Implantation Flashcards
Implantation
outline the process of implantation
think what the blastocyst adheres to for first step
for the second step, think what the trophoblast cells do to become 2 separate groups of cells and name these groups.
- Blastocyst adheres to endometrium
- At same time, trophoblast (non-embryo) cells divide and differentiate into 2 separate groups:
- cytotrophoblast (inner layer of cells in blastocyst
- syncytiotrophoblast (expanding multi-nucleated syncytium)
implantation
What 2 things does the syncytiotrophoblast release?
think enzymes and what they digest in the uterus
think of the name of a hormone which can be detected in pregnancy testing
- Enzymes to digest endometrium of uterine wall
- human chorionic gonadotropin (HCG), which is detected in pregnancy testing
implantation
Give 3 features of the cytotrophoblast
think trophoblast, syncytiotrophoblast and a type of villi
- inner layer of trophoblast
- forms syncytiotrophoblast
- forms chorionic villi
implantation
what hormones does the syncytiptrophoblast produce
- progesterone
- human chorionic gonadotropin (hCG)
- human placental lactogen (HPL)
Prologation of the corpus luteum
outline how hCG prolongs the corpus luteum and luteal phase of the menstrual cycle
for first step, think syncytiotrophoblast producing a hormone, what day it does this and then where it passes into
for second step, think what hCG binds to and on what cells
for third step, explain what hCG binding to this thing maintains and what this causes.
- hCG produced by syncytiotrophoblast approx. day 6-7 and then passes into maternal blood circulation
- hCG binds to LH receptors on luteal cells (in corpus luteum) in ovary
- This maintains progesterone release from corpus luteum; progesterone will actively promote survival of corpus luteum by autocrine stimulation (positive feedback loop)
abnormal implantation sites
What is the most common site of implantation in the female?
think a place on the wall of the uterus
- the upper posterior wall of the body of the uterus
abnormal implantation sites
what are 5 abnormal implantation sites
think tubes, a pouch, intestines, ovaries, cervix opening
- uterine tube
- rectouterine pouch
- intestinal mesenteries
- ovary
- Cervical internal os
week 2: the bilaminar disc
What happens to the embryoblast (inner cell mass of blastocyst) in week 2 and what is these two layers together known as?
for first part think 2 tissue layers
for second part think bi…. disc
Splits into:
- epiblast tissue layer
- hypoblast tissue layer
Known as the Bilaminar disc
Week 2: the bilaminar disc
What does the epiblast layer form?
think embryo and amnioblasts
forms:
- Embryo proper
- Amnioblasts lining the amnion (amniotic sac)
week 2: the bilaminar disc
what does the amniotic cavity do after forming inside epiblast and why is this important?
think what the cavity fills with for first part
for second part think about support the fetus
- fills with amniotic fluid
- important for physically supporting/protecting the embryo/fetus
week 2: the bilaminar disc
What does the hypoblast layer form and why is this important?
think yolk sac for first part
think nutrition before a certain point for second part
- Primary yolk sac (exocoelomic cavity)
- Important as an initial source of nutrition for embryo before placenta is functional
The embryo at the start of week 3
What is the embryo surrounded by at the start of week 3, what is the primary yolk sac replaced by and what are 3 other features of the embryo at the start of week 3?
think
- surrounded by chorionic cavity and embryonic tissues of the developing placenta
- primary YS is replaced by secondary YS
3 features are:
- connecting stalk marks where umbilical cord will be in future
- 2 distinct epiblast and hypoblast cell layers
- epiblast layer undergoes gastrulation
Gastrulation
In Gastrulation, what is the first stage and why is this important? (hint: there are 2 parts to the first first stage)?
- primitive streak appears in midline at caudal (tail) end of epiblast
- Epiblast cells then migrate towards primitive streak
- important of establishing left and right sides of the embryo
Gastrulation: formation of the primary germ layers
Where do epiblast cells migrate towards and what do they undergo?
- migrate toward primitve streak
- undergo epithelial-to-mesenchymal transition
Gastrulation: formation of the primary germ layers
what do the first cells through the primitive streak do and what do they form
think hypoblast and endoderm
displace hypoblast and form endoderm
