pregnancy + development

1. pregnancy + development • In your textbook

2. Fertilization & Pregnancy • Conception: What fertilization and implantation are referred to as • Development begins as embryo is moved to uterus • After about 3 days, embryo implants into the endometrium • HCG secretes through membranes surrounding embryo • Uterine tissues form placenta, which exchanges gases and nutrients between fetal & maternal blood

3. Control of Reproduction 41.4 in your textbook • Abstinence: Not engaging in sexual intercourse. Most reliable. Prevents transmission of sexually transmitted diseases (STDs). • Male and female condoms. • Changes in signal transduction pathways can alter cellular response. • Preven: Kit made up of four synthetic progesterone pills. Upsets normal uterine cycle, making it difficult for embryo to implant itself in the endometrium. Studies show it is 85% effective in preventing unintended pregnancies.

4. Control of Human Reproduction 41.4 in your textbook • Contraceptive vaccines are now being developed. • Types intended to women against HCG, the necessary hormone to maintaining the implantation of the embryo. Immunization wears off with time, studies show. • Research for developing safe/effective hormonal birth control for males. Implants, pills, patches, and injections are all being tested as ways to deliver testosterone and/or progesterone to suppress sperm production. Still in experiment unlikely to be available outside of clinical trials for at least a few more years.

6. Reproductive Technologies 41.4 in your textbook • Infertility: The inability of a couple to achieve pregnancy after one year of regular, unprotected intercourse. • Females (if healthy body weight/no obstruction is apparent in their body) may take fertility drugs, gonadotrophic hormones that stimulate the ovaries and bring about ovulation. May result in multiple ovulations and multiple births. • Adoption

7. Reproductive Technologies 41.4 in your textbook • Assisted Reproductive Technologies (ARTs) developed to increase chances of pregnancy. Lab settings. • Artificial Insemination by Donor (AID): Sperm are placed in vagina by a physician. Especially helpful if male has low sperm count. Donor sperm is common. • IUI (intrauterine insemination) fertility drugs given to stimulate ovaries but donor’s sperm is placed in uterus. • Surrogate Mothers: Women are contracted and paid to have babies. Sperm and oocytes of couple inside woman’s body.

8. Reproductive Technologies 41.4 in your textbook • In Vitro Fertilization (IVF): Union of sperm and an egg to form a zygote occurs in laboratory glassware. • Retrieve immature oocytes by using a needle • Immature oocytes mature in glassware, then concentrated sperm are added. • After 2-4 days, embryos are ready to be transferred to the uterus of the woman, who is in the secretory phase of her uterine cycle (because she is under fertility drugs).

9. Ethical Concerns With IVF • Little evidence to suggest that children born as a result of standard IVF protocols are different in any way from children conceived naturally. Equality is important in esteeming them! • Potential risks in drug treatments given to woman. Concerns about artificial selection of sperm and injection. • Natural selection of sperm doesn’t occur. Unhealthy ones are bypassed. Evidence shows higher rates of abnormality in offspring.

10. Sexually Transmitted Diseases 41.5 in your textbook • Caused by organisms such as viruses and bacteria. • AIDS: Acquired immunodeficiency syndrome caused by HIV (human immunodeficiency virus). Transmitted by sexual contact with an infected person, needle-sharing, etc. HIV attacks helper T cells and makes them decline in number. This makes a person become more susceptible to other types of infections. Epidemic disease. • Genital Herpes: Caused by Type 2 herpes simplex virus. Repeatedly flares up.

11. STDs continued 41.5 in your textbook • Hepatitis: Infects liver and can cause cancer and death. • Hepatitis A - usually acquired from sewage-contaminated drinking water, but also can be transmitted through sexual/oral contact. • Hepatitis B - can be spread by blood transfusions and bodily fluids. • Hepatitis C - “posttransfusion hepatitis” can be transmitted through sexual contact. No vaccines available for this type.

12. STDs continued... 41.5 in your textbook • Chlamydia: Caused by tiny bacterium clled Chlamydia trachomatis. • Men: 8-21 days after infection men may experience a mild burning sensation on urination and a mucoid discharge. • Women: May have vaginal discharge or symptoms of a urinary tract infection. Can cause cervical ulcerations, which increase the risk of acquiring AIDS. Possible risk of pelvic inflammatory disease if untreated--which can lead to sterility and infertility.

13. STDs continued 41.5 in your textbook • Gonorrhea: Caused by bacterium Neisseria gonorrhoeae. Latent infection leads to pelvic inflammatory disease in both genders--which affects the vasa deferentia or oviducts. As inflamed tubules heal, they may become partially or completely blocked by scar tissue, resulting in infertility or sterility. If baby is exposed during birth, an eye infection leading to blindness can result. All newborns are given eyedrops to prevent this possibility. • Gonorrhea proctitis, infection of the anus. Causes anal pain and blood or pus in feces. Oral/genital contact can cause infection of the mouth, throat, and tonsils. Can spread to internal parts of body, causing heart damage or arthritis. • Up to now, gonorrhea was curable by antibiotic therapy, but resistance to antibiotics is becoming more and more common.

14. STDs continued....... 41.5 in your textbook • Syphilis: Caused by Treponema pallidum. 3 stages separated by latent periods. • Primary stage: hard chancre (ulcerated sore w/ hard edges) appears. Secondary Stage: Rash appears all over body--even palms of hands. Tertiary stage: may affect cardiovascular and/or nervous system. • Infected person may become mentally retarded, blind, walk with shuffle, or show signs of insanity.

15. Asexual Reproduction • Single parent gives rise to an identical offspring, unless mutations have occurred • Good because you can reproduce rapidly and colonize quickly • Many different means • Sponges produce gemmules that develop into individuals • Cnidarians reproduce by "budding", where an outgrowth from the parent becomes an individual • Fragmentation, and regeneration from fragments, is seen among many planaria, sponges, echinoderms

16. continued • Flatworms, roundworms, insects, some turkeys, etc. can reproduce pathogenically • Modification of sexual reproduction were an unfertilized egg develops into a complete individual • In bees, queen selectively fertilizes some eggs with stored sperm • Unfertilized eggs become haploid males

17. Sexual Reproduction • Sex cells (gametes) produced by parents unite, forming a genetically unique being • Hermaphroditic organisms (have both sets of sex organs) can self-fertilize • Sex reversal can also occur • Animals produce gametes in regions called gonads (sponges are the exception) • Testes and ovaries • Eggs or sperm are derived from germ cells, which are specialized for this in early development

18. Life History Strategies • Oviparous- Any animal that deposits an egg in the external environment • Usually leads to larval stage (immature) • When terrestrial animals lay eggs, they contain an extraembryonic membrane to prevent drying out & protect embryo • One membrane surrounds the yolk, which is nutrient rich material • Viviparous- Animals who have young inside them in placenta, which supports the baby until it's ready for independence

19. Fertilization 42.1 in your textbook • Fertilization is the union of a sperm and an egg to form a zygote. It requires a series of events that will result in the diploid zygote. • Acrosome reaction is the reaction that occurs in the acrosome of the sperm as it approaches the egg. • Cortical reaction occurs in fertilization when a sperm cell unites with the egg’s plasma membrane. (zona reaction)

20. Process of Fertilization • Vesicles in the egg called cortical granules secrete enzymes that turn the zona pellucida, forming an impenetrable fertilization membrane; this is called “Slow Block.” • As soon as plasma membranes of the sperm and egg fuse, the zona pellucida lifts away from the surface of the egg, forming a moat that prevents entrance of any other sperm. • The diploid zygote forms when a nuclear envelope surrounds the sperm and egg chromosomes.

21. Process of Fertilization • Several sperm penetrate the corono radiata and several sperm attempt to penetrate the zona pellucida • One sperm enters the egg and their nuclei eventually fuse • After the sperm head binds tightly to the zona pellucida, the acrosome enzymes digest and form a pathway for the sperm through the zona pellucida. • The head, middle piece and usually the tail enters the egg • Prevention of polyspermy depends on changes in the egg plasma membrane when the sperm touches the egg and depolarizes the egg plasma membrane; this is called “Fast Block.”

23. Tissue Stages • Early gastrula stage- inward movement (invagination) of the blastula wall to form a gastrula of two to three primary germ layers • Outer layer of cells to become ectoderm- the beginnings of the epidermis, epithelial lining of mouth and rectum, and the nervous system • Inner layers become endoderm- beginnings of the lining of the digestive and respiratory tract, and glands • Pore created by the inward movement (invagination) of the blastopore

24. Cellular Stages of Development • An organism is an embryo during the first stages of development. • After fertilization, a zygote undergoes cleavage, cell division without growth. • DNA replication and mitosis occur repeatedly, cells get smaller with each division. • A cavity called the blastocoel develops forming a hollow ball called the blastula

25. Late gastrula stage- middle dermal layer forms called mesoderm • Mesoderm is two layered and the space between is called coelom that will now contain body organs • Mesoderm gives ride to skeleton, dermis, muscles, excretory system, reproductive system, • Germ layers later fuse to become organs

27. Organ Stages • Mesoderm cells congregate into a line on the main axis, forms dorsal notochord, later becomes vertebral column • Nervous system develops from midline ectoderm • Ectoderm cells fuse to form neural plate • Folds in on itself to form neural tube • Now the embryo is called a neurula! • Neural tube grows brain on one end and rest becomes spinal cord • The rest of midline mesoderm two masses of tissue, these form into segmental muscles, and the vertebral bones in vertebrates

29. Stages of Birth • When fetal brain matures, androgens are released. • Placenta uses androgens as precursors for estrogens that stimulate the production of prostaglandin and oxytocin. • estrogen, oxytocin, prostaglandin cause uterus to contract and expel fetus. • Positive feedback: mechanism that brings about an ever greater change in the same direction. Baby’s head presses on cervix due to contractions and signals are sent to brain. Signals cause pituitary gland to release oxytocin. As oxytocin increases, so do contractions until birth occurs. • Process of birth (parturition) has 3 stages: dilation of cervix, birth of the baby, and expulsion of the placenta. Initiated by prostaglandins in humans.

30. positive feedback loop w/ oxytocin

31. Embryonic Development • An organism is called an embryo during the first stages of development. • The cellular stages of development are (1) cleavage resulting in a multicellular embryo and (2) formation of the blastula. • Cleavage is a cell division without growth. It increases only the number of cells. • Morula ball of cells, a result of cleavage. Then continues to divide to form a blastula, or a hollow ball of cells that have a fluid-filled cavity called blastocoel.

32. Embryonic Development • Covers events from conception (fertilization followed by implantation) to birth (parturition). • Human development is divided into embryonic and fetal development • The embryonic period, months 1 and 2 of pregnancy, is when the major organs are formed • Fetal development is during months 3-9, when organ systems are refined.

33. Embryonic development • Development can also be divided into trimesters • First trimester: embryonic and early fetal development occurs • Second trimester: development of organs and organ systems; fetus is distinctly human at the end of the second trimester • Third trimester: fetus grows rapidly and organ systems become functional

34. Structure and Function of Placenta • Placenta begins formation once the embryo is fully implanted. Provides gas, nutrient and waste exchange. • Chorionic vill are treelike extensions of the chorion • Chorionic villi project into the maternal tissues. Later, the chorionic villi disappear in all areas except where the placenta develops. • Exchange of molecules between the fetal and maternal blood takes place across the walls of the chorionic villi.

35. By the tenth week, the placenta is fully formed and has already begun to produce progesterone and estrogen. Due to the negative feedback control by the hypothalamus and anterior pituitary, no new follicles mature. They maintain the lining of uterus and there is no menstruation during pregnancy. Exchange of molecules between the fetal and maternal blood takes place across the walls of the chorionic villi. CO2 and wastes move across from fetus; O2 and nutrients flow from the menstrual side. The umbilical cord stretches between the placenta and fetus.

36. Human chorionic gonadotropin (HCG): produced by the placenta, which surrounds the embryo. • Maintains the corpus luteum that surrounds the egg until the placenta begins to produce its own progesterone and estrogen. Maintains the uterine lining to provide a place for uterine development until placenta eventually forms. • Hormone detected in pregnancy tests, since it’s present in the mother’s blood and the urine as soon as 10 days after conception • Aminion surrounds the embryo and cushions it with amniotic fluid to insulate against thermal changes and protect it from harm.

38. Fig. 42.15

39. Stages of Birth • 1.When the fetal brain matures, the hypothalamus causes the pituitary to stimulate the adrenal cortex so that androgens are released. • 2.The placenta uses androgens as precursors for estrogens that stimulate the production of prostaglandin and oxytocin. • 3.The hormones estrogen, prostaglandin, and oxytocin all cause the uterus to contract and expel the fetus. • 4.The process of birth (parturition) has three stages: dilation of the cervix, birth of the baby, and expulsion of the placenta.

40. Expulsion • The expulsion stage lasts 2-60 minutes. • Contractions last 50-90 seconds and they are 1-2 minutes apart. • Expulsion ends when the baby is pushed through the vagina. • A baby is born with its umbilical cord still attached • The birth of the baby is followed by the delivery of the placenta (the afterbirth) • http://www.youtube.com/watch?v=Xath6kOf0NE