Embryology booklet Flashcards
What is the normal human gestation period?
38 weeks
What happens during fertilisation?
A sperm fuses with an ovum to create a zygote
What structure is formed by the rapid division of the zygote?
Morula
What is the term for the early stage of the fertilised egg before implantation?
Zygote
What is the bilaminar disc?
A structure formed from the inner cell mass with two layers: epiblast and hypoblast
What process leads to the formation of the trilaminar disc?
Gastrulation
What three layers are formed in the trilaminar disc?
- Ectoderm
- Mesoderm
- Endoderm
What does the ectoderm primarily develop into?
Epithelial and covering tissues, including skin and neural tissues
What does the mesoderm develop into?
Muscles and skeletal tissues
What does the endoderm develop into?
Linings of gastrointestinal and respiratory tracts, and major glandular tissues
What is the notochord?
The first part of the skeletal structure that will become the intervertebral discs
What is the neural plate?
A structure that develops into the spinal cord and brain
What are somites?
Pairs of mesodermal tissue that develop alongside the neural tube
How many pairs of somites typically develop?
42-44 pairs
What initiates limb development in the foetus?
The Apical Ectodermal Ridge (AER)
What is apoptosis in limb development?
Pre-programmed cell death that shapes the digits
Where does the development of the gut primarily occur?
Outside the body cavity of the embryo
What are the three sections of the developing gut?
- Foregut
- Midgut
- Hindgut
What is the role of blood flow in the developing baby?
Facilitates low-rate blood flow for lung development and bypasses the liver
What happens to the foramen ovale after birth?
It closes and becomes part of the septum
Fill in the blank: The first part of the skeletal structure forms as a tube called the _______.
[notochord]
True or False: The Ductus Arteriosus closes on the first breath and becomes a suspensory ligament.
True
What is the timeline for the transition from embryo to foetus?
Embryo phase ends at week 8, foetal development begins
What key feature is developed by week 24?
Earliest potential survival if born
What significant development occurs by week 26?
Touch sense well developed and responsive
What happens to the Ductus Venosus after birth?
It closes and becomes a suspensory ligament
What is the significance of the Apical Ectodermal Ridge?
It initiates limb development in the foetus
What alignment occurs in the Inner Cell Mass during the bilaminar and trilaminar disc stages?
The Inner Cell Mass aligns into two layers called the bilaminar disc.
The bilaminar disc consists of the Epiblast facing the amniotic cavity and the hypoblast facing the yolk sac.
What is the normal gestation period?
38 weeks
How is the morula formed?
By mitotic division
What structures arise from the mesodermal layer?
Somites
What determines limb bud development?
AER (Apical Ectodermal Ridge)
What protein defines the digit that develops into the thumb or greater toe?
Sonic Hedgehog protein
From how many precursors does the liver form?
Two precursors
What are the three early structures in brain development?
Prosencephalon, Rhombencephalon, Messencephalon
List the key stages in early embryonic development.
- 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
What is the primitive streak?
A structure that forms on the surface of the Epiblast
What layers are formed during the trilaminar disc stage?
- Ectoderm (replacing Epiblast)
- Endoderm (replacing hypoblast)
- Mesoderm (new layer in between)
What happens to the Foramen Ovale after birth?
Closes on first breath
What does the Ductus Arteriosus become after it closes?
Ligamentum arteriosum
What happens to the Ductus Venosus near the liver after birth?
Closes within the first week and becomes ligamentum venosum
Fill in the blank: The three shunts in fetal circulation include the Foramen Ovale, Ductus Arteriosus, and _______.
Ductus Venosus
