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Fetal Development

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Page 1: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Fetal Development

Page 2: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

The Placenta Mammalian structure that functions in gas,

nutrient, and waste exchange between the embryo (later fetus)and mother’s cardiovascular systems

First are chorionic villi (treelike projections) that project into endometrium

Later, these disappear except where the placenta is formed

By Week 10, the placenta is fully formed and is producing estrogen and progesterone

Page 3: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

The Placenta cont. Two effects of these hormones: 1) negative feedback control of hypothalamus and anterior pituitary prevention of any new follicles from maturing2) Maintain the uterine lining so that the corpus lutuem is no longer neededNo menstruation during pregnancy!

Page 4: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

More of the placenta Fetal side = chorion Maternal side = uterine tissues Note: the chorionic villi are surrounded by

maternal blood BUT maternal and fetal blood do not mix under normal conditions because exchange happens over plasma membranes

C02 and other wastes go from the fetal to the maternal side

Nutrients and oxygen go from the maternal side to the fetal side

Page 5: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Umbilical Cord The umbilical cord connects the placenta and the

fetus and takes fetal blood to and from the placenta Lifeline of the fetus Contains umbilical arteries and vein (transport these

wastes and nutrients in and out with placenta acting as gatekeeper)

If the placenta tears from the uterine wall prematurely, the lives of mother and child are at risk

Another concern is harmful chemicals crossing the placenta, especially during the embryonic period when many structures are forming, although each organ has a sensitive period

Page 6: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s
Page 7: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s
Page 8: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Fetal Development Fetal development occurs from month 3

to month 9. There is a drastic size increase – weight multiplies 600 times (28 grams to 3 kilograms) and the fetus grows about 50 cm in length.

The genitals grow in the third month so the sex can be determined at that time.

After that, hair, eyebrows, eyelashes, toenails, and fingernails grow.

Page 9: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Fetal Development cont. Lanugo (fine downy hair) covers arms and torso. Vernix caseosa (waxy substance) protects skin

from amniotic fluid The skin is wrinkly because the fetus is growing

so quickly. At month four, the fetus has increased

movement which is why the mother begins to feel it at this time.

At the end of month four, the heartbeat can be heard with a stethoscope.

Page 10: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

The Birth Process

Page 11: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

The Stages of Birth Latest findings: when the fetal brain is

mature enough, the hypothalamus causes the pituitary gland to stimulate the adrenal cortex which releases androgens into the bloodsteam that the placenta uses to make estrogens

These estrogens catalyze the production of prostaglandin and oxytocin

These hormones cause contractions in the uterus that will push the fetus out.

Page 12: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

The Stages of Birth cont. Parturition (process of birth) – 3 stages1. The cervix dilates to allow the baby’s

head and body to pass. This stage is also typically when the amnion bursts.

2. The baby is born and the umbilical cord is cut.

3. The placenta is delivered.

Page 13: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Infertility The inability of a couple to achieve

pregnancy after one year of regular, unprotected intercourse

Some infertility can be solved by females taking fertility drugs that have hormones stimulating the ovaries to cause ovulation

Others will decide to adopt

Page 14: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Artificial Insemination by Donor (AID) Sperm is placed in the vagina by a doctor Helpful if the male has a low sperm count

because the sperm can be collected over time

Sperm can be sorted through a DNA-staining chemical into those thought to be X-bearing or Y-bearing to increase chances of having a child of that sex if the parent(s) desire

Page 15: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

In Vitro Fertilization (IVF) The sperm and the egg unite outside of the

body Ultrasounds pick out follicles in the ovaries that

hold immature ooctyes that are brought to maturity in glassware before the sperm is added

After two to four days, the embryos are placed in the uterus

This method is useful to overcome issues involving conception, including blocked oviducts

Page 16: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

In Vitro Process1. Week 1. A drug is injected daily for three weeks

that stops the woman’s normal menstrual cycle.

2. Week 4. FSH is injected in large doses daily for 10 to 12 days. This stimulates the ovaries so they will develop lots of follicles.

3. Week 5. HCG is injected 36 hours before the egg collection. This loosens the egg in the follicles and matures it.

4. Week 5. The man provides semen and it is processed to pool the healthy sperm.

Page 17: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

In Vitro Process cont.5. Week 5. The eggs are taken out of the follicles.6. Week 5. Each egg is mixed with sperm. They are placed in shallow dishes that sit in an incubator over night.7. Week 5/6. Check the dishes!!8. Week 5/6. Two or three embryos are picked and put into the uterus.9. Beginning of week 8. A pregnancy test is done to see if any implanted.10. End of week 9. If so, a scan is done to ensure that the pregnancy is normal. The fetal heartbeat should be present.

Page 18: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Ethical Issues – IB Standards Aim 8: There is great variation between

human societies around the world on the views held on IVF. This is the result of cultural and religious diversity. There is little evidence to suggest that children born as a result of standard IVF protocols are different in any way from children conceived naturally. It is important that there is parity of esteem for all children, however they are conceived.

Page 19: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Ethical Issues – IB Standards TOK: There are potential risks in the drug

treatments that the woman is given, and there are concerns about the artificial selection of sperm and the injection of them into the eggs that occurs with some IVF protocols. The natural selection of sperm with consequent elimination of unhealthy ones is bypassed and there is evidence that there are higher rates of abnormality in the offspring as a result.

Page 20: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Ethical Issues

Against IVF Inherited forms of infertility may be

passed on to children. Extra embryos are sometimes

killed. Embryologists pick which embryos

to transfer to the uterus so humans decide which ones live and die.

IVF is an unnatural process occurring in a lab, not an act of love with natural conception.

Infertility should be accepted as the will of God and it is wrong to use IVF to circumvent it.

For IVF Many forms of infertility are because

of the environment so children won’t get them.

The embryos cannot feel pain or suffer because they don’t have a nervous system.

Suffering because of genetic disease could decrease because embryos are screened.

Parents willing to go through IVF really want kids and will probably be good parents.

Infertility makes many people unhappy and IVF can overcome this.

Page 21: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Animal Reproduction

Page 22: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Asexual Reproduction Sponges: asexual gemmules new individuals Cnidarians (ex. Hydra): budding Flatworms: parasitic and reproduce during certain

stages of their life cycles Annelids and echinoderms (ex. starfish): regenerate

from fragments Parthenogenesis – modification of sexual

reproduction in which an unfertilized egg develops into a complete individual

Example – the queen honey bee will make and store sperm that she will selectively use to fertilize eggs; any unfertilized egg will become a haploid male

Page 23: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Sexual Reproduction The egg of one parent is fertilized by the

sperm of another Most animals are dioecious (separate

sexes); some are monoecious or hermaphroditic (both female and male sex organs in the same body)

Some monoecious organisms self fertilize (ex. Tapeworm) while others cross fertilize (ex. Earthworms)

Page 24: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Sexual Reproduction Animals typically produce gametes in gonads

(specialized organs – testes and ovaries) Many aquatic animals practice external fertilization Copulation – sexual union to faciliate the

reception of sperm by a female Terrestrial vertebrates – males usually have a

penis to deposit sperm into the vagina of females Birds – lack a penis and vagina and instead have a

cloaca (chamber that receives products from the digestive, urinary, and reproductive tracts) that the two sexes press together

Page 25: Fetal Development. The Placenta  Mammalian structure that functions in gas, nutrient, and waste exchange between the embryo (later fetus)and mother’s

Life History Strategies Oviparous – animal will deposit egg into

external environment (most aquatic animals) Most oviparous animals have a larval stage

(immature form capable of feeding) Extraembryonic membranes – contained in

leathery-shelled eggs to protect and help the embryo; typically found in reptiles

Viviparous – placental mammals; do not lay eggs and development occurs inside the female’s body until offspring can live on their own