2387-551: The Njambayargin tree ( bauhinia rufescens ) were fetched by these ancient people because they believed the tree to possess elements which boosted the growth of their crops and produce much fruit. Ritual prayers were made to the supreme spirit Roog (or Koox among the Cangin ), totally distinct from the prayers that would later become afforded to other Serer spiritual entities such as the Pangool. In Serer cosmogony , trees play

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2464-534: The West Bank , dated to between 112 and 94 million years old. Based on genomic analysis it is certain that snakes descend from lizards . This conclusion is also supported by comparative anatomy , and the fossil record. Pythons and boas —primitive groups among modern snakes—have vestigial hind limbs: tiny, clawed digits known as anal spurs , which are used to grasp during mating. The families Leptotyphlopidae and Typhlopidae also possess remnants of

2541-409: The blastocyst shortly after implantation . It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate maternal and fetal circulations, and is an important endocrine organ , producing hormones that regulate both maternal and fetal physiology during pregnancy . The placenta connects to the fetus via the umbilical cord , and on the opposite aspect to

2618-428: The cancer testis antigen PAGE4 and expressed in cytotrophoblasts , CSH1 and KISS1 expressed in syncytiotrophoblasts , and PAPPA2 and PRG2 expressed in extravillous trophoblasts. 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

2695-543: The chorion and allantois . In humans, the placenta averages 22 cm (9 inch) in length and 2–2.5 cm (0.8–1 inch) in thickness, with the center being the thickest, and the edges being the thinnest. It typically weighs approximately 500 grams (just over 1 lb). It has a dark reddish-blue or crimson color. It connects to the fetus by an umbilical cord of approximately 55–60 cm (22–24 inch) in length, which contains two umbilical arteries and one umbilical vein . The umbilical cord inserts into

2772-476: The chorionic plate (has an eccentric attachment). Vessels branch out over the surface of the placenta and further divide to form a network covered by a thin layer of cells. This results in the formation of villous tree structures. On the maternal side, these villous tree structures are grouped into lobules called cotyledons . In humans, the placenta usually has a disc shape, but size varies vastly between different mammalian species. The placenta occasionally takes

2849-501: The new moon in April. The descendants of Lamane Jegan Joof (the Joof family of Tukar) play a vital role in this religious affair. The Pangool are related to the transcendence of the divine. In the Serer home, the altar of the Pangool can not conceal that of the divine. The Pangool provide the vital energies relating to the realities of the Serer people especially those forces outside

2926-479: The slowworm , glass snake , and amphisbaenians . Leptotyphlopidae Gerrhopilidae Typhlopidae Xenophidiidae Anomalepididae Aniliidae Tropidophiidae Xenopeltidae Loxocemidae Pythonidae Boidae Bolyeridae Xenophidiidae Uropeltidae Anomochilidae Cylindrophiidae Acrochordidae Xenodermidae Pareidae Viperidae Homalopsidae Colubridae Lamprophiidae Elapidae The fossil record of snakes

3003-434: The yellow-bellied sea snake and the banded sea krait ). The now extinct Titanoboa cerrejonensis was 12.8 m (42 ft) in length. By comparison, the largest extant snakes are the reticulated python , measuring about 6.95 m (22.8 ft) long, and the green anaconda , which measures about 5.21 m (17.1 ft) long and is considered the heaviest snake on Earth at 97.5 kg (215 lb). At

3080-508: The Cretaceous period known as dolichosaurs and not directly related to snakes. An alternative hypothesis, based on morphology , suggests the ancestors of snakes were related to mosasaurs —extinct aquatic reptiles from the Cretaceous —forming the clade Pythonomorpha . According to this hypothesis, the fused, transparent eyelids of snakes are thought to have evolved to combat marine conditions (corneal water loss through osmosis), and

3157-584: The Hox gene expression in the axial skeleton responsible for the development of the thorax became dominant. As a result, the vertebrae anterior to the hindlimb buds (when present) all have the same thoracic-like identity (except from the atlas , axis , and 1–3 neck vertebrae). In other words, most of a snake's skeleton is an extremely extended thorax. Ribs are found exclusively on the thoracic vertebrae. Neck, lumbar and pelvic vertebrae are very reduced in number (only 2–10 lumbar and pelvic vertebrae are present), while only

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3234-527: The Indian and Pacific oceans. Around thirty families are currently recognized, comprising about 520 genera and about 3,900 species . They range in size from the tiny, 10.4 cm-long (4.1 in) Barbados threadsnake to the reticulated python of 6.95 meters (22.8 ft) in length. The fossil species Titanoboa cerrejonensis was 12.8 meters (42 ft) long. Snakes are thought to have evolved from either burrowing or aquatic lizards, perhaps during

3311-452: The Serers as extended relatives of human beings, because they came from the same divine placenta at the time of the coronation . Many Pangool are spirits of early ancestors who had died. They represent both Pangool of the paternal line ( pangool o kurcala ) and those of the maternal line ( pangool o ƭeen yaay ). These ancestors guide and protect their descendants. Many Serer families have

3388-416: The barrier function of the placenta. The placenta grows throughout pregnancy . Development of the maternal blood supply to the placenta is complete by the end of the first trimester of pregnancy week 14 (DM). 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

3465-422: The colour red. They usually are the protectors of Serer cities and the defenders of the weak. The history regarding the veneration of the Pangool is found within the hermeneutics of Serer religion, oral tradition and archaeological discoveries. Prior to the widespread veneration of the Pangool, the religious habit of the ancient Serers included holding prayers at the beginning of the rainy season. The branches of

3542-436: The control of humanity. The religious practices and representations of the Pangool helps the Serer people dominate the hostile forces of nature, hence the advent of the Pangool veneration. Through their sacred intercession with the divine, these Pangool act as protectors and transmitters of vital energy to the world of the living. They can be humans, plants, animals, places, supernatural beings, etc. Animals and trees are viewed by

3619-443: The distance between objects and itself. The heat sensing ability of a pit viper is so great that it can react to a difference as small as one third of a degree Fahrenheit. Other infrared-sensitive snakes have multiple, smaller labial pits lining the upper lip, just below the nostrils. Placenta The placenta ( pl. : placentas or placentae ) is a temporary embryonic and later fetal organ that begins developing from

3696-531: The ears. Some primitive snakes are known to have possessed hindlimbs, but their pelvic bones lacked a direct connection to the vertebrae. These include fossil species like Haasiophis , Pachyrhachis and Eupodophis , which are slightly older than Najash . This hypothesis was strengthened in 2015 by the discovery of a 113-million-year-old fossil of a four-legged snake in Brazil that has been named Tetrapodophis amplectus . It has many snake-like features,

3773-621: The external ears were lost through disuse in an aquatic environment. This ultimately led to an animal similar to today's sea snakes . In the Late Cretaceous , snakes recolonized land, and continued to diversify into today's snakes. Fossilized snake remains are known from early Late Cretaceous marine sediments, which is consistent with this hypothesis; particularly so, as they are older than the terrestrial Najash rionegrina . Similar skull structure, reduced or absent limbs, and other anatomical features found in both mosasaurs and snakes lead to

3850-522: 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. Deoxygenated fetal blood passes through umbilical arteries to the placenta. At the junction of umbilical cord and placenta, the umbilical arteries branch radially to form chorionic arteries . Chorionic arteries, in turn, branch into cotyledon arteries . In

3927-407: The former is more ancient as a general rule. The non-human Pangool include ancient sacred places with vital spiritual energies and personalized as such. These Pangool generally are the personifications of natural forces. Human Pangool on the other hand became Pangool once they are canonized after death. Thus some are ancient, others are medieval . Through their intercession with the divine, they form

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4004-438: The girl skill in digging clams, and expose boys' placentas to ravens to encourage future prophetic visions. In Turkey , the proper disposal of the placenta and umbilical cord is believed to promote devoutness in the child later in life. In Transylvania and Japan , interaction with a disposed placenta is thought to influence the parents' future fertility. Several cultures believe the placenta to be or have been alive, often

4081-402: The head of the lineage schooled in the rituals can make a libation to the relevant Pangool or Fangool (the ancestor). In the other world , the ancestors are the actual carrying-holders of transcendent sacred energies. However, the Pangool are superior in title because they were not transformed in the sacred energy. Thus the distinction between a fangool (non-human) and a human-ancestor lies in

4158-437: The head, between the nostrils and the eyes. In fact the pit looks like an extra pair of nostrils. All snakes have the ability to sense warmth with touch and heat receptors like other animals ;however, the highly developed pit of the pit vipers is distinctive. Each pit is made of a pit cavity and an inner cavity, the larger one lies just behind and generally below the level of the nostril, and opens forward. Behind this larger cavity

4235-568: The intervillous spaces of the placenta with maternal blood allows the transfer of nutrients and oxygen from the mother to the fetus and the transfer of waste products and carbon dioxide back from the fetus to the maternal blood. Nutrient transfer to the fetus can occur via both active and passive transport . 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 or obesity , can increase or decrease levels of nutrient transporters in

4312-587: The lobes get in the way of fetal presentation during labor , which is called vasa previa . 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 . Examples of proteins with elevated expression in placenta compared to other organs and tissues are PEG10 and

4389-562: The maternal uterus in a species -dependent manner. In humans, a thin layer of maternal decidual ( endometrial ) tissue comes away with the placenta when it is expelled from the uterus following birth (sometimes incorrectly referred to as the 'maternal part' of the placenta). Placentas are a defining characteristic of placental mammals , but are also found in marsupials and some non-mammals with varying levels of development. Mammalian placentas probably first evolved about 150 million to 200 million years ago. The protein syncytin , found in

4466-410: The maternal-fetal barrier. Deterioration in placental functioning, referred to as placental insufficiency , 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

4543-515: The mode of their participation in the transcendence. In either case, Roog is the first source of the transcendence of sacred energies. Offerings of fruits, vegetables, crops, milk, or the sacrifice of domesticated animals are made to the Pangool in different places, e.g.: at the foot of trees, in forests, at community shrines, etc. There are Pangools whose scope is therapeutic, those who deliver justice (see also Takhar – spirit of justice) and those who are personal Pangool The following table provides

4620-545: The modern burrowing blind snakes, which have often been seen as the most primitive group of extant forms. One extant analog of these putative ancestors is the earless monitor Lanthanotus of Borneo (though it is also semiaquatic ). Subterranean species evolved bodies streamlined for burrowing, and eventually lost their limbs. According to this hypothesis, features such as the transparent , fused eyelids ( brille ) and loss of external ears evolved to cope with fossorial difficulties, such as scratched corneas and dirt in

4697-428: 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. The placenta and fetus may be regarded as a foreign body inside the mother and must be protected from

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4774-412: The normal immune response of the mother that would cause it to be rejected . The placenta and fetus are thus treated as sites of immune privilege , with immune tolerance . For this purpose, the placenta uses several mechanisms : However, the placental barrier is not the sole means of evading the immune system, as foreign fetal cells also persist in the maternal circulation, on the other side of

4851-575: The other end of the scale, the smallest extant snake is Leptotyphlops carlae , with a length of about 10.4 cm (4.1 in). Most snakes are fairly small animals, approximately 1 m (3.3 ft) in length. Some of the most highly developed sensory systems are found in the Crotalidae, or pit vipers—the rattlesnakes and their associates. Pit vipers have all the sense organs of other snakes, as well as additional aids. Pit refers to special infrared-sensitive receptors located on either side of

4928-515: The other instead of side by side, and most have only one functional lung . Some species retain a pelvic girdle with a pair of vestigial claws on either side of the cloaca . Lizards have independently evolved elongate bodies without limbs or with greatly reduced limbs at least twenty-five times via convergent evolution , leading to many lineages of legless lizards . These resemble snakes, but several common groups of legless lizards have eyelids and external ears, which snakes lack, although this rule

5005-679: The outer barrier of the placenta (the syncytiotrophoblast ) between mother and fetus, has a certain RNA signature in its genome that has led to the hypothesis that it originated from an ancient retrovirus : essentially a virus that helped pave the transition from egg-laying to live-birth . The word placenta comes from the Latin word for a type of cake , from Greek πλακόεντα/πλακοῦντα plakóenta/plakoúnta , accusative of πλακόεις/πλακούς plakóeis/plakoús , "flat, slab-like", with reference to its round, flat appearance in humans. The classical plural

5082-465: 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

5159-451: The pelvic girdle, appearing as horny projections when visible. Front limbs are nonexistent in all known snakes. This is caused by the evolution of their Hox genes , controlling limb morphogenesis . The axial skeleton of the snakes' common ancestor, like most other tetrapods, had regional specializations consisting of cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvic), and caudal (tail) vertebrae. Early in snake evolution,

5236-428: 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

5313-408: The placenta has a spirit and needs to be buried outside the family house. Some Malays would bury the baby's placenta with a pencil (if it is a boy) or a needle and thread (if it is a girl). In some cultures, the placenta is eaten, a practice known as placentophagy . In some eastern cultures, such as China , the dried placenta ( ziheche 紫 河 车 , literally "purple river car") is thought to be

5390-474: The placenta is believed to protect and ensure the health of the baby and the mother. If a mother dies in childbirth, the Aymara of Bolivia bury the placenta in a secret place so that the mother's spirit will not return to claim her baby's life. The placenta is believed by some communities to have power over the lives of the baby or its parents. The Kwakiutl of British Columbia bury girls' placentas to give

5467-435: The placenta potentially resulting in overgrowth or restricted growth of the fetus. Waste products excreted from the fetus such as urea , uric acid , and creatinine are transferred to the maternal blood by diffusion across the placenta. The placenta functions as a selective barrier between maternal and fetal cells, preventing maternal blood, proteins and microbes (including bacteria and most viruses ) from crossing

5544-486: The placental barrier. The trophoblast is the outer layer of cells of the blastocyst (see day 9 in Figure, above, showing the initial stages of human embryogenesis). Placental trophoblast cells have a unique genome-wide DNA methylation pattern determined by de novo methyltransferases during embryogenesis . This methylation pattern is principally required to regulate placental development and function, which in turn

5621-430: 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 may be no medical reason to do this; on the contrary, not cutting the cord could sometimes help the baby in its adaptation to extrauterine life , for preterm infants. The placenta

5698-428: 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. Placental mammals, including humans, have a chorioallantoic placenta that forms from

5775-435: 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". 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

5852-502: 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 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

5929-575: Was the general word for snake. The other term, serpent , is from French, ultimately from Indo-European * serp- 'to creep', which also gave Ancient Greek ἕρπω ( hérpō ) 'I crawl' and Sanskrit sarpá ‘snake’. All modern snakes are grouped within the suborder Serpentes in Linnean taxonomy , part of the order Squamata , though their precise placement within squamates remains controversial. The two infraorders of Serpentes are Alethinophidia and Scolecophidia . This separation

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