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Study for Quiz 2/27

· Freud

· Erikson

· Skinner

· Pavlov

· Bandura

· Piaget

· Brofenbrenner

· Vygotsky

Human Genome

Gene abnormalities

Know Freud stages

Pavlov

Correlations

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Chapter Three

Prenatal Development

Learning Objectives

Describe the events that occur during the germinal stage of prenatal development.

Explain the developmental processes that occur during the embryonic stage of prenatal development.

Characterize the growth and actions of the fetus in the fetal stage of prenatal development.

Learning Objectives

Discuss how maternal health, weight, and nutrition can affect the developing fetus

Describe the potential effects of substances that can cross the placental barrier on the embryo and fetus.

Describe the impact of maternal stress on the fetus.

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3.1 The Germinal Stage

Wanderings

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Newly fertilized egg cells survive without any nourishment from the mother for more than a week. TRUE It is true that newly fertilized egg cells survive without any nourishment from the mother for more than a week. They are nourished by the yolk of the ovum until they become implanted in the wall of the uterus.

Your heart started beating when you were only one-fourth of an inch long and weighed a fraction of an ounce. TRUE. It is true that your heart started beating when you were only one-fourth of an inch long and weighed a fraction of an ounce. The major organ systems develop within the first 2 months of pregnancy. The heart will continue to beat without rest every minute of every day for perhaps 80 or 90 years, or more.

The Germinal Stage (pp. 78-9)

Conception to implantation

Blastocyst

Embryonic disk

Trophoblast

Umbilical cord

Placenta

Yolk

Bleeding

From “Present” mode, double click on the above video to play it in this slide. You may view it in YouTube, too, where you may access captions. The URL for the video may be found below.

The section on the germinal stage is short. This is likely because the germinal stage, itself, is relatively short. However, a lot happens between conception and implantation. the zygote turns into 2 cells, then 4, then 8, then becomes a blastocyst, or a “fluid-filled ball of cells” (p. 78).

The embryonic disk is “the platelike inner part of the blastocyst that differentiates into the ectoderm, mesoderm, and endoderm of the embryo” (p. 78). You will learn more about those layers in the section about the embryonic stage. For now, the other part of the blastocyst that is important to understand is the trophoblast. The trophoblast is a layer of cells that becomes the structures that will support the developing baby, including the umbilical cord and the placenta. The umbilical cord “connects the fetus to the placenta” (p. 78). The placenta is the organ that transfers nutrients and wastes between the fetus and the mother. This exchange is why things that the mother ingests could affect the baby. We will learn more about that later on in the chapter, too.

At the beginning, the cluster of cells that will become the baby is nourished by the yolk of the ovum. When implantation happens, sometimes some bleeding occurs. Bleeding at this point might not be an issue, but it could also be the sign of spontaneous abortion (i.e., miscarriage). “Nearly one-third of all pregnancies result in miscarriage” (p. 79).

To learn more about implantation, this short video goes a bit more in depth about what happens during the implantation process: https://youtu.be/1KL8HAm3uSY

Reference: kahnacademymedicine (2014, October 24). Implantation [Video file]. Retrieved from https://youtu.be/1KL8HAm3uSY

The Germinal Stage

Period from conception to implantation (approximately 2 weeks)

Zygote begins to divide within 36 hours of conception

Blastocyst – Cell differentiation

Two distinct layers in the inner part of blastocyst – embryonic disk

Outer part of the blastocyst differentiates into four membranes - trophoblast

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If it were not for the secretion of male sex hormones a few weeks after conception, we would all develop external sex organs that look like those of females. TRUE. It is true that without male sex hormones (androgens), all people—whether genetically female or male—would develop female external sex organs. However, apparent “females” who have a male XY sex chromosomal structure are infertile (Reichman et al., 2014).

Fetuses suck their thumbs and hiccup, sometimes for hours on end. TRUE. It is true that sharp spasms of the diaphragm, or fetal hiccups, may last for hours. If you have any doubts, check with a weary pregnant woman.

Parents in wealthy nations have more children. FALSE. Table 3.1 shows that in countries such as Spain, Greece, Italy, Japan, Canada, Russia, and the United Kingdom, parents are not coming close to reproducing themselves.

The Ovarian Cycle, Conception, and the Early Days of the Germinal Stage

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Figure 3.1 The Ovarian Cycle, Conception, and the Early Days of the Germinal Stage. The zygote first divides about 36 hours after conception. Continuing division creates the hollow sphere of cells termed the blastocyst. The blastocyst normally becomes implanted in the wall of the uterus.

The same disease organism or chemical agent that can seriously damage a 6-week-old embryo may have no effect on a 4-month-old fetus. TRUE. It is true that the same disease organism or chemical agent that can do serious damage to a 6-week-old embryo may have no effect on a 4-month-old fetus. Because the major organ systems differentiate during the embryonic stage, the embryo is generally more vulnerable to teratogens than the fetus. But many teratogens are harmful throughout the entire course of prenatal development.

Babies can be born addicted to narcotics and other drugs. TRUE. Narcotics readily cross the placental membrane, and the fetuses of women who use narcotics regularly can become addicted.

It is harmless to the embryo and fetus for a pregnant woman to have a couple glasses of wine in the evening. FALSE. It cannot be guaranteed that one glass of wine a day is harmless to the embryo and fetus. Research suggests that even moderate drinkers place their offspring at increased risk.

Without Visible Means of Support

Prior to implantation, the dividing cells are nourished by the yolk of the original egg

No gain in mass until implantation

Failed Pregnancy

Miscarriage (spontaneous abortion)

Usually stems from abnormalities in development

One-third of all pregnancies result in miscarriage

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3.2 The Embryonic Stage

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The Embryonic Stage (pp. 79-84)

Implantation to end of 2nd month

Major organs

Endoderm, ectoderm, mesoderm (Video)

Proximodistal

Cephalocaudal

From “Present” mode, double click on the above video to play it in this slide. You may view it in YouTube, too, where you may access captions. The URL for the video may be found below.

The embryonic stage follows the germinal stage and encompases the period between implantation until the end of the first two months. Think about it: a trimester is 3 months in length. The mother goes through two whole stages of prenatal development and begins the final stage before the first trimester is even over! Interestingly, the mother might not even know she is pregnant for quite a bit of this time.

A lot of development occurs during the embryonic stage. The major organ systems are developing. The embryonic disk, which we discussed in the germinal stage, becomes the endoderm, ectoderm, and mesoderm.

What are the ectoderm, mesoderm, and endoderm? To learn more, check out the video in the slide above or at this URL: https://youtu.be/QPvhl66QCqo

Two things that are important to remember about development, even beyond the embryonic stage, are that development occurs in a proximodistal and a cephalocaudal pattern. When you look at a newborn baby, pay attention to the baby’s head and body. The head is bigger proportionally than when compared with an adult. This is because development is cephalocaudal. The head grows the most at first and the feet grow last. We develop from head to toe. Babies’ hands are tiny, too. This is because development is proximodistal. We grow from the inside to the outside extremities. Have you ever heard people go “goo goo” and “gaa gaa” over a baby’s teeny hands and their big, wide eyes? The cephalocaudal and proximodistal pattern of development is why babies look the way they do, which we generally consider to be “cute” (remember last week’s video on “cuteness?”). If you think babies have a large head and small feet and hands, wait until you see images during the embryonic period. The head is massive compared with the rest of the body. It almost doesn’t look human. Human qualities start to creep up quickly, though. On page 83, you can see an image of a human embryo at 7 weeks. You can already start to see the head, eyes, and nose area.

Be sure to read all of the details about development at this time on pages 79 through 81. A lot of neural development also occurs at this time. It is amazing to consider that “the embryo’s kidneys are filtering acid from the blood, and its liver is producing red blood cells” (p. 81). A lot is happening!

Reference: kahnacademymedicine (2014, October 24). Germ layer derivatives [Video file]. Retrieved from https://youtu.be/QPvhl66QCqo

The Embryonic Stage

Begins with implantation (3rd week) through 8th week

Major organ systems differentiate

Developmental trends

Cephalocaudal – head takes precedence over lower parts of the body

Proximodistal – central axis of body outward

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Human Embryos and Fetuses at Various Stages of Development

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Figure 3.2 Human Embryos and Fetuses at Various Stages of Development. Development proceeds in cephalocaudal and proximodistal directions. Development of the head takes precedence over development of the lower parts of the body, enabling the brain to participate in subsequent developments.

Truth or Fiction Revisited.

Newly fertilized egg cells survive without any nourishment form the mother for more than a week. (TRUE) It is true that newly fertilized egg cells survive without any nourishment from the mother for more than a week. They are nourished by the yolk of the ovum until they become implanted in the wall of the uterus.

The Embryonic Stage

Embryonic disk

Ectoderm (outer layer) develops into nervous system, sensory organs, nails, hair, teeth, and outer layer of skin

Endoderm (inner layer) forms the digestive and respiratory systems, liver, and pancreas

Mesoderm (middle layer) develops into the excretory, reproductive and circulatory system, muscles, skeleton, and inner layer of skin

Neural tube – develops into brain/spinal cord

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The Embryonic Stage

Head and blood vessels begin to form (3rd week)

Arm buds and leg buds appear (4th week)

Eyes, ears, nose and mouth begin to take shape

Limbs are elongating, facial features become distinct (8th week)

Teeth buds have formed, kidneys and liver are functioning (8th week)

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The Embryonic Stage

By end of first month, neural tube is producing 400 million neurons per day

Neurons migrate to parts of the brain where they will function as different brain structures

Neurons form cerebral hemispheres (5th week)

Cells in the nervous system begin to release neurotransmitters (2nd month)

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Sexual Differentiation

Nondescript sex organs formed (5 to 6 weeks)

Internal and external genitals at this stage resemble female structures

Müllerian (female) ducts; Wolffian (male) ducts

Sex organs begin to differentiate, based on genetic code (7th week)

Y chromosome causes testes to differentiate

No Y chromosome causes ovaries to differentiate

Distinct external genital structures (4 months)

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Development of Internal Genital Organs

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Figure 3.3. Development of the Internal Genital Organs from the Age of 5-6 Weeks after Conception.

Sex Hormones and Sexual Differentiation

Male hormonal influences

Testes produce androgens

Testosterone differentiates male duct system (Wolffian)

DHT (dihydrotestosterone) triggers development of male external genital organs

Müllerian inhibiting substance (MIS) prevents Müllerian ducts from developing into female duct system

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Truth or Fiction Revisited.

Your heart started beating when you were only one-fourth of an inch long and weighed a fraction of an ounce. (TRUE) It is true that your heart started beating when you were only one-fourth of an inch long and weighed a fraction of an ounce. The major organ systems develop within the first 2 months of pregnancy. The heart will continue to beat without rest every minute of every day for perhaps 80 or 90 years, or more.

Sex Hormones and Sexual Differentiation

Female hormonal influences

Small amounts of androgens are produced

Play a role in secondary sexual characteristics in adolescence

Important in sex drive of females

Wolffian ducts degenerate and Müllerian ducts develop into Fallopian tubes, uterus, and inner part of the vagina

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Amniotic Sac and Placenta

Amniotic Sac

Sac is surrounded by clear membrane and contains amniotic fluid

Protects the embryo/fetus within the uterus

Placenta

Mass of tissue exchanges nutrients and wastes between embryo/fetus and mother

Umbilicial cord connects the fetus to the placenta

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Functions of the Placenta

Acts as a filter between the bloodstream of the mother and the bloodstream of the embryo/fetus

Oxygen and nutrients reach the child

Carbon dioxide and waste pass to the mother

Many germs and drugs may also reach the child

Secretes hormones that prepare breasts for nursing, and stimulate contractions that prompt childbirth

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3.3 The Fetal Stage

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Truth or Fiction Revisited.

If it were not for the secretion of male sex hormones a few weeks after conception, we would all develop female external sex organs. (TRUE) It is true that without male sex hormones (androgens), all people—whether genetically female or male—would develop female external sex organs. However, apparent “females” who have a male XY sex chromosomal structure are infertile (Reichman et al., 2014).

The Fetal Stage: End of First Trimester

Third month through birth

End of first trimester

Major organ systems formed

Fingers and toes formed

Eyes can be distinguished

Sex of fetus can be determined visually

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The Fetal Stage: End of Second Trimester

End of second trimester

Opens and shuts eyes

Sucks thumb

Alternates between sleep and wakefulness

Responds to light and sound

Born at 22 to 25 weeks - about 50% survival rate

Survival rate is related to quality of care

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The Fetal Stage: End of Third Trimester

End of third trimester

Heart and lungs increasingly capable of sustaining independent life

Gains in weight and length

During 7th month, fetus turns upside-down in uterus

Born at end of 7th month – nearly 90% survival rate

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The Fetal Stage: Movement

First movements begin about 4th or 5th month

By 29-30 weeks, fetus:

Moves vigorously, turns somersaults

Begins slow squirming movements

Begins sharp jabbing and kicking movements

As fetus grows, movements becomes restricted

Prenatal activity predicts activity levels after birth

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Trimesters

Video on first trimester

Video on second trimester

Video on third trimester

The chart on pages 88-89 might be helpful, but I also thought it might be nice to view a few short videos about development during the prenatal period. Be sure to review the three videos above to help reinforce what you have been reading! The full links and references are also below for you.

First Trimester Video:

https://searchcenter.intelecomonline.net.prox.miracosta.edu/playClipDirect.aspx?id=A277A194C8D7B59BC77355767E97E3DC17721F093BAC2187495A4E749D00BB7692D5BA5FE170F5A2782545C07680D22B

Second Trimester Video: http://searchcenter.intelecomonline.net.prox.miracosta.edu/playClipDirect.aspx?id=A277A194C8D7B59BC77355767E97E3DC636A6A6CD033B7598D3FFCCD0A1898E9F6F6A407A9388F1D2461EC4BA765C813

Third Trimester Video:

https://searchcenter.intelecomonline.net.prox.miracosta.edu/playClipDirect.aspx?id=A277A194C8D7B59BC77355767E97E3DCB7A4210A2018EEFF1EAE273B1B61EF1B617EC62C5740FFD2F28D0CE9FD3A8D70

Population Health Innovations with Animated Biomedical Productions. Pregnancy 1st Trimester. Retrieved September 13, 2015, from

http://www.intelecomonline.net.prox.miracosta.edu/Default.aspx

Population Health Innovations with Animated Biomedical Productions. Pregnancy 2nd Trimester. Retrieved September 13, 2015, from

http://www.intelecomonline.net.prox.miracosta.edu/Default.aspx

Population Health Innovations with Animated Biomedical Productions. Pregnancy 3rd Trimester. Retrieved September 13, 2015, from

http://www.intelecomonline.net.prox.miracosta.edu/Default.aspx

3.4 Environmental Influences on Prenatal Development

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How Does Maternal Nutrition Affect Prenatal Development?

Malnutrition in mother (esp. last trimester)

Linked to low-birth-weight, prematurity, stunted growth, retardation of brain development, cognitive deficiencies, behavioral problems, cardiovascular disease

Effects of fetal malnutrition can sometimes be overcome by supportive caregiving environment

Maternal obesity

Linked to higher risk of stillbirth

Increases risk of neural tube defects

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Truth or Fiction Revisited.

Fetuses suck their thumbs and hiccup, sometimes for hours on end. (TRUE) It is true that sharp spasms of the diaphragm, or fetal hiccups, may last for hours. If you have any doubts, check with a weary pregnant woman.

What Should a Pregnant Woman Eat?

Nutrients

Protein

Vitamins A, B, C, D, and E

Iron; trace minerals zinc and cobalt; folic acid

Calcium

Calories

Most women who eat a well-rounded diet do not need supplements, but most doctors recommend them to be safe

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How Much Weight Should a Pregnant Woman Gain?

Mothers who are too slim risk preterm deliveries and low-birth-weight babies

Maternal obesity is linked to a higher risk of stillbirth

Amount of recommended weight gain depends on pre-pregnancy weight

BMI below 18.5 – gain 28 to 40 pounds

Normal weight – gain 25 to 35 pounds

BMI between 25 and 29.9– gain 15 to 25 pounds

BMI over 30 – gain 11 to 20 pounds

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What are Teratogens?

Teratogens – environmental agents that can harm embryo or fetus

Drug ingested by mother

Substance produced by mother

Heavy metals such as lead and mercury

Excessive hormones

Radiation

Pathogens – bacteria and viruses

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What Are the Critical Periods of Vulnerability?

Critical periods of vulnerability

Correspond to times when organs are developing

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Critical Periods in Prenatal Development

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Figure 3.5. Critical Periods in Prenatal Development. Knowledge of the sequence of prenatal development allows one to understand why specific teratogens are most harmful during certain periods of prenatal development. Major structural abnormalities are most likely to occur when teratogens strike during the embryonic period. National Institutes of Health. National Institute on Alcohol Abuse and Alcoholism. Pubs.niaaa.nih.gov (Accessed December 8, 2012)

Sexually Transmitted Infections (STIs)

Syphilis

Can cause miscarriage, stillbirth, or congenital syphilis

Can be diagnosed by routine blood tests early in pregnancy

Baby probably will not contract syphilis if infected mother is treated before 4th month of pregnancy

If infected mother not treated

Baby has 40-70% chance of being infected in utero or developing congenital syphilis

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Sexually Transmitted Infections (STIs)

HIV/AIDS (human immunodeficiency virus/acquired immunodeficiency syndrome)

Disables body’s immune system

Lethal unless treated

Do not always work

Long term outcome is uncertain

About 25% of babies born to HIV/AIDS-infected mothers become infected

Many babies are infected during childbirth

HIV is also found in breast milk

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Other Prenatal Risks

Influenza (Flu)

Respiratory infection that may be related to fetal brain abnormalities, autism, and schizophrenia

Rubella (German measles)

Viral infection may cause birth defects

Pre-Eclampsia (Toxemia)

May cause premature or undersized babies

A cause of pregnancy-related maternal death

Other Prenatal Risks

Rh Incompatibility

Transfer of maternal antibodies that may cause brain damage or death

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Truth or Fiction Revisited.

The same disease organism or chemical agent that can seriously damage a 6-week-old embryo may have no effect on a 4-month-old fetus. (TRUE) It is true that the same disease organism or chemical agent that can do serious damage to a 6-week-old embryo may have no effect on a 4-month-old fetus. Because the major organ systems differentiate during the embryonic stage, the embryo is generally more vulnerable to teratogens than the fetus. But many teratogens are harmful throughout the entire course of prenatal development.

Video, part 1

This video looks at some teratogens and how they may impact a developing fetus.

From “Present” mode, double click on the above video to play it in this slide. You may view it in YouTube, too, where you may access captions. The URL for the video may be found below.

I found this video about teratogens. It’s from another class and instructor, but the information is helpful! It doesn’t contain all of the teratogens we have studied in this chapter, but you might find it helpful to listen to this instructor share some main points about teratogens.

Reference:

Appel, K. (2014, August 26). Video lecture teratogens part 1 Kim Appel [Video file]. Retrieved from https://youtu.be/1LSOoL4bnJk

Video, part 2

This video continues the teratogen discussion from part 1.

From “Present” mode, double click on the above video to play it in this slide. You may view it in YouTube, too, where you may access captions. The URL for the video may be found below.

This is the second part of the video. It goes into other environmental factors that can have teratogenic effects.

Reference:

Appel, K. (2014, August 26). Video lecture teratogens part 2 Kim Appel [Video file]. Retrieved from https://youtu.be/1LSOoL4bnJk

What Are the Effects of Drugs Taken by the Mother?

Accutane

Prescribed for difficult cases of acne

Linked to numerous abnormalities during first trimester

Thalidomide

Missing or stunted limbs

Antibiotics

Tetracycline may lead to yellowed teeth and bone abnormalities

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What Are the Effects of Drugs Taken by the Mother?

Hormones

Progestin can masculinize external sex organs of female embryo

DES can cause cervical and testicular cancer

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What Are the Effects of Drugs Taken by the Mother?

Vitamins

High doses of vitamins A and D are associated with central nervous system damage, small head size and heart defects

Heroin and Methadone

Maternal addiction linked to low-birth-weight, prematurity, and toxemia

Baby may be born addicted

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What Are the Effects of Drugs Taken by the Mother?

Marijuana (Cannabis)

Risk of low-birth-weight, immature development of nervous system

Predisposes offspring to dependence on opiates, even in adulthood

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What Are the Effects of Drugs Taken by the Mother?

Cocaine

Maternal use of cocaine increases risk of stillbirth, low-birth-weight, and birth defects

In utero exposure results in problems throughout childhood

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What Are the Effects of Drugs Taken by the Mother?

Alcohol

Alcohol passes through placenta and poses risks for death of fetus and neonate, malformations, and growth deficiencies

Fetal Alcohol Spectrum Disorders

Fetal Alcohol Syndrome (FAS)

Physical and psychological defects

Fetal Alcohol Effect (FAE)

What Are the Effects of Drugs Taken by the Mother?

Caffeine

Inconsistent findings, but some studies show increased risk of miscarriage and low-birth-weight

Cigarettes

Nicotine and carbon monoxide pass through the placenta

Nicotine stimulates fetus

Carbon monoxide is toxic and decreases oxygen to fetus

More likely to deliver smaller babies

More likely to be stillborn or die soon after birth

What Are the Effects of Drugs Taken by the Mother?

Cigarettes

Long-term effects

Short attention spans, hyperactivity, lower cognitive scores, poor grades

Men who smoke are more likely to produce abnormal sperm

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Truth or Fiction Revisited. Babies can be born addicted to narcotics and other drugs. (TRUE) It is true that babies can be born addicted to narcotics and other substances used regularly by their mothers. They are usually weaned off the substance through gradual tapering of doses.

What Are the Effects of Environmental Hazards During Pregnancy?

Heavy metals (lead, mercury, cadmium, selenium, zinc)

Threatens baby’s cognitive development

PCBs

Connected with smaller, less responsive babies

Babies more likely to develop cognitive deficits

Radiation

Can cause defects in a number of organs (including eyes), central nervous system, skeleton

Increased risk of intellectual disabilities

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Truth or Fiction Revisited. It is harmless to the embryo and fetus for a pregnant woman to have a couple of glasses of wine in the evening. (FALSE) It is not true that it is safe for a pregnant woman to drink a glass of wine a day. Although some health professionals “allow” pregnant women to drink a glass of wine with dinner, research suggests that even moderate drinkers place their offspring at increased risk for a less severe set of effects known as fetal alcohol effect (FAE) . Here is the key takeaway: There is no guaranteed safe minimum amount of drinking during pregnancy (Kelly et al., 2013)

What Are the Apparent Effects of Maternal Stress on the Child?

Maternal stress linked to secretion of stress hormones

Adrenaline stimulates the mother’s heart and respiratory rates

Corticosteroids decrease the growth of the placenta

Extreme anxiety has been linked to low birth weight, prematurity, and miscarriage

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