Embryology (week 3, week 4-8, and abnormal development)

Question 1

What is the formation of the germ layer called

Answer 1

Gastrulation

Question 2

Where is the primitive streak found

Answer 2

formed in the midline of the epiblast by the invagination of cells

Question 3

When can the axis of the embryo be determined

Answer 3

by the formation of the primitive streak

Question 4

The epiblast cells displace to between the hypoblast around day 15 and from what

Answer 4

a trilaminar disc - specialised germ layers

Question 5

What is the three layers of the trilaminar disc

Answer 5

Endoderm
Mesoderm
Ectoderm

Question 6

What is NEURULATION

Answer 6

neural tube formation

Question 7

What is the formation of the notochord

Answer 7

Cells sink down from primitive streak in the ectoderm and sit below the mesoderm

Question 8

What does the notochord induce and how?

Answer 8

The formation of the neural tube
sends signal up for the ectoderm to thicken forming a neural plate, the neural plate then sink down forming a neural tube

Question 9

What induces the mesoderm to thicken

Answer 9

the neural tube

Question 10

What three parts does the mesoderm separate into

in order of the closest to the neural tube to the furthest away

Answer 10

Paraxial mesoderm
Intermediate plate mesoderm
Lateral plate mesoderm

Question 11

What does the paraxial mesoderm segment to from

Answer 11

somites

Question 12

What does the intermediate plate mesoderm go on the develop

Answer 12

urogenetial system (reproductive and urinary)

Question 13

The lateral plate mesoderm splits to from what

Answer 13

somatic mesoderm

splanchnic mesoderm

Question 14

What does the lateral plate mesoderm go on to develop

Answer 14

The body cavities
The pleura
The peritoneum - forms the lining of the abdominal cavity

Question 15

What is the space between the splanchnic and the somatic mesoderm in the later plate called

Answer 15

intraembryonic coelom

Question 16

What is the 4th - 8th week of development called

Answer 16

Organogenetic period

Question 17

What days does the heart start to beat

Answer 17

day 24

Question 18

How many pairs of somities from from the paraxial mesoderm

Answer 18

43

Question 19

Where does gut formation occur

Answer 19

the endoderm

Question 20

During what period does limbs bud and the neck from

Answer 20

Organogenetic period

Question 21

What further development happens to the neural tube during the Organogenetic period

Answer 21

forebrain, midbrain, hindbrain and spinal cord development

Question 22

What surrounds the mesoderm

Answer 22

the ectoderm

Question 23

The lateral plate mesoderms splits to from the splanchnic and somatic mesoderm what membranes do these form
Therefore what is the intraembryonic coelom space inbetween the membranes formed

Answer 23

Splanchnic - viscera pleura
somatic -parietal pleura

intraembryonic coelom - the pleural cavity

Question 24

What do the somites divide further into 3 parts

Answer 24

Dermatome
Myotome
Sclerotome

Question 25

What does the dermatome develop into

Answer 25

the dermis of the skin

Question 26

what does the myotome develop into

Answer 26

the muscles of the body

Question 27

what does the Sclerotome develop into

Answer 27

the bones and vertebra of the body

Question 28

What cavity surround the entire embryo

Answer 28

the amniotic cavity

Question 29

What initially provides nourishment while the placenta matures and is fully formed

Answer 29

the yolk sac

Question 30

What surround the embryo in the amniotic sac

Answer 30

nutrients

Question 31

What is Teratology

Answer 31

study of when things go wrong during development

Question 32

what are environmental factors that cause abnormal development called

Answer 32

teratogens

Question 33

What are the causes of abnormal development

Answer 33

``` Drugs tobacco radiation alcohol infectious agents ``` ALSO Genetic factors - structural or numerical increased mothers age

Question 34

How do these factors affect foetus development

Answer 34

as transfer through the placenta from the mother to the foetus

Question 35

What is the risk of teratogens depend on

Answer 35

The time of the exposure - e.g. critical development the dosage of substance the embryos susceptibility

Question 36

What period week has the greatest risk of teratogens and why

Answer 36

weeks 3 - 8 | period of greatest sensitivity as this the most crucial development point

Question 37

what time period has low effect of teratogens but has the highest risk of death

Answer 37

week 1 - 2

Question 38

how can malformations be diagnosed prenatal

Answer 38

Blood ultrasound amniocentesis

Question 39

What is the main thing that happens week 4 in the development of the foetus

Answer 39

folding of the embryo