File Name: postnatal stages of growth and development .zip
While you might think of child development as something that begins during infancy, the prenatal period is also considered an important part of the developmental process. Prenatal development is a time of remarkable change that helps set the stage for future psychological development. The brain develops over the course of the prenatal period, but it will continue to go through more changes during the early years of childhood.
- Influence of Prenatal and Postnatal Growth on Intellectual Functioning in School-aged Children
- Prenatal development
- Growth Stages 1: Infancy and Early Childhood
- Factors Predicting Ante- and Postnatal Growth
Influence of Prenatal and Postnatal Growth on Intellectual Functioning in School-aged Children
Prenatal development , also called antenatal development , in humans, the process encompassing the period from the formation of an embryo , through the development of a fetus , to birth or parturition. The human body , like that of most animals, develops from a single cell produced by the union of a male and a female gamete or sex cell. This union marks the beginning of the prenatal period, which in humans encompasses three distinct stages: 1 the pre-embryonic stage, the first two weeks of development, which is a period of cell division and initial differentiation cell maturation , 2 the embryonic period, or period of organogenesis , which lasts from the third to the eighth week of development, and 3 the fetal period , which is characterized by the maturation of tissues and organs and rapid growth of the body.
The prenatal period ends with parturition and is followed by a long postnatal period. Only at about age 25 years are the last progressive changes completed. Much of the embryonic developmental machinery the cellular apparatus used in human development is similar to that used by other vertebrates as well as some invertebrates.
The machinery is essential for four processes: cell proliferation, cell specialization, cell interaction, and cell movement. During these processes, the approximately 20,—25, genes in the human genome give rise to as many as , different proteins , which give the conceptus form and substance.
The development and liberation of the male and female gametes are steps preparatory to their union through the process of fertilization. Active movements first bring some spermatozoa into contact with follicle cells adhering to the secondary oocyte immature egg , which still lies high in the uterine tube. The sperm then propel themselves past the follicle cells and attach to the surface of the gelatinous zona pellucida enclosing the oocyte.
Some sperm heads successfully penetrate this capsule by means of an enzyme they secrete, hyaluronidase , but only one sperm makes contact with the cell membrane and cytoplasm of the oocyte and proceeds farther.
This is because the invading sperm head releases a substance that initiates surface changes in the oocyte that render its membrane impermeable to other spermatozoa. The successful sperm is engulfed by a conical protrusion of the oocyte cytoplasm and is drawn inward.
Once within the periphery of the oocyte, the sperm advances toward the centre of the cytoplasm; the head swells and converts into a typical nucleus , now called the male pronucleus , and the tail detaches.
It is during the progress of these events that the oocyte initiates its final maturation division. Following the separation of the second polar body one or two polar bodies are produced during division , the oocyte nucleus typically reconstitutes and is then called the female pronucleus of the ripe egg.
It is now ready to unite with its male counterpart and thereby consummate the total events of fertilization. The two pronuclei next approach, meet midway in the egg cytoplasm, and lose their nuclear membranes.
Each resolves its diffuse chromatin material into a complete single set of 23 chromosomes. Each chromosome is composed of two chromatids held together by a centromere. During mitosis ordinary cell proliferation by division , the centromeres attach to a bundle of microtubules known as the mitotic spindle, which is formed by centrioles cylindrical cell structures. This climax in the events of fertilization creates a joint product known as the zygote , which contains all the factors essential for the development of a new individual.
The fundamental results of fertilization are the following: 1 reassociation of a male and female set of chromosomes, thus restoring the full number and providing the basis for biparental inheritance and for variation , 2 establishment of the mechanism of sex determination for the new individual this depending on whether the male set of chromosomes included the X or the Y chromosome , and 3 activation of the zygote, initiating further development.
Through the process of mitosis , the relatively enormous zygote directly subdivides into many smaller cells of conventional size, suitable as early building units for the future organism. This process is called cleavage and the resulting cells are blastomeres. The tendency for the progressive increase in cell numbers to follow a doubling sequence is soon disturbed and then lost. Each blastomere receives the full complement of paternal and maternal chromosomes.
Subdivision of the zygote into blastomeres begins while it is still high in the uterine tube. The cohering blastomeres are transported downward chiefly, at least, by muscular contractions of the tubal wall. Such transport is relatively rapid until the lower end of the tube is reached, and here cleavage continues for about two days before the multicellular cluster is expelled into the uterus. The full reason for this delay is not clear, but it serves to retain the cleaving blastomeres until the uterine lining is suitably prepared to receive its prospective guest.
Since the human egg contains little inert yolk material and since this is distributed rather evenly throughout the cytoplasm, the daughter cells of each mitosis are practically equal in size and composition. This type of cleavage is known as total, equal cleavage. The sticky blastomeres adhere, and the cluster is still retained for a time within the gelatinous capsule—the zona pellucida—that had enclosed the growing and ovulated oocyte.
There is no growth in the rapidly dividing blastomeres, so that the total mass of living substance does not increase during the cleavage period. By the fourth day after fertilization, a cluster of about 12 blastomeres passes from the uterine tube into the uterus. At this stage the cluster is called a morula.
By the time some 30 blastomeres have been produced, pools of clear fluid accumulate between some of the internal cells, and these spaces soon coalesce into a common subcentral cavity. The resulting hollow cellular ball is a blastula of a particular type that occurs in mammals and is called a blastocyst ; its cavity is the blastocoel.
An internal cellular cluster, eccentric in position and now named the inner cell mass, will develop into the embryo. The external capsule of smaller cells, enveloping the segregated internal cluster, constitutes the trophoblast. It will contribute to the formation of a placenta and fetal membranes. During its stay within the uterine cavity, the blastocyst loses its gelatinous capsule, imbibes fluid, and expands to a diameter of 0.
Probably several hundred blastomeres have formed before the blastocyst attaches to the uterine lining. Prenatal development Article Media Additional Info. Article Contents. Print print Print. Table Of Contents. While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.
Facebook Twitter. Give Feedback External Websites. Let us know if you have suggestions to improve this article requires login. External Websites. She joined Britannica in and See Article History. An ultrasound image of a human fetus. Human embryonic and fetal development, from fertilization to birth. The embryos of many animals appear similar to one another in the earliest stages of development and progress into their specialized forms in later stages. A sperm cell attempting to penetrate an egg ovum to fertilize it.
Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now. Early stages of human development. A—D Cleavage of the ovum. E—F Blastocyst development.
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Human growth is an outcome of complex interactions between genes and the environment. A human being undergoes a synchronized balance of growth and development of body proportions throughout the prenatal and postnatal phases. Growth commences immediately after conception and can be divided into prenatal and postnatal growths. The growth gradient proportion has been reported in textbooks without any evidence-based study. The earliest written records of human growth are from the Mesopotamian civilization. He undertook human dissection of the placenta, fetus, and stillborn. He used his scientific study of human growth to produce drawings that correctly rendered child and adult body proportions.
It would seem obvious to say that development does not stop at birth. In fact many systems cardiovascular, respiratory, gastrointestinal, homeostasis undergo significant changes at birth, and many others neural have not yet completed their development. Postnatal development can be broadly divided into the age categories of: Neonatal birth to 1 month , Infancy 1 month to 2 years , Childhood 2 years to puberty , Puberty 12 years to mid-teens and Young Adult a new category late teens to early twenties. Neurological development continues postnatally with both growth and reorganization of the central nervous system. The amount of simple physical growth is shown by the skeletal flexibility designed around the brain and spinal cord, which allows continued postnatal growth of these structures.
(type I, V and XII collagen, glycoproteins, bone proteoglycans), and > 10% water (3, 4). Bone matrix is formed in 2 stages, deposition and.
Growth Stages 1: Infancy and Early Childhood
Learn about The Nobel Prizes that have been awarded since , as well as the criteria and nomination process that are used to select the winners. NASA Kids is an excellent site for "kids" of all ages and provides an abundance of information, images, and interesting things to do on astronomy and the space sciences. In this lesson, students learn about sources of high-energy radiation and calculate student exposure to ionizing radiation over the past year. To introduce students to the stages of human growth and development that take place during infancy and early childhood. This lesson is the first of a two-part series aimed at introducing students to the different stages of physical growth and development in human beings from birth to 18 years of age.
Multiple-stage least squares analyses were used to generate uncorrelated residuals of postnatal growth. Analyses included adjustment for maternal, household, and school characteristics.
Factors Predicting Ante- and Postnatal Growth
Such cares are of nutritional, behavioral and lifestyle natures, and also involve the father and the whole family. Human development, from conception to maturity, consists of a critical and important period due to the multitude of intrinsic genetic and environmental factors that influence, positively or negatively, the person's entire life. The fragility of development continues throughout the preschool, school and adolescent periods during which proper nutrition with a balanced lifestyle is essential and depends on guidance from the parents, caregivers and teachers. It is important to make the distinction between two terms that overlap in practice, namely, growth and development. Growth refers simply to the increase in body size, both weight and stature, while development represents changes in parameters that may or may not depend on growth, involving a very complex series of factors: genetic, epigenetic, nutritional, environmental and lifestyle, amongst others HURLEY, ; STANNER et al. Development is the sequence of ordered alterations that occurs within the organism as from fertilization of the ovum formed in the ovaries, by sperm produced in the testicles, resulting in the oocyte first diploid cell of the new organism to be formed.
Development of the human body is the process of growth to maturity. The process begins with fertilization , where an egg released from the ovary of a female is penetrated by a sperm cell from a male. The resulting zygote develops through mitosis and cell differentiation , and the resulting embryo then implants in the uterus , where the embryo continues development through a fetal stage until birth. Further growth and development continues after birth, and includes both physical and psychological development, influenced by genetic, hormonal, environmental and other factors. This continues throughout life: through childhood and adolescence into adulthood.
of fetal and postnatal growth and development were conducted in a subgroup months. It may be that at this stage of the pregnancy, the fetus.
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Prenatal development , also called antenatal development , in humans, the process encompassing the period from the formation of an embryo , through the development of a fetus , to birth or parturition. The human body , like that of most animals, develops from a single cell produced by the union of a male and a female gamete or sex cell. This union marks the beginning of the prenatal period, which in humans encompasses three distinct stages: 1 the pre-embryonic stage, the first two weeks of development, which is a period of cell division and initial differentiation cell maturation , 2 the embryonic period, or period of organogenesis , which lasts from the third to the eighth week of development, and 3 the fetal period , which is characterized by the maturation of tissues and organs and rapid growth of the body. The prenatal period ends with parturition and is followed by a long postnatal period. Only at about age 25 years are the last progressive changes completed. Much of the embryonic developmental machinery the cellular apparatus used in human development is similar to that used by other vertebrates as well as some invertebrates. The machinery is essential for four processes: cell proliferation, cell specialization, cell interaction, and cell movement.
Всю свою жизнь она посвятила взламыванию шифров, отвергая саму возможность разработки абсолютно стойкого шифра.
Около часа, говоришь? - хмуро спросил. - А что ты скажешь о проверках пределов памяти, которые мы выполняли. Сьюзан пожала плечами. - Ну, если вы имеете в виду и диагностику, то времени уходило .
Он не хотел, чтобы оно попало в АНБ. Но чего еще можно было ждать от Танкадо - что он сохранит кольцо для них, будучи уверенным в том, что они-то его и убили. И все же Сьюзан не могла поверить, что Танкадо допустил бы. Ведь он был пацифистом и не стремился к разрушению. Он лишь хотел, чтобы восторжествовала правда.
Она совсем. - Вот и прекрасно. Мистер Густафсон остановился. Наверное, он сейчас у .
Сьюзан собралась с мыслями и шагнула в дверной проем. Компьютер зафиксировал ее прибытие. Хотя Сьюзан практически не покидала шифровалку в последние три года, она не переставала восхищаться этим сооружением.