Repro embryology Flashcards
Sonic hedgehog gene
patterning along the anteroposterior axis and CNS development
Mutation in the sonic hedgehog gene can result in
holoprosencephaly - failure of the prosencephalon (the embryonic forebrain) to sufficiently divide into the double lobes of the cerebral hemispheres. The result is a single-lobed brain structure and severe skull and facial defects.
Wnt-7 gene
produced at apical ectodermal ridge
important for dorsal-ventral axis organization
Fibroblast growth factor (FGF) gene
produced at apical ectodermal ridge
stimulates mitosis of underlying mesoderm –> lengthening of limb
Homeobox (HOX) genes
involved in segmental organization of embryo in a craniocaudal direction
code for transcription factors
HOX mutations –> appendages in wrong locations
ovulation secretes
secondary oocyte
When does hCG secretion begin and implantation of blastocyst
hCG secretion begins and implantation of blastocyst
Within week 1 development
think blastoSIX –> day 6
When does the fetus develop bilaminar disc of epiblast and hypoblast
Week 2 development ( weeks = 2 layers)
bilaminar disc of epiblast and hypoblast
when does the epiblast invaginate to form the primitive streak and results in endoderm, mesoderm, ectoderm
Week 3 development
3 weeks= 3 layers
gastrulation forms trilaminar embryonic disc
epiblast invaginate to form the primitive streak and results in endoderm, mesoderm, ectoderm
notochord arises from midline mesoderm
overlying ectoderm becomes neural plate
when is the fetus extremely susceptible to teratogens
weeks 3-8 (embryonic period) development
EXTREMELY susceptible to teratogens because this is when neural tube is formed by neuroectoderm and closes by week 4. Also have organogenesis
before week 3 its an all or none effect
after week 6 its a growth and function affect
Heart beats and limb buds form
Week 4
4 weeks=4 limbs and 4 heart chambers
fetal cardiac activity visible on tranvaginal ultrasound
Week 6
Fetal movement starts at
week 8
8 is GAIT
Genitalia develop male or female characterisitics
Tenitalia
week 10
craniopharyngioma
benign rathke pouch tumor with cholesterol crystals, calcifications
Embryonic derivatives of the surface ectoderm
epidermis adenohypophysis from Rathke pouch lens of eye epithelial linings of oral cavity sensory organ of ear olfactor epithelium anal canal below the pectinate line parotid sweat mammary glands
Embryonic derivatives of the neural tube
Brain
Retina
Spinal cord
neuroectoderm –> think CNS
neural plate –> nucleus pulpulsos
Embryonic derivatives of the Neural crest
Melanocytes Myenteric (Aurbach)plexus Odontoblasts Endocardial cushions Laryngeal cartilage Parafollicular cells of thyroid PNS Adrenal medlla and all ganglia Spiral membrane Schwann cells Pia and arachnoid bones of skull
“PNS and non neural structure nearby”
Embryonic derivatives of the mesoderm
Muscle Bone CT Serous linings of body cavities spleen cardiovascular structures lymphatics blood wall of gut tube upper vagina kidneys adrenal cortex dermis testes ovaries
Mesodermal defects
VACTERL
Vertebral defects Anal atresia Cardiac defects Tracheo esophageal fistula Renal defects Limb defects
Embryonic derivatives of the endoderm
gut tube epithelium
anal canal above the pectinate line epithelium
most of urethra and lower vagina
luminal epithelia derivatives
aplasia vs agenesis
agenesis is absent organ due to absent primordial tissue
aplasia is absent organ despite presence of primordial tissue
deformation vs malformation
deformation is extrinsic disruption that occurs after embryonic period
malformation is intrinsic disruption that occurs during embryonic period (weeks 3-8)
sequence error
abnormalities result from a single primary embryologic event
Teratogen medications: ACEi
renal damage
Teratogen medications: Alkylating agents
absence of digits, multiple anomalies
Teratogen medications: aminoglycosides
ototoxicity
“a mean ol’ guy hit baby in the ear”
Teratogen medications: antiepileptic drugs
neural tube defects
cardiac defects
cleft palate
skeletal abnormalities
Teratogen medications: Diethylstilbestrol
vaginal clear cell adenocarcinoma
congenital mullerian anomalies
Teratogen medications: folate antagonists
neural tube defects
trimethoprim
Methotrexate
Teratogen medications: Isotretinoin
multiple severe birth defects
contraception mandatory
think isoTERATinion
Teratogen medications: Lithium
ebstein anomaly (apical displacement of tricuspid valve)
Teratogen medications: Methimazole
aplasia cutis congenita
Teratogen medications:Tetracyclines
discolored teeth
inhibited bone growth
Teethracyclines
Teratogen medications: Thalidomide
limb defects
tha-limb-domide
Teratogen medications: warfarin
bone deformities, fetal hemorrhage, abortion, ophthalmologic abnormalities
do not wage war on the baby. Keep it heppy with herparin because it does not cross the placenta
Teratogen: maternal diabetes
caudal regression syndrome (anal atresia to sirenomelia)
congenital heart defects Neral tube defects macrosomia neonatal hypoglycemia Polycythemia
Teratogen: vitamin A excess
extremely high risk for spontaneous abortions and birth defects like cleft palate and cardiac
Baby has a smooth philtrum, thin vermillion border (upper lip), small palpebral fissures, limb dislocation, heart defects
Fetal alcohol syndrome
can also have microcephaly
if very severe: heart lung fistulas and holoprosencephaly in most severe form
mechanism? failure of cell migration
Neonatal abstinence syndrome
complex disorder involving CNS, ANS, GI systems
Secondary to maternal opiate use/abuse
dizygotic twins
arise from a separate egg and sperm
dichorionic
diamniotic
Monozygotic twins
1 egg and 1 sperm
Monozygotic twin’s chorionicity and amnionicity depends on time of cleavage
0-4 days: dichorionic and diamniotic
4-8 days: monochorionic and diamniotic
8-12 days: monochorionic and monoamniotic
13+ days: shared body (conjoined) and monochorionic, monoamniotic
fetal component of the placenta
cytotrophoblast (inner) –> makes cells
syncytiotrophoblast (outer) –> synthesizes hormones
lack of ____ expression in fetal placenta decreases the chance of attack by maternal immune system
MHC-I
hCG from the syncytiotrophoblast
stimulates the corpus luteum to secrete progesterone during first trimester
Maternal component of the placenta
decidua basalis which is derived from endometrium
maternal blood in lacunae
most common type of monozygotic twins? second most?
most common is monochorionic diamniotic
second most common is dichorionic and diamniotic
components of the umbilical cord
2 umbilical arteries
1 umbilical vein
role of umbilical arteries and veins
arteries return deoxy blood from fetal internal iliac arteries to placenta
veins supply oxygenated blood from placenta to fetus and drains into IVC via liver or via ductus venosus
umbilical arteries and veins are derived from
allantois
Yolk sac forms the _____ in the 3rd week
allantois
which extends into urogenital sinus
The allantois becomes the ______, a duct between fetal bladder and umbilicus
urachus
obliterated urachus is the
median umbilical ligament
patent urachus
urine discharge from umbilicus
urachal cyst
partial failure in obliteration of urachus
fluid filled cavity lined with uroepithelium between umbilicus and bladder
can become infected and present as painful mass below umbilicus
Vesicourachal diverticulum
slight failure of urachus to obliterate
outpouching of bladder
vitelline duct connects the ____ to the ____. It is obliterated in the ____ week
yolk sac to the midgut lumen
7th
vitelline fistula
vitelline duct fails to close and meconium discharge from ubilicus
Meckel diverticulum
partial closure of vitelline duct
patent portion attached to ileum (true diverticulum)
can get melena, hematochezia, abdominal pain
aortic arch derivatives : 1st
1 is maximal
maxillary artery
aortic arch derivatives : 2nd
stapedial artery
hyoid artery
2 arteries
aortic arch derivatives : 3rd
common carotid artery
internal carotid artery
C is the 3rd letter of alphabet
aortic arch derivatives : 4th
left: aortic arch
Right: proximal R. subclavian artery
aortic arch derivatives : 5th
proximal part of pulm arteries ductus arteriosus (left)
____ nerve loops around the R. subclavian artery
right recurrent laryngeal nerve
_____ nerve loops around aortic arch distal to the ductus arteriousus
left recurrent laryngeal nerve
Branchial apparatus
CAP
Branchial cleft –> ectoderm
Branchial arches –> mesoderm and neural crest
Branchial Pouches –> endoderm
Branchial cleft derivatives
1st cleft: EAM
2nd-4th: temporal cervical sinuses
persistent cervical sinuses
normally obliterated by proliferation of 2nd arch mesenchyme
branchial cleft cyst within lateral neck, anterior to sternocleidomastoid muscle
Branchial arch derivatives: 1st branchial arch
Cartilage: maxilla, zygomatic, meckel cartilage, mandible, malleus, incus, sphenomandibular ligament
mm: muscles of mastication(temporalis, masseter, lateral and medial pterygoids), mylohyoid, anterior belly of digastric, tensor tympani, anterior 2/3 of tongue, tensor veli palatini
CN V3
“chewing”
Branchial arch derivatives: 2nd branchial arch
cartilage: reichert cartilage, stapes, styloid process, lesser horn of hyoid, stylohyoid ligament
mm: muscles of facial expression, stapedius, stylohyoid, platysma, posterior belly of digastric
CN7
“smile”
Pierre robin sequence
micrognathia, glossoptosis, cleft palate, airway obstruction
Branchial arches 1 and 2
Treacher collins syndrome
neural crest dysfunction causing mandibular hypoplasia and facial abnormalities
branchial arches 1 and 2
Branchial arch derivatives: 3rd
cartilage: greater horn of hyoid
mm: stylopharyngeus
CN 9 (glossopharyngeal) "swallow"
Branchial arch derivatives: 4th-6th
Cartilage: arytenoids, cricoid, corniculate, cuneiform, thyroid
Muscles: 4th arch is most pharyngeal constrictors, cricothyroid, levator veli palatini
6th arch: all intrinsic muscles of larynx except cricothyroid
arch 3 and 4 make the posterior 1/3 of tongue
arch 5 makes no major developmental contributions
CN X (superior laryngeal branch) for 4th arch
“swallow”
CN X (recurrent/inferior laryngeal branch) for 6th arch
“speak”
CNs for branchial arches mnemonic
children tend to first CHEW, then SMILE, then SWALLOW STYLishly, or simply SWALLOW, and then SPEAK
Branchial pouch derivatives: 1st
middle ear cavity
eustachian tube
mastoid air cells
endoderm lined structures of the ear
Branchial pouch derivatives 2nd
epithelial lining of palatine tonsil
Branchial pouch derivatives 3rd
dorsal wings –> inferior parathyroids
ventral wings –> thymus
ends up below 4th pouch structures
Branchial pouch derivatives 4th
Dorsal wings –> superior parathyroids
Ventral wings –> ultimobranchial body and parafollicular (C) cells of thyroid
mnemonic for Branchial pouch derivatives
Ear, tonsils, bottom to top
1 ear 2 tonsils 3 bottom for inf parathyroids (dorsal) 3 to =thymus (ventral) 4 top (superior parathyroids)
what pouches are problematic in digeorge
3rd and 4th puches
3rd ventral = thymus
3rd dorsal and 4 = parathyroids
t cell deficiency due to thymic aplasia and hypocalcemia due to failure of parathyroid development
What is the developmental defect in cleft lip
failure of fusion of the maxillary and merged medial nasal processes
What is the developmental defect in cleft palate
failure of fusion of the two lateral palatine shelves or failure of fusion of lateral palatine shelves with the nasal septum and/or median palatine shelf (formation of secondary palate)
female genital embryology: the mesonephric duct ____ and the ___ duct develops
degenerates
paramesonephric duct
the SRY gene on Y chromosome produces
testis determining factor
sertoli cells secrete ____ that suppresses the development of the ___ ducts
mullerian inhibitory factor (MIF)
paramesonephric duct
male development
leydig cells secrete androgens that stimualte the development of _____ ducts
mesonephric ducts
male development
Paramesonephric (mullerian) duct
develops into female internal structures : fallopian tubes, uterus, upper portion of vagina (lower portion is from the urogenital sinus)
male remnant: appendix testes
Mesonephric (wolffian) duct
develops into male internal structures except the prostate : seminal vesicles, epididymis, ejaculatory duct, ductus deferens
female remnant is gartner duct
Mullerian agenesis (MAyer Rokitansky Kuster Hauser syndrome)
primary amenorrhea (due to lack of uterine development in females) with fully developed secondary sexual characteristics (functional ovaries)
What if after the undifferentiated gonads have been exposed to the testis determining factor (due to SRY gene) , they lack sertoli cells and mor mullerian inhibitory factor?
develop male and female internal genitalia
male external genitalia
SRY gene has already made the testes but without sertoli cells/MIF we cannot inhibit paramesonephric mullerian duct development into internal female genitalia
What if after external genitalia has been differentiated into testes, there is a 5alpha reductase deficiency
inability to convert testosterone into DHT
male internal genitalia
but ambiguous external genitalia until puberty when the testosterone levels cause masculinization
leydig cells
leydig cells LEAD to male internal and external sexual differentiation
Sertoli cells
sertoli cells SHUT down female (internal) sexual differentiation
incomplete fusion of the mullerian ducts
bicornuate uterus
incomplete resorption of septum
septate uterus
complete failure of mullerian duct fusion
uterus didelphys
double uterus, cervix, vagina
pregnancy possible
Genital tubercle male and female homolog
male: via dihydrotestosterone form the glans penis, corpus cavernosum and spongiosum
female: via estrogen form glans clitoris and vestibular bulbs
Urogenital sinus male and female homolog
male: via dihydrotestosterone forms bulbourethral glands of cowper and the prostate gland
female: via estrogen forms the greater vestibular glands of bartholin and the urethral and paraurethral glands of skene
Urogenital folds male and female homolog
male: via dihydrotestosterone forms ventral shaft of penis (penile urethra)
female: via estrogen forms labia minora
Labioscrotal swelling male and female homolog
male: via dihydrotestosterone forms scrotum
female: via estrogen forms labia majora
Penile abnormality due to failure of urethral folds to fuse
hypospadias - abnormal opening of penile urethra on ventral surface
associated with inguinal hernia and cryptorchidism
more common than epispadias
penile abnormalities due to faulty positioning of genital tubercle
epispadias- abnormal opening of penile urethra on dorsal surface of penis
associated with exstrophy of bladder
Gubernaculum
male remnant: anchors tests within scrotum
female remnant: ovarian ligament + round ligament of uterus
Processus vainalis
male remnant: forms tunica vaginalis
female remnant: obliterated
