Reproductive embryology and anatomy Flashcards
What are some important genes of embryogenesis?
Sonic hedgehog gene
Wnt-7 gene
FGF gene
Homeobox (Hox) genes
Where is the sonic hedgehog gene produced? What is it involved in? what can mutation cause?
Base of limbs in zone of polarizing activity
Patterning along A/P axis
CNS development
Holoprosencephaly
Where is the Wnt-7 gene produced? What is it necessary for?
Apical ectodermal ridge (thickened ectoderm at distal end of each developing limb)
Proper organization along dorsal-ventral axis)
Where is FGF gene produced? What is its function?
Apical ectodermal ridge
Stimulates mitosis of underlying mesoderm, limb lengthening
What is the Homeobox gene involved in? What does it code for? What do mutations lead to?
Segmental organization of embryo in craniocaudal direction
Transcription factors
Appendages in wrong locations
Early fetal development
Day 0: Week 1: W2: W3: W3-8: Week 4: Week 6: Week 10:
Day 0:fertilization by sperm, forming zygote, initiating embryogenesis
Week 1: hCH secretion begins around the time of implantation of blastocyst (“sticks” at day 6)
W2: Bilaminar disc (epiblast, hypoblast) (2 weeks=2 layers)
W3: Trilaminar disc (3W=3 layers), gastrulation, primitive streak, notochord, mesoderm and its organization, and neural plate begins to form
W3-8: Embryonic period (neural tube formed by neuroectoderm and closes by week 4; organogenesis; extremely susceptible to teratogens)
Week 4: Heart begins to beat; upper and lower limbs begin to form (4 limbs, 4 chambers=4 weeks)
Week 6: Fetal cardiac activity visible by T/V U/S
Week 10: Genitalia have male/female characteristics
What is gastrulation? How does it start?
Process that forms trilaminar embryonic disc
Establishes ectoderm, mesoderm, and endoderm germ layers
epiblast invaginating to form the primitive streak
What are the 3 embryologic derivatives? Location? What are the 3 types of ectoderm?
Ectoderm=external
Mesoderm=middle/meat
Endoderm=internal
Surface ectoderm
neuroectoderm
neural crest
What is made of surface ectoderm?
Epidermis Adenohypophysis (Rathke pouch) Lens of eye Epithelial linings of oral cavity Sensory organs of ear Olfactory epithelium Epidermis Anal canal below pectinate line Parotic, sweat, and mammary glands
What is made of neuroectoderm?
Brain (neurohypophysis, CNS neurons, oligodendrocytes, astrocytes, ependymal cells, pineal gland)
Retina and optic nerve
Spinal cord
What is made of neural crest cells?
PNS (dorsal root ganglia, schwann cells, CNs, celiac ganglion, ANS) Melanocytes Chromaffin cells of adrenal medulla Parafollicular C cells of thyroid Pia and arachnoid Bones of the skull Odontoblasts Aorticopulmonary septum
What is made of mesoderm? What do mesoderm defects lead to?
Muscles Bone CT Serous linings of body cavities (peritoneum) spleen (foregut mesentary) CV structures Lymphatics Blood Wall of gut tube Vagina Kidneys Adrenal cortex Dermis Testes Ovaries Notochord (nucleus pulposus)
Vertebral defects Anal Atresia Cardiac defects TEF Renal defects Limb defects
What is made up of endoderm?
Gut tube epithelium (including anal canal above pectinate line)
Most of urethra (urogenital sinus)
Luminal epithelial derivatives (lungs, liver, gallbladder, pancreas, eustachian tube, thymus, parathyroid, thyroid follicular cells)
What is
Agenesis: Aplasia: Hypoplasia: Deformation: Disruption: Malformation: Sequence:
Agenesis: Absent organ due to absent primordial tissue
Aplasia: Absent organ despite presence of primordial tissue
Hypoplasia: incomplete organ develop.; primordial tissue present
Deformation: Extrinsic disruption; occurs after embryonic period
Disruption: secondary breakdown of previously normal tissue or structure (amniotic band syndrome)
Malformation: intrinsic disruption; occurs during embryonic period
Sequence: Abnormalities result from single embryological event (potter sequence)
When are fetuses most susceptible to teratogens? What happens before that? After that?
3rd to 8 weeks
Before-all or none
After-growth and function affected
What effects do these drugs have on fetus?
ACEI: Alkylating agents Aminoglycosides: Carbamazepine: DES: Folate antag: Isotretinoin: Lithium: Methimazole: Phenytoin: Tetracyclines: Thalidomide: Valproate: Warfarin:
ACEI: Renal damage
Alkylating agents: Absence of digits
Aminoglycosides: CN VIII toxicity
Carbamazepine: Facial dysmorphism, devel. delay, neural tube defects, phalanx/fingernail hypoplasia
DES: Vaginal clear cell adenoCA, congenital mullerian anomalies
Folate antag: Neural tube defects
Isotretinoin: multiple severe birth defects (Contraception mandatory
Lithium: Ebstein anomaly
Methimazole: Aplasia cutis congenita
Phenytoin: Fetal hydantoin syndrome=cleft palate, cardiac defects, phalanx/fingernail hypoplasia
Tetracyclines: discolored teeth
Thalidomide: limb defects (phocomelia, micromelia)
Valproate: inhibition of maternal folate absorption leading to neural tube defects
Warfarin: bone deformities, fetal hemorrhage, abortion, opthalmologic abnorm.
What effects do these substances have on the fetus?
Alcohol:
Cocaine:
Smoking (nicotine/CO):
Alcohol: Common cause of birth defects; FAS
Cocaine: Abnormal fetal growth and fetal addiction; placental abruption
Smoking (nicotine/CO): Low birth weight, preterm labor, placental problems, IUGR, ADHD (nicotine leads to vasoconstriction; CO leads to impaired O2 delivery)
What does a lack or excess of iodine lead in the fetus? Maternal diabetes? Vitamin A excess? x-rays?
Iodine: congenital goiter or hypothyroidism (cretinism)
MDM: Caudal regression syndrome (anal atresia to sirenomelia), congenital heart defects, neural tube defects
Vit. A: Extremely high risk for spontaneous abortions and birth defects (cleft palate, cardiac)
X-rays: microcephaly, intellectual disability
Epid of FAS? What does it lead to in newborns? In most severe form? Mechanism?
Leading cause of intellectual disability in the u.s.
Incr. incidence of congenital abnormalities:
Prenatal and postnatal developmental retardation
microcephaly
facial abnormalities (smooth filtrum, hypertelorism)
Limb dislocation
heart defects
Severe: Heart/lung fistulas, holoprosencephaly
Failure of cell migration
What do dizygotic twins come from? Results in placenta? HOw common? What do monozygotic twins arise from? What is the result if the cleavage occurs during days 0-4? What is this period called? How common is this? Same questions for 4-8, 8-12, >13
Dizygotic (80%)=2 eggs and two sperms
Dichorionic diamniotic
Monozygotic=1 egg and 1 sperm that split into 2 zygotes early on.
0-4 days (25%)=zygote splits leading to dichorionic diamniotic with either fused placenta or separate placenta
4-8 days (75%)=morula splits leading to monochorionic diamniotic
8-12 days (13 days=embryonic disc is already formed then splits leading to monochorionic monoamniotic conjoined twins.
What is the function of the placenta? Describe basic anatomy of placenta. Origin of cytotrophoblast? Location? Function? Origin of syncytiotrophoblast? Location? Function? What does it lack? Origin of decidua basalis?
Primary site of nutrient and gas exchange between mother and fetus
Baby is surrounded by amniotic fluid. On the other side of the amniotic lining, there are fetal arteries and veins. These arteries branch up into lacunae toward the mothers side of the placenta. Inside of the lacunae is the mother’s blood. On the other side of the lacunae (mother’s side), there is the decidua basalis. The maternal artery and vein directly connect with lacuna. The villi are lined with cytotrophoblasts on its inner side, and syncytiotrophoblasts on its outer layer. Therefore, the lacunae are lined by sync on its inner layer and cyto on its outer layer. The villi communicate with the mother’s blood in lacunae. The fetal arteries and veins form into the umbilical arteries and vein in the umbilical cord.
Cytotrophoblast: Makes cells (fetal component)
Sync: Secrete hCG (similar to LH; stimulates corpus luteum to secrete progesterone during 1st tri)
Lacks MHC-I=decr. chance of attack by maternal immune system
Decidua basalis=endometrium
How many umbilical arteries are there? function? What is the function of the umbilical veins? How many? What are they derived from? What else is located within the umbilical cord? What is single umbilical artery associated with?
UA (2)=return deoxygenated blood from fetal internal iliac arteries to placenta
UV (1)=supplies oxygenated blood from placenta to fetus; drains into IVC via liver or ductus venosus
Derived from allantois
Single UA is associated with congen and chromosom abnormal.
Allantoic duct and wharton jelly
Describe the development of the urachus. Timeline? What is a patent urachus? Result? What is a urachal cyst? Pathphys? Complications? What is a vesicourachal diverticulum? Result?
3rd week-yolk sac forms the allantois, which extends into urogenital sinus. Allantois becomes the uraches, a duct b/w the fetal bladder and yolk sac
Total failure of urachus to obliterate leads to urine d/c from umbilicus
partial failure of urachus to obliterate
Fluid filled cavity line with uroepithelium b/w umbilicus and bladder
Infection and AdenoCA
Slight failure of urachus to obliterate leads to outpouching of bladder
Decribe the destruction of vitelline duct. Timeline? What is a vitelline fistula? Result? What is pathophys of meckel diverticulum? Symptoms?
7th week-obliteratation of vitelline duct (omphalo-mesenteric duct), which connects yolk sac to midgut lumen
Vitelline fistula=vitelline duct fails to close=meconium d/c from umbilicus
Meckel=partial closure of vitelline duct, with patent portion attached to ileum.
Heteropic gastric/panc tissue
melena, hematochezia, abdominal pain
What do the aortic arch derivatives develop into? What deriv 1-6 result in? Where do right and left recurrent laryngeal nerves loop around?
1st=part of maxillay artery (external carotid)
1st arch is maximal
2nd=stapedial artery and hyoid artery
Second=Stapedial
3rd=Common carotid artery and proximal part of ICA
C is third letter of alphabet
4th=On left, aortic arch; on right, proximal part of right subclavian artery
4th arch=4 limbs=systemic
6th=proximal part of pulmonary arteries and ductus arteriosus
6th=pulmonary and pulmonary to systemic shunt
Right=beneath right subclavian
Left=beneath aortic arch
What is the branchial apparatus? Another name? What is it composed of? What are branchial clefts (another name), arches, and pouches derived from?
Pharyngeal apparatus
Clefts, arches, and pouches
CAP covers from outside to inside
Cleft/Groove=ectoderm
Arches=mesoderm and neural crest
Pouches=Endoderm
