Topic 5 - Early Human Development

Question 1

How many weeks is the pre-embryonic period and when?

Answer 1

first 2 weeks

Question 2

What is part of the pre-embryonic period?

Answer 2

1. Zygote
2. Morula
3. Blastocyst

Question 3

Zygote

• how many cells?
• diploid or haploid?

Answer 3

• 1 cell
• Diploid

Question 4

What does the Zygote undergo?

Answer 4

undergoes rapid mitotic divisions called cleavage divisions

Question 5

what are cleavage divisions?

Answer 5

rapid mitotic divisions

Question 6

Morula

how many hours?

Answer 6

72

Question 7

Morula

• describe its physical appearance
  
  • how many cells? what are the cells called?
  • same size as what?

Answer 7

• solid ball of 16-32 cells (Cells called blastomeres)
• SAME size as ovum/zygote

Question 8

what is the same size as a zygote?

Answer 8

morula

Question 9

Blastocyst

how long is the duration?

Answer 9

5 days

Question 10

Describe the blastocyst

Answer 10

• fluid filled cavity develops = blastocoel/blastocyst cavity
• inner cell mass
• trophoblast (made of trophoblast cells)

Question 11

go into detail about the inner cell mass of the blastocyst

Answer 11

cells divide and differentiate (undergo changes to

become more specialized) to form the embryo

Question 12

go into detail about the trophoblast of the blastocyst

Answer 12

cells will divide and differentiate to form chorion - provides nutrients to developing embryo

Question 13

what does the blastocyst do?

• moves from where?
• attaches to what?
• what is that called?
• how many days after ______?

Answer 13

blastocyst moves from uterine tube and attaches to endometrium of uterine wall = implantation

5 - 7 days after fertilization

Question 14

describe the blastocyst after implantation

Answer 14

• inner cell mass forms a 1 layered (bilayered) embryonic disc composed of:
  
  • epiblast
  • hypoblast

Question 15

epiblast

Answer 15

will undergo mitosis to form

1. amnion - with a fluid filled amniotic cavity
2. 3 germ layers of the embryo

Question 16

hypoblast

Answer 16

will undergo mitosis to form the yolk sac

Question 17

how long is the duration of the Embryonic period?

Answer 17

3rd week to the end of the 8th week

Question 18

describe the embryonic period

• how many layers
• what does it form?
• how were the layers formed?

Answer 18

• 3 germ layers are now present forming the embryo (Each layer was formed from mitosis and differentiation of epiblast cells):
  
  1. Ectoderm
  2. Mesoderm
  3. Endoderm

Question 19

Ectoderm

what will it form?

Answer 19

will form the nervous system and the epidermis

Question 20

Mesoderm

what will it form?

Answer 20

will form

1. muscles
2. cardiovascular system
3. dermis
4. most bones

Question 21

Endoderm

what will it form?

Answer 21

• will form epithelial linings of
  
  1. digestive
  2. respiratory
  3. urinary
  4. reproductive systems and their associated glands

Question 22

what happens during the embryonic period?

1. what happens to the major organ systems?
2. what happens to the heart?
3. what happens to the limb buds?
4. what forms during this period?

Answer 22

1. major organ systems almost completely formed
2. heart begins to beat
3. limb buds differentiate
4. embryonic membranes form

Question 23

what happens during the embryonic period?

Answer 23

1. major organ systems almost completely formed
2. heart begins to beat
3. limb buds differentiate
4. embryonic membranes form

Question 24

what embryonic membranes are formed?

Answer 24

1. yolk sac
2. amnion
3. allantois
4. chorion

YAAC

Question 25

chorion 1. derived from what? 2. surrounds what? 3. projections of what? 4. what will these projections form? 5. what are these projections called?

Answer 25

1. derived from **trophoblast** 2. surrounds **all embryonic membranes** 3. projections of **the chorion containing blood vessels** 4. that will form **fetal part of placents** 5. called **chorionic villi**

Question 26

what is the chorion derived from?

Answer 26

trophoblast cells

Question 27

derived from trophoblast cells

Answer 27

chorion

Question 28

surrounds all embryonic membranes

Answer 28

chorion

Question 29

projections of the chorion containing the blood vessels that will form fetal part of placenta

Answer 29

chorionic villi

Question 30

amnion 1. derived from? 2. forms what? 3. which surrounds?...

Answer 30

1. derived from **epiblast** 2. forms **amniotic cavity** 3. amniotic cavity surrounds **embryo/fetus with amniotic fluid**

Question 31

what is the function of the amniotic fluid?

Answer 31

1. shock absorption 2. temperature regulation

Question 32

what has this function? 1. shock absorption 2. temperature regulation

Answer 32

amniotic fluid of the amnion

Question 33

derived from epiblast

Answer 33

amnion

Question 34

forms amniotic cavity - surrounds embryo/ fetus with amniotic fluid

Answer 34

amnion

Question 35

yolk sac 1. derived from? 2. forms? 3. produces? 4. source of?

Answer 35

1. derived from **hypoblast** 2. forms **part of gut (gastrointestinal tract)** 3. produces **earliest blood cells and vessels** 4. source of **primordial germ cells (**reproductive cells = primary oocytes + primary spermatocytes)

Question 36

derived from hypoblast

Answer 36

yolk sac

Question 37

forms part of gut (gastrointestinal tract)

Answer 37

yolk sac

Question 38

produces earliest blood cells and vessels

Answer 38

yolk sac

Question 39

source of primordial germ cells

Answer 39

yolk sac

Question 40

allantois * what part of the yolk sac? * what does it form?

Answer 40

* **out-pocket** of yolk sac * forms the **umbillical cord** and the **urinary bladder**

Question 41

out-pocket of yolk sac

Answer 41

allantois

Question 42

forms the umbilical cord and the urinary bladder

Answer 42

allantois

Question 43

what week does the **fetal period** begin and end? and what occurs during this period?

Answer 43

* 9th week to the end of the 40th week * growth and maturation of organs occurs

Question 44

9th week to the end of the 40th week

Answer 44

fetal period

Question 45

growth and maturation of organs occurs during this period

Answer 45

fetal period

Question 46

3rd week to end of the 8th week

Answer 46

embryonic period

Question 47

* major organ systems almost completely formed * heart begins to beat * limb buds differentiate * embryonic membranes form during this period:

Answer 47

embryonic period

Question 48

what provides nutrients to the developing embryo?

Answer 48

chorion