Human Growth and Development Module 3

What two major categories of factors affect prenatal growth and development?

Hereditary factors and environmental factors.

What are hereditary factors in prenatal development?

Genetic information inherited from the ovum and sperm.

How many chromosomes does each human ovum and sperm typically provide?

23 chromosomes each.

How many chromosomes are usually present in a human zygote?

46 chromosomes, 23 from each parent.

What sex chromosome does an ovum normally contribute?

An X chromosome.

Which sex chromosomes can a sperm normally contribute?

An X or a Y chromosome.

According to the slides, which chromosome combination typically produces a biological female?

XX.

According to the slides, which chromosome combination typically produces a biological male?

XY.

What is a dominant gene or allele?

One that can express a trait with a single copy, as described in the slides.

What is a recessive gene or allele?

One generally requiring two copies to express its recessive trait.

What are environmental factors during pregnancy?

Maternal practices, choices, and environmental exposures affecting prenatal development.

What three health practices support a healthy pregnancy in the slides?

Good nutrition, exercise, and adequate rest.

What is a teratogen?

A physical or chemical agent that can harm the developing fetus.

Name three examples of teratogenic exposures from the slides.

Alcohol, tobacco, and certain drugs.

Which infections are given as examples of prenatal transmission risks?

Rubella, HIV, and toxoplasmosis.

Which environmental hazards should be avoided during pregnancy according to the slides?

Pesticides, harmful chemicals, and radiation.

When does the prenatal period begin and end?

From fertilization until birth.

How long does pregnancy last according to the presentation?

Approximately 40 weeks or 280 days.

What three stages make up prenatal development?

Pre-embryonic, embryonic, and fetal.

What days correspond to the pre-embryonic stage in the slides?

Days 0–14.

What days correspond to the embryonic stage in the slides?

Days 14–56.

What days correspond to the fetal stage in the slides?

Days 56–280.

What is a zygote?

The fertilized egg formed when sperm and ovum unite.

What happens to the zygote as it travels through the fallopian tube?

It repeatedly divides into more cells.

What is a morula?

A solid mass of cells formed by early zygote divisions.

What is a blastocyst?

A later stage of the developing conceptus that can implant in the uterus.

Where does the blastocyst implant?

In the uterine lining or wall.

About how long after fertilization does implantation begin according to the slides?

About 7 days.

What is the developmental sequence from fertilization to implantation?

Zygote → morula → blastocyst → implantation.

By about which week have the embryo's essential structures formed according to the slides?

By week 8, when it is described as a fetus.

What are the three stages of labour in order?

Dilation, expulsion, and delivery of the placenta.

What happens during the dilation stage of labour?

Uterine contractions lead to complete dilation of the cervix.

What happens during the expulsion stage of labour?

The baby is born.

What happens during the third stage of labour?

The placenta is delivered.

Is the length of each labour stage the same for everyone?

No; each stage varies between individuals.

What major developmental process occurs in the first trimester?

The body's basic structures form during this critical period.

How can poor maternal nutrition affect prenatal development?

It may alter anatomy, physiology, metabolism, and the number of cells formed.

Which prenatal indicators are associated with later coronary disease or stroke in the slides?

Low placental weight and small head circumference.

What can early lower respiratory infections suggest according to the slides?

Impaired lung growth and possible increased risk of adult chronic bronchitis.

What effect does prenatal smoking have on later respiratory health according to the slides?

Increased vulnerability to bronchitis and other respiratory problems.

Which maternal dietary factors in late pregnancy are linked to later disease risk in the slides?

Protein balance, cholesterol levels, and fat intake.

At week 4, how long is the developing embryo according to the chart?

About 1/4 inch (0.6 cm).

At week 4, what body shape is described?

Curled, with the head touching the tail.

At week 4, which limb structures begin to appear?

Arm and leg buds.

At week 4, what organ has formed according to the chart?

The liver.

Around which days does the heart begin pulsating in the week-4 chart?

Around days 14–24.

What early circulatory development is noted at week 4?

Primitive blood cells are present.

At weeks 6–8, what is the approximate length in the chart?

1 inch (2.5 cm).

At weeks 6–8, how much does the embryo weigh in the chart?

About 1/30 oz (1 g).

At weeks 6–8, what is happening to the heart?

The chambers of the heart develop.

At weeks 6–8, what major nervous-system change occurs?

Rapid brain development.

At weeks 6–8, what develops in the limbs?

Primitive limb structures; fingers and toes begin forming.

At weeks 6–8, what facial structures are forming?

Eyes, ears, nose, palate, and upper lip.

At weeks 6–8, what developmental process is completed in the chart?

Organogenesis, or organ formation.

At weeks 9–12, what are the approximate length and weight?

3 inches (7.5 cm) and 1 oz (28 g).

At weeks 9–12, what changes occur in the fingers and toes?

Nail beds begin to form.

At weeks 9–12, what appears in the developing bones?

Ossification centres.

At weeks 9–12, what does the chart say begins in the kidneys?

Kidney secretion by about week 10.

At weeks 9–12, what movements are noted?

Spontaneous movements and breathing-like reflex movements.

At weeks 9–12, what happens to the fetal intestines?

They retract from the umbilical cord into the abdomen.

At weeks 9–12, what happens to the palate?

The palate completes fusion.

At weeks 9–12, what external sexual change becomes apparent?

Distinguishing sexual characteristics become evident.

At weeks 13–16, what are the approximate length and weight?

6–7 inches (15.2–17.7 cm) and 4 oz (112 g).

At weeks 13–16, what fetal movement might the mother first perceive?

Quickening, or perceived fetal movement.

At weeks 13–16, what appears on the head?

Downy lanugo hair.

At weeks 13–16, what development involves the placenta?

The placenta is distinct.

At weeks 13–16, what circulatory development is noted?

The heart circulates blood through the fetal body.

At weeks 13–16, how can respiratory-type movements be observed?

They can be detected with a sonogram.

At weeks 13–16, which hormonal glands begin functioning?

The fetal thyroid gland begins functioning.

At weeks 17–20, what are the approximate length and weight?

10 inches (25 cm) and 8–10 oz (224–280 g).

At weeks 17–20, how may the fetal heartbeat be heard?

With a stethoscope, according to the chart.

At weeks 17–20, what hair growth is described?

Scalp hair and lanugo, especially on shoulders.

At weeks 17–20, what skin changes are noted?

Less-transparent skin; vernix caseosa is present.

At weeks 17–20, what visible features are present?

Eyebrows and fingernails and toenails.

At weeks 21–24, what are the approximate length and weight?

12 inches (30.5 cm) and 1.5 lb (672 g).

At weeks 21–24, what appearance does the skin have?

Wrinkled, pink, and translucent.

At weeks 21–24, what happens to vernix caseosa?

Increasing amounts of vernix cover the skin.

At weeks 21–24, what becomes well defined around the eyes?

Eyebrows and eyelashes.

At weeks 21–24, what remains true of the external ears?

They are soft, flat, and shapeless according to the chart.

At weeks 21–24, what breathing-related activity may be observed?

Some breathing efforts become evident.

At weeks 25–28, what are the approximate length and weight?

15 inches (37.5 cm) and 2.5 lb (1,120 g).

At weeks 25–28, what covering appears on the fetal skin?

Vernix caseosa on red, wrinkled skin.

At weeks 25–28, what changes happen to the eyes?

Eye membranes disappear and eyelids open.

At weeks 25–28, what happens to scalp hair?

It becomes well developed.

At weeks 25–28, what fatty tissue begins appearing?

Subcutaneous fat.

At weeks 25–28, where are the testes located according to the chart?

At or below the internal inguinal ring.

At weeks 29–32, what are the approximate length and weight?

15–17 inches (37.5–42.5 cm) and 3.5–4 lb (1,568–1,792 g).

At weeks 29–32, what happens to fetal skin?

It becomes pink and smooth.

At weeks 29–32, what happens to scalp and body hair?

The hair becomes fine and woolly.

At weeks 29–32, what body fat change occurs?

Subcutaneous fat deposits are present.

At weeks 29–32, how may the fetus respond to sound?

It can respond to sounds outside the mother's body.

At weeks 29–32, what happens to the testes according to the chart?

They begin descending into the inguinal canal.

At weeks 33–36, what are the approximate length and weight?

19 inches (47.5 cm) and 5–6 lb (2,240–2,688 g).

At weeks 33–36, what gives the body and limbs a more rounded appearance?

Increased fat deposits.

At weeks 33–36, what happens to lanugo?

It disappears according to the chart.

At weeks 33–36, what happens to the breast tissue?

Breast tissue develops beneath the nipples.

At weeks 37–40, what are the approximate length and weight?

20 inches (50 cm) and 7–7.5 lb (3,136–3,360 g).

At weeks 37–40, what is the overall body shape?

A plump body with well-developed fat stores.

At weeks 37–40, what is the status of lanugo?

It is gone from the face.

At weeks 37–40, what happens to the testes according to the chart?

They are in the scrotum.