Development Flashcards
What happens in the first Week of development?
Fertilisation, zygote cleavage, blastocyst formation, implantation
What is fertilisation?
The merging of genetic material (from egg/sperm) into a single diploid nucleus
What is (zygote) cleavage?
The mitotic cell divisions (occurring in the zygote) that initially increase cell number but not size of cell mass
How long after fertilisation does zygote cleavage begin?
24 hours
What are the smaller cells produced by cleavage called?
Blastomeres
What is a morula?
A solid sphere of cells, produced by rapid zygote cleavage
What is uterine milk?
A secretion which provides nourishment for the developing morula (during blastocyst formation)
How is the blastocyst cavity formed?
The fluid (uterine milk+nutrients from cytoplasm) enters the morula and collects between the blastomeres before reorganising them into the cavity.
What two distinct cell populations arise during formation of the blastocyst cavity?
Embryoblast and trophoblast
What does the embryoblast do?
Eventually develops into embryo and some extraembryonic membranes
What does the trophoblast do?
Is the sphere-like wall of blastocyst. Will develop into the outer chorionic sac (placenta).
What is implantation?
When the blastocyst loosely attaches to the endometrium
What is the decidua?
Functional layer of the endometrium
Name layers of the decidua
Decidua basalis, decidua capsularsis, decidua parietalis
What happens in the 2nd Week of development?
Development of the trophoblasts, bilaminar embryonic disc, amnion, yolk sac, sinusoids, extraembryonic coelom and chorion
