6M: Bilaminar Germ Disc Flashcards

1
Q

Fertilization

A
  • oocyte (plus corona radiata cells) is ovulated from the ovary and swept into the uterine tube
  • spermatozoa (sperm) must undergo:
    1. capacitation
    2. acrosome reaction
  • sperm can be viable in female reproductive tract for several days
  • fertilization occurs 12-24 hours following ovulation (likely occuring in the ampulla)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

define:
a. capacitation
b. acrosome reaction

A

a. biochemical changes to sperm in the uterine tube (removal of glycoprotein coat and seminal plasma proteins & exposure of receptors on sperm acrosome cap)
- allows sperm to penetrate corona cells
b. leads to the penetration of the Zona Pellucida
- sperm bind to the ZP through ZP3 (ligand for receptor on sperm). That binding induces enzyme release from sperm acrosomal cap.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

define:
a. cortical reaction
b. zona reaction

A

a. contact leads to release of lysosomal enzyme from the cortical granules in the oocyte plasma membrane
b. ZP properties are altered to prevent polyspermy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Development of zygote (up to 16 cell stage)

A

2 cell stage: 30 hpf
4 cell stage: 40 hpf
16 cell stage: 3 days pf (morula)
- ZP persists until early blastocyst stage (about 5 days pf)
- at 8-cell stage, compaction occurs (segregation of inner and outer cells). loss of totipotency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Formation at 3 days

A
  • morula is formed by 3 days with inner and outer cell masses
    inner: embryo proper, amnion, yolk sac
    outer: trophoblast
  • enters uterine cavity at about 4 days
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Formation at 4.5-6 days

A

day 4.5-5: fluid penetration into intercellular spaces of the inner cell mass results in blastocoele cavity (creating the blastocyst)
day 5: blastocyst “hatches” from the ZP. Can’t insert into endometrium without hatching.
day 6: Implantation occurs by cell-cell and cell-ECM interactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Formation at day 7.5

A

both trophoblast and embryoblast differentiate into 2 layers
Embryoblast: 1. epiblast (with amnioblasts) 2. hypoblast
Trophoblast: 1. syncytiotrophblast: outer multinucleated cell layer. produces hCG which maintains CL 2. cytotrophoblast: inner mononucleated layer that divides and migrates into syncytiotrophoblast and fuse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Formation at day 9

A

Deeper Embedment

  • lacunae formation
  • exocoelomic cavity formation (primitive yolk sac)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Formation at day 12

A
  • Syncytiotrophoblast erode maternal capillaries
  • trophoblast lacunae connect to maternal sinusoids
  • blastocyst starts to protrude into uterus lumen
  • extraembryonic/chorionic cavity forms
  • exocoelomic membrane splits to become extraembryonic splanchnopleuric membrane and somatopleuric membrane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Formation at day 13

A
  • secondary yolk sac forms
    • exocoelomic cysts pinch off
  • primary villi form (initial stages of uteroplacental circulation)
    • this can lead to a little bit of bleeding
    • cytotrophoblast cells surrounded by
      syncytiotrophoblast
  • connecting stalk forms (later to become the umbilical cord)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly