Embryology

Question 1

oocyte

Answer 1

femal gamete also refered to as egg or ovum

Question 2

sperm

Answer 2

male gamete

Question 3

zygote

Answer 3

single cell resulting from fusion of oocyte and sperm, immediately begins cleavage

Question 4

blastomere

Answer 4

early embryonic cells

Question 5

morula

Answer 5

a soilid mass of blastomeres, still surrounded by ZP

Question 6

blastocyst

Answer 6

around day 4-5
morula has developed a fluid filled cavity within, inner cell mass develops into embryo, outer cells develop into trophoblast and eventually form placenta, cells in the ICM (inner cell mass) differentiate into hypoblast and epiblast which establishes dorso-ventral axis.

Blastocyst hatches out of ZP so it can implant

Question 7

embryo

Answer 7

developing human during embryonic stages (up to end of 8th week)

Question 8

fetus

Answer 8

developing human after 9th week to full gestation

Question 9

teratogen

Answer 9

agent that harms development of embryo or fetus e.g. prescription, recreational drugs, alcohol, heavy metals, ionising radiation, infection

Question 10

congenital disease

Answer 10

to be born with at birth

Question 11

organogenesis

Answer 11

creation of organs- occurs within week 3-8

Question 12

Implantation: when? stages?

Answer 12

Occurs on day 6

-apposition- blastocysts move to endometrium
- adhesion- blastocysts anchors to endometrium
- invasion- blastocyst burrows (controlled by cell signalling) into uterine endometrium

Question 13

Layers of the inner cell mass?

Answer 13

bilaminar disc (epiblast and hypoblast) and an amniotic cavity develops between them forming the yolk sac

Question 14

gastrulation: week 3

Answer 14

• bilaminar disc becomes a trilaminar disc, three germ layers that will create all tissues of embryo
• a groove called the primative streak , epiblast cells invaginate through it, settle between epiblast and hypoblast forming a third layer- mesoderm
• body axes continued to develop- head,tail, front,back, left,right

Question 15

Neurelation- week 4

Answer 15

starts with appearnace of neural plate- thickening of surface ectoderm, nueral plate is inducted by notochord, plate bends to form a groove, cells at top of fold are nueral crest cells which fuse and detaches from surface ectoderm to form neural tube, cranial ends expands but caudal end ramains tubular

Question 16

fertilisation: day 1

Answer 16

• moveemnt of sperm to fallopian tube by uterine contraction
• capacitation- modificatiion of head of surface of egg so its can penetrate egg
• sperm penetrates corona radiata and zona pellucida(ZP)
• ZP changes so no more sperm can enter oocyte- prevents polyspermy