Embryology basics

Question 1

how long is the gestation period and how is it divided

Answer 1

there are 3 trimesters over the 9 months

Question 2

name of weeks 0-3

Answer 2

conceptus/embryo

Question 3

name of weeks 3-8

Answer 3

embryonic period

Question 4

name of weeks 9-40

Answer 4

fetal period

Question 5

what are the 6 phases of embryogenesis

Answer 5

gametogenesis
fertilisation
cleavage
gastrulation
formation of body plan
organogenesis

Question 6

describe gametogenesis

Answer 6

gamete cells are produced by mitosis and meiosis, leads to genetic variation

Question 7

what is a gamete cell

Answer 7

a cell with inly 23 chromosomes(half of set)

Question 8

describe spermatogenesis

Answer 8

male gametes are produced(sperm/spermatozoa), occurs during puberty and never stops

Question 9

describe oogenesis

Answer 9

female gametes produced(oocytes), starts during development and ends at menopause
by weeks 28-30 primary oocytes begin meiosis but are in arrest until puberty

Question 10

describe fertilisation

Answer 10

fusion of sperm and oocyte, forms a zygote

Question 11

what is a zygote

Answer 11

a diploid cell created by fusion of M and F gametes, its a single cell with sex determination 46 XX or XY

Question 12

describe cleavage

Answer 12

period of rapid cell division, with no increase in size. eventually forms blastocyste

Question 13

describe gastrulation

Answer 13

formation of germ layers, establishes left and right sides of the body putting things in the correct place

Question 14

what are the 3 germ layers

Answer 14

ectoderm, mesoderm and endoderm

Question 15

describe the formation of the body plan phase

Answer 15

embryonic folding occurs, the endoderm folds to create the gut tube and the ectoderm folds to become the skin/body wall. creating a tube-within-a-tube

Question 16

describe organogenesis and when it is in place

Answer 16

formation of organs and organ systems, basis of these in place by end of embryonic period

Question 17

describe the changes in weight and growth during the foetal period

Answer 17

mainly grows in length during 2nd trimester, most weight added during 3rd trimester

Question 18

describe changes to the body during foetal period

Answer 18

tissues mature and become functional, bone laid down, connections to CNS made, overt sexual difference

Question 19

describe the orientation of the body in terms of a foetus

Answer 19

cranial = head/top
caudal = feet/bottom
dorsal = back
ventral = front

Question 20

what are the primary processes during the transition from a zygote to a human

Answer 20

cell division, cell attachment, apoptosis and cell differentiation, induction and cell migration

induction = one cell causes another to differentiate

Question 21

what are the secondary processes of zygote to human

Answer 21

axis formation/polarity (which way is up)

folding/rotation (allows formation of organ structures)

Question 22

how is development controlled

Answer 22

genetic expression
preferential expression of maternal or paternal gene
environmental factors (smoking etc.)