Embryology

Question 1

what is the zona pellucida?

Answer 1

a thick transparent membrane surrounding an ovum before implantation

Question 2

what does sperm bind to during fertilisation?

Answer 2

the zona pellucida glycoprotein (ZP3)

Question 3

where the acrosome?

Answer 3

at the head of the sperm

Question 4

where are acrosomal enzymes released from?

Answer 4

the sperm head

Question 5

what do acrosomal enzymes do when they are released from the sperm head?

Answer 5

they allow the sperm to digest into the egg

Question 6

what does sperm entry trigger?

Answer 6

completion of meiosis 2 and the release of granules by oocyte

Question 7

what do the granules released from oocytes do?

Answer 7

they cause the fertilised oocyte to harden up to prevent more sperm entering/polysperming and break down ZP3 receptor

Question 8

many smaller daughter cells formed when the zygote undergoes mitotic divisions

Answer 8

blastomeres

Question 9

blastomeres up to the 8 cell stage are thought to be…?

Answer 9

totipotent

Question 10

what is mitotic nondisjunction?

Answer 10

The failure in mitosis for the two members of a chromosome pair to separate (to disjoin) normally so that both chromosomes go to one daughter cell while none go to the other daughter cell.

Question 11

what are blastomeres?

Answer 11

the individual daughter cells from the zygote divisions

Question 12

how many blastomeres make up a morula?

Answer 12

16+

Question 13

name of outer cell mass

Answer 13

trophoblast

Question 14

name of inner cell mass

Answer 14

embryoblast

Question 15

when does the thing become a blastocyst?

Answer 15

when there is a separation between the inner and outer layer

Question 16

what happens when the blastocyst gets so big?

Answer 16

it breaks free from the zona pellucida

Question 17

where does implantation usually happen?

Answer 17

on the anterior or posterior uterine wall

Question 18

typically, by what day does implantation happen?

Answer 18

day 6

Question 19

as the trophoblast attaches to the uterine wall, the trophoblast separates into?

Answer 19

the cytotrophoblast and the syncytiotrophoblast

Question 20

as the embryo attaches to the uterine wall, the embryo organises itself into what two layers? at what stage?

Answer 20

the epiblast and the hypoblast

day 7.5 - bilaminar embryo

Question 21

epiblast

Answer 21

the dorsal surface of the embryo

Question 22

hypoblast

Answer 22

the ventral surface of the embryo

Question 23

what completes implantation?

Answer 23

closure by fibrin coagulum

Question 24

day 9 - two cavities are formed?

Answer 24

amniotic cavity (epiblast) and primitive yolk sac (hypoblast)

Question 25

epiblast cell shape?

Answer 25

tall columnar cells

Question 26

hypoblast cell shape?

Answer 26

cuboidal cells

Question 27

what does hCG stand for?

Answer 27

human chorionic gonadotropin

Question 28

what does hCG stimulate?

Answer 28

the corpus luteum which secretes oestrogen and progesterone

Question 29

what replaces the corpus luteum?

Answer 29

the placenta

Question 30

when does the bilaminar embryo need its own uteroplacental circulation?

Answer 30

day 12

Question 31

where do vacuoles appear in?

Answer 31

in the syncytiotrophoblast

Question 32

what happens when the vacuoles in the syncytiotrophoblast unite?

Answer 32

they form lacunae

Question 33

where does maternal blood flow into to establish the embryos uteroplacental circulation?

Answer 33

into lacunae to diffuse to the embryoblast

Question 34

where does the primitive streak appear from?

Answer 34

the midline at the caudal end of the epiblast

Question 35

three parts of the primitive streak

Answer 35

primitive pit, primitive node and primitive groove

Question 36

what is found at the cranial end of the primitive streak?

Answer 36

primitive pit and node

Question 37

what is gastrulation?

Answer 37

the movement of epiblast cells through the primitive streak to form the three primary germ layers

Question 38

what establishes the body axes?

Answer 38

the primitive streak

Question 39

how many days in does gastrulation happen?

Answer 39

14-15

Question 40

what replaces hypoblast cells?

Answer 40

definitive endoderm

Question 41

what replaces the epiblast cells?

Answer 41

ectoderm

Question 42

what are the names of the three germ layers?

Answer 42

ectoderm, mesoderm and endoderm

Question 43

what is the fate of the ectoderm?

Answer 43

produces the epidermis of skin (also hair, nails and associated glands) and the nervous system (brain, spinal cord, peripheral nerves)

Question 44

what is the fate of the mesoderm?

Answer 44

it becomes divided into three regions across both sides of the notochord

Question 45

what are the 3 mesoderm regions?

Answer 45

paraxial, intermediate and lateral (visceral and somatic)

Question 46

fate of the paraxial mesoderm?

Answer 46

axial skeleton, voluntary skeletal muscle, part of dermis (back)

Question 47

fate of the intermediate mesoderm?

Answer 47

urogenital systems such as kidney and ureter and gonads and associated structures

Question 48

fate of the somatic lateral plate of mesoderm

Answer 48

makes most of dermis, lining of body wall and part of limbs

Question 49

fate of visceral lateral plate of mesoderm

Answer 49

makes the cardiovascular system, mesothelial covering of organs and smooth muscle

Question 50

fate of the endoderm

Answer 50

lining of the gut tube, respiratory tract and bladder and urethra