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115 Cards in this Set

  • Front
  • Back

Syncytiotrophoblast

layer which penetrates endometrium, outermost layer of embryo, secretes hCG

Cytotrophoblast

next / middle layer

Extraembryonic mesoderm

lines the blastocyst cavity, between primary yolk sac and cytotrophoblast, forms at 10-11 days

Epiblast

will be the dorsal surface of embryo

Hypoblast

will be the ventral surface of the embryo
Heuser’s membrane
cells of the hypoblast which migrate to line the blastocyst cavity

Trophoblastic lacuna

gaps in the syncytiotrophoblast

Coagulation plug

heals the gap where the embryo entered the endometrium, full implantation 9 days

Primary yolk sac

at 10 days, this is what used to be the blastocyst cavity, now lined by hypoblast cells
Chorionic cavity
12/13 days, opens up within the extraembryonic mesoderm

Secondary yolk sac

aka definitive yolk sac, forms at 12/13 days adjacent to primary, pushes secondary away
Connecting stalk
suspends embryo in chorionic cavity (14/ 15 days)
Fimbriae
fingers on ampulla neck, sweep oocyte into infundibulum

Ampulla

first part of oviduct
Infundibulum
funnel of oviduct
Foramen ovale
hole in the heart, gap between atria
Caudal
tail end

Sagittal section

divides left and right sides of the body

Transverse section

cut through the tummy, divide top and bottom

Coronal section

think of a halo, divide front and back
Menstrual age
clinicians and obstetricians, dates from last period – 3 trimesters

Fertilisation age

embryologists, 14 days later
Embryologists: pregnancy phase 1
early / pre-embryonic: weeks 1-2 (from fertilisation)
Embryologists: pregnancy phase 2
embryonic / organogenesis: weeks 3-8
Horseshoe kidney
1/500
Accessory renal artery
formed as kidneys move up pelvis
Embryologists: pregnancy phase 3
foetal: 9 weeks - birth
Congenital malformations at birth
2-3%
Congenital malformations by age 5
2-3% in addition to birth
Infant deaths due to birth defects
21%
Down’s Syndrome
trisomy 21

Zona reaction

enzyme secreted by zona pellucida, prevent further sperm

Corona radiate
‘halo’ of cells surrounding ovum
Acrosome reaction
sperm secrete enzyme to break down zona
Morula
16-32 cewlls
Embryoblast
inner cell mass, embryo proper
Trophoblast
outer cell mass
Blastocyst
next stage after morula, 5 days, fluid filled cavity
Environmental factors which cause birth defects
teratogens
Teratogens: TORCH
toxoplasmosis, other (hep B, syphilis), rubella, cytomegalovirus, herpes (all can cross placenta, cause defects)
Toxoplasmosis
hydro/microcephaly, microphthalmia: undercooked meat / cat poo, 1/3 popn affected
Rubella
microcephaly, heart, cataracts, hearing
Cytomegalovirus
microcephaly, microphthalmia, cerebral calc, growth retard
Capacitation
happens to sperm in female reproductive tract
Amniotic cavity
8 days, small fluid filled cavity in epiblast
hCG
maintains endometrium, help immunotolerance
abnormal implantation
2% pregnancies, 9% maternal deaths
bleeding in late pregnancy
placenta previa
calcified dead abdominal pregnancy
lithopaedion
empty egg fertilised
hydatidiform mole
gastrulation
bilaminar -> trilaminar, starts week 3
primitive streak
pit, node, groove – appears in week 3 (15/16 days), start of gastrulation
oropharyngeal membrane
mouth area, cranial end of embryo
cloacal membrane
where gut and urinary system will develop
situs inversus
R to L symmetry of organs reversed
Kartagener syndrome
20% of situs inversus patients, disease of cilia
Dextrocardia
partial situs inversus, isolated R H heart
definitive endoderm
replaces all hypoblast, forms from epiblast cells multiplying and moving in via primitive streak, 14-15 days
ectoderm
was the epiblast, the part left after gastrulation
ectoderm
NERVES EYES AND SKIN (epidermis only)
mesoderm
formed from epiblast cells, enter via primitive streak, 16 days
mesoderm
muscle, blood vessels, heart, adrenal cortex, kidneys, ureters, gonads, cartilage, bones BONES MUSCLES HEART KIDNEYS REPRODUCTIVE
endoderm
glands, trachea, lungs, GI, bladder, liver, pancreas – GUTS
paraxial mesoderm
near midline: SKELETON, MUSCLES, DERMIS
somites
day 20, paraxial mesoderm subdivisions, starts at cranial end, 3-4 pairs per day -> 42-44 pairs formed (good for age estimation)
intermediate mesoderm
gonads, reproductive tracts, kidneys
lateral plate mesoderm
outermost, lining body cavities
primitive streak regression
towards caudal region, day 17, notochordal process laid down
sirenomelia
insufficient mesoderm formed to make bones and muscles of legs, also urogenital
sacroccygeal teratoma (SCT)
too much mesoderm laid down in gastrulation, because remnants of primitive streak remains, epiblast cells keep moving in, 80% of cases are female
notochordal process
hollow tube formed from primitive node
notochord
days 16-22, notochordal process fuses with endoderm, separates, becomes solid not hollow
notochordal plate
endoderm + notochordal process (days 16-22)
neurulation is started by
signals from the notochord
neurulation
‘zipping’ up of embryo along neural folds; starts in cervical region, head first, then tail
induction
initiating signals from the notochord to form neural plate
abnormal induction of sclerotomes
spina bifida, vertebrae not correctly formed
spina bifida occulta
hairy dimpled skin on back, hidden S B
meningocele
sac of spinal fluid protrudes out of back
myelomeningocele
sac of fluid and cord / nerves protrude, not covered by skin, damage during birth
bone and cartilage differentiation of somites
sclerotome
skeletal muscle differentiation of somites
myotome
dermis differentiation of somites
dermatome
induces differentiation of somites
induced by notochord
surrounds notochord and neural tube, will form verterbrae
sclerotome
nucleus pulposus
could be remnants of notochord, inside vertebrae
parietal mesoderm layer
nearest dorsal surface, surrounds amnion (top on most diagrams)
visceral mesoderm layer
nearest endoderm, ventral surface (lower on most diagrams)
intra-embryonic body cavity
forms at neurulation, as parietal mesoderm and amnion fold around neural plate
neuroectoderm
thickening of ectoderm, gives rise to neural plate
neural folds
lateral edges of neural plate elevate to form these
anterior neuropore
the ‘head’ end (cranial) of embryo, fuses on day 25, will form brain
pericardial bulge
at cranial end
posterior neuropore
caudal end, fuses on day 28, will form spinal cord
anencephaly
forebrain not formed, brainstem is present, usually shortlived (a few hours) or stillborn ☹ anterior neuropore not fused
rachischisis
failure of posterior neuropore to fuse, spinal cord not formed properly, paralysis
spina bifida
sclerotome is not inducted properly by notochord, spinal cord unprotected or even exposed
folic acid
reduces NTDs by 50-70%
NTD
neural tube defect; spina bifida, anencephaly, rachischisis, 1 in 1000 births affected in UK
Neural crest cells
top edges of neural folds, these separate off, migrate and form different structures
4th germ layer
neural crest cells
cranial neural crest derivatives
eye connective tissue; dermis of face and neck, skull dermal bones, cranial ganglia
spinal neural crest derivatives
adrenal medulla, ganglia
neurofibromatosis
NF1 gene mutation, increased cell division, benign skin and head bone tumours (“Elephant Man”), also seen as melanocytes in skin
craniocaudal folding
‘lengthways’, week 4, head curves towards tail
lateral folding
‘widthways’, week 4, long edges fold round so parietal mesoderm (top) encapsulates visceral mesoderm in it, at midgut small connection to yolk sac remains (umbilical cord / connecting stalk) – leaving embryo ‘floating’ in amniotic cavity
dorsal mesentery
connects gut tube to paraxial mesoderm
vitelline duct
connection between yolk sac and midgut, above allantois, together these form umbilical cord
allantois
connected to fetal bladder, runs alongside vitelline duct to form umbilical cord
splanchnic mesoderm
visceral mesoderm
ectopia cordis
heart outside body (lateral folds didn’t fuse)
gastroschisis
intestines outside body (lateral folds didn’t fuse)
lens placode
precursor to eye lens

otic placode

ear precursor
pharyngeal arches

precursor of mouth, thyroid and nerves here