Embryology Flashcards
What is a morula and when is it formed?
~6 days
16 undifferentiated cells
Undergoes differentiation so inner cells differ from outside
What are the components of a blastocyst?
- Outer layer trophectoderm
- Inner cell mass
- Fluid filled cavity
Where does the blastocyst hatch from?
Zona Pellucida
day 6
Describe gastrulation.
When does it occur?
Convertion of bilayer (of hypoblast and epiblast cells) into a trilaminar embryo, containing 3 layers of Germ cells (Ectoderm, Mesoderm, Endoderm)
14-18 days post-fertilisation
What does the ectoderm give rise to?
Skin, CNS
What does the mesoderm give rise to?
Muscles, blood, skeleton, heart, kidney
What does the endoderm give rise to?
Gut
Lungs
Liver
What happens immediately before gastrulation is complete?
Neurulation - differentiation of ectoderm (epiblast) to generate CNS under the control of notocord in the mesoderm of the developing embryo
Where is the notocord located during neurulation?
Deep to neural groove
When are the precursors of all internal tissues laid down by?
End of week 4
Closure of neural tube
Heart, Face and arms initiated
When does the formation of the upper limb bud start?
week 5, 32 days
When do the lungs, liver and kidneys start development?
week 8
Where & when does heart tube formation begin?
Week 3
Cardiogenic area inferior to notocord
Horseshoe shaped primary heart field forms from day 16-18 from progenitor heart cells
Outline the stages of formation of heart.
i. Heart tube formation and fusion (week 3)
ii. Cardiac loop formation (week 4)
iii. Septum formation (week 4-5)
Between LA and RA first
iv. Outflow tract formation
When does the heart tube start to pulsate?
Day 32
What are 3 possible congenital heart defects?
Septal defects
Great vessel defects
Tetralogy of Fallot
What is the Tetralogy of Fallot?
RV hypertrophy
Overriding aorta
VSD
Pulmonary stenosis
State the stages of human lung development.
Embryonic Pseudoglandular Canalicular Saccular Alveolar
In which development stage is surfactant produced?
Saccular
What is a possible lung defect?
Respiratory distress syndrome
due to surfactant deficiency
How do you avoid RDS?
Glucocorticoid injection to mother 2-3 days prior to delivery to increase in utero production
