embryology Flashcards
what is gametogenesis?
formation of gametes
what is a gamete
haploid cells
23 chromosomes
what does gametogenesis involve
mitosis then meiosis
what is Spermatogenesis
formation of male gametes
how long does Spermatogenesis take
64 days
what is oogenesis
formation of female gametes
when is oogenesis halted and restarted
halted at prophase
meiosis restarts at puberty
what is nondisjunction
failure of sister chromatids to separate during cell division
what is trisomy 21
down syndrome
what can nondisjunction in meiosis cause
trisomy
what is fertilisation
fusion of sperm and oocyte to form a zygote
what is a zygote
diploid single cell that will develop into an embryo
what is cleavage
mitotic cell division of the zygote
what is formed during cleavage
morula
why is there no increase in size during cleavage
because of the presence of the zona pellucida
what is gastrulation?
formation of the three primary germ layers
what are the three primary germ layers
ectoderm
mesoderm
endoderm
what is established during gastrulation
body axes
where does fertilisation occur
ampulla
what does sperm bind to in fertilisation
zona pellucida
what is released by the head of sperm when attached to the ZP
acrosomal enzymes
what happens to the oocyte once the membranes of the sperm and the oocyte have fused
completes meiosis 2
releases cortical granules
what occurs when the morula undergoes compaction
cells become closely associated with each other by forming cell junctions to maximise space
what is formed when fluid enters through the zona pellucida
the blastocyst cavity
what is the outer layer of a blastocyst called
trophoblast layer
what do cells form when they group together in a blastocyst
inner cell mass
why does the blastocyst break free of the ZP
it is restrictive, and to implant
when does implantation usually occur
day 6
when is a bilaminar embryo formed
day 8
what are the two layers that the trophoblast splits into
cytotrophoblast
syncytiotrophoblast
what is the syncytiotrophoblast
outer multinucleate layer
what is the cytotrophoblast
inner mononucleate layer
what two layers does the inner cell mass split into
epiblast
hypoblast
what is the small cavity in the epiblast known as
the amniotic cavity
what layer penetrates the uterine lining
syncytiotrophoblast
how is the heusers membrane formed and when
day 9
cells from the hypoblast cover the cytotrophoblast
what does heusers membrane line
the primitive yolk sac
what forms in the synctiotrophoblast
trophoblastic lacunae
what is ectopic pregnancy
when implamtation occurs outwith the uterus
when does the primitive streak form
day 15
where does the primitive streak appear
the midline of the epiblast layer
what is at the cranial end of the primitive streak
primitive pit/node
when does gastrulation occur
day 16
how are the 3 primary germ, layers formed?
epibklast cells move through the primitive streak
fate of the ectoderm?
skin
nervous system
fate of the endoderm?
lining of gut tubes, respiratory tract, bladder, urethra
what are the three regions of the mesoderm
paraxial
intermediate
lateral plate
what two parts make up the lateral plate mesoderm
somatic and visceral
fate of the paraxial mesoderm
axial skeleton
skeletal muscle
dermis of the back
fate of the intermediate mesoderm
urogenital systems
somatic lateral plate mesoderms fate?
dermis
lining of body wall
limbs
visceral lateral plate mesoderms fate?
CVS
smooth muscle
mesothelium
