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Flashcards in Developmental Biology Deck (31):
1

Cleavage

Rapid mitotic divisions in early embryonic development

2

What happens to the cell size in cleavage?

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

3

When does first cleavage occur?

-32 hrs after fertilization

4

What is the order of development?

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

5

What is the morula?

-Solid ball of embryonic cells

6

What marks blastulation?

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

7

Which cell stage implants in uterus?

-Blastula

8

What is an ectopic pregnancy?

-When the blastula implants outside the uterus

9

At what week is the embryo fully implanted?

-Week 2

10

What is the three-layered structure called?

-Gastrula

11

What does the ectoderm form?

-Integumentary system, lens, retina, nervous sys

12

What does the endoderm form?

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

13

What does the mesoderm form?

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

14

What is neurulation?

-End of gastrulation
-Regions of germ layers --> rudimentary nervous sys

15

Notochord

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

16

What is the inductive effect of the notochord?

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

17

Neural crest cells

-Cells at top of neural tube that migrate laterally
-Sensory ganglia, autonomic ganglia, adrenal medulla, Schwann cells

18

What can prevent spina bifida?

-Folic acid

19

Amnion

-Thin, tough membrane containing amniotic fluid

20

What develops into the placenta?

-Chorion

21

What is the chorion?

-Membrane that completely surrounds the amnion
-Assist with transfer of nutrients from mother to fetus

22

Allantois

-Develops as outpocketing of gut
-Blood vessels enlarge --> umbilical vessels

23

What is the function of the umbilical vessels?

-Connect fetus to developing placenta

24

Yolk sac

Site of early development of blood vessels

25

First trimester

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

26

Second trimester

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

27

Third trimester

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

28

What are the three stages of labor?

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

29

Teratogens

-Chemical and biological agents that can cause congenital disorders

30

Which plant stems allow for growth in length?

-Apical meristems at tips of roots/stems

31

Which plant stems allow for growth in diameter?

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