Embryology: Principles

Question 1

how long does pregnancy last

Answer 1

9 months, 38-40 weeks, 3 trimesters

Question 2

what period are weeks 0-3

Answer 2

conceptus/embryo

Question 3

what period are weeks 3-8

Answer 3

embryonic period

Question 4

what period are weeks 9-40

Answer 4

foetal period

Question 5

what are the 6 phases of embryogenesis (in order)

Answer 5

• gametogenesis
• fertilisation
• cleavage
• gastrulation
• formation of a body plan
• organogenesis

Question 6

gamete

Answer 6

cell with a chromosome complement of 23 (haploid)

Question 7

spermatogenesis

Answer 7

formation of male gametes

Question 8

when does spermatogenesis occur

Answer 8

at puberty and continues throughout life

Question 9

how long is once cycle of spermatogenesis

Answer 9

~64 days

Question 10

production of sperm (increases/decreases) with age

Answer 10

decreases

Question 11

sperm contain how many chromosomes and what sex chromosome(s)

Answer 11

22 X/Y

Question 12

oogenesis

Answer 12

formation of female gametes

Question 13

when does oogenesis occur

Answer 13

starts in development (arrests in prophase of meiosis) and begins again in puberty, stopping in menopause

Question 14

when is female reproductive life span determined

Answer 14

in foetal life

Question 15

fertilisation

Answer 15

fusion of female and male gametes to form zygote

Question 16

zygote

Answer 16

diploid cell with full chromosome complement

Question 17

cleavage

Answer 17

rapid mitotic cell division with NO increase in size (stays in same area as original zygote)

Question 18

the zygote forms a _ then _

Answer 18

morula, blastocyst

Question 19

morula

Answer 19

16+ cells

Question 20

blastocyst

Answer 20

days 1-4

Question 21

gastrulation

Answer 21

formation of germ layers and boxy axes established

Question 22

germ layers

Answer 22

ectoderm (external), mesoderm (middle) and endoderm (internal)

Question 23

formation of body plan

Answer 23

embryonic folding

Question 24

organogenesis

Answer 24

formation of organs and organ systems

Question 25

when are the basis of all organs and systems in place

Answer 25

end of embryonic period (develops throughout foetal period)

Question 26

what happens in the foetal period (5)

Answer 26

• weight gain (3rd trimester) and growth (2nd trimester)
• tissues mature and become functional
• sexual differentiation
• bone laid down
• connections made in CNS

Question 27

what are the 6 primary processes

Answer 27

• cell division
• differentiation
• apoptosis
• cell migration
• induction
• cell attachment

Question 28

cell attachments

Answer 28

physical/functional linkages, formation of tissues

Question 29

induction

Answer 29

ability of one cell to cause another to differentiate

Question 30

name the 2 secondary processes

Answer 30

• axis formation/polarity

- folding/rotation

Question 31

axis formation/polarity

Answer 31

which way is which - cells know where they are in relation to others and the embryo

Question 32

folding/rotation

Answer 32

entire embryo and strictures fold allowing formation of complex organ structures and giving the embryo its 3D structure

Question 33

what 3 factors control development of the embryo

Answer 33

• genetic
• epigenetic
• environmental

Question 34

epigenetic

Answer 34

preferential expression of either maternal or paternal genes