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Sexual Reproduction in Humans

Sexual Reproduction in Humans


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Is the human egg cell (ova) considered motile? We know that is is not actively motile but it is transferred via the fallopian tube to the uterus. Does that make it motile?


The fallopian tubes, also known as uterine tubes are uterine appendages, lined from inside with ciliated simple columnar epithelium, leading from the ovaries of female mammals into the uterus, via the uterotubal junction. They enable the passage of egg cells from the ovaries to the uterus.

The egg cell is typically not capable of active movement and hence not motile


Sexual Reproduction in Humans

Each testis is packed with seminiferous tubules (laid end to end, they would extend more than 20 meters) where spermatogenesis occurs.

Spermatogenesis

The walls of the seminiferous tubules consist of diploid spermatogonia, stem cells that are the precursors of sperm.

Meiosis of each spermatocyte produces 4 haploid spermatids. This process takes over three weeks to complete.

Then the spermatids differentiate into sperm, losing most of their cytoplasm in the process.

For simplicity, the figure shows the behavior of just a single pair of homologous chromosomes with a single crossover. With 22 pairs of autosomes and an average of two crossovers between each pair, the variety of gene combinations in sperm is very great.

Sperm

  • a head, which has
    • an acrosome at its tip and
    • contains a haploid set of chromosomes in a compact, inactive, state.

    This electron micrograph (courtesy of Dr. Don W. Fawcett and Susumu Ito) shows the sperm cell of a bat. Note the orderly arrangement of the mitochondria. They supply the ATP to power the whiplike motion of the tail.

    An adult male manufactures over 100 million sperm cells each day. These gradually move into the epididymis where they undergo further maturation. The acidic environment in the epididymis keeps the mature sperm inactive.

    In addition to making sperm, the testis is an endocrine gland. Its principal hormone, testosterone, is responsible for the development of the secondary sex characteristics of men such as the beard, deep voice, and masculine body shape. Testosterone is also essential for making sperm.

    Link to more on testosterone.
    Testosterone is made in the interstitial cells (also called Leydig cells) that lie between the seminiferous tubules.


    How Human Reproduction Works

    In the Middle Ages, the summer solstice was a big event for Europeans. Weddings were planned for that day, and many communities held large parties with plenty of adult beverages. As a result, nine months after that day, quite a lot of babies would be born. Coincidentally, white storks returned from their migratory travels exactly nine months after the summer solstice as well, and it's believed that storks gained their reputation for bringing babies to mothers because of this scheduling sync-up [source: Adams].

    Many adults may still turn to the story of the stork when they want to avoid an awkward conversation of how babies are made, but here at HowStuffWorks.com, we don't shy away from any of the tough questions. In this article, we'll explore the biology of sex -- otherwise known as human sexual reproduction. We'll examine the body's sexual organs, the biological cycles of sex and the process of fertilization. If you need a refresher on the birds and the bees, this is the article for you.

    There are many reasons why people have sexual intercourse -- it improves intimacy between a couple by releasing hormones that help them bond, and studies have shown that sexual activity relieves stress, boosts immunity, reduces pain and burns calories [source: Doheny]. Those are benefits that anyone can reap from sex, no matter their gender or their sexuality. But for the subject at hand -- making a baby -- a man and a woman and their unique genetic information is required. On the next few pages, we'll discuss the reproductive systems of men and women.


    Female Reproductive System

    The female germ-cells or eggs are produced in the ovaries.

    The egg is transported from the ovary to the womb through a thin oviduct known as fallopian tube.

    The two oviducts unite and form an elastic bag-like structure known as the uterus, which opens into the vagina through the cervix.

    During the sexual intercourse, most likely, the egg and the sperm (zygote) get fertilized and implanted in the lining of the uterus.

    The thickened lining (of the uterus) and richly supplied blood nourish the growing embryo (in the uterus).

    The embryo receives nutrition from the mother’s blood with the help of a special tissue known as placenta.

    Likewise, the development of a child inside the mother’s body, takes about nine months.


    Evolution of Sexual Reproduction

    Many organisms reproduce asexually that is, they produce genetically identical clones. All of an asexual individual's offspring can also produce offspring, but for a sexual female that produces both daughters and sons, only the daughters can bear young. If an asexual individual and a sexual female each produce the same total number of offspring in an unchanging environment, then the asexual individual will have twice as many grandchildren as will the sexual female (since only half of the sexual female's children will bear young), four times as many great-grandchildren, and so on. In this sense, sex is evolutionarily very costly that is, it appears to have a lower fitness than a strictly asexual strategy. Sex also carries other costs such as energy expenditures associated with finding and competing for mates and the risk of exposure to sexually transmitted diseases. So why has sex evolved and why does it persist?

    Most explanations for sex are based on the fact that sexual reproduction results in genetically variable offspring, whereas asexual reproduction does not. Genetic variation among offspring is valuable, particularly when environments change over time. If the environment changes for the worse, an asexual mother may lose all of her offspring, while a sexual mother is likely to have at least some of her offspring survive the new conditions. Environments usually do change, particularly in terms of the adaptations of other organisms with which a species interacts. In such uncertain environments sexual reproduction should be favored by natural selection. But as in much of biology, there is no single widely accepted answer for the evolution and persistence of sex in all organisms.


    Human Reproductive Biology

    This acclaimed text has been fully revised and updated, now incorporating issues including aging of the reproductive system, and updates on the chapters on conception and Gamete Transport and Fertilization, and Pregnancy.

    Human Reproductive Biology, Third Edition emphasizes the biological and biomedical aspects of human reproduction, explains advances in reproductive science and discusses the choices and concerns of today. Generously illustrated in full color, the text provides current information about human reproductive anatomy and physiology.

    • All material competely updated with the latest research results, methods, and topics now organized to facilitate logical presentation of topics
    • New chapters on Reproductive Senescence, Conception: Gamete Transport, Fertilization, Pregnancy: Maternal Aspects and Pregnancy: Fetal Development
    • Full color illustrations

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    Об авторе (2006)

    Richard E. Jones has published more than 100 research papers in his field and has received the NIH Research Career Development Award for his research efforts in the study of reproductive biology and endocrinology. In 1990 he received the Student Organization for Alumni Relations Teaching Recognition Award for his teaching of an annual undergraduate course, Human Reproductive Biology, and a course on human anatomy. Dr. Jones obtained his B.A., M.A. and Ph.D. from the University of California at Berkeley. He is now Professor Emeritus of Biology at the University of Colorado, Boulder, where his research interests include reproductive biology as well as reproductive endocrinology.

    Kristin H. Lopez teaches human reproductive biology through the Department of Integrative Physiology at the University of Colorado-Boulder. With a background in comparative reproduction and endocrinology, she is an editor of the fi ve-volume work Hormones and Reproduction of Vertebrates (Academic Press, 2011). Her ongoing work with Colorado Diversity Initiative promotes increased access to higher education of underrepresented students in STEM.


    Hormonal Control of Reproduction

    The human male and female reproductive cycles are controlled by the interaction of hormones from the hypothalamus and anterior pituitary with hormones from reproductive tissues and organs. In both sexes, the hypothalamus monitors and causes the release of hormones from the anterior pituitary gland. When the reproductive hormone is required, the hypothalamus sends a gonadotropin-releasing hormone (GnRH) to the anterior pituitary. This causes the release of follicle stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary into the blood. Although these hormones are named after their functions in female reproduction, they are produced in both sexes and play important roles in controlling reproduction. Other hormones have specific functions in the male and female reproductive systems.


    Sexual Reproduction

    Sexual reproduction produces the possibility of hundreds of thousands of variations for natural selection to choose from.

    Explanation:

    In the human genome it is estimated that there are more than 30,000 genes. In sexual reproduction there is a vast number of possible combinations and expression of these genes.

    Natural selection can not produce information it can only choose the information best suited or adapted to a particular environment by eliminating and causing the extinction of those variations that are less well adapted.

    Sexual reproduction provides a vast selection of variations for Natural Selection to chose from. Think about all the variations of humans on the planet some suited to some environments better than other variations.

    The genome of the grey wolf has given birth to a vast array of dog breeds. Artifical selection has chosen different variations of the genome, eliminating some parts to create. all the different varieties of dogs, that are still the same species.

    Answer:

    Sexual reproduction is the reproduction in Which two parents are required.

    Explanation:

    In this reproduction genetic variations occurs.
    This variation is helpful on survival of organism at different conditions.
    As the offspring is formed by the fusion of 2 gametes
    Male and female gamete.


    Human Reproductive Biology

    The fourth edition of Human Reproductive Biology—winner of a 2015 Textbook Excellence Award (Texty) from The Text and Academic Authors Association—emphasizes the biological and biomedical aspects of human reproduction, explains advances in reproductive science and discusses the choices and concerns of today. Generously illustrated in full color, the text provides current information about human reproductive anatomy and physiology. This expansive text covers the full range of topics in human reproduction, from the biology of male and female systems to conception, pregnancy, labor and birth. It goes on to cover issues in fertility and its control, population growth and family planning, induced abortion and sexually transmitted diseases. This is the ideal book for courses on human reproductive biology, with chapter introductions, sidebars on related topics, chapter summaries and suggestions for further reading.

    The fourth edition of Human Reproductive Biology—winner of a 2015 Textbook Excellence Award (Texty) from The Text and Academic Authors Association—emphasizes the biological and biomedical aspects of human reproduction, explains advances in reproductive science and discusses the choices and concerns of today. Generously illustrated in full color, the text provides current information about human reproductive anatomy and physiology. This expansive text covers the full range of topics in human reproduction, from the biology of male and female systems to conception, pregnancy, labor and birth. It goes on to cover issues in fertility and its control, population growth and family planning, induced abortion and sexually transmitted diseases. This is the ideal book for courses on human reproductive biology, with chapter introductions, sidebars on related topics, chapter summaries and suggestions for further reading.


    Human Reproductive Biology

    Human Reproductive Biology focuses on the processes, concerns, and trends in human reproduction. Divided into four parts with 19 chapters, the book starts by tracing the history of human reproduction biology and the questions and choices involved. The first part focuses on the male and female reproductive systems. The text notes the different organs involved in reproduction, including the penis, scrotum, vagina, oviducts, and mammary glands. The book discusses sexual development and differentiation, particularly noting the variance of sex ducts and glands, external genitalia, and disorders of sexual development and determination. The text also looks at puberty. Concerns include gonadal changes from birth to puberty mechanisms that influence puberty and puberty and psychosocial adjustment. The second part deals with menstrual cycle, fertilization, pregnancy, labor, and birth. Some of the concerns include length of menstrual cycle absence of menstruation transport of sperm and ovum in the oviduct and semen release. The text also highlights labor and birthing processes as well as the relationship of neonates and parents. The third part looks at the medical aspects of human reproduction, infertility, and sexually transmitted diseases. Concerns include contraception, abortion, herpes genitalis, and vaginitis. The text folds with discussions on human sexual behavior, population growth, and family planning. Concerns include sexual dysfunction the effects of overpopulation and population control. The book is a vital source of data for readers interested in human reproduction.

    Human Reproductive Biology focuses on the processes, concerns, and trends in human reproduction. Divided into four parts with 19 chapters, the book starts by tracing the history of human reproduction biology and the questions and choices involved. The first part focuses on the male and female reproductive systems. The text notes the different organs involved in reproduction, including the penis, scrotum, vagina, oviducts, and mammary glands. The book discusses sexual development and differentiation, particularly noting the variance of sex ducts and glands, external genitalia, and disorders of sexual development and determination. The text also looks at puberty. Concerns include gonadal changes from birth to puberty mechanisms that influence puberty and puberty and psychosocial adjustment. The second part deals with menstrual cycle, fertilization, pregnancy, labor, and birth. Some of the concerns include length of menstrual cycle absence of menstruation transport of sperm and ovum in the oviduct and semen release. The text also highlights labor and birthing processes as well as the relationship of neonates and parents. The third part looks at the medical aspects of human reproduction, infertility, and sexually transmitted diseases. Concerns include contraception, abortion, herpes genitalis, and vaginitis. The text folds with discussions on human sexual behavior, population growth, and family planning. Concerns include sexual dysfunction the effects of overpopulation and population control. The book is a vital source of data for readers interested in human reproduction.


    Watch the video: Sexual #reproduction in human beings puberty. 10th biology. ncert class 10 science cbse syllabus (July 2022).


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