Fertilisation to Trilaminar

Question 1

Where does fertilisation take place

Answer 1

ampulla

Question 2

what does the sperm bind to in first stage of fertilisation

Answer 2

sperm binds in human specific interaction with zone pellucida glycoprotein (tough coat, fluid can enter)

Question 3

during fertilisation what enzyme is released from sperm head and the enzymes function

Answer 3

acrosomal enzymes released, helps break down zone pellucida so sperm can digest its way into egg
sperm and egg membrane fuse and sperm contents enter egg

Question 4

what sperm entry into egg trigger

Answer 4

completion of meiosis 2

release of cortical granules by oocyte

Question 5

function of fimbriae

Answer 5

finger like projections responsible for moving oocyte from ovum to uterus

Question 6

what are blastomeres

Answer 6

once fertilisation occurs the zygote - pronuclei (maternal and paternal) undergoes a series of mitotic divisions which subdivide the fertilised egg into smaller daughter cells

Question 7

What cells are totipotent

Answer 7

up to 8 cell stage (16) blastomeres are thought to be totipotent

Question 8

What is formed when there is 16 cells

Answer 8

morula

Question 9

what is compaction

Answer 9

cell junction formation
cells confined in zone pellucida maximise space by coming into closer contact with each other
outer cells (in contact with zona pellucida) form extensive gap junctions

Question 10

What are trophoblasts

Answer 10

embryonic part of placenta

form blastocyst wall

Question 11

what is the name of the inner cell mass of an embryo

Answer 11

embryo proper/embryoblast/amnio and yolk sac

Question 12

what has occurred 1 week after fertilisation

Answer 12

implantation in uterus

Question 13

what happens once embryo reaches uterine cavity

Answer 13

blastocyst hatching, blastocyst breaks free of zone pellucida by breaking its walls so plantation occurs

Question 14

what are the normal implantation sites

Answer 14

middle or upper dorsal uterine wall

Question 15

what are the abnormal sites of implantation that can lead to ectopic pregnancy or miscarriage

Answer 15

ovary, ampulla, uterine tube, lower part of uterus, cervix, peritoneum

Question 16

why is implantation of an embryo dangerous

Answer 16

wherever embryo implants a dense network of blood vessels form, if implantation in abnormal site vessels can rupture and haemorrhage

Question 17

What is implantation driven by

Answer 17

trophoblasts

Question 18

what do trophoblast divide into during implantation

Answer 18

cytotrophoblasts (made of individual cells)

Syncytiotrophoblasts (single multinucleated cells)

Question 19

During implantation what 2 layers does the embryo organise into

Answer 19

epiblast - in dorsal surface of embryo
hypoblast in ventral surface of embryo
amniotic cavity begins to form

Question 20

when is implantation complete

Answer 20

day 9
embryo - bilaminar disc
each layer associated with a different space: epiblast + amniotic cavity, hypoblast + yolk sac
from edges of the hypoblast cells move out and form original blastocyst membrane

Question 21

what begins to form on day 12

Answer 21

chronic cavity begins to form within the extraembryonic mesoderm, trophoblastic lacunae fills with blood

Question 22

what has formed on day 13

Answer 22

definitive/secondary yolk sac forms

Question 23

What happens once the embryo is implanted and the placenta starts to form

Answer 23

syncytiotrophoblast extends and contacts maternal blood

Question 24

where is the amniotic cavity located in the embryo

Answer 24

above the bilaminar embryonic disc and the definitive yolk sac below

Question 25

where is the chronic cavity located

Answer 25

encircles entire embryo

Question 26

Where is the primitive streak located

Answer 26

appears in midline at caudal end of epiblast

looks like a scratch on surface of embryo

Question 27

what is the cranial end of the primitive streak

Answer 27

primitive pit and node

Question 28

What is gastrulation

Answer 28

2 layers become 3
epiblast cells migrate through primitive streak forming 3 primary germ layers
begins at start of 3rd week

Question 29

what are the 3 layers formed in gastrulation

Answer 29

ectoderm
mesoderm
endoderm

Question 30

What is the face of the ectoderm

Answer 30

Epidermis of skin - hair, nails, associated glands

Nervous system - brain, spinal cord, peripheral nerves

Question 31

What is the fate of the mesoderm

Answer 31

Mesoderm becomes divided into 3 regions either side of the notochord
Paraxial
Intermediate
Lateral plate (somatic mesoderm, visceral mesoderm)

Question 32

What is the fate of the paraxial mesoderm

Answer 32

axial skeleton
voluntary muscle
parts of dermis

Question 33

What is the fate of the intermediate mesoderm

Answer 33

Urogenital systems
kidney and ureter
Gonads and associated structures

Question 34

What is the fate of the lateral plate mesoderm (somatic part)

Answer 34

Lining of body wall, most of dermis, parts of limbs

Question 35

What is the fate of the lateral plate mesoderm - visceral part

Answer 35

Cardiovascular system
mesothelial covering of organs
smooth muscle

Question 36

What is the fate of the endoderm

Answer 36

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