Reproductive Flashcards
Sonic hedgehog gene
- Produced at base of limbs in zone of polarizing activity - - Involved in patterning along anteroposterior axis and CNS development
- Mutation can cause holoprosencephaly
Wnt-7 gene
- Produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb)
- Necessary for proper organization along dorsal-ventral axis
FGF gene
- Produced at apical ectodermal ridge
- Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs
Homeobox (Hox) genes
- Involved in segmental organization of embryo in a craniocaudal direction
- Code for transcription factors
- Hox mutations → appendages in wrong locations
Within week 1
- hCG secretion begins around the time of implantation of blastocyst
- Blastocyst sticks at day 6
Within week 2
- Bilaminar disc (epiblast, hypoblast)
- 2 weeks = 2 layers
Weeks 3-8
- Gastrulation forms trilaminar embryonic disc
- Cells from epiblast invaginate → primitive streak → endoderm, mesoderm, ectoderm
- Notochord arises from the midline mesoderm
- Overlying the ectoderm becomes neural plate
- 3 weeks = 3 layers
Week 4
- Heart begins to beat
- Upper and lower limb
- 4 weeks = 4 limbs and 4 heart chambers
Week 6
Fetal cardiac activity visible by transvaginal ultrasound
Week 8
- Fetal movements start
- “Gait at week 8”
Week 10
Genitalia have male/female characteristics
Surface ectoderm
- Epidermis
- Adenohypophysis (from Rathke pouch)
- Lens of eye
- Epithelial linings of oral cavity, sensory organs of ear, and olfactory epithelium
- Epidermis
- Anal canal below the pectinate line
- Parotid, sweat and mammary glands
Neuroectoderm
- Brain (neurohypophysis, CNS neurons, oligodendrocytes, astrocytes, ependdymal cells, pineal gland)
- Retina
- Spinal cord
“Neuroectoderm - think CNS”
Neural crest
- PNS (dorsal root ganglia, cranial nerves, autonomic ganglia, Scwann cells)
- Melanocytes
- Chromaffin cells of adrenal medulla
- Parafollicular (C) cells of thyroid
- Pia and arachnoid
- Bone of skull
- Odontoblasts
- Aorticopulmonary septum
- Endocardial cushions
Mesoderm
- Muscle
- Bone
- Connective tissue
- Serous linings of body cavities (eg peritoneum)
- Spleen (derived from foregut mesentery)
- Cardiovascular structures
- Lymphatics
- Blood
- Wall of gut tube
- Upper vagina
- Kidneys
- Adrenal cortex
- Dermis
- Testes
- Ovaries
- Notochord induces ectoderm to form neuroectoderm (neural plate), its only postnatal derivative is the nucleus pulposus of the intervertebral disc
Mesodermal defects = VACTERL
- Vertebral defects
- Anal atresia
- Cardiac defects
- Tracheo-Esophageal fistula
- Renal defects
- Limb defects (bone and muscle)
Endoderm
- Gut tube epithelium (including anal canal above the pectinate line)
- Most of the urethra and lower vagina (derived from urogenital sinus)
- Luminal epithelial derivatives (eg lungs, liver, gallbladder, pancreas, eustachian tube, thymus, parathyroid, thyroid follicular cells)
Deformation vs malformation
DEFORMATION: extrinsic disruption; occurs after embryonic period
MALFORMATION: intrinsic disruption; occurs during embryonic period (weeks 3-8)
ACE inhibitors
Renal damage
Alkylating agents
Absence of digits, multiple anomalies
Aminoglycosides
Ototoxicity
Antiepileptic drugs
- Neural tube defects
- Cardiac defects
- Cleft palate
- Skeletal abnormalities (eg phalanx/nail hypoplasia, facial dysmorphism)
- High dose folate supplementation recommended.
- Most commonly valproate, carbamazepine, phenytoin, phenobarbital
Diethylstibestrol
- Vaginal clear cell adenocarcinoma
- Congenital Mullerian anomalies
Folate antagonists
- Neural tube defects
- Includes trimethroprim, methotrexate, antiepileptic drugs
Isotretinoin
- Multiple severe birth defects
- Contraception mandatory