Arkansas Tech University
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This 4 page Class Notes was uploaded by Sydney Thornton on Sunday February 14, 2016. The Class Notes belongs to 1014-004 at Arkansas Tech University taught by Blake Whitt in Winter 2016. Since its upload, it has received 30 views. For similar materials see Intro to biological sciences in Biology at Arkansas Tech University.
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Date Created: 02/14/16
Chapter 6: Reproduction What Kind of Baby Is It? How do males and females form? o Some people are born with a disorder of sexual development (DSD) in which genitalia are atypical with respect to the number of chromosomes generally associated with the male or female sex. o Different species have different methods for sex determination. o In humans the first set of instructions is found on the sex chromosomes. Males are XY Females are XX o These are responsible for primary sex determination: Whether ovaries (female) or testes (male) form. o Secondary sex determination governs the development of other sexrelated characteristics. o Certain hormones (chemical signs) are responsible for these secondary instructions. Chromosomes Instructions o At first the embryo has biopotential for sex that is no physical commitment has been made. o The structures that will be sex organs await instructions. Male SRY gene: on the Ychromosomes leads to development on the testes. Female DAX1 gene on both X chromosomes leads to development of the ovaries. o Whether male or female the embryo has precursors of the internal features of both sexes. Set of tubes and ducts called Wolffian ducts in males and Mullerian ducts in females. One of these ducts may disappear. Hormone Instructions o In XY, two critical hormones are released: AntiMullerian hormones which destroys Mullerian ducts. Testosterone which triggers further development of Wolffian ducts, the prostate gland, and the penis. Also regulates descent of testes and inhibits breast formation. o In XX, ovaries secrete estrogen: Promotes the development of the Mullerian ducts, oviducts, uterus, and upper end of the vagina. What if hormone signals are missing or misread? o A whole myriad of disorders exist, two of these are: Androgeninsensitivity syndrome (AIS) Pseudohermaphroditism Androgen Insensitivity Syndrome (AIS) o In AIS individuals are XY but do not develop male parts. They lack receptors for testosterone They have testes and testes make testosterone but no external male genitals form. o AIS embryos are exposed to estrogen from the mother. Responsible for breast development Female appearance Pseudohermaphroditism o In pseudohermaphroditism an XY individual develop testes but lacks enzyme that enables testosterone to send the right signals. o External genitals appear female but the Mullerian ducts degenerate. o At puberty, testosterone is produced. The clitoris becomes a penis and the young girl becomes a man. Life Application Gender Testing Sports o This aside deals with sexidentity and athletic competition. o READ P. 162!!! How do men produce sperm? o Men make sperm continuously. o Sperm production has to occur below body temp which is why testes are located outside the body. o Testes contain seminiferous tubules lined in stem cells. The stem cells give rise to cells that will become sperm. Sperm and Semen o After meiosis is complete, the sperm mature in the epididymis a coiled structure that sits atop each testis. o Semen consists of more than just sperm. Accessory organs will contribute fluids to make semen. Prostate gland: secretes a fluid that neutralizes the acidity of the vagina. Bulbourethral glands: neutralizes any urine residue that may be present in the male urethra. Seminal vesticles: secrete fructose and prostaglandins a signal that causes muscle contradiction in the female reproductive trait. How do women produce eggs? o The production of eggs is called oogenesis and starts with an immature egg called a primary oocyte, o Women release one egg per month. This monthly pattern is regulated by hormones. o Oogenesis begins before birth with the oocyte starting meiosis 1 and then pausing until puberty. o Once puberty starts, one primary oocyte completes meiosis 1, each month. One of the cells produced the secondary oocyte retains most of the cytoplasm. o Secondary oocyte starts meiosis 2 but stops and then exits the ovary which is called ovulation. o If the secondary oocyte fuses with the sperm it completes meiosis 2. o Hormones carefully coordinate the process. Hormones and Pregnancy o After fertilization menstruation must be prevented. o Human chronic gonadotropin (hCG) is released which allows the corpus luteum to survive. “How do we know?” The Female Reproductive Tract Helps Sperm Find Egg o A number of challenges await for the sperm after ejaculation. o READ PAGE 171!!!! What causes Infertility and How can it be treated? o Infertility failure to conceive and become pregnant after one year of regular unprotected intercourse. o One common cause of male infertility is low sperm count. o Another is a shortage of healthy sperm. o Sperm counts are declining in men in industrialized nations. Could be because of sedentary lifestyle or exposure to pollutants. o Infertility in women can have several causes too. Endometriosis is a condition in which uterine tissue grows elsewhere in the body and disrupts ovulation. o Pelvic Inflammatory disease: (PID) infertility is caused by blocked oviducts. This could be a result of an STD or an infection caused by an IUD. o Disorders of sexual development can cause infertility. AIS individuals are sterile as they lack ovaries and a uterus and are a XY. Infertility Treatments o Assisted Reproductive Technology (ART): reproductive procedures used to bring sperm and eggs together so that fertilization is possible. Artificial Insemination sperm from the male partner are placed in the female partner’s vagina. Intrauterine Insemination sperm are placed directly into the uterus. o In vitro fertilization (IVF) oocytes are isolated and placed in a petridish and then combined with sperm. In 2 to 4 days some of the embryos are transferred to the uterus. o Gamete infallopian transfer (GIFT) the zygote can be placed in the oviduct instead. o Intracytoplasmic sperm injection (ICS) sperm is injected into the egg. The embryos is then placed in the uterus. o Sometimes the treatments don’t work other options include: Surrogacy: an embryo placed in the uterus of a woman who is not biological mother in order to establish a healthy pregnancy. Fertility drugs can stimulate ovaries and help with ovulation. Surgery can remove blockage of ovary ducts. Technology Connection: Home Pregnancy Tests o All work the same way o Antibodies detect hCG in the urine o Tests are 99% accurate especially if the first urine of the day is tested. o Could get a negative result but still be pregnant.
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