A fetus is a stage in the prenatal development of vivipar organisms. In human development, the fetal fetus or ( ; fetus or fetus fetus is) prenatal humans between the state of embryo and birth. The fetal stage of human development tends to be taken as early as eleven weeks of gestation, nine weeks after conception. However, in biological terms, prenatal development is a continuum, with no distinct features that distinguish embryos from the fetus. The fetus is also characterized by the presence of all major organs, although they are not yet fully developed and functional and some have not been in their last anatomical location.
Video Fetus
Etimologi
The word fetus (plural fetus ) comes from the Latin f? Tus ("heredity", "spawn", "young hatch"). The English, Irish and Commonwealth Spellings are fetuses , which have been used since at least 1594. Spellings with -oe - appear in Latter Latin, where the difference between the vowel sounds -oe - and -e - has been lost. This spelling is the most common in most Commonwealth countries, except in the medical literature, where fetus is used. The more classic spellings fetus are used in Canada and the United States. In addition, Maps Fetus
Development
Week 9 to 16 (2 ¼ to 4 months)
In humans, the fetal stage begins at the beginning of the ninth week. At the beginning of the fetal stage, the fetus is usually about 30 millimeters (1.2 inches) from the crown to the buttock, and weighs about 8 grams. Its head reaches nearly half the size of the fetus. Movements like a breathing fetus are needed to stimulate the development of the lungs, rather than to get oxygen. Heart, hands, feet, brain and other organs are present, but only at the beginning of development and have minimal surgery. Fetal genitals begin to form and the placenta becomes fully functional during week 9.
At this point in development, unrestrained gestures and twitches occur as muscles, brain, and pathways begin to develop.
17 to 25 weeks (4Ã,¼) up to 6Ã,¼ months)
A pregnant woman for the first time (primipara), usually senses fetal movement about 21 weeks, while a woman who has given birth at least once (multipara), will usually feel the movement for 20 weeks. At the end of the fifth month, the fetus is about 20 cm (8 inches).
26 to 38 weeks (6½ to 9½ month)
The amount of body fat increases rapidly. The lungs are not fully mature yet. Thalamic brain connections, which mediate sensory input, form. Bone is fully developed, but is still soft and supple. Iron, calcium, and phosphorus become more abundant. The fingernails reach the tip of the fingertip. The lanugo, or fine hair, begins to disappear, until it disappears except in the upper arm and shoulders. Small breast shoots are present in both sexes. Head hair becomes rough and thick. Birth is near and occurs around the 38th week after conception. The fetus is considered full-term between week 36 and 40, when the fetus is developed enough for life outside the womb. The length may be 48-53 cm (19 to 21 inches), when it is born. Control of movement is limited at birth, and voluntary voluntary movements develop into puberty.
Variations in growth
There are many variations in the growth of the human fetus. When the size of the fetus is less than expected, a condition known as intrauterine growth restriction (IUGR) is also called fetal growth restriction (FGR); factors affecting fetal growth can be mother , placenta , or fetus .
Maternal factors include maternal weight, body mass index, nutritional status, emotional stress, exposure to toxins (including tobacco, alcohol, heroin, and other drugs that may also harm the fetus by other means), and uterine blood flowing.
Placental factors include size, microstructure (density and architecture), umbilical blood flow, transporter and binding protein, nutrient utilization and nutrient production.
Factors Fetal include the fetal genome, nutritional production, and hormonal output. Also, female fetuses tend to weigh less than men, at full time.
Growth of the fetus is often classified as follows: small for gestational age (SGA), appropriate for gestational age (AGA), and great for gestational age (LGA). SGA can cause low birth weight, although preterm birth can also result in low birth weight. Low birth weight increases the risk of perinatal death (immediate postnatal death), asphyxia, hypothermia, polycythemia, hypocalcemia, immune dysfunction, neurological disorders, and other long-term health problems. SGA may be associated with growth delay, or may be associated with absolute growth growth.
Feasibility
Viability refers to a point in the development of the fetus where the fetus can survive outside the womb. The lower limit of viability is about 5-3/4 months of gestational age and usually later.
There are no sharp limits of development, age, or weight in which the fetus automatically becomes eligible. According to data from 2003-05, survival rates were 20-35% for infants born at 23 weeks gestation (5-3/4 months); 50-70% at 24-25 weeks (6 - 6-1/4 months); and & gt; 90% at 26-27 weeks (6-1/2 - 6-3/4 months) and ends. It is rare for babies weighing less than 1.1 pounds (0.50 kg) to survive.
When the premature baby is born, the main cause of perinatal death is that the respiratory system and central nervous system are not completely differentiable. If a postnatal care specialist is given, some fetus weighing less than 1.1 pounds (0.50 kg) may survive, and are referred to as very low birth weight or an unmarried .
Premature birth is the most common cause of perinatal death, accounting for nearly 30 percent of neonatal deaths. At an incidence rate of 5% to 18% of all deliveries, it is also more common than postmature birth, which occurs in 3% to 12% of pregnancies.
Fetal pain
Fetal pain, its existence and its implications are politically and academically debated. According to the conclusions of the review published in 2005, "Evidence on the capacity for fetal pain is limited but shows that fetal perception of pain is not possible before the third trimester." However, developmental neurobiology experts argue that the establishment of thalamocortical connections (about 6-1/2 months) is an important event related to the perception of fetal pain. Nevertheless, the perception of pain involves sensory, emotional and cognitive factors and it is "impossible to know" when pain is experienced, even if known when a thalamocortical connection is established. Some authors suggest that fetal pain is possible from the second half of pregnancy: "Available scientific evidence allows, perhaps even, that the perception of fetal pain occurs long before pregnancy is late," wrote KJS Anand in the journal IASP.
Whether the fetus has the ability to feel pain and suffering is part of the abortion debate. In the United States, for example, pro-life supporters have proposed legislation that would require abortion providers to inform women that their fetus may feel pain during the procedure and that would require every woman to accept or reject anesthesia for the fetus.
Circulation system
The heart and blood vessels that make up the circulatory system, form relatively early during embryonic development, but continue to grow and thrive in the complexity of the growing fetus. Functional circulatory system is a biological need, because mammalian tissue can not grow more than several layers of thick cells without active blood supply. Prenatal blood circulation differs from circulation after birth, especially since the lungs are not used. The fetus gets oxygen and nutrients from the mother through the placenta and umbilical cord.
The blood from the placenta is brought to the fetus by the umbilical vein. About half of this enters the fetus of the ductus venosus and is brought to the inferior vena cava, while the other half enters the liver just from the inferior border of the liver. The umbilical vein branch that supplies the right lobe first joins the portal vein. The blood then moves into the right atrium of the heart. In the fetus, there is an opening between the right and left atria (foramen ovale), and most of the blood flows from right to left atrium, thus passing through the pulmonary circulation. The majority of blood flow to the left ventricle from which it is pumped through the aorta into the body. Some blood moves from the aorta through the internal iliac artery to the umbilical artery, and reenter the placenta, where carbon dioxide and other fecal products of the fetus are taken and into the female circulation.
Some blood from the right atrium does not enter the left atrium, but enters the right ventricle and is pumped into the pulmonary artery. In the fetus, there is a special relationship between the pulmonary artery and the aorta, called the ductus arteriosus , which directs most of this blood out of the lungs (which is not used for respiration at this time). point like the fetus is suspended in amniotic fluid).
Postnatal development
With the first breath after birth, the system changes suddenly. Lung resistance diminishes dramatically, encouraging more blood to move into the pulmonary artery from the right atrium and heart ventricles and less flowing through the foramen ovale into the left atrium. The blood from the lungs travels through the pulmonary vein to the left atrium, resulting in an increase in pressure that pushes the septum primum against the septum secundum, closes the foramen ovale and completes separation of the baby's circulation system to the standard left and right sides. After that, foramen ovale is known as fossa ovalis .
The ductus arteriosus normally closes within one or two days of birth, leaving ligamentum arteriosum , while umbilical veins and ductus venosus usually cover within two to five days after birth, leave, respectively, the liver ligamentum terrace and ligamentum venosus .
Difference between fetus and postnatal
Remnants of fetal circulation can be found in adults.
In addition to differences in circulation, the developing fetus also uses different types of oxygen transport molecules in its hemoglobin from birth and breathing its own oxygen. Fetal hemoglobin increases the ability of the fetus to attract oxygen from the placenta. The oxygen-hemoglobin dissociation curve shifts to the left, meaning that it is able to absorb oxygen at lower concentrations than adult hemoglobin. This allows fetal hemoglobin to absorb oxygen from adult hemoglobin in the placenta, where the oxygen tension is lower than in the lungs. Until about the age of six months, the human hemoglobin molecule consists of two alpha and two gamma chains (2? 2?). The gamma chain is gradually replaced by the beta chain until the molecule becomes hemoglobin A with two alpha and two beta chains (2? 2?).
Immune system
The placenta serves as a maternal-fetal barrier to microbial transmission. When this is not enough, transmission of infectious diseases from mother to child can occur.
Maternal IgG antibodies cross the placenta, giving fetal passive immunity to diseases whose mothers have antibodies. The transfer of antibodies to humans starts from the fifth month (gestational age) and of course in the sixth month.
Developmental issues
The developing fetus is highly susceptible to anomalies in growth and metabolism, increasing the risk of birth defects. One of the things that concerns is the lifestyle choices of pregnant women made during pregnancy. Diet is very important in the early stages of development. Studies show that dietary supplementation of women with folic acid reduces the risk of spina bifida and other neural tube defects. Another dietary concern is whether breakfast is eaten. Skipping breakfast can cause a long period of lower than normal nutrients in a woman's blood, leading to a higher risk of prematurity, or other birth defects in the fetus. During this time alcohol consumption may increase the risk of developing fetal alcohol syndrome, a condition that causes intellectual disability in some infants.
Smoking during pregnancy can also cause reduced birth weight. Low birth weight is defined as 2500 grams (5.5 pounds). Low birth weight is a concern for medical providers because of the tendency of these babies, described as "prematurely based on weight", to have a higher risk of secondary medical problems. Several studies have shown that fetal ultrasound (including Doppler, 3D/4D ultrasound and 2D ultrasound) can have a negative effect on birth weight and neurodevelopment.
Congenital anomalies are obtained before birth. Infants with certain congenital anomalies of the heart may survive only as long as the duct remains open: in cases such as ductal closure may be delayed by prostaglandin administration to allow sufficient time for surgical correction of anomalies. In contrast, in the case of patent ductus arteriosus, in which the duct does not close properly, drugs that inhibit prostaglandin synthesis can be used to induce closure, so surgery can be avoided.
Human pregnancy abortion is legal and/or tolerated in most countries, although with a pregnancy deadline that normally prohibits long-term abortions.
The use of the word fetus has been banned by the United States government from publications by the Centers for Disease Control and Prevention.
Other animals
The fetus is the stage in the prenatal development of vivipar organisms. This stage lies between embryogenesis and birth. Many vertebrates have a fetal stage, ranging from most mammals to many fish. In addition, some young live invertebrates, including some onychophora species and many arthropods. The prevalence of convergent evolution to the fetal stage suggests that it is relatively easy to develop. This may result from delaying the release of eggs, with eggs that hatch inside the mother before it is laid. Over time, the robustness of the egg wall can be reduced to a little more than a bag.
The fetus of most mammals lies with the human fetus in their mother. However, the anatomy of the region around the fetus differs in animals carrying impurities compared to humans: every animal fetus carrying garbage is surrounded by placental tissue and lodged in one of two long uteri rather than a single uterus found in a human woman.
The development at birth varies greatly among animals, and even among mammals. Altricial species are relatively helpless at birth and require considerable care and parental protection. Instead, precocial animals are born with open eyes, have hair or down, have large brains, and are instantly on the move and somewhat able to escape from, or defend themselves against, predators. Primates are precocial at birth, with the exception of humans.
The duration of pregnancy in placental mammals varied from 18 days in mice that jumped to 23 months on elephants. In general, larger fetal mammal fetuses require longer gestation periods.
The benefits of the fetal stage mean that young people are more developed when they are born. Therefore, they may need less parental care and may be better able to take care of themselves. However, bringing the fetus out of money to the mother, who has to take additional food to encourage the growth of her offspring, and her mobility and comfort may be affected (especially towards the end of the fetal stage).
In some cases, the presence of the fetal stage allows the organism to adjust the time of birth of their child to a good season.
See also
References
External links
- The Pranatal Image Gallery Index on the Endowment for Human Development website, displays many images of human fetal movement.
- "In the Womb" (National Geographic video).
Source of the article : Wikipedia
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