Early Development Flashcards
(21 cards)
What is the embryo dependent on until 4-8 cell stage and why?
Maternal mRNAs and proteins
—> genes of embryo not transcribed
What is the Zona Pellucida?
Hard protein shell inhibiting polyspermy and protects early embryo
What type of cells are in the inner cell mass?
Pluripotent embryonic cells —> contribute to final organism
What type of cells are in the trophoectoderm?
Extra-embryonic cells —> contribute to extraembryonic structures that support development
How is the blastocoel formed?
Trophoblast pumping Na+ ions into cavity
What must happen for the blastocyst to implant?
Needs to escape the zona pellucida
How does the blastocyst escape the zona pellucida?
Enzymatic degradation
Cellular contractions
Trophoblast cells fuse to form…
Syncitiotrophoblast
What do syncititiotrophoblast do?
Destroy local maternal cells in the endometrium and create interface between embryo and maternal blood supply
What to syncitiotrophoblasts secrete?
hCG —> detection of beta subunit in blood or urine is bases of pregnancy testing
What is the bi-laminar embryonic disc made of?
Epiblast
Hypoblast
When the bilaminar disc is formed, what to cavities are there?
Amniotic cavity
Blastocoel
At around 15 days post fertilisation what is the name of the structure that form along the midline of the epiblast?
Primitive streak
What is gastrulation?
Conversion of a bilaminer embryonic disc into a trilaminer
What is the notochord?
Rod-like structure formed of cartilage-like cells
Key organising centre for neurulation and mesoderm development
What are somites?
Blocks of mesoderm
One of each pair either side of the neural tube
What two types of tissue do somites initially form?
Sclerotome —> vertebrate and rib cartilage
Dermomyotome
What does dermomyotome divide into?
Dermatome —> dermis of skin, some fat and connective tissue of neck and trunk
Myotome —> muscle do the embryo
Through what types of folding does the primitive gut arise from?
Ventral folding —> head and tail ends curl together
Lateral folding —> two sides of the embryo roll
The presence of what gene in the Y chromosome directs gonaodal cells to become sertoli cells?
SRY
What does an absence SRY lead to?
And what does it require reinforcement from?
Gonadal cells adopt a granulosa cell fate and ovary development
Requires reinforcement by FOXL2
