Embryology booklet

Question 1

What is the normal human gestation period?

Answer 1

38 weeks

Question 2

What happens during fertilisation?

Answer 2

A sperm fuses with an ovum to create a zygote

Question 3

What structure is formed by the rapid division of the zygote?

Answer 3

Morula

Question 4

What is the term for the early stage of the fertilised egg before implantation?

Answer 4

Zygote

Question 5

What is the bilaminar disc?

Answer 5

A structure formed from the inner cell mass with two layers: epiblast and hypoblast

Question 6

What process leads to the formation of the trilaminar disc?

Answer 6

Gastrulation

Question 7

What three layers are formed in the trilaminar disc?

Answer 7

• Ectoderm
• Mesoderm
• Endoderm

Question 8

What does the ectoderm primarily develop into?

Answer 8

Epithelial and covering tissues, including skin and neural tissues

Question 9

What does the mesoderm develop into?

Answer 9

Muscles and skeletal tissues

Question 10

What does the endoderm develop into?

Answer 10

Linings of gastrointestinal and respiratory tracts, and major glandular tissues

Question 11

What is the notochord?

Answer 11

The first part of the skeletal structure that will become the intervertebral discs

Question 12

What is the neural plate?

Answer 12

A structure that develops into the spinal cord and brain

Question 13

What are somites?

Answer 13

Pairs of mesodermal tissue that develop alongside the neural tube

Question 14

How many pairs of somites typically develop?

Answer 14

42-44 pairs

Question 15

What initiates limb development in the foetus?

Answer 15

The Apical Ectodermal Ridge (AER)

Question 16

What is apoptosis in limb development?

Answer 16

Pre-programmed cell death that shapes the digits

Question 17

Where does the development of the gut primarily occur?

Answer 17

Outside the body cavity of the embryo

Question 18

What are the three sections of the developing gut?

Answer 18

• Foregut
• Midgut
• Hindgut

Question 19

What is the role of blood flow in the developing baby?

Answer 19

Facilitates low-rate blood flow for lung development and bypasses the liver

Question 20

What happens to the foramen ovale after birth?

Answer 20

It closes and becomes part of the septum

Question 21

Fill in the blank: The first part of the skeletal structure forms as a tube called the _______.

Answer 21

[notochord]

Question 22

True or False: The Ductus Arteriosus closes on the first breath and becomes a suspensory ligament.

Answer 22

True

Question 23

What is the timeline for the transition from embryo to foetus?

Answer 23

Embryo phase ends at week 8, foetal development begins

Question 24

What key feature is developed by week 24?

Answer 24

Earliest potential survival if born

Question 25

What significant development occurs by week 26?

Answer 25

Touch sense well developed and responsive

Question 26

What happens to the Ductus Venosus after birth?

Answer 26

It closes and becomes a suspensory ligament

Question 27

What is the significance of the Apical Ectodermal Ridge?

Answer 27

It initiates limb development in the foetus

Question 28

What alignment occurs in the Inner Cell Mass during the bilaminar and trilaminar disc stages?

Answer 28

The Inner Cell Mass aligns into two layers called the bilaminar disc. ## Footnote The bilaminar disc consists of the Epiblast facing the amniotic cavity and the hypoblast facing the yolk sac.

Question 29

What is the normal gestation period?

Answer 29

38 weeks

Question 30

How is the morula formed?

Answer 30

By mitotic division

Question 31

What structures arise from the mesodermal layer?

Answer 31

Somites

Question 32

What determines limb bud development?

Answer 32

AER (Apical Ectodermal Ridge)

Question 33

What protein defines the digit that develops into the thumb or greater toe?

Answer 33

Sonic Hedgehog protein

Question 34

From how many precursors does the liver form?

Answer 34

Two precursors

Question 35

What are the three early structures in brain development?

Answer 35

Prosencephalon, Rhombencephalon, Messencephalon

Question 36

List the key stages in early embryonic development.

Answer 36

* Initial division of the zygote into 2, 4, 8, and 16 cells to form a morula * Movement along the fallopian tube * Development of the blastocyst * Formation of the Inner Cell Mass

Question 37

What is the primitive streak?

Answer 37

A structure that forms on the surface of the Epiblast

Question 38

What layers are formed during the trilaminar disc stage?

Answer 38

* Ectoderm (replacing Epiblast) * Endoderm (replacing hypoblast) * Mesoderm (new layer in between)

Question 39

What happens to the Foramen Ovale after birth?

Answer 39

Closes on first breath

Question 40

What does the Ductus Arteriosus become after it closes?

Answer 40

Ligamentum arteriosum

Question 41

What happens to the Ductus Venosus near the liver after birth?

Answer 41

Closes within the first week and becomes ligamentum venosum

Question 42

Fill in the blank: The three shunts in fetal circulation include the Foramen Ovale, Ductus Arteriosus, and _______.

Answer 42

Ductus Venosus