Embryology part 1 Flashcards by nathan hawkey

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

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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

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FGF gene

Prodeced at apical ectodermal ridge. Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs; defect= short limbs

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Homeobox (Hox) gene

Involved in segmental organization of embryo in a craniocaudal direction. Mutations = appendages in wrong location

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day 2

zygote

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day 3

morula

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day 5

blastocyst

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day 6

blastocyst implantation

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week 1

hCG secretion after implantation

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Week 2

bilaminar disc (epiblast, hypoblast); 2 germ layers, 2 cavities (amniotic and yolk), 2 placenta components (cyto/syncytiotrophoblast)

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Week 3

Trilaminar disc (3 week, 3 germ layers). Gastrulation. Primitive streak, notochord, mesoderm and its organization and neural plate begins to form

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Week 3 to 8

Embryonic period. Neural tube formed by neuroectoderm and closes by week 4. Organogenesis. Extremely susceptible to teratogens

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Week 4

4 week, 4 heart chambers, 4 limbs. Heart begins to beat. Upper and lower limb buds begin to form.

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Week 8 (fetal period)

fetal movement, fetus looks like a baby

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Week 10

genitalia have male/female characteristics

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Alar plate

dorsal. Sensory

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Basal plate

ventral. Motor

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Notochord derivative

induces overlying ectoderm to become neuroectoderm and form neural plate which gives rise to neural tube and neural crest

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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

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Neuroectoderm derivatives

Brain (neurohypophysis, CNS neurons, oligodendrocytes, astrocytes, ependymal cells, pineal gland), retin, spinal cord

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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.

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Endodermal derivatives

Gut tube epithelium (anal canal above pectinate) and derivatives (lungs, liver, pancreas, thymus, parathyroid, thyroid follicular cells)

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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