Embryology part 1 Flashcards
Sonic Hedgehog gene
Organizes embryo along anterior-posterior axis; Produced at base of limbs in zone of polarizing activity. Involved in patterning along anterior-posterior axis
Wnt-7 gene
Dorsal-ventral axis; Produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb). Necessary for proper organization along dorsal-ventral axis
FGF gene
Prodeced at apical ectodermal ridge. Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs; defect= short limbs
Homeobox (Hox) gene
Involved in segmental organization of embryo in a craniocaudal direction. Mutations = appendages in wrong location
day 2
zygote
day 3
morula
day 5
blastocyst
day 6
blastocyst implantation
week 1
hCG secretion after implantation
Week 2
bilaminar disc (epiblast, hypoblast); 2 germ layers, 2 cavities (amniotic and yolk), 2 placenta components (cyto/syncytiotrophoblast)
Week 3
Trilaminar disc (3 week, 3 germ layers). Gastrulation. Primitive streak, notochord, mesoderm and its organization and neural plate begins to form
Week 3 to 8
Embryonic period. Neural tube formed by neuroectoderm and closes by week 4. Organogenesis. Extremely susceptible to teratogens
Week 4
4 week, 4 heart chambers, 4 limbs. Heart begins to beat. Upper and lower limb buds begin to form.
Week 8 (fetal period)
fetal movement, fetus looks like a baby
Week 10
genitalia have male/female characteristics
Alar plate
dorsal. Sensory
Basal plate
ventral. Motor
Notochord derivative
induces overlying ectoderm to become neuroectoderm and form neural plate which gives rise to neural tube and neural crest
Surface ectoderm Derivatives
Adenohypophysis from Rathke’s pouch (craniopharyngioma-tumor with cholesterol crystals and calcification); lens; epithelial linings of oral cavity, sensory organs of ear, olfactory epithelium; epidermis; anal canal below pectinate line; salivary, sweat, mammary glands
Neuroectoderm derivatives
Brain (neurohypophysis, CNS neurons, oligodendrocytes, astrocytes, ependymal cells, pineal gland), retin, spinal cord
Neural Crest
ANS, dorsal root ganglia, cranial nerves, celiac ganglion, melanocytes, chromaffin cells of adrenal medulla, parafollicular cells of thyroid, Schwann cells, pia and arachnoid, bones of skull, odontoblasts, aorticopulmonary septum.
Endodermal derivatives
Gut tube epithelium (anal canal above pectinate) and derivatives (lungs, liver, pancreas, thymus, parathyroid, thyroid follicular cells)
Mesoderm Derivatices
Notochord (nucleus pulposus), Muslce, bone, CT, serous linings, spleen, cardiovascular structures, lymph, blood, bladder, urethra, vagina, eustachian tube, kidneys, adrenal cortex, skin dermis, testes, ovaries.
Malformation
intrinsic disruption of developing structure; weeks 3 to 8 are critical
Deformation
extrinsic disruption that occurs usually after the embryonic period
Agenesis
is an absent organ due to absent primordial tissue
Hypoplasia
incomplete organ development and primordial tissue is usually present
Aplasia
absent organ despite present primordial tissue
ACE Teratogen
Renal damage
alkylating agent Teratogen
absence of digits, multiple anomalies
aminoglycosides Teratogen
CN VIII toxicity
Carbamazepine Teratogen
Neural tube defects, craniofacial defects, fingernail hypoplasia, developmental delay
DES
vaginal clear cell adenocarcionoma
Folate Antagonists
Neurl tube defects
Lithium Teratogen
ebstein’s anomaly (atrialized right ventricle)
Phenytoin Teratogen
fetal hydantion syndrome: microcephaly, dysmorphic craniofacial features, hypoplastic nails and distal phalanges, cardiac defects, IUGR, mental retardation
Tetracycline Teratogen
Discolored teeth
Thalidomide
Limb defects
Valproate Teratogen
Inhibitition of maternal folate absorption leading to neural tube defects
Warfarin Teratogen
Bone deformitites, fetal hemorrhage, abortion, ophthalmologic abnormalities
Alcohol Teratogen
Leading cause of birth defects and retardation and microcephaly
Cocaine Teratogen
placental abruption; addiction
Smoking Teratogen
preterm labor, placental problems, ADHD
Iodide Teratogen
Congenital goiter or hypothyroidism
Maternal diabetes Teratogen
Caudal regression syndrome (anal atresia to sirenomelia), congenital heart defects, neural tube defects)
Vitamin A excess in gestation
Extremely high risk of spontaneous abortions and birth defects (cleft palate, cardiac abnormalities)
Developing brain primary vesicles
Week 4: Forebrain (prosenecephalon), Midbrain (mesencephalon), Hindbrain (rhombencephalon)
Secondary vesicles of brain (after week4)
Telencephalon and Diencephalon (from prosencephalon); Mesencephalon (from mesencephalon); Metencephalon and myelencephalon (from rhombencephalon)
Telencephalon adult structures
Cerebral hemispheres and lateral ventricles
Diencephalon
from prosencephalon; thalamus and third ventricle
Mesencephalon adult structures
From mesencephalon; Midbrain and aqueduct
Metencephalon adult structures
From rhombencephalon; pons and cerebellum and upper fourth ventricle
Myelencephalon adult derivatives
From rhombencephalon; Medulla, lower part of fourth ventricle
Anencephaly
malformation of anterior end of neural tube; no brain/calvarium, elevated AFP
Holoprosencephaly
Associated with Fetal alcohol and Patau’s; no separation of hemispheres across midline; cyclopia
Chiari II
Herniation through foramen magnum with aqueductal stenosis and hydrocephayly, assoc. with syringomyelia and lumbar myelomeningocele
Dandy-walker
Large posterior fossa; absent cerebellar vermis with cystic enlargement of 4th ventricle. Can lead to spina bifida
