Chapter 8 - Stages of Prenatal Development

Question 1

Zygote

Answer 1

• Weeks 1-2
• After fertilization
• Travels down fallopian tube and implants into uterine wall.
• Triggers hormonal changes to stop menstration
• Center of zygote contains germ disk

Question 2

Chromosomes

Answer 2

Threadlike structures in the nuclei of cells that contain genetic material

Question 3

Gene

Answer 3

Any group of DNA compounds creating instructions for a specific biochemical unit.

Question 4

Genotype

Answer 4

Complete set of genes that one has inherited

Question 5

Phenotype

Answer 5

Combination of genotype and environmental influences resulting in the actual expression of traits

Question 6

Alleles

Answer 6

• Different forms in which genes come.
• Carry instructions for a specific variation of a trait

Question 7

Homozygous Alleles

Answer 7

• Both alleles are the same (both dominant, both recessive)
• Both parents contribute similar genes for a trait

Question 8

Heterozygous Alleles

Answer 8

• Alleles for a trait are different
• Parents contributed different versions of a trait

Question 9

Autosomes

Answer 9

First 22 pairs of chromosomes

Question 10

23rd pair of chromosomes

Answer 10

Sex chromosomes (XX or XY)

Question 11

Baby’s gender is determined
Hint: zygote

Answer 11

Day 5 of gestation

Question 12

Embryo

Answer 12

• Weeks 3-8
• Body structures, internal organs, and three layers of embryo develop.
• Amniotic sac fills with fluid
• Umbilical cord’s blood vessels join placenta to embryo

Question 13

• Neural tube forms; spinal cord and brain grow.
• Limb buds form, heartbeat begins, organs are recognizable.

Answer 13

Week 4
*Day 35 - heat is beating and eye and limb buds are visible.

Question 14

Head and tail folds form, optical vesicles form, head is recognizable.

Answer 14

Week 3

Question 15

3 layers of the embryo

Answer 15

1) Ectoderm
2) Mesoderm
3) Endoderm

Question 16

• Eyes, ears, nose, mouth, and digits form
• Sensory organs develop
• Some bone ossifications begins

Answer 16

Week 8

Question 17

Neural tube closure

Answer 17

Day 28
- Spina bifida happens when the neural tube does not close and the meninges protrude posteriorly through the spinal column.

Question 18

Fetus

Answer 18

• Weeks 9-39
• Differentiation of the ovaries and testes (week 9)
• Circulatory system begins to function (week 12)
• Movements felt by mother (week 16)

Question 19

• Sex is externally recognizable
• Head is very large for body
• Brain configuration nearly complete
• Blood is forming in the bone marrow
• Circulatory system begins to function

Answer 19

Week 12

Question 20

• Motor activity; movements felt by mother
• Scalp hair present, trunk is gaining on head in size
• Heart muscle is developed
• Sense organs are formed

Answer 20

Week 16

Question 21

All organ systems are formed and functioning to some extent.

Answer 21

4 months

Question 22

• Myelination of spinal cord begins
• Eyebrows, eyelashes, scalp hair
• Skin thickens and is covered by protective, greasy vernix
• Legs have grown appreciably

Answer 22

Week 20

Question 23

Age of viability

Answer 23

22-28 Weeks
- Most body systems function adequately
- Senses active
- Baby can remember voices, music, and tastes

Question 24

• Respiratory-like movements begin
• Cerebral cortex layers are formed

Answer 24

Week 24

Question 25

• Increasing fat tissue development
• Retina layered and light-receptive

Answer 25

Week 28

Question 26

• Weight increases more than length
• Taste is operative

Answer 26

Week 32

Question 27

• Auditory thresholds are similar to adult preferences

Answer 27

Week 34

Question 28

• Body more rounded
• Ossification begins in distal femur

Answer 28

Week 36

Question 29

• Skin smooth and pink
• Ossifications begins in proximal tibia
• Pulmonary branching 2/3 complete
• Myelination begins in brain

Answer 29

Week 40