Embryology and Reproductive Anatomy Review Flashcards
Sonic Hedgehog Gene
Produced at the bottom of extending limb buds. Causes AP axis patterning. Involved in CNS development. Mutation can cause holoprosencephaly.
WNT-7
Produced at the edge of the extending limb buds. Causes dorsoventral patterning.
FGF
Produced at the apical ectodermal ridge. Stimulates mitosis of underlying endoderm which causes lengthening of limbs. FGF3 is mutated in achondroplasia.
HOX genes
Cause segmental patterning in a craniocaudal direction. Code for DNA binding proteins. Hox mutations cause appendages in the wrong locations, syndactyly.
Why is vitamin A teratogenic?
Because it interferes with Hox signaling
When does HCG secretion begin?
Around week 1, when the morula becomes a blastocyst.
What happens week 2 of development
Bilaminar disk with epiblast and hypoblast, 2 cavities, 2 types of placental tissue (cytotrophoblast and syncitiotrophoblast).
What happens week 3?
Trilaminar disk (primitive streak, notochord, mesoderm, and neuralplate begin to form). Neurulation and gastrulation occur.
What is the embryonic period?
Weeks 3-8, most vital to development. Terratogens here cause serious problems. Neural tube closes by week 4. Organogenesis happens in this time.
What happens in week 4?
Heart begins to beat, limbs begin to form. Heart beat is visible in week 6.
What happens by week 10?
Genitalia are distinguishable as male/female. Can identify gender at week 10.
Gastrulation
Process that forms the trilaminar disc, this establishes the ectoderm, mesoderm, endoderm. Epiblast invaginates to form the primitive streak.
What structure of the egg prevents implantation?
Zona pellucida. When it is dissolved by acrosomal enzymes the egg can implant.
Components of surface ectoderm
Adenohypophysis from rathke’s pouch, lens, oral cavity, sensory organs of ear, olfactory epithelium, anal canal below the pectinate line.
Components of neuroectoderm
Brain, oligodendrocytes, astrocytes, ependymal cells, pineal gland, retina and optic nerve, spinal cord.
Components of neural crest
PNS – schwann cells, dorsal root ganglia, celiac ganglion, melanocytes, chromaffin cells of adrenal medulla, C cells of thyroid, pia and arachnoid, bones of skull
Mesodermal components
Bone, muscle, connective tissue, peritoneum, SPLEEN, lymphatics, blood, vagina, kidneys, adrenal cortex, dermis, testes, ovaries.
Endodermal components
Gut tube epithelium (including anus above pectinate line), most of urethra, lungs, liver, gallbladder, pancreas, eustacian tube, thymus, parathyroid, thyroid follicular cells.
Agenesis
Absent organ development due to lack of primordial tissue
Aplasia
Absent organ development despite presence of primordial tissue
Hypoplasia
Incomplete organ development
Deformation
Extrinsic force stops development (twins)
Disruption
Breakdown of a previously normal tissue (amniotic band syndrome)
Malformation
Intrinsic disruption during the embryonic period
Sequence
Abnormalities due to a single etiology. Potter sequence is renal agenesis, oligohydramnios, pulmonary hypoplasia.
ACE inhibitor terratogen effect
Renal damage
Alkylating agents
Absence of digits and more
Aminoglycosides
Cause ototoxicity (CN VIII)
Carbamazepine
Neural tube defects, craniofacial defects,
DES
Vaginal clear cell adenocarcinoma, mullerian anomalies
Lithium
Ebstein Abnormaility
Methimazole
Aplasia cutis congenita (no skin)
Phenytoin
Fetal hydantoin syndrome: microcephaly, dysmorphic craniofacial features, hypoplastic nails, cardiac defects.
Tetracyclines
Discolored teeth
Thalidomide
Dolphin limbs