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Lifespan > Prenatal development (ch 4) > Flashcards

Prenatal development (ch 4) Flashcards

1
Q

Germinal Period

A

First stage of prenatal dev.

  • lasts approximately two weeks –
  • zygote divides through mitosis and forms blastocyst that implants into blood vessels of uterine wall
  • Only half of fertilized ova implant successfully
  • 15-20 percent recognized pregnancies miscarry
  • 50 percent of unrecognized pregnancies miscarry
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2
Q

Day 1 of Germinal period

A

Fertilization usually occurs within 24 hours of ovulation

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3
Q

Day 2 of Germinal period

A

The single-celled zygote begins to divide 24-36 hours after fertilization

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4
Q

Day 3-4 of Germinal period

A
  • The mass has 16 cells – called morula

- Travelling down fallopian tube to the uterus

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5
Q

Day 5 of Germinal period

A
  • Inner cell mass forms – entire mass called Blastocyst

- Size of pinhead

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6
Q

Day 6-7 of Germinal period

A

Blastocyst attaches to the wall of the uterus

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7
Q

Day 8-14 of Germinal period

A

Blastocyst becomes fully embedded in the wall of the uterus

- Now have approximately 250 cells

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8
Q

Embryonic period

A
  • week 3-8
  • Organogenesis - formation of every major organ
  • Layers of blastocyst differentiate forming structures that sustain development
  • Sexual differentiation
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9
Q

Events of embryonic period - Wk 3

A
  • Embryo 1/10 of an inch
  • Become elongated
  • Three layers emerge: ectoderm, mesoderm, and endoderm
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10
Q

Embryonic period Week 4:

A
  • Embryo so curved that the two ends almost touch
  • Outer layer (ectoderm) folds into the neural tube
  • From mesoderm, a tiny heart forms and begins to beat
  • Endoderm differentiates into gastrointestinal tract and lungs
  • 21-28 days: eyes develop
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11
Q

Embryonic period: week 5

A
  • Ears, mouth, throat take shape
  • Arm and leg buds appear
  • Handplate from which fingers will emerge appears
  • Heart divides into two regions
  • Brain differentiates into forebrain, midbrain, and hindbrain
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12
Q

Embryonic - Week 6-7

A
  • Embryo almost 1 inch long
  • Heart divides into four chambers
  • Fingers emerge from handplate
  • Primative facial features evident
  • Sexual differentiation begins
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13
Q

Embryonic - Week 8

A
  • Most structures and organs present
  • Ovaries and testies are evident
  • Embryo begins to straighten and assumes more human appearance
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14
Q

Neural tube defects occur during which period

A
  • during embryonic period – 25-29 days after conception

- 1 in 1000 pregnancies – neural tube fails to close completely

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15
Q

Spina bifida:

A
  • Neural tube defect

- part of the spinal cord not fully encased in the protective covering of the spinal cord

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16
Q

Anencephaly:

A
  • Neural tube defect
  • top of neural tube does not close and main portion of brain above brain stem does not develop
  • Most common when mother is deficient in folic acid
17
Q

Fetal period

A
  • 9 weeks to birth
  • Cells proliferate, migrate, and differentiate
  • Differentiation of cells occurs according to where cells migrate
  • Organ systems continue to grow and begin to function
  • Sex organs appear during 3rd month of pregnancy
  • When survival is possible if brain and respiratory system are sufficiently developed
  • Weight gain
  • Organized and adaptive behaviors develop
  • Patterns of heart rate, activity level
18
Q

Age of viability reached at about

A

23 weeks

19
Q

Fetal period: Week 9

A
  • Bone tissue emerges and embryo becomes a fetus
  • Head of the fetus looks huge compared to the rest of the body – takes up about ½ length of fetus
  • Fetus can open and close its mouth and turn its head
20
Q

Fetal - Week 10-12

A

Fingers and toes are clearly formed

  • External genitalia developed
  • Movements increased substantially
  • Arms and legs kick vigorously but fetus still too small for mother to feel movement
  • Fetus also shows breathing movements with its chest
  • Some reflexes
21
Q

Fetal - Week 13-16:

A
  • Heartbeat should be audible with stethoscope
  • Fetal movements may become apparent to mothy
  • Fetus 4.5 inches long
  • Skeleton becomes harder
22
Q

Fetal - Week 17-22:

A
  • Fingernails and toenails, hair, teeth buds, and eyelashes grow
  • Brain development is phenomenal and brainwaves detectable
23
Q

Fetal - Week 23-25:

A
  • Age of viability – fetus has change of surviving outside the womb
  • 12 inches long, 1 pound
24
Q

Fetal - Week 26-32:

A
  • Fetus gains weight and its brain grows

- Nervous system becomes better organized

25
Q

Fetal - Week 33-38:

A
  • Last 6 weeks of full term pregnancy bring further weight gain and brain activity
  • Lungs mature and begin to expand and contract
26
Q

Teratogens:

A

Any disease, drug, or environmental agent that can harm a developing organism
- effects = worse during critical period

27
Q

Newborns routinely screened with Apgar test, which is quick assessment of:

A
  • Heart rate
  • Respiration
  • Color
  • Muscle tone
  • Reflexes
28
Q

leading cause of infant mortality

A

prematurity

29
Q

Low birth weight

A
  • weighing less than 5.5 pounds (or 2500 grams)
  • Extremely LBW weigh less than 2-3 lbs (or 1000 grams)
  • Micropreemies weigh less than 1.75 lbs (or 800 grams)
  • Less than 1 percent of births but comprise 36 percent of hospital costs
30
Q

LBW associated with…

A
  • lower SES
  • African-American ethnicity
  • smoking, stress
  • multiple births
31
Q

Werner’s 40 year longitudinal study revealed:

A
  • Effects of prenatal and perinatal complications decrease over time
  • Outcomes of early risk depend on quality of postnatal environment
  • Protective factors - Personal resources: intelligence, sociability, communication that help them choose or create more nurturing or stimulating environments
32
Q

Considered infertile after

A

one year of trying to get pregnant

33
Q

Effect of alcohol during 1st trimester

A

Facial abnormalities

34
Q

Effect of alcohol during 2nd and 3rd trimester

A

Growth and brain development = stunted

Lifespan (11 decks)

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