Conception and Development

Where does fertilization usually occur?

Ampulla

What cell results when sperm and ovum nuclei fuse?

Zygote

Approximately how long is the ovum fertile after ovulation?

24 hours

What reaction makes the ovum membrane impenetrable toa dditional sperm?

Zonal reaction

The zygot’es rapid miotic divisions produce cells called ____.

Blastomeres

What is the solid ball of approximately 16 cells called?

Morulla

What structure forms when fluid separates cells in the developing conceptus?

Blastocyst

Where does implantaiton normally occur?

Endometrium

When does implantation usually occur after fertilization?

6-10 days

In which region of the uterus does implantation occur according to the guide?

Funda region

What structures develop for nutrient and gas exchange after implantation?

Chorionic villi

Order of developmental stages from earliest to latest:

1. Fertilization

2. Cleavage

3. Morula

4. Blastocyst

5. Implantation

During which weeks does the pre-embryonic period occur?

Weeks 1-2

During cleavage, the zygote divides rapidly without increasing in overall size.

True

During which weeks does the embryonic period occur?

Weeks 3-8

During which period does organogenesis occur?

Embryonic period

When is the developing human most vulnerable to teratogens?

Embryonic period (Weeks 3-8)

Which are the characteristics of the embryonic period?

• Organogenesis occurs

• Germ layers form

• Sensitivity to teratogens is high

Match each germ layer with a structure or tissue it forms:

• Ectoderm = Nervous system

• Mesoderm = Bones and muscles

• Endoderm = Digestive tract lining

Which germ layer forms the nervous system and epidermis?

Ectoderm

Which germ layer forms bones, muscles, and the cardiovascular system?

Mesoderm

Which germ layer forms the digestive and respiratory tract linings?

Endoderm

When does the fetal period begin?

Week 9

Which changes characterize the fetal period?

• Organ growth

• Functional refinement

• Increasing system function

What does viability mean in fetal development?

Survival outside the uterus

The brain remains vulnerable to teratogens throughout gestation because it develops for the longest period.

True

What factors influence the effect of a terotogen?

• Developmental stage

• Genetic susceptibility

• Extent of exposure

The first three months of pregnancy are among the most critical times for developmental effects from teratogens.

True

What may happen when teratogens act before day 15?

No effect or miscarriage

What is the placenta’s primary exchange role?

Exchange in oxygen, nutrients, & wastes

Which substance can cross through placental exchange?

• Oxygen

• -nutrients

• antibodies

• wastes

Which umbilical vessel carries oxygenated, nutrient-rich blood to the fetus?

Umbilical vein

Which umbilical vessels carry fetal wastes toward the placenta?

Umbilical arteries

How many arteries and veins are normally in the umbilical cord?

2 arteries and 1 vein

What protects the umbilical cord vessels?

Wharton jelly

A two-vessel cord should prompt assessment of the baby’s kidneys.

True

What are functions of amniotic fluid?

• Cushions the fetus

• Maintains temperature

• Allows movement

• Supports lung development

Which hormone maintains the corpus luteum early in pregnancy?

hCG

Which hormone maintains the endometrium and reduces uterine contractility?

Progesterone

Which hormone promotes uterine and breast growth?

Estrogen

Which hormone increases uterine blood flow?

Estrogen

What is the primary role of human placental lactogen?

Supports fetal nutrition

What is the primary role of human placental lactogen?

Supports fetal nutrition

Which hormone relaxes ligaments and softens the cervix?

Relaxin

Match each hormone with its primary function:

• hCG = Maintains corpus luteum

• Progesterone = Maintains endometrium

• Estrogen = Promotes uterine growth

• Relaxin = Softens cervix

Order fetal blood flow from the placenta toward the fetus:

1. Placenta

2. Umbilical vein

3. Ductus venosus

4. Inferior vena cava

5. Right atrium

Which fetal vessel bypasses the liver?

Ductus venosus

Which fetal structure connects the pulmonary artery with the aorta?

Ductus arteriosus

Order the major fetal circulation pathway from the placenta back to the placenta?

1. Placenta

2. Umbilical vein

3. Ductus venosus

4. Inferior vena cava

5. Right atrium

6. Foramen ovale

7. Left atrium

8. Ductus arteriosus

9. Pulmonary artery

10. Aorta

11. Umbilical artery

A newborn is diagnosed with a congenital defect affecting the skin and the peripheral nerves. Which embryonic germ layer failed to develop normally?

Ectoderm

An ultrasound reveals a fetal heart malformation along with abnormal kidney development. Which germ layer gives rise to both of these organs?

Mesoderm

A fetus is found to have a tracheoesophageal abnormality affecting the lining of the respiratory tract. Which germ layer forms this lining?

Endoderm

A patient has a tumor arising from the lining of the gastrointestinal tract. Which germ layer originally gave rise to this tissue?

Endoderm

A newborn presents with skeletal muscle weakness traced to abnormal muscle development in utero. Which germ layer forms skeletal muscle?

Mesoderm

A child is diagnosed with a tumor of the adrenal cortex. Which germ layer gives rise to the adrenal cortex?

Mesoderm

A patient develops melanoma, a cancer of pigment producing skin cells. Which germ layer gives rise to the epidermis?

Ectoderm

A fetus has both a liver abnormality and a pancreatic abnormality affecting their epithelia linings. Which germ layer forms these organs’ linings?

Endoderm

A newborn has a defect in tooth enamel and the lens of the eye. Which germ layer gives rise to these structures?

Ectoderm

A congenital deffect affects both the spleen’s connective tissue framework and the blood vessels supplying it. Which germ layer forms these structures?

Mesoderm