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Human Fertilization
Human fertilization is the union of an egg and sperm, occurring primarily in the ampulla of the fallopian tube. The result of this union leads to the production of a fertilized egg called a zygote, initiating embryonic development. Scientists discovered the dynamics of human fertilization in the 19th century. The process of fertilization involves a sperm fusing with an ovum. The most common sequence begins with ejaculation during copulation, follows with ovulation, and finishes with fertilization. Various exceptions to this sequence are possible, including artificial insemination, ''in vitro'' fertilization, external ejaculation without copulation, or copulation shortly after ovulation. Upon encountering the secondary oocyte, the acrosome of the sperm produces enzymes which allow it to burrow through the outer shell called the zona pellucida of the egg. The sperm plasma then fuses with the egg's plasma membrane and their nuclei fuse, triggering the sperm head to disconnect f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zona Pellucida
The ''zona pellucida'' (Latin meaning "transparent zone") is the specialized area surrounding mammalian oocytes (eggs). It is also known as an egg coat. The ''zona pellucida'' is essential for oocyte growth and fertilization. The ''zona pellucida'' is an extracellular matrix that surrounds the plasma membrane of the egg cell. It helps protect the egg, and has an essential role in fertilization by sperm. It is surrounded by the corona radiata. The corona is composed of cells that care for the egg when it is emitted from the ovary. Structure The zona pellucida is a translucent matrix of cross-linked glycoprotein filaments that surrounds the mammalian oocyte and is 6.5–20 μm thick depending on the species. Its formation, which depends on a conserved zona pellucida-like (ZP) module that mediates the polymerization of egg coat components, is critical to successful fertilization. In non-mammals, it is called the vitelline membrane or vitelline envelope. Function The thick ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
In Vitro
''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology and its subdisciplines are traditionally done in labware such as test tubes, flasks, Petri dishes, and microtiter plates. Studies conducted using components of an organism that have been isolated from their usual biological surroundings permit a more detailed or more convenient analysis than can be done with whole organisms; however, results obtained from ''in vitro'' experiments may not fully or accurately predict the effects on a whole organism. In contrast to ''in vitro'' experiments, ''in vivo'' studies are those conducted in living organisms, including humans, known as clinical trials, and whole plants. Definition ''In vitro'' (Latin language, Latin for "in glass"; often not italicized in English usage) studies are conducted ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egg Cell
The egg cell or ovum (: ova) is the female Reproduction, reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is not capable of movement (non-motile). If the male gamete (sperm) is capable of movement, the type of sexual reproduction is also classified as oogamous. A nonmotile female gamete formed in the oogonium of some algae, fungi, oomycetes, or bryophytes is an oosphere. When fertilized, the oosphere becomes the oospore. When egg and sperm fuse together during fertilisation, a diploid cell (the zygote) is formed, which rapidly grows into a new organism. History While the non-mammalian animal egg was obvious, the doctrine ''ex ovo omne vivum'' ("every living [animal comes from] an egg"), associated with William Harvey (1578–1657), was a rejection of spontaneous generation and preformationism as well as a bold assumption that mammals als ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antonie Van Leeuwenhoek
Antonie Philips van Leeuwenhoek ( ; ; 24 October 1632 – 26 August 1723) was a Dutch microbiologist and microscopist in the Golden Age of Dutch art, science and technology. A largely self-taught man in science, he is commonly known as " the Father of Microbiology", and one of the first microscopists and microbiologists. Van Leeuwenhoek is best known for his pioneering work in microscopy and for his contributions toward the establishment of microbiology as a scientific discipline. Raised in Delft, Dutch Republic, Van Leeuwenhoek worked as a draper in his youth and founded his own shop in 1654. He became well-recognized in municipal politics and developed an interest in lensmaking. In the 1670s, he started to explore microbial life with his microscope. Using single-lensed microscopes of his own design and make, Van Leeuwenhoek was the first to observe and to experiment with microbes, which he originally referred to as , or . He was the first to relatively determine t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spermatozoon
A spermatozoon (; also spelled spermatozoön; : spermatozoa; ) is a motile sperm cell (biology), cell produced by male animals relying on internal fertilization. A spermatozoon is a moving form of the ploidy, haploid cell (biology), cell that is the male gamete that Fertilization, joins with an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.) Sperm cells contribute approximately half of the nuclear gene, genetic information to the diploid offspring (excluding, in most cases, mitochondrial DNA). In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing an X chromosome will lead to a female (XX) offspring, while one bearing a Y chromosome will lead to a male (XY) offspring. Sperm cells were first observed in Antonie van Leeuwenhoek's laboratory in 1677. Mammalian spermatozoa Humans The sperm cell of ''Homo sapiens'' is the small Gamete, reproductive cell produced by m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nova (American TV Series)
''Nova'' (stylized as ''NOVΛ'') is an American popular science television program produced by WGBH-TV, WGBH in Boston, Massachusetts, since 1974. It is broadcast on PBS in the United States, and in more than 100 other countries. The program has won many major television awards. ''Nova'' often includes interviews with scientists doing research in the subject areas covered and occasionally includes footage of a particular discovery. Some episodes have focused on the history of science. Examples of topics covered include the following: Colditz Castle, the Drake equation, elementary particles, the 1980 eruption of Mount St. Helens, Fermat's Last Theorem, the AIDS epidemic, global warming, Silicon carbide, moissanite, Project Azorian, Project Jennifer, storm chasing, German submarine U-869, Unterseeboot 869, Vinland map, Vinland, Tarim mummies, and the COVID-19 pandemic. The ''Nova'' programs have been praised for their pacing, writing, and editing. Websites that accompany the se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fetus
A fetus or foetus (; : fetuses, foetuses, rarely feti or foeti) is the unborn offspring of a viviparous animal that develops from an embryo. Following the embryonic development, embryonic stage, the fetal stage of development takes place. Prenatal development is a continuum, with no clear defining feature distinguishing an embryo from a fetus. However, in general a fetus is characterized by the presence of all the major body organs, though they will not yet be fully developed and functional, and some may not yet be situated in their final Anatomy, anatomical location. In human prenatal development, fetal development begins from the ninth week after Human fertilization, fertilization (which is the eleventh week of Gestational age (obstetrics), gestational age) and continues until the childbirth, birth of a newborn. Etymology The word ''wikt:fetus#English, fetus'' (plural ''wikt:fetuses#English, fetuses'' or rarely, the solecism ''wikt:feti#English, feti''''Oxford English Dict ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aristotle's Biology
Aristotle's biology is the theory of biology, grounded in systematic observation and collection of data, mainly zoology, zoological, embodied in Aristotle's books on the science. Many of his observations were made during his stay on the island of Lesbos, including especially his descriptions of the marine biology of the Pyrrha lagoon, now the Kalloni#Bay and lagoon, Gulf of Kalloni. His theory is based on Hylomorphism, his concept of form, which derives from but is markedly unlike Plato's theory of Forms. The theory describes five major biological processes, namely metabolism, temperature regulation, information processing, embryogenesis, and inheritance (biology), inheritance. Each was defined in some detail, in some cases sufficient to enable modern biologists to create mathematical models of the mechanism (biology), mechanisms described. Aristotle's method, too, resembled the style of science used by modern biologists when exploring a new area, with systematic data collection ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Menstruation
Menstruation (also known as a period, among other colloquial terms) is the regular discharge of blood and Mucous membrane, mucosal tissue from the endometrium, inner lining of the uterus through the vagina. The menstrual cycle is characterized by the rise and fall of hormones. Menstruation is triggered by falling progesterone levels, and is a sign that pregnancy has not occurred. Women use feminine hygiene products to maintain hygiene during menses. The first period, a point in time known as menarche, usually begins during puberty, between the ages of 11 and 13. However, menstruation starting as young as 8 years would still be considered normal. The average age of the first period is generally later in the developing world, and earlier in the developed world. The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women; in adults, the range is between 21 and 35 days with the average often cited as 28 days. In the b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Harvey
William Harvey (1 April 1578 – 3 June 1657) was an English physician who made influential contributions to anatomy and physiology. He was the first known physician to describe completely, and in detail, pulmonary and systemic circulation as well as the specific process of blood being pumped to the brain and the rest of the body by the heart (though earlier writers, such as Realdo Colombo, Michael Servetus, and Jacques Dubois, had provided precursors to some of his theories). Family William's father, Thomas Harvey, was a jurat of Folkestone where he served as mayor in 1600. Records and personal descriptions delineate him as an overall calm, diligent, and intelligent man whose sons “... revered, consulted and implicitly trusted in him...” (they) made their father the treasurer of their wealth when they acquired great estates...(He) kept, employed, and improved their gainings to their great advantage." Thomas Harvey's portrait can still be seen in the central panel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epigenesis (biology)
In biology, epigenesis (or, in contrast to preformationism, neoformationism) is the process by which plants, animals and fungi develop from a seed, spore or egg through a sequence of steps in which cells differentiate and organs form. Aristotle first published the theory of epigenesis in his book ''On the Generation of Animals.'' Although epigenesis appears to be an obvious fact in today's genetic age, historically, creationist theories of life's origins hindered its acceptance. However, during the late 18th century an extended and controversial debate among biologists finally led epigenesis to eclipse the long-established preformationist view.Conference, Abstracts of papers presented. The embryologist Caspar Friedrich Wolff refuted preformationism in 1759 in favor of epigenesis, but this did not put an end to preformationism. See also * Epigenetics * Epigenesis (other) References External links Aristotle: ''On the Generation of Animals The ''Generation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pythagoras
Pythagoras of Samos (; BC) was an ancient Ionian Greek philosopher, polymath, and the eponymous founder of Pythagoreanism. His political and religious teachings were well known in Magna Graecia and influenced the philosophies of Plato, Aristotle, and, through them, Western philosophy. Modern scholars disagree regarding Pythagoras's education and influences, but most agree that he travelled to Croton in southern Italy around 530 BC, where he founded a school in which initiates were allegedly sworn to secrecy and lived a communal, ascetic lifestyle. In antiquity, Pythagoras was credited with mathematical and scientific discoveries, such as the Pythagorean theorem, Pythagorean tuning, the five regular solids, the theory of proportions, the sphericity of the Earth, the identity of the morning and evening stars as the planet Venus, and the division of the globe into five climatic zones. He was reputedly the first man to call himself a philosopher ("lover of wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
