ECC Chapter 3 PSY 218 Spring 2015.pptx

Conception, Prenatal

Development, and

The First 9 Months

•

_{The period of development from conception to birth is known as}

Gestation.

• Lasts approximately 280 days.

• Divided into three main stages of development:

• Zygote

• Embryo

Conception and the Zygote: The

First Two Weeks

•

_{Conception begins with a sperm piercing the membrane of an ovum}

(egg).

•

_{During ovulation, a follicle in the woman’s ovaries ruptures and}

releases a mature ovum which moves down the fallopian tube to the

uterus.

• _{Takes about 5 days.}

•

_{During puberty, males begin to produce about 2 million sperm per}

Conception and the Zygote: The

First Two Weeks

• _{During intercourse, the male ejaculates over 500 million sperm which swim}

through the cervix, uterus, and fallopian tubes.

• _{Of the 100 sperm that complete the journey, only one fertilizes the egg.}

• The insemination of the egg by the sperm.

• _{Within hours the ovum and sperm create a new cell called a zygote.}

• _{Contains 23 chromosomes from mom and 23 chromosomes from dad – creates a new}

genotype.

• _{As the zygote moves to the uterus, it begins differentiation.}

• _{The process of cells taking on specialized roles.}

Conception and the Zygote: The

First Two Weeks

•

_{Implantation involves the zygote embedding itself into the uterus in}

order to get nutrients and survive.

•

_{This is the basic series of events from the first two weeks after}

conception, however not everyone is able to complete all of these

steps.

•

_{Infertility affects 2 million couples in the U.S.}

Conception and the Zygote: The

First Two Weeks

• _{There are many factors that can lead to infertility such as infection, malnutrition, obesity,}

and age.

• Risk of infertility increases around 32 for females and 35 for males.

• Infertility is treatable and distinct from sterility.

• _{If infertility is due to the female’s failure to ovulate regularly, infertility drugs can stimulate ovulation.} • If the infertility is due to the male, then artificial insemination may be helpful.

• In vitro fertilization (IVF) is helpful ni more complex cases of infertility.

• _{Women are given fertility drugs to stimulate ovulation.} • The ova are extracted and placed in a dish with perm.

Conception and the Zygote: The

First Two Weeks

•

Variations of IVF include prenatal adoption.

• Allows for an infertile couple to experience pregnancy even though the child won’t have their genes.

• _{This may also require a surrogate mother if the infertile mother cannot sustain pregnancy.}

• In most cases, the surrogate carries an embryo that has the gametes of the individuals who he or she will call “parents”

•

_{Use of reproductive technology does not generally increase the risk of}

birth defects.

• The main risk involves multiple births, with about 30% of IVF deliveries resulting in twins.

The Embryo: Weeks Three Through

Eight

•

_{The embryonic period begins about two weeks after conception, after}

implantation.

•

_{The embryo’s cells form specialized layers:}

• _{The Ectoderm (outer layers) become skin, nerves, and sense organs.}

• _{The Mesoderm (middle layers) become muscle, bones, circulatory system,}

and some organs.

• _{The Endoderm (inner layers) become digestive system, lungs, urinary tract,}

The Embryo: Weeks Three Through

Eight

•

_{During the 6-week embryonic period, the basic structure of a human}

being begin to appear and organs begin to function.

• The production of neurons or nerve cells.

• Neuron development during the 9-months of gestation is approximately 250,000 neurons per minute.

•

_{By the end of the embryonic period (two months after conception), all}

The Fetus: Week Eight to Birth

•

_{During this period – primitive organ and body parts develop, grow,}

and increase in complexity.

• _{e.g., the formation of joints, fingers, and nails.}

•

_{Neurogenesis is typically complete by the end of the sixth month, and}

the rain starts to organize itself.

• _{This allows some neurons to die while others begin to form new connections.}

The Fetus: Week Eight to Birth

•

_{Brain development is bi-directional.}

• _{Genetically determined brain development permits new behaviors and}

environmental interactions.

• These interactions affect brain development.

• Long-term potentiation, for example.

•

_{Fetal behavior becomes increasingly organized.}

• _{3 months – The fetus swallows, urinates, hiccups, blinks, and yawns.} • _{6 months – fetus breathes, cries, and has distinct sleep-wake patterns.} • _{7/8 months – Fetus is less active but more vigorous, mostly due to space}

The Fetus: Week Eight to Birth

•

Evidence supports the idea that fetuses are able to learn to recognize

familiar sounds and rhythms.

• _{However, listening to Mozart will not result in a child being born with musical}

appreciation, or becoming a skilled performer.

•

_{Individual differences are also apparent in the fetal stage.}

• For example, fetuses with higher heartbeats while in the womb may be more advanced in language and play as children.

• _{Children who were more active as fetuses also show differences in temperament.}

• _{E.g., more active fetal responses are associated with earlier motor development, higher}

Boy or Girl

• _{Gender differentiation begins at conception, with most girls having two X}

chromosomes and boys an X and Y chromosome genotype.

• _{Prenatal gender development can be divided into four stages:}

• During the first month and a half, the embryo is Unisex; having both female and male sex organ ducts.

• _{At 7 weeks the Y chromosome and testosterone stimulate the development of the sex}

differences. Testosterone develops male sex organs and block development of female reproductive organs. If embryo doesn’t receive this signal, female organs are produced.

• At 2.5-3 months external genitalia form as the result of the release of testosterone.

Boy or Girl

•

_{The basic plan of nature is female, as the Y chromosome must trigger}

the development of male sex characteristics.

• _{In Turner’s Syndrome, the fetus has only one X chromosome.}

• In the absence of the Y, female characteristics develop.

• _{Testosterone is also required to stimulate male development and without its}

effects, an embryo will develop female external genitalia.

• _{In the case of testicular-feminizing syndrome male (XY) has a genetic defect}

Boy or Girl

•

_{Sex differences are not merely anatomical and are related to how}

people treat the infant.

• _{However, people treat infants in particular was based on their anatomical}

structures.

• _{Prenatal sex development may also differentially affect the developing brain}

and result in males being more responsive to certain aspects of the environment than females.

Evaluating Prenatal Development

•

_{Ultrasound Imaging}

• _{High-frequency sound waves creates a sonogram (echo image) on a monitor}

• Allows for prediction of multiple births, birth problems, and fetal abnormalities.

•

_{Most disorders tat a fetus might have, are general multifactoral}

disorders.

• _{Due to an interaction among multiple genes and those genes and the}

Evaluating Prenatal Development

•

_{Chromosomal malformations are often caused by mutations during}

meiosis.

• _{For example, Down Syndrome results from a child having three 21}st

chromosomes rather than two.

• Risk increases with maternal age – 1 in 2,000 for women age 20/1 in 20 for women over 45.

•

_{Most genetic disorders are carried on a}

_{recessive gene}

_.

• _{Such as Sickle Cell Anemia.}

• Children who inherit the gene from both parents and suffer shortness of breath, fatigue, pain, and some fatal crises related to organ failure.

Evaluating Prenatal Development

•

_{Other disorders are sex-linked, such as colorblindness or hemophilia.}

because they have a second normal X chromosome, they are almost never affected.

• However, there is a 50-50 chance they pass the defective X chromosome on to their sons, who will express the trait because they do not have a second X chromosome.

•

_{The most famous sex-linked disorder is hemophilia, which results in a}

person’s body being unable to produce blood-clotting factor.

Evaluating Prenatal Development

• _{Genetic Couseling helps people understand the effects heredity might have on their}

children.

• _{Uses history and a karyotype (picture of the man and woman’s individual chromosomes) to}

help identify recessive genetic.

• For example, Tay-Sachs Disease leads to death in individuals before the age of four.

• Disorder occurs if both parents carry the recessive trait and pass it to the child.

• When only one parent carries the recessive trait, the probability of having the disorder is ¼.

• _{Some genetic defects can be identified or mitigated before birth.}

• _{Preimplantation Genetic Diagnosis helps pick an embryo free of genetic defects for people}

using IVF.

Protecting the Fetus

•

_{Age plays a major role in risk for problems in pregnancy and birth.}

• Teenage mothers tend to wait longer to see prenatal care and are at risk for preterm delivery.

• Mothers over age 30 have higher risk of birth complications, miscarriage, and high blood pressure.

•

_{Diet and Nutrition are also important factors that impact the health of the}

fetus.

• Severe malnutrition in early pregnancy can increase risk of birth defects and schizophrenia:

Protecting the Fetus

• Very high stress in pregnancy increases risk of premature birth, birth defects, and lower birth weight – particularly in the first trimester.

• Stress is generally only part of a package of issues that come along with stress and can also cause health defects in the child.

• Teratogens are any substance (virus, drugs, pollutants) that can have a negative impact on the fetal development.

• _{Generally the result of some sort outside influence.}

• The fetus is generally protected from numerous bacteria, but not viruses.

Protecting the Fetus

•

_{Many medications that are good for the mother can also be harmful}

to a fetus.

• _{For example, in the 50’s and 60’s, hundreds of thousands of women took the}

drug DES to prevent miscarriage.

• 30 years later we found out that it increased the risk of cervical cancer and vaginal cancer in women as well as infertility risk in men whose mothers had taken the drug.

Protecting the Fetus

•

_{Drugs also have important effects on fetal development.}

• _{Nicotine – may not harm the fetus, but smoking does.}

• _{Heroin – babies born to heroin addicted mothers are themselves addicted,}

have lower IQ scores and more behavioral problems.

• _{Cocaine – causes low birth weights, small head, irritability, hypersensitivity,}

The Importance of Timing

•

_{The impact of substances on the development of the fetus depends on the}

timing and duration of exposure.

• _{Thalidomide was used as a treatment for morning sickness.}

• Later found out that women who took it during weeks six and seven of pregnancy gave birth to infants with arm and leg buds rather than fully developed limbs.

• Taken at other times, the drug did not impact fetal development.

•

_{Exposure during sensitive periods may alter anatomy or function.}

• The embryonic stage of development is at a high vulnerability due to organ development at this time.

•

_{While some environmental factors have immediate effects, others have}

Birth

•

_{The average birth occurs 280 days after conception.}

• _{Begins when the pituitary gland releases oxytosin, which triggers uterine}

contractions and the baby is pushed into the world.

•

_{Stages of birth:}

• _{First half of labor – Uterine contractions pull the cervix open.} • _{Second stage – contractions push the baby into the birth canal.}

• _{Third stage – Contractions expel the placenta, fetal membranes, and}

Birth Complications and

Controversies

• _{Some complications involve fetal birthing positions:} • Breech – feet or buttocks first

• Hammock – cross-wise position

• _{Anoxia is a significant complication.}

• _{Caused by the umbilical cord being pinched due to:}

• The placenta pulling away from the wall of the uterus. • The placenta blocking exit from the womb.

• Can cause brain damage if experienced long term.

Newborns at Risk

• Very small babies face a number of challenges:

• Preterm Babies – Born before 37 weeks of gestation

• Very Preterm Babies- Born before 32 weeks.

• Low-Birth-Weight Babies – Weigh less than 5.5 lbs.

• Very Low-Birth-Weight-Babies – Weigh less than 2.5 lbs.

• Preterm babies often suffer from Respiratory Distress Syndrome.

• Oxygen is unable to be carried into the lungs and carbon dioxide cannot get out of the lungs.

• Also vulnerable to infection.

Newborns at Risk

•

_{The survivability of preterm infants is relatively high.}

• _Currently:

• Infants weighing less than 5.5lbs survive 90% of the time.

• Infants weighing between 1.65 and 2.2lbs survive 67% of the time.

• Infants weighing 1.1 to 1.65lbs survive 33% of the time.

•

_{However, they are at risk for heart disease, learning difficulties, and}