Lecture 9 (Second week of development) Flashcards

1
Q

What are Epiblast cells?

A

Epiblast cells adjacent to the cytotrophoblast are called AMNIOBLASTS and together with the rest of the EPIBLAST line the amniotic cavity

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

Describe the endometrial stroma adjacent to the implantation site

A
  • Oedematous
  • Highly vascular
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the function of the large tortuous glands?

A

Secrete glycogen and mucus

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

What happens on Day 8?

A
  • Blastocyst is partially embedded in the ENDOMETRIAL STROMA
  • Trophoblast has differentiated into two layers in the area over the embryoblast
  • Cells in the CYTOTROPHOBLAST divide and migrate into the SYNCYTIOTROPHOBLAST where they fuse and lose their individual cell membrane
  • Cells of the inner cell mass/embryoblast differentiate into two layers
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the two layers that the cells of the inner cell mass/embryoblast differentiate into in Day 8?

A
  • HYPOBLAST LAYER = a layer of small cuboidal cells adjacent to the blastocyst cavity
  • EPIBLAST LAYER = a layer of high columnar cells adjacent to the amniotic cavity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the two layers the Trophoblast differentiates into in day 8?

A
  • CYTOTROPHOBLAST = inner layer of mononucleated cells
  • SYNCTIOTROPHOBLAST = outer multinucleated zone without distinct cell boundaries
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens on Day 9?

A
  • Blastocyst is more deeply embedded in ENDOMETRIUM and penetration defect is closed by a FIBRIN COAGULUM
  • Vacuoles appear in SYNCYTIUM and fuse forming TROPHOBLASTIC LACUNAE (LACUNAR STAGE)
  • EXOCOELOMIC (HEUSER) MEMBRANE with the HYPOBLAST forms the lining of the EXOCOELOMIC CAVITY called the PRIMITIVE YOLK SAC
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What happens on Day 11 & 12?

A
  • Blastocyst is completely embedded in the endometrial
  • Trophoblastic lacunae are in open connection with MATERNAL SINUSOIDS in the endometrial stroma -> maternal blood enters the lacunar system
  • EXTRAEMBRYONIC MESODERM proliferates and fills the space between the EXOCOELOMIC MEMBRANE and the inner aspect of the trophoblast
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe how the Uteroplacental circulation is established

A

As the trophoblast continues to erode more and more sinusoids -> Maternal blood begins to flow through the trophoblastic system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the Extraembryonic cavity/Chorionic cavity?

A

Large cavities that develop in the extra embryonic mesoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the Decidua reaction that occurs in Day 12

A
  • Cells of the endometrium become POLYHEDRAL and loaded with glycogen and lipids
  • Intercellular spaces are filled with extravasate
  • Tissue is oedematous
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens on Day 13?

A
  • Surface defect in the endometrium has healed
  • Bleeding occurs at the implantation site due to increased blood flow into the lacunar spaces
  • Secondary yolk sac/Definitive yolk sac is formed
  • Connecting stalk from extraembryonic mesoderm for the UMBILICAL CORD
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

In which day do Primary villi appear?

A

Day 13

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the Syncytiotrophoblast responsible for?

A

Hormone production including HUMAN CHORIONIC GONADOTROPIN (hCG) which serves as the basis for pregnancy testing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does the maternal body not reject the embryo despite it being “foreign” since 50% is the father’s genome?

A

There is a shift from cell-mediated immunity to humoral (antibody-mediated) immunity

[this makes the mother at increased risk for certain infections such as influenza]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Where in the uterus can abnormal implantation sometimes occur?

A

Normally the human blastocyst implants along the ANTERIOR or POSTERIOR wall of the uterus but sometimes it implants close to the cervix -> Obstructs cervix -> Later in development the placenta causes severe, even life-threatening bleeding in the second part of pregnancy and during delivery

17
Q

What are Ectopic pregnancies?

A

Pregnancies when implantation takes place outside the uterus

18
Q

Where is the most common site for Ectopic pregnancies?

A

95% if pregnancies occur in the uterine tube and 70% of those in the AMPULLA

19
Q

What happens in ectopic pregnancies?

A

The embryo dies about the SECOND MONTH of gestation and may result in severe haemorrhaging in the mother

20
Q

Where does the blastocyst attach itself to in the abdominal cavity in Ectopic pregnancies?

A
  • Peritoneal lining of the Rectouterine cavity (POUCH OF DOUGLAS)
  • Peritoneal covering of the intestinal tract or to the OMENTUM
21
Q

What is a Hydatidiform mole?

A

The trophoblast develops and forms placental membranes although little or no embryonic tissue is present

[these moles secrete high levels of hCG and may produce benign or malignant tumours]

22
Q

Describe how large doses of progestins and/or oestrogens inhibit implantation

A

Large doses of progestins and/or oestrogens do not prevent fertilisation but prevent implantation of the blastocyst -> Endometrium progresses to the LUTEAL PHASE of the menstrual cycle as the zygote forms, undergoes cleavage and enters the uterus -> Large amount of oestrogen disturbs the normal balance between oestrogen and progesterone necessary for implantation

23
Q

How do Intrauterine devices (IUD) work?

A
  • Interferes with implantation causing a LOCAL INFLAMMATORY RESPONSE
  • Contain progesterone -> interferes with endometrium development prevention implantation
  • Copper wire -> Toxic to sperms and causes uterine endothelial cells to produce substances toxic to sperms