Developmental Biology

Question 1

Cleavage

Answer 1

Rapid mitotic divisions in early embryonic development

Question 2

What happens to the cell size in cleavage?

Answer 2

• Decreases
• Increasing nuclei to cytoplasm ratio
• Increases gas/nutrient exchange

Question 3

When does first cleavage occur?

Answer 3

-32 hrs after fertilization

Question 4

What is the order of development?

Answer 4

Fertilized egg –> 2-cell stage –> 4-cell stage –> 8-cell –> 16 cell –> morula –> blastula –> gastrula

Question 5

What is the morula?

Answer 5

-Solid ball of embryonic cells

Question 6

What marks blastulation?

Answer 6

-Morula develops fluid-filled cavity called blastocoel which becomes hollow sphere of cells called blastula

Question 7

Which cell stage implants in uterus?

Answer 7

-Blastula

Question 8

What is an ectopic pregnancy?

Answer 8

-When the blastula implants outside the uterus

Question 9

At what week is the embryo fully implanted?

Answer 9

-Week 2

Question 10

What is the three-layered structure called?

Answer 10

-Gastrula

Question 11

What does the ectoderm form?

Answer 11

-Integumentary system, lens, retina, nervous sys

Question 12

What does the endoderm form?

Answer 12

-Epithelial lining of digestive/respiratory tract, liver, pancreas, thyroid, bladder lining

Question 13

What does the mesoderm form?

Answer 13

-Muscoskeletal system, circulatory system, excretory system, gonads, connective tissue, portions of digestive/respiratory

Question 14

What is neurulation?

Answer 14

• End of gastrulation

- Regions of germ layers –> rudimentary nervous sys

Question 15

Notochord

Answer 15

-Rod of mesodermal cells developing along longitudinal axis of embryo under dorsal layer of ectoderm

Question 16

What is the inductive effect of the notochord?

Answer 16

-Causes ectoderm to fold in to form groove which forms closed tube –> spinal cord and brain

Question 17

Neural crest cells

Answer 17

• Cells at top of neural tube that migrate laterally

- Sensory ganglia, autonomic ganglia, adrenal medulla, Schwann cells

Question 18

What can prevent spina bifida?

Answer 18

-Folic acid

Question 19

Amnion

Answer 19

-Thin, tough membrane containing amniotic fluid

Question 20

What develops into the placenta?

Answer 20

-Chorion

Question 21

What is the chorion?

Answer 21

• Membrane that completely surrounds the amnion

- Assist with transfer of nutrients from mother to fetus

Question 22

Allantois

Answer 22

• Develops as outpocketing of gut

- Blood vessels enlarge –> umbilical vessels

Question 23

What is the function of the umbilical vessels?

Answer 23

-Connect fetus to developing placenta

Question 24

Yolk sac

Answer 24

Site of early development of blood vessels

Question 25

First trimester

Answer 25

• Major organ development
• Heart beat at 22 days
• Eyes, gonads, limbs, liver
• Cartilaginous skeleton –> bone

Question 26

Second trimester

Answer 26

• Rapid growth
• Face appears human
• Toe/finger elongation

Question 27

Third trimester

Answer 27

• Rapid growth
• Brain development
• Antibodies transported by highly selective active transport
• Growth slows, fetus less active

Question 28

What are the three stages of labor?

Answer 28

1. Cervix thins and dilate, amniotic sac ruptures
2. Rapid contractions, birth of baby
3. Uterus contracts to expel placenta and umbilical cord

Question 29

Teratogens

Answer 29

-Chemical and biological agents that can cause congenital disorders

Question 30

Which plant stems allow for growth in length?

Answer 30

-Apical meristems at tips of roots/stems

Question 31

Which plant stems allow for growth in diameter?

Answer 31

• Lateral meristem or cambium located between xylem and phloem
• Not active in monocots or herbaceous dicots