Embryology 2 Flashcards
(10 cards)
Describe process of body folding
End of the third week: the embryo is flat, ovoid, trilaminar disc
Fourth week:
o Embryo growth rapidly, especially in length
o Process of folding to generate body form
o Main force: differential growth of various tissues
o Embryonic disc and amnion high growth rate
o Yolk sac: almost no growth
o Developing notochord; neural tube and somites
stiffen dorsal axis
Briefly state the fate of the mesoderm
- Divided into:
1. Paraxial mesoderm
> Dermis of skin
> Axial skeleton
> Axial and limb muscles
2. Intermediate mesoderm
> Urogenital system
3. Lateral mesoderm
> Divided into somatic (parietal) and splanchnic
(visceral)
> Ventro-lateral body wall (connective tissue, not
muscle)
> Heart and vasculature
> Wall of gut
> Bones of the limbs
Explain formation of paraxial mesoderm
- Also called the somitic mesoderm
- In trunk region:
o Forms somites, which will produce muscle, bone, and dermis
o During somite formation mesenchymal (phenotype) cells will turn unto epithelial (phenotype) cells – MET pathway
Explain formation of intermediate mesoderm
- The urogenital system:
o Kidneys
o Gonads
o Respective duct systems
Gonads
o Develop a bipotential precursor (genital ridge)
o Genital tracts develop from 2 ducts:
Nephric = mesonephric = Wolffian duct
Mullerian duct (develops by invagination)
o In males (XY): SRY on Y drives genital ridge to develop into testis, which produces:
1. AMH = degeneration of Mullerian duct
2. Testosterone = Wolffian duct develops into epididymis, vas deferens, seminar vesicle
o In females (XX): no SRY, genital ridge develops into ovary, therefore:
1. No AMH: Mullerian duct develops into oviduct, uterus, upper part of vagina
2. No testosterone: Wolffian duct disappears
Explain formation of lateral mesoderm
Development of cardiovasculature system
1. Vasculogenesis:
- De novo assembly of blood vessels from
mesodermally derived cells
- Requires both recruitment of mesodermal
progenitors to the endothelial cell lineage and
organisation of their progeny into micro vessels
- Occurs only during embryogenesis
2. Angiogenesis:
- Blood vesses formation from pre-existing
vasculature
- Organisation into a precise spatial pattern within a
particular tissue
- Occurs during embryogenesis and in the adult
Describe process of vasculogenesis
Describe process of Angiogenesis
- Vessel formation from pre-existing blood vessels
- All the cells in the embryo proliferate as it grows bigger in size so if you have an area in which the cells highly proliferate, they use up a lot of oxygen and there’s nothing to provide new oxygen, you get an area that is hypoxic (Low oxygen availability)
- Any cell placed in hypoxic conditions will start generating and secreting a factor called VEGF-A (Vascular endothelial growth factor A) so you get this gradient of VEGF-A
- If the VEGF-A reaches the blood vessel, it activates these endothelial that line the blood vessels, start forming the tip cells that start growing toward that gradient of VEGF-A and the other endothelial cells proliferate formatting stalk cells which results in new blood vessels forming that grows towards the area of hypoxia
- Parasites then recruited to stabilise the vessels
What is tumour angiogenesis
o Tumour cells are highly proliferative
o If the tumour gets to a certain size, it uses all of the oxygen and can’t grow any bigger, but then the tumour secretes VEGF-A which causes blood vessels to grow towards the tumour, allowing it to grow bigger, tumour cells can then migrate to other body cells through blood vessels.
Describe development stages of heart
- Two endocardial tubes
- Fuse into a primitive heart tube
- The primitive heart tube forms 4 regions called the Truncus arteriosis, bulbus cordis, primitive ventricle, primitive atrium
- Rotation of ventricle and bulbus cordis
- Aortic arch arteries and left and right atriums form
Describe development stages of lymphatic system
