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226 Cards in this Set
- Front
- Back
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What are the important genes of embryogenesis? |
- Sonic hedgehog (Shh)
- Wnt-7 gene - FGF gene - Homeobox (Hox) genes |
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Where is the Sonic hedgehog gene produced? Function?
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- Produced at base of limbs in zone of polarizing activity
- Involved in patterning along anterior-posterior axis - Involved in CNS development |
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What can a mutation in Sonic hedgehog gene cause?
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Holoprosencephaly
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Where is the Wnt-7 gene produced? Function?
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- Produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb)
- Involved in proper organization along dorsal-ventral axis |
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Where is the FGF gene produced? Function?
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- Produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb)
- Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs |
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What is the function of the Homeobox (Hox) genes?
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Involved in segmental organization of embryo in a craniocaudal direction
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What can a mutation in Homeobox (Hox) gene cause?
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Appendages in wrong locations
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What gene is necessary for patterning along the anterior-posterior axis?
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Sonic hedgehog gene
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What gene is necessary for organization along the dorsal-ventral axis?
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Wnt-7 gene
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What gene stimulates mitosis of the underlying mesoderm, allowing for the lengthening of limbs?
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FGF gene
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What gene is involved in the segmental organization of embryo in a craniocaudal direction?
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Homeobox (Hox) gene
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A mutation in what gene can cause holoprosencephaly?
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Sonic hedgehog gene
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A mutation in what gene can cause appendages in wrong locations?
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Homeobox (Hox) genes
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What happens on day 0 of fetal development?
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Fertilization of egg by sperm (in fallopian tube)
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What happens during the first week of fetal development?
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Formation of:
- Zygote (day 2) - Morula (day 3) - Blastocyst (day 5) Implantation of Blastocyst |
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What happens during the second week of fetal development?
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- Formation of Bilaminar disc: Epiblast and Hypoblast
- 2 weeks = 2 layers |
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What happens during the third week of fetal development?
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Formation of Trilaminar disc
- 3 weeks = 3 layers Gastrulation - Formation of primitive streak, notochord, mesoderm and its organization, and neural plate |
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What happens during the "embryonic period"? When does this occur?
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- Neural tube formed by neuroectoderm and closes by week 4
- Organogenesis (weeks 3-8) |
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During what period is the fetus extremely susceptible to teratogens?
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Weeks 3-8 (embryonic period) - this is when organogenesis takes place
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What forms the neural tube? When does it close?
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- Formed by neuroectoderm
- Closes by week 4 |
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When does the heart begin to beat?
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Week 4
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When do the limb buds start to form?
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Week 4
(4 weeks = 4 limbs) |
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When is fetal cardiac activity visible by transvaginal ultrasound?
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Week 6
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When do the genitalia begin to display distinctive male/female characteristics?
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Week 10
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What is the process that forms the trilaminar embryonic disc?
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Gastrulation
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What occurs during gastrulation?
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Formation of trilaminar embryonic disc (3 germ layers):
- Ectoderm - Mesoderm - Endoderm |
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How does gastrulation begin?
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Starts with the epiblast invaginating to form the primitive streak
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What are the embryologic derivatives of the ectoderm?
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- Surface ectoderm
- Neuroectoderm - Neural crest |
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What are the embryologic derivatives of the surface ectoderm?
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- Adenohypophysis (from Rathke pouch)
- Lens of eye - Epithelial lining of oral cavity - Sensory organs of ear - Olfactory epithelium - Epidermis - Anal canal below pectinate line - Parotid, sweat, and mammary glands |
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What is the embryologic origin of the adenohypophysis (anterior pituitary)?
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Rathke pouch - from surface ectoderm
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What kind of tumor forms from a remnant of the Rathke pouch? Characteristics?
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Craniopharyngioma
- Benign Rathke pouch tumor - With cholesterol crystals and calcifications |
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What types of glands originate from surface ectoderm?
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- Parotid glands
- Sweat glands - Mammary glands |
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What types of epithelium originate from surface ectoderm?
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- Epithelium of oral cavity
- Olfactory epithelium |
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What are the embryological derivatives of the neuroectoderm?
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Think CNS:
- Brain (including neurohypophysis, CNS neurons, oligodendrocytes, astrocytes, ependymal cells, pineal gland) - Retina - Optic nerve - Spinal cord |
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What are the embryological derivatives of the neural crest?
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Think PNS and non-neural structures nearby:
- PNS (including dorsal root ganglia, cranial nerves, celiac ganglion, Schwann cells, ANS) - Melanocytes - Chromaffin cells of adrenal medulla - Parafollicular (C) cells of thyroid - Pia and arachnoid mater - Bones of skull - Odontoblasts - Aorticopulmonary septum |
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Which non-PNS structures originate from the neural crest?
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- Melanocytes
- Chromaffin cells of adrenal medulla - Parafollicular (C) cells of thyroid - Pia and arachnoid mater - Bones of skull - Odontoblasts - Aorticopulmonary septum |
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What components of the PNS originate from the neural crest?
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- Dorsal root ganglia
- Cranial nerves - Celiac ganglion - Schwann cells - ANS |
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What are the embryologic derivatives of the mesoderm?
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- Muscle, bone, CT
- Serous linings of body cavities (eg, peritoneum) - Spleen (from foregut mesentery) - Cardiovascular structures - Lymphatics - Blood - Wall of gut tube - Vagina - Kidneys - Adrenal cortex - Dermis - Testes and ovaries |
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What signal tells the ectoderm to form the neuroectoderm?
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Notochord induces ectoderm to form neuroectoderm
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What is the postnatal derivative of the notochord?
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Nucleus pulposus of the intervertebral disc
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What are the possible defects caused by problems with the development of the mesodermal derivatives?
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VACTERL:
- Vertebral defects - Anal atresia - Cardiac defects - Trachio-Esophageal fistula - Renal defects - Limb defects (bone and muscle) |
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What are the derivatives of the endoderm?
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- Gut tube epithelium (up to anal canal above pectinate line)
- Most of urethra (from urogenital sinus) - Luminal epithelial derivatives (eg, lungs, liver, gallbladder, pancreas, eustachian tube, thymus, parathyroid, thyroid follicular cells) |
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What are the luminal epithelial derivatives of the endoderm?
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- Lungs
- Liver - Gallbladder - Pancreas - Eustachian tube - Thymus - Parathyroid - Thyroid follicular cells |
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What are the cells of the thyroid derived from?
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- Parafollicular (C) cells of thyroid: neural crest (ectoderm)
- Thyroid follicular cells: endoderm |
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What are the types of errors in organ morphogenesis?
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- Agenesis
- Aplasia - Hypoplasia - Deformation - Disruption - Malformation - Sequence |
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What is the term for the absence of an organ due to absent primordial tissue?
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Agenesis
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What is the term for absent organ despite presence of primordial tissue?
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Aplasia
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What is the term for incomplete organ development with primordial tissue present?
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Hypoplasia
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What is the term for an extrinsic disruption, that occurs after the embryonic period?
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Deformation
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What is the term for the secondary breakdown of a previously normal tissue or structure (eg, amniotic band syndrome)?
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Disruption
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What is the term for the intrinsic disruption of an organ that occurs during the embryonic period (weeks 3-8)?
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Malformation
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What is the term for abnormalities that result from a single primary embryological event (eg, oligohydramnios → )?
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Sequence
(eg, Potter sequence) |
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What is the difference between a deformation and a malformation?
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- Deformation: extrinsic disruption, occurs after embryonic period
- Malformation: intrinsic disruption, occurs during embryonic period (weeks 3-8) |
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When are fetuses most susceptible to teratogens?
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3rd-8th weeks (embryonic period - organogenesis)
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What happens if a fetus is exposed to a teratogen before week 3?
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All or none effects
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What happens if a fetus is exposed to a teratogen after week 8?
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Growth and function affected
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What is the effect on the fetus, of a mother taking ACE inhibitors during her pregnancy?
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Renal damage
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What is the effect on the fetus, of a mother taking alkylating agents during her pregnancy?
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- Absence of digits
- Multiple anomalies |
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What is the effect on the fetus, of a mother taking aminoglycosides during her pregnancy?
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CN VIII toxicity ("a mean guy hit the baby in the ear")
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What is the effect on the fetus, of a mother taking carbamazepine during her pregnancy?
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- Neural tube defects
- Craniofacial defects - Fingernail hypoplasia - Developmental delay - IUGR |
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What is the effect on the fetus, of a mother taking Diethylstilbestrol (DES) during her pregnancy?
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- Vaginal clear cell adenocarcinoma
- Congenital Müllerian anomalies |
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What is the effect on the fetus, of a mother taking folate antagonists during her pregnancy?
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Neural tube defects
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What is the effect on the fetus, of a mother taking Lithium during her pregnancy?
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Ebstein Anomaly (atrialized RV)
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What is the effect on the fetus, of a mother taking Methimazole during her pregnancy?
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Aplasia cutis congenita
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What is the effect on the fetus, of a mother taking Phenytoin during her pregnancy?
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Fetal Hydantoin Syndrome:
- Microcephaly - Dysmorphic craniofacial features - Hypoplastic nails and distal phalanges - Cardiac defects - IUGR - Intellectual disability |
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What is the effect on the fetus, of a mother taking Tetracycline antibiotics during her pregnancy?
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Discolored teeth
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What is the effect on the fetus, of a mother taking Thalidomide during her pregnancy?
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Limb defects:
- Phocomelia - Micromelia - "Flipper" limbs |
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What is the effect on the fetus, of a mother taking Valproate during her pregnancy?
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Inhibition of maternal folate absorption → neural tube defects
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What is the effect on the fetus, of a mother taking Warfarin during her pregnancy?
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- Bone deformities
- Fetal hemorrhage - Abortion - Ophthalmologic abnormalities "Do not wage WARFARe on the baby, keep it HEPpy with HEParin (does not close the placenta) |
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Which medication taken during pregnancy can cause renal damage?
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ACE-Inhibitors
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Which medication taken during pregnancy can cause absence of digits?
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Alkylating agents
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Which medication taken during pregnancy can cause CN VIII toxicity?
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Aminoglycosides
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Which medication taken during pregnancy can cause neural tube defects?
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- Carbamazepine
- Folate antagonists - Valproate |
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Which medication taken during pregnancy can cause fingernail hypoplasia?
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- Carbamazepine
- Phenytoin |
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Which medication taken during pregnancy can cause Intrauterine Growth Restriction?
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- Carbamazepine
- Phenytoin |
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Which medication taken during pregnancy can cause vaginal clear cell adenocarcinoma?
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Diethylstilbestrol (DES)
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Which medication taken during pregnancy can cause congenital Müllerian anomalies?
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Diethylstilbestrol (DES)
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Which medication taken during pregnancy can cause Ebstein anomaly?
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Lithium (atrialized RV)
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Which medication taken during pregnancy can cause aplasia cutis congenita?
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Methimazole
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Which medication taken during pregnancy can cause fetal hydantoin syndrome?
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Phenytoin
- Microcephaly - Dysmrophic craniofacial features - Hypoplastic nails and distal phalanges - Cardiac defects - IUGR - Intellectual disability |
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Which medication taken during pregnancy can cause discolored teeth?
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Tetracycline
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Which medication taken during pregnancy can cause limb defects?
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Thalidomide
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Which medication taken during pregnancy can cause bone deformities?
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Warfarin
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Which medication taken during pregnancy can cause fetal hemorrhage?
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Warfarin
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Which medication taken during pregnancy can cause ophthalmologic abnormalities?
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Warfarin
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What is a common cause of birth defects and intellectual disability?
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Alcohol (Fetal Alcohol Syndrome)
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What are the effects of a mother taking cocaine while pregnant?
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- Abnormal fetal growth
- Fetal addiction - Placental abruption |
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What is a leading cause of low birth weight in developed countries?
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Smoking (nicotine, CO)
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What is smoking during pregnancy associated with?
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- Low birth weight
- Preterm labor - Placental problems - IUGR - ADHD |
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How does the amount of iodine in the diet of the mother affect a fetus?
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Iodine (lack or excess) → congenital goiter or hypothyroidism (cretinism)
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What are the possible consequences to the fetus of having a mother with maternal diabetes?
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- Caudal regression syndrome (anal atresia to sirenomelia)
- Congenital heart defects - Neural tube defects |
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What are the possible consequences of having excess Vitamin A on the fetus?
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Extremely high risk for spontaneous abortions and birth defects:
- Cleft palate - Cardiac abnormalities |
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What are the possible consequences of a mother receiving x-rays while she is pregnant?
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- Microcephaly
- Intellectual disability |
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What is one of the leading causes of congenital malformations in US?
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Fetal Alcohol Syndrome
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What abnormalities are associated with Fetal Alcohol Syndrome?
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- Intellectual disability
- Pre- and post-natal developmental retardation - Microcephaly - Holoprosencephaly - Facial abnormalities (smooth philtrum, tin upper lip, small palpebral fissures, hypertelorism) - Limb dislocation - Heart defects |
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What do dizygotic twins arise from?
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2 eggs, separately fertilized by 2 different sperm → two zygotes
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How many amniotic sacs and placentas (chorions) can dizygotic twins have?
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- 2 separate amniotic sacs
- 2 separate placentas (chorions) |
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What do monozygotic twins arise from?
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- 1 fertilized egg + 1 sperm
- Splits into 2 zygotes in early pregnancy |
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What determines the degree of separation between monozygotic twins?
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Depends on when the fertilized egg splits into 2 zygotes: determines the number of chorions and the number of amnions
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What are the results of cleavage of a zygote during days 0-4?
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Dichorionic and Diamniotic
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What are the results of cleavage of a zygote during days 4-8?
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Monochorionic and Diamniotic
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What are the results of cleavage of a zygote during days 8-12?
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Monochorionic and Monoamniotic
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What are the results of cleavage of a zygote after day 13?
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Monochorionic and Monoamniotic; conjoined twins
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Which is more common: monozygotic or dizygotic twins?
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- Monozygotic (20%)
- Dizygotic (80%) |
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What is the primary site of nutrient and gas exchange between the mother and fetus?
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Placenta
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What are the fetal components of the placenta?
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- Cytotrophoblast
- Syncytiotrophoblast |
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What is the maternal component of the placenta?
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Decidua basalis
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What are the layers of the chorionic villi? Which is inner/outer?
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- Inner: cytotrophoblast
- Outer: syncytiotrophoblast |
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What is the function of the cytotrophoblast?
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Inner layer of chorionic villi (fetal component of placenta)
- Cytotrophoblast makes Cells |
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What is the function of the syncytiotrophoblast?
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Outer layer of chorionic villi (fetal component of placenta)
- Secretes hCG → stimulates corpus luteum to secrete progesterone during first trimester |
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What is hormone is hCG similar to structurally? Source in placenta?
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- Structurally similar to LH
- Secreted from syncytiotrophoblast (outer layer of chorionic villi) - Stimulates corpus luteum to secrete progesterone during first trimester |
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What is the origin of the decidua basalis? What is in it?
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Maternal component of placenta
- Derived from endometrium - Maternal blood is found in lacunae |
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What are the contents of the umbilical cord?
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- 2 umbilical arteries
- 1 umbilical vein |
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What structure returns deoxygenated blood from the fetal internal iliac arteries to the placenta?
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Umbilical arteries
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What structure supplies oxygenated blood from the placenta to the fetus?
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Umbilical vein
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What does the umbilical vein flow into?
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Drains into the IVC via the liver or via the ductus venosus
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What is a single umbilical artery associated with?
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Associated with congenital and chromosomal anomalies
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What are the umbilical arteries (2) and vein (1) derived from?
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Allantois
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What is the origin of the allantois?
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In the third week, the yolk sac forms the allantois
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What does the allantois extend into?
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Urogenital sinus
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What does the allantois become?
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Becomes the urachus: a duct between the fetal bladder and yolk sac
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What does the urachus connect?
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Duct between the fetal bladder and yolk sac
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What are the potential complications if the urachus fails to obliterate?
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- Patent urachus
- Urachal cyst - Vesicourachal diverticulum |
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What causes urine discharge from the umbilicus?
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Patent urachus (failure of urachus to obliterate)
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What can cause formation of a fluid-filled cavity lined with uroepithelium between the umbilicus and bladder? What is this called?
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Urachal Cyst
- Partial failure of urachus to obliterate |
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What is a urachal cyst? Cause? What can it lead to?
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- Fluid-filled cavity lined with uroepithelium
- Caused by a partial failure of the urachus to obliterate - Can lead to infection or adenocarcinoma |
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What is the name for an outpouching of the bladder caused by the failure of the urachus to obliterate?
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Vesicourachal diverticulum
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What is the function of the vitelline duct?
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Connects yolk sac to midgut lumen
(aka Omphalo-Mesenteric Duct) |
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What can a failure of the vitelline duct to close result in?
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- Vitelline fistula
- Meckel diverticulum |
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What causes meconium discharge from the umbilicus?
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Vitelline Fistula (due to failure of the vitelline duct to close)
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What causes melena, periumbilical pain, and ulcers?
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Meckel Diverticulum (due to partial closure of the vitelline duct)
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What are the characteristics / cause of a Vitelline Fistula?
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- Failure of vitelline duct to close
- Meconium discharges from umbilicus |
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What are the characteristics / cause of a Meckel Diverticulum?
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- Partial closure of Vitelline duct with patent portion attached to ileum (true diverticulum)
- May have ectopic gastric mucosa and/or pancreatic tissue → melena, periumbilical pain, and ulcers |
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What do the aortic arch derivatives develop into?
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Arterial system
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What is the derivative of the 1st aortic arch?
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Part of maxillary artery (branch of external carotid)
*1st arch is MAXimal* |
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What is the derivative of the 2nd aortic arch?
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Stapedial artery and hyoid artery
*Second arch = Stapedial* |
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What is the derivative of the 3rd aortic arch?
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- Common Carotid artery
- Proximal part of internal Carotid artery *C = 3rd letter of alphabet* |
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What is the derivative of the 4th aortic arch?
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- On left: aortic arch
- On right: proximal part of R subclavian artery *4th arch (4 limbs) = systemic* |
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What is the derivative of the 5th aortic arch?
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No 5th aortic arch!
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What is the derivative of the 6th aortic arch?
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- Proximal part of pulmonary arteries
- On left: ductus arteriosus *6th arch = pulmonary and the pulmonary-to-systemic shunt (ductus arteriosus)* |
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What is the maxillary artery derived from?
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1st aortic arch
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What is the stapedial artery derived from?
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2nd aortic arch
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What is the hyoid artery derived from?
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2nd aortic arch
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What is the common carotid artery derived from?
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3rd aortic arch
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What is the proximal part of the internal carotid artery derived from?
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3rd aortic arch
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What is the aortic arch derived from?
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Left 4th aortic arch
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What is the proximal part of the right subclavian artery derived from?
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Right 4th aortic arch
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What is the proximal part of the pulmonary arteries derived from?
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6th aortic arch
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What is the ductus arteriosus derived from?
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Left 6th aortic arch
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What are the components of the branchial / pharyngeal apparatus?
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From outside to inside:
- Branchial clefts - Branchial arches - Branchial pouches |
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What are the branchial clefts derived from?
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Derived from ectoderm
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What are the branchial arches derived from?
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Derived from mesoderm (muscles arteries) and neural crest (bones, cartilage)
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What are the branchial pouches derived from?
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Derived from endoderm
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How many pharyngeal arches are there?
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Four
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What is the derivative of the 1st branchial cleft?
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External auditory meatus
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What is the derivative of the 2nd-4th branchial clefts?
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Temporary cervical sinuses (obliterated by proliferation of 2nd arch mesenchyme)
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What happens if there is a persistent cervical sinus?
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Formation of branchial cleft cyst within lateral neck
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What are the cartilaginous derivatives of the 1st branchial arch?
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Meckel Cartilage:
- Mandible - Malleus - Incus - Spheno-manidbular ligament |
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What are the muscular derivatives of the 1st branchial arch?
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- Muscles of mastication (temporalis, masseter, lateral and medial pterygoids)
- Mylohyoid - Anterior belly of digastric - Tensor tympani - Tensor veli palatini |
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What are the nervous derivatives of the 1st branchial arch?
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CN V2 and V3 (for chewing)
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What are the implications of abnormalities of the derivatives of the 1st branchial arch?
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Treacher Collins Syndrome:
- 1st-arch neural crest fails to migrate → mandibular hypoplasia, facial abnormalities |
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What are the cartilaginous derivatives of the 2nd branchial arch?
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Reichert Cartilage:
- Stapes - Styloid process - Lesser horn of hyoid - Stylohyoid ligament |
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What are the muscular derivatives of the 2nd branchial arch?
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- Muscles of facial expression
- Stapedius - Stylohyoid - Platysma - Belly of digastric |
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What are the nervous derivatives of the 2nd branchial arch?
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CN VII (facial expression)
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What are the implications of abnormalities of the derivatives of the 2nd branchial arch?
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Congenital Pharyngocutaneous Fistula:
- Persistence of cleft and pouch → fistula between tonsillar area and lateral neck |
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What are the cartilaginous derivatives of the 3rd branchial arch?
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Cartilage: greater horn of hyoid
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What are the muscular derivatives of the 3rd branchial arch?
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Stylopharyngeus
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What are the nervous derivatives of the 3rd branchial arch?
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CN IX (stylopharyngeus) swallow stylishly
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What are the cartilaginous derivatives of the 4th-6th branchial arches?
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Cartilage: thyroid, cricoid, arytenoids, corniculate, and cuneiform
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What are the muscular derivatives of the 4th branchial arch?
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- Most pharyngeal constrictors
- Cricothyroid - Levator veli palatini |
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What are the muscular derivatives of the 6th branchial arch?
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All intrinsic muscles of larynx except cricothyroid
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What are the nervous derivatives of the 4th branchial arch?
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CN X (superior laryngeal branch) = simply swallow
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What are the nervous derivatives of the 6th branchial arch?
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CN X (recurrent laryngeal branch) = speak
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What are the implications of abnormalities of the derivatives of the 4th-6th branchial arch?
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- Arches 3 and 4 form posterior 1/3 of tongue
- Arch 5 makes no major developmental contributions |
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How do you remember the functions of the branchial arches?
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When at the restaurant of the golden ARCHES, children tend to first CHEW (1), then SMILE (2), then SWALLOW STYLishly (3) or SIMPLY SWALLOW (4), and then SPEAK (6)
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Which precursor structure provides cartilage, muscles, and nerves primarily aimed at chewing? What structures?
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1st branchial arch
- Meckel cartilage (mandible, malleus, incus, spheno-mandibular ligament) - Muscles of mastication: temporalis, masseter, lateral and medial pterygoids), Mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini - CN V2 and V3 |
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Which precursor structure provides cartilage, muscles, and nerves primarily aimed at facial expression? What structures?
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2nd Branchial Arch
- Reichert cartilage (stapes, styloid process, lesser horn of hyoid, stylohyoid ligament) - Muscles: stapedius, stylohyoid, platysma, belly of digastric - CN VII (facial nerve) |
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Which precursor structure provides cartilage, muscles, and nerves primarily aimed at swallowing? What structures?
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3rd Branchial Arch
- Cartilage: greater horn of hyoid - Stylopharyngeus (think of stylopharyngeus, innervated by glossopharyngeal nerve) - CN IX 4th Branchial Arch - Most pharyngeal constrictors, cricothyroid, levator veli palatini - CN X (superior laryngeal branch) |
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Which precursor structure provides cartilage, muscles, and nerves primarily aimed at speaking? What structures?
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6th Branchial Arch
- All intrinsic muscles of larynx except cricothyroid - CN X (recurrent laryngeal branch) |
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Which precursor structure forms the posterior 1/3 of the tongue?
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Branchial arches 3 and 4
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What are the derivatives of the 1st branchial pouch?
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- Develops into middle ear cavity, eustachian tube, mastoid air cells
- Contributes to endoderm-lined structures of ear |
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What are the derivatives of the 2nd branchial pouch?
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Develops into epithelial lining of palatine tonsil
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What are the derivatives of the 3rd branchial pouch?
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- Dorsal wings: develops into inferior parathyroids
- Ventral wings: develops into thymus Contributes to 3 structures: thymus, left and right inferior parathyroids *These structures end up below 4th pouch structures* |
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What are the derivatives of the 4th branchial pouch?
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- Dorsal wings: develops into superior parathyroids
*These structures end up above 3rd pouch structures* |
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How do you remember the branchial pouch derivatives?
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Ear, Tonsils, Bottom-to-Top
1 - ear 2 - tonsils 3 - dorsal (bottom = inferior parathyroids) 3- ventral (to = thymus) 4 - top = superior parathyroids |
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What developmental precursor is abnormal in DiGeorge syndrome?
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3rd and 4th pouches
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What are the implications of DiGeorge Syndrome?
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- Aberrant development of 3rd and 4th pouches
- T-cell deficiency (thymic aplasia) and hypocalcemia (failure of parathyroid development) - Associated with cardiac defects (conotruncal anomalies) |
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What genetic abnormality is present in MEN 2A syndrome?
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Mutation of germline RET (in neural crest cells)
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What can MEN 2A syndrome lead to?
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- Pheochromocytoma (adrenal medulla)
- Parathyroid tumor (3rd/4th pharyngeal pouch) - Medullary Thyroid Cancer (parafollicular cells) - derived from neural crest cells, associated with 4th/5th pharyngeal pouches |
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Medullary thyroid cancer (parafollicular cells) are associated with what branchial precursor?
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4th/5th pharyngeal pouches
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Parathyroid tumors are associated with what branchial precursor?
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3rd/4th pharyngeal pouch
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What causes a cleft lip?
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Failure of fusion of the maxillary and medial nasal processes (formation of 1° palate)
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What causes a cleft palate?
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- Failure of fusion of the two lateral palatine processes
OR - Failure of fusion of lateral palatine processes with the nasal septum and/or median palatine process (formation of 2° palate) |
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What is the result of a failure of fusion of the maxillary and medial nasal processes?
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Cleft lip
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What is the result of a failure of fusion of the two lateral palatine processes or failure of fusion of lateral palatine processes with the nasal septum and/or median palatine process?
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Cleft palate
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What is the default genital development? What develops and when degenerates?
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Female Genitals are Default:
- Mesonephric duct degenerates - Paramesonephric duct develops |
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What is necessary for the default genital development to switch to male genital development?
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SRY gene on Y chromosome: produces testis-determining factor (testes development)
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What prevents development of the paramesonephric ducts in males?
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Sertoli cells secrete Müllerian Inhibitory Factor (MIF)
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What stimulates development of the mesonephric ducts in males?
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Leydig cells secrete Androgens
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What is the source of Müllerian Inhibiting Factor? Function?
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- Secreted from Sertoli cells in males
- Suppresses development of paramesonephric ducts (female genitalia) |
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What is the source of androgens during fetal development? Function?
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- Secreted from Leydig cells in males
- Stimulates development of mesonephric ducts (male genitalia) |
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What forms the female internal structures? What are these structures?
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Paramesonephric (Müllerian) Duct
- Fallopian tubes - Uterus - Upper portion of vagina (lower portion from urogenital sinus) |
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What can abnormalities of the Müllerian duct lead to?
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Anatomical defects that may present as 1° amenorhea in females with fully developed 2° sexual characteristics (indicator of functional ovaries)
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What forms the male internal structures? What are these structures?
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Mesonephric (Wolffian) duct
- Seminal vesicles - Epididymis - Ejaculatory duct - Ductus deferens (SEED) |
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What results from incomplete fusion of the paramesonephric ducts?
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Bicornuate Uterus
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What results from complete failure of fusion of the paramesonephric ducts?
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Double uterus and vagina
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What causes a Bicornuate uterus? Consequences?
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Incomplete fusion of the paramesonephric ducts
- May lead to recurrent miscarriages |
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What causes a double uterus and vagina?
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Complete failure of fusion of the paramesonephric ducts
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What are the implications of a patient with no sertoli cells or no Müllerian Inhibitory Factor?
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- Develops both male and female internal genitalia (because no MIF to prevent female internal organs from developing)
- Develops male external genitalia (due to Testosterone) |
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What are the implications of a patient with a 5α-reductase deficiency?
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Inability to convert T → DHT
- Formation of male internal genitalia with ambiguous external genitalia until puberty - At puberty, testosterone levels increase causing masculinization |
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What does the undifferentiated genital tubercle become when exposed to estrogen vs dihydrotestosterone?
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- Estrogen → Glans Clitoris & Vestibular Bulbs
- DHT → Glans Penis & Corpus Cavernosum and Spongiosum |
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What does the undifferentiated urogenital sinus become when exposed to estrogen vs dihydrotestosterone?
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- Estrogen → Greater Vestibular Glands (of Bartholin) & Urethral and Paraurethral Glands (of Skene)
- DHT → Bulbourethral Glands (of Cowper) & Prostate Gland |
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What does the undifferentiated urogenital folds become when exposed to estrogen vs dihydrotestosterone?
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- Estrogen → Labia Minora
- DHT → Ventral shaft of Penis (Penile Urethra) |
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What does the undifferentiated Labioscrotal Swelling become when exposed to estrogen vs dihydrotestosterone?
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- Estrogen → Labia Majora
- DHT → Scrotum |
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What are the types of congenital penile abnormalities? Which is more common?
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- Hypospadias = more common
- Epispadias |
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Which congenital penile abnormality on the underside of the penis?
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Hypospadias (ventral side)
*Hypo is below* |
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Which congenital penile abnormality on the superior of the penis?
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Epispadias (dorsal side)
*When you have Epispadias, you hit your Eye when you pEE* |
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What causes an abnormal opening of the penile urethra on the inferior (ventral) side of the penis?
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Hypospadis = failure of the urethral folds to close
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What causes an abnormal opening of the penile urethra on the superior (dorsal) side of the penis?
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Epispadias = faulty positioning of the genital tubercle
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Why do you need to fix hypospadias (abnormal opening of penile urethra on inferior side of penis)?
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Prevent UTIs
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What is associated with Epispadias?
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Exstrophy of the bladder is associated with Epispadias
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What anchors the testes within the scrotum?
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Gubernaculum (band of fibrous tissue)
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What forms the tunica vaginalis in males?
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Processus vaginalis (evagination of peritoneum)
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What forms the ovarian ligament and round ligament of the uterus?
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Gubernaculum (band of fibrous tissue)
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What is the remnant of the gubernaculum in males and females?
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- Males: anchors testes within scrotum
- Females: ovarian ligament and round ligament of uterus |
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What is the remnant of the processus vaginalis in males and females?
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- Males: forms tunica vaginalis
- Females: obliterated |
