Pre-implantation Embryo/ Development Implantation Flashcards
What sperm protein triggers oocyte activation
Phospholipase C zeta
Describe the role of Ca in fertilisation
Oocyte activation activates the egg to release calcium from internal stores and this rise in Ca facilitates fertilisation
Prior to day 4-8 cell stage the development control depends on
Maternally derived stores of RNA laid down during oogenesis
What is the genetic control occurs in a 4-8 cell embryo
Activation of the embryonic genome and start of embryonic transcription
Define totipotent in regards to blastomeres
The nuclei of individual blastomeres are each capable of forming an entire foetus
How many cells are in a morula
Around 16
What forms the placenta
Trophectoderm
How does metabolic and biosynthetic activity differ in early cleavage vs blastocyst
Low in early cleavage
High in blastocyst
Where does the embryo get nutrients from
Cumulus cells
Fallopian tube secretions - Ca, Na
Uterine secretions - Fe, glucose
What factor enhances embryo-endo interaction
Leukaemia inhibitory factor
Give 3 ways the uterus changes for implantation.
Endometrial cell changes to he,o absorption of uterine fluid - bring blastocyst nearer to the endometrium and immobilises it
Changes in thickness of endometrium and its blood supply development
Formation of decidua
Which substances mediate the cross talk between endometrium and the developing embryo
Sex hormones
Cell adhesion molecules
Proteases
Cytokines, growth factor
Describe the apposition stage of embryo implantation
Unstable adhesion of the blastocyst to the uterine lining
Synchronisation of embryo and endometrium
Hatched blastocysts predicated via embryonic pole - always attaches at area above inner cell mass
What promotes placental formation
Decidual reaction
Describe What differentiates into decidual cells
Stromal cells adjacent to the blastocyst differentiate into metabolically active decidual cells under the influence of progesterone
What is the role of progesterone
Stimulates stromal oedema and secretory activity
Modifies distribution of oestrogen receptors
Increases volume of blood vessels
Stabilises lysosomes
What prevents maternal recognition of the embryo ad a foreign body
Leukocytes in the endometrial stroma secrete interleukin-2 during the early stages of implantation
Where are a) human chorionic gonadotropin- alpha and b) hCG-b synthesised
A) cytotrophoblast cells
B) syncytiotrophoblast cells of placenta
Rising levels of……… from day 7-8 signify onset of implantation
hCG-b levels
What are some roles of hCG
ensures the corpus luteum continues to produce progesterone throughout the first trimester of pregnancy - prevents menstruation
Interact with endometrium via specific receptors
Immunosuppressive- highly negative charge which may repel immune cells of mother and protect foetus
