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H2O Module 3- Reproduction Janett Noyan Crystal Sutherland Olicia Sylvester Toni-anne Murray What is the Placenta? • Mass of tissue that unites foetus to the uterus • Formed by interlocking of membranes of the • • foetus with the lining of the womb. Is soft, disc-shaped, dark red and has villi which fit closely in the uterus wall. Is supplied with a network of blood vessels though which oxygen and nourishment pass form the mother’s blood to that of the foetus. THE PLACENTA Functions of Placenta 1. The placenta allows for exhange of materials between the mother and foetus without the two bloods mixing. This is so since the fetal blood may be different from the mother due to the influence of the fathers gene. 2. Oxygen, water, amino acids, glucose, essential minerals among many others, are transferred from maternal to fetal blood to nourish the developing baby (fetus). Placenta 3. Carbon dioxide and waste materials diffuse from the foetus and are carried away in mother’s blood. This to ensure that no harm comes to the fetus. At birth, the placenta reduces the secretion of progesterone which stimulates the pituitary gland to secrete oxytocin. Oxytocin stimulates contractions of the uterus wall. Placenta 4. The placenta provides some immunity to the fetus, meaning certain maternal antibodies pass into the developing baby. The term for this is passive immunity. 5. Certain pathogens and their toxins are prevented from entering the amniotic fluid then the fetus. An exception is the Rubella (German measles), gonorrhoea, syphilis etc., virus can also pass over the [placenta, for example HIV. PLACENTA 6. The placenta further protects the foetus by creating a barrier against maternal hormones, which can cause adverse effects in the fetal development. 7. Since the two blood systems- the mother’s and fetus’ blood systems- are not directly mixed the placenta allow to operate at different pressures without causing harm to the mother or child. Placenta 8. During the pregnancy, the placenta takes on the role of hormone production. It produces progesterone, which prevents ovulation and menstruation. It also secrete human choriogonadotrophin (HCG), a hormone whose presence in the urine of pregnant women is the basis of most pregnancy test. Blood flow in the placenta The Amnion • This is a strong membrane. • Inside the amnion is a liquid called amniotic fluid. • This fluid helps to support the embryo and to protect it. Contraceptive methods • These methods are carried out to prevent pregnancy. Knowledge of the human reproductive anatomy and physiology has been applied to the development of these methods. One of such methods is the use of condoms. The male covers his penis with this thin rubber sheath when it becomes erect. Sperms are caught in the end of the condom when they are ejaculated, therfore do not reach the egg. Images Contraceptives used by FEMALES • Females also wear condoms, these are called diaphram. They are thin sheaths of rubber or polyurethane with rings at both ends which are inserted into the vagina. The female may also take contraceptive pills which contains hormones similar to those produced during the menstrual cycle. These hormones prevent the release of the egg from the ovary. Images Contraceptive methods • Females may also use a coil, which is a small spring-shaped stucture made of plastic or copper and must be inserted by a doctor inside the uterus. As it fits inside the uterus, it is called an intra-uterine device (IUD). The coil interrups the preparation of the womb for the fertilised egg and so prevents implantation. An intra-uterine device (IUD) Contraceptive methods: sterilization • Surgical sterilization is available in the form of tubal ligation for women and vasectomy for men. Possible effects of maternal behavior on foetal development: Nutrition • A balanced, nutritious diet is an important aspect of a healthy pregnancy. Eating a healthy diet, balancing carbohydrates, fat, and proteins, and eating a variety of fruits and vegetables, usually ensures good nutrition. Adequate periconceptional folic acid (also called folate or Vitamin B9) intake has been proven to limit fetal neural tube defects, preventing spina bifida, a very serious birth defect. Possible effects of maternal behavior on foetal development: Nutrition • DHA omega-3 is a major structural fatty acid in the brain and retina, and is naturally found in breast milk. It is important for the woman to consume adequate amounts of DHA during pregnancy and while nursing to support her well-being and the health of her infant. Developing infants cannot produce DHA efficiently, and must receive this vital nutrient from the woman through the placenta during pregnancy and in breast milk after birth. Possible effects of maternal behavior on foetal development: use of drugs • Drugs used during pregnancy can have temporary or • permanent effects on the fetus. Therefore many physicians would prefer not to prescribe for pregnant women. Drugs have been classified into categories A,B,C,D and X based on the Food and Drug Administration (FDA) rating system to provide therapeutic guidance based on potential benefits and foetal risks. Drugs like multivitamins that have demonstrated no fetal risks after controlled studies in humans are classified as Category A. On the other hand drugs like thalidomide with proven fetal risks that outweigh all benefits are classified as Category X. Possible effects of maternal behavior on foetal development: alcohol • Alcohol ingestion during pregnancy may cause fetal alcohol syndrome, a permanent and often devastating birthdefect syndrome. Possible effects of maternal behavior on foetal development: cigarette smoking • Numerous studies show that children exposed to prenatal cigarette smoke may experience a wide range of behavioral, neurological, and physical difficulties. Possible effects of maternal behavior on foetal development: Sexual activity during pregnancy • Most pregnant women can enjoy sexual activity during pregnancy throughout gravidity. • A significant number of women report greater sexual satisfaction throughout their pregnancies. Summary • Placenta: provides large suface area for • • exchange of substances between mother’s and embryo’s/ foetus’ blood. Wall of placenta: prevents mixing of mother’s and foetus’ blood, therefore preventing unwanted substances entering foetus’ blood. Contraceptive methods: used to prevent pregnancies, eg. Use of condoms, coil (IUD), contraceptive pills, the rhythm method, and sterilisation. Method How it works Effectiveness Advantages Disadvantage Sterilization Male(vasectomy)- the vas defrence are cut and tied off. Female(tubal ligation)the oviducts are cut and tied off. 100% No artificial appliance is involved. Once the operation has been performed there is not futher cost. Irreversible in normal circumstances. Prevention of ovulation Oral contraceptive99% contains artificial oestrogen and progesterone Implant 100% contraceptv- implant placed under skin which releases artificial oestrogen and progesterone. Very reliable if taken regularly Occasional side effects: nausea, breast tenderness Almost totally reliable. Each implant lasts 5 years. Can cause irregular menstrual bleeding. Morning-after Pillblocks the action of progesterone. Intra-Uterine Device- device usually made of plastic&/or copper whhich is inserted into the womb by a doc. And which prevents implantation. Can be used after rather than before intercourse. Once fitted, no further action is required except for annual check-ups. 1.High dose of oestrogen can produce sideeffects. Not suitable for regular use. 2.Possible menstrual discomfort. May be displaced or rejected. Prevention of implantation Not widely used but probably 99100% 98% Method Barriers which prevent sperm reaching the egg Natural Method How it works Effectivenes s Advantage Disadvantage Female (Diaphragm, cap) – A Dome-shaped sheet of thin rubber, with a thicker spring rim, which is inserted into the vagina over the cervix.Best used with spermicide. Female (condom) Sheath of thin rubber with two springy rings. Smaller inserted into vagina, larger remains outside. Very reliable if used with a spermicide Reliable. Available for use by all women. Must be inserted prior to intercourse and should be removed 824 hours after intercourse. Initial fitting must be by a trained practitioner. Male (Condom, Sheath) – A sheath of thin rubber unrolled onto the erect penis prior to intercourse. Seamen is collected in teat at the tip. Best used with a spermicide. Very reliable 90% and up to 98% if used with a spermocide Rhythm methodrefraining from intercourse during those times in the menustral cycle, when conception is most likely. Variable-not very reliable 76% and up to 98% with practice. Very reliable Readily available, quite easy to fit. Gives some protection against sexually transmitted diseases. Easily available and easy to use. Available for use by all men. Gives some protection against sexually transmitted disease including AIDS. No appliance required.Only acceptable method to some religious groups. May reduce enjoyment of intercourse. May reduce sensitivity of the penis and so interfere with enjoyment. Not reliable.Restricts times when intercourse can take place. Multiple choice questions 1) Which would be referred to as the least reliable method of birth control? Use of condom Intra-uterine device (IUD) or coil Rhythm method Sterilisation Multiple choice questions 2) At birth, what hormone is secreted by the pitutary gland to stimulate contractions of the uterus wall? Progesterone Oxytocin Oestrogen Testosterone