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Flashcards in L12 Early Emb Dev 2 Deck (6)
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Desc mig mesod through primit streak.

Est 3 germ lays and so ori all TOB. Trilam emb disc. Set axis obs in ad-ant/post, dorsal/ventral, L/R.
-begins- primit streak app=driver and coord. Primit node with primit pit. Once est can't study emb.
Cell rearr- mig and diff tight contr. Invag-interdigit other lays. End wk 2 epiblast uniform disc. Wk 3 dorsal surf node at cranial end, pit at sentre node, primit streak to edge. Streak= narr groove bulge edges. Defines cranial end.
-3 germ lays est- primit streak regresses. Dev proc cranial to caudal- rule for dev, head end more dev til compl. Streak regress this direc.
-Mig and invag- epiblast cells move and dig and diff. Pile either side primit streak. Penet through epiblast lay and spread through emb disc. All tiss traced to epib. Hypog not int, has done its job lining YS.
-displ of hypob and creation of 3rd lay- as more cells mig through streak spread LT and cephalon tow head. Mesod spreads out btw endo/ectod- 2 exceps- ectod touch endod 2 locates- fut mouth and anus.


LO3: est of bod plan, axes set.

-notochord- cranial part primit node. Ultim fate of invag epib dep on where in streak/node they invag. Primit node orchestrates. Notochord defines phylum Chordata. Basis for axial skel form. Drives format of CNS (neurulat). Prenotochordal cells of epib mig through cranial part of primit pit. Form sol rod of cells running in midline with imp sig role. NOT spread and diff like other epib cells. Notochord regresses- vesting remn in ad=nuc purposes of inverteb discs- herniates in slipped.
-axes- hum clearly def regs. Medico anat termin relies on univ use anat posit. Axes set in early emb. Sup/inf, ant/post, R/L, dorsal/vent.
-streak, node and axes- primit streak apps 1 end bilam disc- defines front and back ie ant (rostral) and post (caudal). Molec sigs from primit node ensure corr dorsal/vent and L/R dev. Symm limbs asymm visc.
-gastrulat summ- wk 3 start emb period. Bilam to trilam disc. Primit streak in caudal epib=mig and invag and diff epib cells. Ensure corr placem of precurs tiss= subseq morphogen- build sys and tiss. Differentiated= committ to 1 fate and func, unless pathol.


LO4: most imp ectod, mesod and endod derivs.

-ECTOD- outs. Organs and skin maint contact outside. Surf ectod- skin and skin derivs eg hair, nails, lens and cornea, linings mouth and anus. Neural ectod- brain, SC, periph nerves, retina, iris.
MESOD- big var in tiss. Supp tiss- smooth, striated and cardiac musc. CT, bone, cartil. Vasc sys incl heart, BV, blood. Urinary sys.
ENDOD- int strucs- epith lining GIT. Parenchyma of glandsasoc dig eg liver and panc. Other gut derivs eg lungs, RT.
-L/R asymm. Bef gastrulat emb disc bilat symm. Neonate L/R diffs eg thoracic and abdo viscera. Beat action of ciliated cells at node=L flow of sig molecs= side specif sig cases init. Absent L=R sidedness sig.
Situs inversis- mirr I'm all visc, comm due to immort cilia, us not more assoc. probs if mixed mirr and norm. Can have other conseqs of immort cilia.
-emb disc end wk3- cephalon audial dev-gastrulat not compl in caudal reg til wk4. Axes and midline are est- primit node maj role. 3 germ lays in pl ant.

-extra emb ectod/mesod/endod outs emb in fatal mems (amnion, chorion, YS). Mesenchyme and its var sub divs in primit streak stage emb.
Cardiogenic area in front of pre chordal plate fur mouth. Notocord through midline. Then primit pit and node and groove to edge at cloacal mem fit anus.


MZ twin

-MZ= 1 fert oocyte forms 2 identic infant. DZ= 2 fert oocyte.
-emb split after 1st cleavage. V early so 22 Sep envs, Sep placenta and mems.
-ICM duplic dur blastocyst format. Sep primit streak and gastrulat. 2 emb share placenta, can=probs.
-split can occ valet-with duplic of primit streak. In 1 ICM, =2 gastrulat events. 2 emb share placenta and same amniot sac. Somet Sep in mol=conjug.



Proc through which norm emb dev disrup. Emb wk 3-8 most sensit to insult. Each organs sys partic sensit window dep of when most dev occs. NS vuln throughout. Pre emb us=loss preg so not suscep.
-teratogenic agents- lot chem and infec agents=dev defec.
Thalia. congenital rubella synd-eas, neck, brain. Alc- small X placenta, even low conc aff CNS dev. Cert therap drugs eg anticonvulsant, warfarin etc X placenta. Ionising rad.


LO1: underst proc of est 3 emb germ lays that form TOB.
Define: bilam disc, germ lay, ectod, endod, dorsal and vent surfs, mesod, primit streak, gastrulat, trilam emb disc.

-end wk2- fert, cleav= blastocyst. Impl and diff=bilam, cytot cellul, syncitioblast.
Extra emb sp- primit YS and amniot 2 cavs. Emb susp by connec stalk within supp chorionic cav.
-emb period wk 3-8: short but critic. Greatest change. All maj strucs (tiss) and sys formed. Most dang for dev child-congenital birth defec.
-week of 3's- 3 cavs-amniot, YS, chronic compl by end wk 2. 3 germ lays est from epiblast- rudim lins to all others.