Embryology (early development)

Question 1

what 4 main functions do cells show

Answer 1

proliferation
movement (chemotaxis) differentiation
loss (apoptosis)

Question 2

how do embryonic cells functon diffferently to omatic cells

Answer 2

mature cells normally show one characteristic at a time-

In an embryo, cells may show the proliferate, move and differentiate simultaneously
simultaneously.

Question 3

how does regulator factor expression produce different outcomes

Answer 3

Gradients/ combinations of regulatory factors;

Spatial/ temporal changes in these factors, or in the responses to them.

Question 4

Embryonic development is usually considered to start with….

Answer 4

fertilisation which leads

immediately into preimplantation development (PID) of the conceptus.

Question 5

wher and over what time period does PID occur

Answer 5

within the fallopian tube over a period of 6 days,

Question 6

what is PID characterised by

Answer 6

characterised by a series of cleavage

divisions that results in the formation of the morula (a ball of undifferentiated cells).

Question 7

what does the morula form

Answer 7

develops into a blastocyst-

Question 8

what are the key features of the blastocyt

Answer 8

has an outer layer of trophectoderm
an inner cell mass
and a fluid filled cavity.

Question 9

when does the blastocyt implant into the uterine lining and hwa happens when it does

Answer 9

(by 10 days post-fertilization)

inner cell mass
becomes a bilayer disk.

Question 10

what does the bilayer disk gve rise to

Answer 10

all of the tissues of the human fetus by

a series of complex changes…

Question 11

what is the bilayer dsk composed of

Answer 11

hypoblast and epiblast cells

Question 12

what are the complex changes which the bilayer disk undergoes

Answer 12

Gastrulation and Neurolation

Question 13

describe the process of gastrulation

Answer 13

convertes bilayer disk to trilaminar embryo, containing the three layers of germ cells.

(precursors to all tisues in the body)

Question 14

when does gastrultion occur

Answer 14

14-18 post-

fertilisation.

Question 15

does neurulation start after astrulation

Answer 15

NO

Neurulation is initiated before gastrulation is complete.

Question 16

describe the process of neurulation, what controls it

Answer 16

differentiation of
the ectoderm to generate the CNS,

under the control of the notochord in the
mesoderm

Question 17

how does the neural plate form a sealed tube

Answer 17

develops two folds which
increase in size until they meet over the neural groove and fuse to form the neural
tube.

Question 18

when does fusion of the 2 neual tubes occur

Answer 18

Fusion occurs during week 4 of development as the CNs becomes a sealed
tube.

Question 19

what is occuring in parallel with neurulation

Answer 19

precursors of other tissues are developing within the

embryo, and it is being converted from a flattened structure into a 3D embryo.

Question 20

during the third week of development whcih strcire outside the embryo are also developing

Answer 20

the primordial germ cells

cardiac/ vascular progenitors

Question 21

in which direcions does folding of the emryo occur

Answer 21

both laterally and in the anterio-posterior direction

Question 22

what can be said of the embrto by the end of week 4

Answer 22

precursors of all internal tissues have been laid down

many external structures are also developing.

Question 23

sumarise the events of week 3

Answer 23

Formation of trilaminar disc (mesoderm),
CNS & somites.
Blood vessel initiation. Initiation of placental villi. (3mm).

Question 24

summarise the events of week 4

Answer 24

Closure of neural tube. Heart, Face, arm initiated.

Umbilical cord. Elaboration of placental villi. (4mm)

Question 25

define conceptus

Answer 25

everything that is produced from the fertilised egg.

Question 26

define embryo

Answer 26

whole product of conception, includes cells that give rise to the baby
and everything else that results from conception such as the placenta and umbilical cord.

Question 27

when does embryonic development cease

Answer 27

after 8 weeks post-fertilisation as the conceptus

is nor clearly human and classified as a fetus.

Question 28

what are the 3 layers of the trilaminar embryo which gastrulation forms

Answer 28

ectoderm
mesoderm
endoderm

Question 29

what does the ectoderm give rise to

Answer 29

skin, nervous system

Question 30

what does the mesodem give rise to

Answer 30

skeleton, muscle, kidney, heart, blood

Question 31

what does the endoderm give rise to

Answer 31

gut, liver, lungs

Question 32

what does the grrove above the neural plate act as

Answer 32

negative regulator to

prevent proliferation occurring at the groove.

Question 33

In the second month what is happening

Answer 33

limbs, face and internal tissues (heart, lungs, gut) develop

looks human by day 56

Question 34

how does fusion of the neural folds occur

Answer 34

fusion point moves anteriorly and

posteriorly with neuropores at each end.

Question 35

how does brain develop

Answer 35

Fusion of tissues and elaborations results in brain

developments. The two halves of the brain form separately and then join.