Prenatal Development From Conception to Birth

Maturation: Biological growth processes that enable orderly changes in behavior, relatively uninfluenced by experience. Prenatal development Other examples?

Critical (or Sensitive) Periods: An optimal period shortly after birth when an organism’s exposure to certain stimuli or experiences produces proper development. Prenatal development Other examples?

Woman are born with all the egg cells they will ever have, that’s about 5,000 egg cells.

Sperm cell production begins at puberty and continues until death (although the rate of production decreases with age). About 1,000 are produced per second, that’s 1.5 million sperm cells in 30 minutes!

Conception

Three stages of prenatal development: 1) zygote (fertilization – 2 weeks) 2) embryo (2 – 8 weeks) 3) fetus (9 – 40 weeks)

The zygote: 1 week after conception In the first week, after dividing about 7 times, the cells start to differentiate, to specialize in function (blood cells, nerve cells, heart cells). This process is directed by the genes. On the 10th day, the zygote attaches to the uterine wall where it will stay for about 37 weeks. The zygote: 1 week after conception

Early embryonic development 16 – 18 days after fertilization, a neural tube, with a brain bulge at one end, forms. This tube will development into the spinal cord. 26 – 28 days The tube will fold in on itself and the brain bulge will enlarge to form the brain’s major sections. The embryo begins to curve into a “C” shape. Early embryonic development

Critical periods: 1st: heart & blood vessels 2nd: heart beat, ears, nose, mouth, limb buds

4 ½ weeks The embryo’s bones are still soft, but the skeleton is well formed. The arms and legs are forming

Which one is human? Human, 31 days Pig, 21 days

Notice the yolk sack in the foreground Notice the yolk sack in the foreground. This is the embryo’s blood cell factory.

The placenta is an organ that connects the developing fetus to the uterine wall. The placenta forms connections with the mother's blood supply to supply oxygen and nutrients. The placenta also connects with the fetus's blood supply, from which it removes waste. The mother and fetus do not share blood supplies. Filters teratogens. The placenta: 9”, 1 lb.

6 weeks The umbilical cord connects the embryo to the placenta. It replaces the yolk sack, and is formed by the 5th week. 22” long

Point out spinal cord and how the skin is still transparent.

Point out the umbilical cord Point out the umbilical cord. Also point out that there is no eye lid yet.

Point out how the eyelid has formed. Point out fingers & toes Point out how the eyelid has formed. Point out fingers & toes. Skin is still transparent, can see into internal organs.

Eight weeks: The fetal period begins, 1” long, <1 oz. Critical periods: backbone, upper/forearms, hand, fingers, toes, skeletal structure

Point out well-formed toes.

Used to treat women with “morning sickness” Thalidomide attacks developing bone tissue in hands/arms/legs during critical period. Thalidomide Used to treat women with “morning sickness” This drug is a teratogen which crosses the placenta causing birth defects.

Another teratogen: Alcohol Fetal Alchohol Syndrome (FAS)

Teratogens and Their Effects on the Developing Brain and Mind The Mind #12 http://www.learner.org/resources/series150 .html?pop=yes&pid=1619

Point out development of ear over time.

Critical period: muscles, bones, major organs, reproductive organs Note that after this month, parents can do an ultrasound to determine sex. 12 weeks 3-4” long, ~1 oz. Critical period: muscles, bones, major organs, reproductive organs

12 weeks Notice how small the yolk sac is. Nourishment now delivered by umbilical cord. Note that mother & baby do not exchange blood supply.

Talk about brain cell migration. 6 – 8 “ long, ~6 oz. Critical period: hair, fingernails, toenails, teethbuds, brain cells begin to migrate.

Note transparency of skin & sucking on thumb!

8 – 12” long, ½ - 1 lb. More complex nerve connections develop. Taste & smell formed. Vestibular system is functional.

14” long, 1 – 1 ½ lbs. Fetus can feel movement & may respond to sound. Notice vernix. Nerve supply to ear complete at 25 weeks.

16 weeks premature infant

Awareness begins, deep sleep What do babies dream? 7 months: Eyes open 8 months: 18” long, ~5lbs. Awareness begins, deep sleep

Briefly discuss labor & movement of baby through birth canal. 8 months 19” long, ~6 lbs.

Happy Birthday! 40 weeks: Average weight 7–8 lbs, 20 “ in length

Note how newborn babies don’t look like a baby food ad Note how newborn babies don’t look like a baby food ad! Wrinkled, swollen, sometimes bruised. A newborn

Note cone head. Talk about how skull is flexible.

Kate Whitlock (now THAT’s a cute baby!) Yes! Very cute baby!!! Kate Whitlock (now THAT’s a cute baby!)

Kate, 1 day old Kate very alert. Trying to see me. Tell students how babies can see about 12” (from their eyes to yours).

Note black/white bumper pads. Babies love contrast. Kate, 2 days old

What can babies do?