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115 Cards in this Set
- Front
- Back
Syncytiotrophoblast |
layer which penetrates endometrium, outermost layer of embryo, secretes hCG
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Cytotrophoblast |
next / middle layer
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Extraembryonic mesoderm |
lines the blastocyst cavity, between primary yolk sac and cytotrophoblast, forms at 10-11 days
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Epiblast |
will be the dorsal surface of embryo
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Hypoblast |
will be the ventral surface of the embryo
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Heuser’s membrane
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cells of the hypoblast which migrate to line the blastocyst cavity
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Trophoblastic lacuna |
gaps in the syncytiotrophoblast
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Coagulation plug |
heals the gap where the embryo entered the endometrium, full implantation 9 days
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Primary yolk sac |
at 10 days, this is what used to be the blastocyst cavity, now lined by hypoblast cells
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Chorionic cavity
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12/13 days, opens up within the extraembryonic mesoderm
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Secondary yolk sac |
aka definitive yolk sac, forms at 12/13 days adjacent to primary, pushes secondary away
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Connecting stalk
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suspends embryo in chorionic cavity (14/ 15 days)
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Fimbriae
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fingers on ampulla neck, sweep oocyte into infundibulum
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Ampulla |
first part of oviduct
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Infundibulum
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funnel of oviduct
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Foramen ovale
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hole in the heart, gap between atria
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Caudal
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tail end
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Sagittal section |
divides left and right sides of the body
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Transverse section |
cut through the tummy, divide top and bottom
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Coronal section |
think of a halo, divide front and back
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Menstrual age
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clinicians and obstetricians, dates from last period – 3 trimesters
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Fertilisation age |
embryologists, 14 days later
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Embryologists: pregnancy phase 1
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early / pre-embryonic: weeks 1-2 (from fertilisation)
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Embryologists: pregnancy phase 2
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embryonic / organogenesis: weeks 3-8
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Horseshoe kidney
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1/500
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Accessory renal artery
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formed as kidneys move up pelvis
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Embryologists: pregnancy phase 3
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foetal: 9 weeks - birth
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Congenital malformations at birth
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2-3%
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Congenital malformations by age 5
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2-3% in addition to birth
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Infant deaths due to birth defects
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21%
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Down’s Syndrome
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trisomy 21
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Zona reaction |
enzyme secreted by zona pellucida, prevent further sperm |
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Corona radiate
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‘halo’ of cells surrounding ovum
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Acrosome reaction
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sperm secrete enzyme to break down zona
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Morula
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16-32 cewlls
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Embryoblast
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inner cell mass, embryo proper
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Trophoblast
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outer cell mass
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Blastocyst
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next stage after morula, 5 days, fluid filled cavity
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Environmental factors which cause birth defects
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teratogens
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Teratogens: TORCH
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toxoplasmosis, other (hep B, syphilis), rubella, cytomegalovirus, herpes (all can cross placenta, cause defects)
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Toxoplasmosis
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hydro/microcephaly, microphthalmia: undercooked meat / cat poo, 1/3 popn affected
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Rubella
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microcephaly, heart, cataracts, hearing
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Cytomegalovirus
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microcephaly, microphthalmia, cerebral calc, growth retard
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Capacitation
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happens to sperm in female reproductive tract
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Amniotic cavity
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8 days, small fluid filled cavity in epiblast
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hCG
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maintains endometrium, help immunotolerance
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abnormal implantation
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2% pregnancies, 9% maternal deaths
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bleeding in late pregnancy
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placenta previa
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calcified dead abdominal pregnancy
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lithopaedion
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empty egg fertilised
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hydatidiform mole
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gastrulation
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bilaminar -> trilaminar, starts week 3
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primitive streak
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pit, node, groove – appears in week 3 (15/16 days), start of gastrulation
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oropharyngeal membrane
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mouth area, cranial end of embryo
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cloacal membrane
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where gut and urinary system will develop
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situs inversus
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R to L symmetry of organs reversed
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Kartagener syndrome
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20% of situs inversus patients, disease of cilia
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Dextrocardia
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partial situs inversus, isolated R H heart
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definitive endoderm
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replaces all hypoblast, forms from epiblast cells multiplying and moving in via primitive streak, 14-15 days
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ectoderm
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was the epiblast, the part left after gastrulation
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ectoderm
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NERVES EYES AND SKIN (epidermis only)
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mesoderm
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formed from epiblast cells, enter via primitive streak, 16 days
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mesoderm
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muscle, blood vessels, heart, adrenal cortex, kidneys, ureters, gonads, cartilage, bones BONES MUSCLES HEART KIDNEYS REPRODUCTIVE
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endoderm
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glands, trachea, lungs, GI, bladder, liver, pancreas – GUTS
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paraxial mesoderm
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near midline: SKELETON, MUSCLES, DERMIS
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somites
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day 20, paraxial mesoderm subdivisions, starts at cranial end, 3-4 pairs per day -> 42-44 pairs formed (good for age estimation)
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intermediate mesoderm
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gonads, reproductive tracts, kidneys
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lateral plate mesoderm
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outermost, lining body cavities
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primitive streak regression
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towards caudal region, day 17, notochordal process laid down
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sirenomelia
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insufficient mesoderm formed to make bones and muscles of legs, also urogenital
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sacroccygeal teratoma (SCT)
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too much mesoderm laid down in gastrulation, because remnants of primitive streak remains, epiblast cells keep moving in, 80% of cases are female
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notochordal process
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hollow tube formed from primitive node
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notochord
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days 16-22, notochordal process fuses with endoderm, separates, becomes solid not hollow
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notochordal plate
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endoderm + notochordal process (days 16-22)
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neurulation is started by
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signals from the notochord
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neurulation
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‘zipping’ up of embryo along neural folds; starts in cervical region, head first, then tail
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induction
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initiating signals from the notochord to form neural plate
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abnormal induction of sclerotomes
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spina bifida, vertebrae not correctly formed
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spina bifida occulta
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hairy dimpled skin on back, hidden S B
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meningocele
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sac of spinal fluid protrudes out of back
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myelomeningocele
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sac of fluid and cord / nerves protrude, not covered by skin, damage during birth
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bone and cartilage differentiation of somites
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sclerotome
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skeletal muscle differentiation of somites
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myotome
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dermis differentiation of somites
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dermatome
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induces differentiation of somites
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induced by notochord
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surrounds notochord and neural tube, will form verterbrae
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sclerotome
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nucleus pulposus
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could be remnants of notochord, inside vertebrae
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parietal mesoderm layer
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nearest dorsal surface, surrounds amnion (top on most diagrams)
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visceral mesoderm layer
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nearest endoderm, ventral surface (lower on most diagrams)
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intra-embryonic body cavity
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forms at neurulation, as parietal mesoderm and amnion fold around neural plate
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neuroectoderm
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thickening of ectoderm, gives rise to neural plate
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neural folds
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lateral edges of neural plate elevate to form these
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anterior neuropore
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the ‘head’ end (cranial) of embryo, fuses on day 25, will form brain
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pericardial bulge
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at cranial end
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posterior neuropore
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caudal end, fuses on day 28, will form spinal cord
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anencephaly
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forebrain not formed, brainstem is present, usually shortlived (a few hours) or stillborn ☹ anterior neuropore not fused
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rachischisis
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failure of posterior neuropore to fuse, spinal cord not formed properly, paralysis
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spina bifida
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sclerotome is not inducted properly by notochord, spinal cord unprotected or even exposed
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folic acid
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reduces NTDs by 50-70%
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NTD
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neural tube defect; spina bifida, anencephaly, rachischisis, 1 in 1000 births affected in UK
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Neural crest cells
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top edges of neural folds, these separate off, migrate and form different structures
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4th germ layer
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neural crest cells
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cranial neural crest derivatives
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eye connective tissue; dermis of face and neck, skull dermal bones, cranial ganglia
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spinal neural crest derivatives
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adrenal medulla, ganglia
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neurofibromatosis
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NF1 gene mutation, increased cell division, benign skin and head bone tumours (“Elephant Man”), also seen as melanocytes in skin
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craniocaudal folding
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‘lengthways’, week 4, head curves towards tail
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lateral folding
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‘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
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dorsal mesentery
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connects gut tube to paraxial mesoderm
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vitelline duct
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connection between yolk sac and midgut, above allantois, together these form umbilical cord
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allantois
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connected to fetal bladder, runs alongside vitelline duct to form umbilical cord
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splanchnic mesoderm
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visceral mesoderm
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ectopia cordis
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heart outside body (lateral folds didn’t fuse)
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gastroschisis
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intestines outside body (lateral folds didn’t fuse)
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lens placode
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precursor to eye lens
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otic placode |
ear precursor
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pharyngeal arches
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precursor of mouth, thyroid and nerves here |