2nd week of development: Bilaminar germ disc

Question 1

summarize day 8

Answer 1

• blastocyts is partially embedded in the endometrium of the uterus
• trophoblast differentiate into 2 layers
  MONONUCLEATED CYTOTROPHOBLAST
  MULTINUCLEATED SYNCTIOTROPHOBLAST
  -mitotic figures present in cytotrophoblast
  -cytotrophoblast differentiate migrate into synctiotrophoblast and fuse lose their membrane
• epiblast lines amniotic cavity
  -hypoblast lines adjacent to blastocete
• a flat disc is made
  -amniotic cavity is made
  -epiblast and adjacent cytotrophoblast form amnioblast and lines the amniotic cavity
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Question 2

summarize day 9

Answer 2

• blastocyst deeply embedded
• penetration defect is fixed by fibrin coagulum
• extensive developmental changes in trophoblast
• vacoule appears at the embryonic end in the synctiotrophoblast, vacoules fuse to form lacunae THIS IS KNOWN AS LACUNAR STAGE
• flattened cells originating from hypoblast form a thin membrane exocoelom membrane which lines the cytotrophoblast
• this membrane together with hypoblast makes the lining of primary yolk sac or exocoelomic cavity

Question 3

11-12 days of development

Answer 3

• the blastocyst is fully embedded
• lacunar space in syncytium form intercommunicating network
• blastocyst from a protrusion in the lumen of uterus
• aembryonic pole you can still see cytotrophoblast

Question 4

how maternal blood enters into lacunar system?

Answer 4

the syncytiotrophoblast erodes the endothelial lining of maternal capillaries, these capillaries are dilated and congested known as sinusoids, the lacunars of syncytial gets continuous with the sinusoids and thats how the maternal blood enters the lacunar system

Question 5

uteroplacental circulation

Answer 5

as more trophoblast erodes sinusoids more maternal blood passes through the trophoblastic layer and that’s how uteroplacental circulation is achieved

Question 6

extraembryonic mesoderm

Answer 6

a new population of cells is made in the inner surafce of cytotrophoblast and outer surface of exocoelomic cavity which are derived from primary yolk sac cells and form a lose connective tissue known as extraembryonic mesoderm

Question 7

extraembryonic mesoderm fills

Answer 7

internally the amnion and extracoelomic cavity and externally the trophoblast

Question 8

extraembryonic cavity

Answer 8

cavities are made within the extraembryonic mesoderm which eventually merges to form extraembryonic cavity or chronic cavity

Question 9

extraembryonic mesoderm lining amnion and cytotrophoblast is

Answer 9

extraembryonic somatic mesoderm

Question 10

extraembryonic mesoderm lining yolk sac is called

Answer 10

extraembryonic splanchnic mesoderm

Question 11

decidua reaction

Answer 11

the endometrium becomes swollen because of the accumulation of fluid and the tissue fluid flows out of the vessels in the endometrium which is initially confined to the site of plantation but soon occur throughout

Question 12

13 DAY - inaccuracy in determining the delivery date is causes by

Answer 12

bleeding that occurs at the implantation site at the 28th day of cycle which is confused with the menstrual bleeding and rhats how inaccuracy occurs

Question 13

primary villi and what day

Answer 13

13 day and the cytotrophoblast proliferate into the synctiotrophoblast and form columnar cells which are surrounded by syncytium
the columnar cells and the surrounding syncytium is called as primary villi

Question 14

formation of secondary yolk sac

Answer 14

hypoblast produces additional cells that migrate inside the exocoelomic cavity and form another cavity which is smaller than the primary yolk sac called as the secondary yolk sac.

Question 15

exocoelomic cyst

Answer 15

during the formation of secondary yolk sac, the exocoelomic cavity pinches off and it is seens as exocoelomic cyst in the exocoelomic cavity or chorionic cavity

Question 16

chorionic cavity and chorionic plate

Answer 16

the extraembryonic cavity expands and form a large cavity known as chorionic cavity
and the extraembryonic mesoderm lining the cytotrophoblast are called chorionic plate