Physiology of Pregnancy and Lactation Flashcards
What is implantation?
The fertilised ovum progressively divides and differentiates into a blastocyst as it moves from the site of fertilisation in the upper oviduct to the site of implantation in the uterus
What is a blastocyst?
a cluster of dividing cells made by a fertilized egg. It’s the early stage of an embryo.
Days 3-5 of implantation?
transport of the blastocyst into the uterus
Days 5-8 of implantation?
blastocyst attaches to the lining of the uterus
What do the inner cells of the blastocyst develop into?
The embryo
What do the outer cells of the blastocyst develop into?
Placenta
When the free-floating blastocyst adheres to the endometrial lining, cords of trophoblastic cells begin to penetrate the endometrium. True/false?
True
How does the blastocyst insert itself into the endometrial lining?
- Advancing cords of trophoblastic cells tunnel deeper into endometrium, carving out a hole for the blastocyst
- The boundaries between cells in the advancing trophoblastic tissue disintegrate
How does the placenta maintain pregnancy?
produces several hormones I.e. progesterone
What are trophoblasts (trophoblastic cells)?
cells forming the outer layer of a blastocyst, which provides nutrients to the embryo, and develops into a large part of the placenta
What is decidual tissue and it’s role?
Decidual tissue (decidua) has been known as maternal uterine tissue, which plays essential roles in protecting the embryo from being attacked by maternal immune cells and provides nutritional support for the developing embryo prior to placenta formation.
What is the placenta derived from?
trophoblast and decidual tissue
Trophoblast cells (chorion) differentiate into multinucleate cells
(syncytiotrophoblasts) which invade decidua and break down
capillaries to form cavities filled with maternal blood. True/false?
True
How is “placental villi” formed?
Developing embryo sends capillaries into the syncytiotrophoblast projections
What does each villus of the placenta contain?
contains fetal capillaries separated from maternal blood by a thin layer of tissue - no direct contact between fetal & maternal blood
What does the villi of the placenta aim to do?
Achieve a 2 way exchange of respiratory gases, nutrients, metabolites etc between mother and foetus, largely down diffusion gradient
Placenta (and foetal heart) functional by what week of pregnancy?
5th week of pregnancy
What signals the corpus luteum to continue secreting progesterone?
HCG