L8 early emb dev

Question 1

LO2: disc changes as fert ovum (zyg) trav down fallop tubes to uterus.
LO3: desc mean of zyg, cleavage, zona pellucida, morula, ovary, fallop tube, uterus.

Answer 1

-fert: oocyte rel from ovary. trav along fallop. fert by sperm in ampulla=zyg. ideal impl post uterine wall, high up, gl epith. oocyte viab 1d, sperm 3d.
WK1:
-day 2- cleavage begin 30hr post fert=2 ident blastomeres. zona pellucida of zyg surrs= gp shell, inexpansib, excls sperm.
-day 3- blastomeres contin mitosis=morula. each cell ident and TOTIPOTENT- capac to become any cell type with sig.
-assisted repro techs- oocytes fert in vitro and div 4/8 cell. morula into uterus. PGD=pre impl genet diag- cell safely rem from morula and tested for ser herit conds prior to transf.

Question 2

LO4: disc format blastocyst and init stages impl.
LO5: disc mean of blastoc, trophob, inn cell mass, impl, cytotrophob, syncitiotrophob.

Answer 2

-day 4- compaction- format 1st cav. blastocyst. morula cells sec fluid, collects and cells coalesce=cav. cells pushed to 1 side= outer shell. diff event!
inner cell mass= embryob go on to be emb.
outer cell mass lines blastocyst cav=trophoblast, goes on to be supp tiss eg mems and placenta.
zona pellucida restrics size.
-after compaction blastocyst cells pluripotent- capac to become 1 of many cell types, multilin poten, more restric.
-day 5- hatching- from zona. free to enlarge and interac uterine surf via chem interac outer cell mass.
-day6/7- impl begins- conceptus now 107 cells. 8 will=emb. 99 supp.
WK2: week of 2’s
- diff- 2 distinct cell lays emerge from:
outer cell mass- syncitiotrophob- multinuc lay good for transp. cytotrophob- seed lay for multinuc sheet, merges, allow syncit incr sa optims transp.
inner mass- forms 2 lay bilaminar disc. epiblast and hypoblast.

Question 3

LO6: desc format emb disc in inner cell mass and init diff within it.

Answer 3

-by end wk2- conceptus implanted. emb and its 2 cavs (amniot and YS) will be susp by connec stalk within a supp sac-chorionic cav.
-day 8- amniot cav above bilam disc- tiss fluid collec, pushes inner mass away from outer, cav where emb grows. bilam disc= epi and hypoblast. cytotrophob outer lining. synciotiotrophob min barr to diffus and AT.
-day 9-10- impl cpmpl. invas, some bleed where broken epith.
-impl-interstitial- conceptus into stroma. acc to gls. ests mat blood flow within placenta. histiotrophic diffus to heamotrophic. gas, nutr, waste exch.
-impl defec- IUGR intrauterine growth restric. pre eclampsia. both rel to impl. ectopic preg and placenta previa rel to begin dev.
inapp site: ectopic- impl outs uterine bod, eg fallop, prob cilia/block, invade large vess, peritoneal or ovarian, haemorr dang. placenta praevia- impl lower uterine segm, placenta x exit, can haemorr, can req c sec.
- emb pole- rap dev of synciot, form laculnae. abembryonic pole- primit YS formed- mem contacts cytotrophob. hypob cov mem.
-day 11- primit YS mem away from cytot by acell extraemb retic. sac lining cells sec. cont gp and prot. retic later forms extraemb mesod by cell mig.
-day 12- mat sinusoids invad by syncitiot=lacunae contin with sinusoids, capill fill mat blood. uteroplacental circ begins. uterine stroma preps to supp emb.
-day13- form sec YS/definit YS=GI. pinches of prim. prim chorionic villi.
-day 14- spaces in extraemb mesod merge=chrionic cav. emb and its cavs susp by connec stalks-col of mesod, fut umb cord. bleed now conf with menstr. v vasc and invas.

Question 4

LO1: defin per-emb, emb, fetal periods hum dev.

Answer 4

• pre emb wk1-2/3 post fert. emb wk2/3- 8/9. fetal wk8/9 -38: growth emb strucs and organs, func and physiol of mat sys.
• pre emb: cleavage= 1st mitot div, after format zyg-forms morula. compaction (assoc with cavitation)=blasotcyst. impl begin. blastoc into endomet.