REPRO EMBRYO Flashcards
What is the role of the sonic hedgehog gene in limb development?
It is located in the zone of polarizing activity and is involved in patterning along an anterior-posterior axis
Which gene, expressed in the zone of polarizing activity is involved in patterning along an anterior posterior axis?
Sonic Hedgehog
Which gene, expressed at the apical ectodermal ridge is responsible for patterning along a dorsal-ventral axis?
Wnt-7
What is the role of the Wnt-7 gene in limb development?
produced in apical ectodermal ridge and responsible for patterning on dorsal ventral axis
What gene is responsible for lengthening limbs?
FGF (mutation in FGF3 responsible for achondroplasia)
What is the role of FGF for limb development?
It is expressed in the apical ectodermal ridge and is responsible for lengthening the limbs
A mutation in which gene would result in a limb being in the wrong place (i.e. a leg where an arm should be)?
Hox genes
What is the role of Hox genes in fetal development?
They are responsible for segmental organization of the embryo in a craniocaudal way and can result in appendages being in the wrong place
What is present in the second week of gestation?
Bilaminar germ disc (epiblast and hypoblast)
When in gestation does hCG secretion start?
within week 1 (after implantation of blastocyst)
During which week does the fetal heart begin to beat?
Week 4 (also when all 4 limbs are present, at least as buds)
How does gastrulation initiate?
The epiblast of the bilaminar germ disc invaginates to form the primitive streak; gastrulation will form 3 germ layers
Which intracranial mass contains cholesterol crystals?
Craniopharyngioma from Rathke’s pouch (congential form =adamantinomatous; adult = papillary)
Where does the parotid gland come from?
surface ectoderm
Where does the lens of the eye come from? The retina and optic nerve?
lens = surface ectoderm; retina and optic nerve = neuroectoderm
Where do the parafollicular cells of the thyroid come from?
Neural crest
Where do pia and arachnoid cells come from embryologically?
Neural crest
Where does the aorticopulmonary septum come from?
Neural crest
Which organ is derived from the mesentery of the foregut?
Spleen
Where does the spleen come from, embryologically?
(Mesoderm; mesentery of the foregut)
A defect in which germ layer yields VACTERL anomaly?
mesoderm (Vertebral, Anal, Cardiac, Tracheo-Esophageal fistula, Renal, and Limb defects)
What germ layer is the notochord from? What is its embryological function?
Mesoderm; induces the ectoderm to form the neural plate (i.e. to become neuroectoderm)
What germ layer forms the eustachian tube?
Endoderm; it is from the 1st pharyngeal POUCH
What effect do ACE inhibitors have on the fetus?
Renal defects
What effect do alkylating agents have on a fetus?
absence of digits
What is the effect of aminoglycosides on fetus?
CN VIII toxicity (congenital syphilis has same etiology)
What effect does carbamazepine have on the fetus?
Neural tube defects, craniofacial defects, fingernail hypoplasia, developmental delay, IUGR
What effect does diethylstilbestrol have on the fetus?
Vaginal clear cell adenocarcinoma in future; congenital mullerian anomalies
What effect can lithium have on the fetus?
Ebstein’s anomaly (atrialization of the right ventricle)
A baby who has an atrialized right ventricle probably had a mother with what underlying condition?
Bipolar disorder, Ebstein’s anomaly is side effect of lithium.
Which drug is notable for causing Ebstein’s anomaly in the fetus?
Lithium
Which drug can cause fingernail hypoplasia and neural tube defects in fetus?
Carbamazepine
Which drug causes clear cell adenocarcinoma?
DES = Diethylstilbestrol
What can tetracylcines to the fetus?
Discolored teeth
What can thalidomide do to the fetus?
limb defects (phocomelia, amelia)
What causes caudal regression syndrome (anal atresia to sirenomelia)?
Maternal diabetes (also transposition of great arteries and anencephaly)
What is the leading cause of congenital malformations in the U.S.?
Fetal alcohol syndrome
What exactly determines the number of amnions and chorions in monozygotic twins?
The timing of when the zygote splits
Which part of the placenta secretes hCG? hCG is structurally similar to what?
syncytiotrophoblast; LH (same alpha subunit)
Which vessel do the fetal umbilical arteries come from?
internal iliac
How does umbilical vein blood get to the IVC?
bypasses through liver via the ductus venosus (ligamentum venosum in adult)
What embryological structure do the umbilical arteries and veins come from?
allantois
Where does the urachus come from? What does a patent urachus present as?
allantois; urine leaking from the belly button
What should you think if urine is coming from the umbilicus? Meconium?
Patent urachus; vitelline fistula
What embryological structure does a Meckel diverticulum come from?
vitelline duct
Which aortic arch does the maxillary artery come from?
First aortic arch
What aortic arch do the stapedial and hyoid arteries come from?
Second aortic arch
What aortic arch do common carotid artery and proximal part of internal carotid artery come from?
3rd aortic arch
What aortic arch gives rise to the definitive aortic arch?
left fourth aortic arch
What aortic arch gives rise to the right proximal subclavian artery?
right fourth aortic arch
What gives rise to the proximal part of the pulmonary arteries and the ductus arteriosus?
Left 6th aortic arch
Where do branchial clefts, arches, and pouches come from?
Clefts are on outside and from ectoderm, arches are the meaty part and from mesoderm, pouches are on inside and are from endoderm
Bones that form from the branchial clefts come from what tissue?
neural crest
What obliterates the 2nd through 4th pharyngeal cleft? What does the 1st cleft form?
Proliferation of the mesenchyme of the second arch; the first cleft forms the external auditory meatus
What is a persistent cervical sinus?
Branchial cleft cyst; patent area overgrown by 2nd arch mesenchyme
What is the name of the cartilage from the first pharyngeal arch and the second pharyngeal arch?
First arch = Meckel’s Cartilage; Second arch = Reichert’s cartilage
How is Treacher-Collins syndrome similar to Hirschsprung’s?
Both are a result of a failure of neural crest to migrate; in Hirschsprungs it is a failure to get to the myenteric plexus, in TC it is a failure to get to the first pharyngeal arch resulting in mandibular hypoplasia as the mandible is from neural crest
What nerve innervates the anterior belly of the digastric? Posterior belly of the digastric?
Anterior belly of digastric is from arch 1 and innervated by V3; posterior belly of digastric is from arch 2 and innvervated by VII
Which syndrome results from a failure of neural crest to migrate to the first pharyngeal arch?
Treacher-Collins
What are the 6 branchial arches innervated by?
Arch 1 = CN V; Arch 2 = CN VII; Arch 3 = CN IX; Arches 4-6 = CN X
Muscles of mastication are from which branchial arch? Muscles of facial expression are from which branchial arch?
First arch; Second arch
Which branchial arch gives rise to the superior laryngeal branch of CN X? Which gives rise to the recurrent laryngeal branch of CN X?
4th arch; 6th arch
What does Meckel’s cartilae give rise to? (4)
From 1st branchial arch: Mandible (implicated in Treacher Collins), Malleus, incus and sphenomandibular ligament
What does Reichert’s cartilage give rise to (4)?
From 2nd branchial arch: Stapes, Styloid process, Stylohyoid ligament, and lesser horn of hyoid
What arch is the stylopharyngeus from? What arch is the stylohyoid ligament from?
Stylopharyngeus is from arch 3 (CN IX); Stylohyoid ligament is from arch 2
What arches do levator veli palatini and tensor veli palatini come from?
Tensor veli palatini is from branchial arch 1; levator veli palatini is from arch 4
What gives rise to the external auditory meatus? Eustachian tube?
External meatus = first pharyngeal cleft; Eustachian tube and internal meatus = first pharyngeal pouch
What structure gives rise to the epithelial lining of the palatine tonsils?
Secoond pharyngeal pouch
What does the 3rd pharyngeal pouch give rise to?
Dorsal aspect gives rise to the inferior parathyroids (while the 4th pouch ascends to become superior parathyroids) and the ventral aspect gives rise to the thymus
Where does the thymus come from?
3rd pharyngeal pouch
MEN 2A is a mutation in RET in the neural crest lineage, explain the significance.
Neural crest gives rise to chromaffin cells (pheochromocytoma), to parathyroids = parathyroid tumor and to parafollicular thyroid cells = medullary thyroid cancer
What cell lineage is affected by MEN 2A?
Neural crest (pheochromocytoma = chromaffin cells, medullary thyroid CA = parafollicular cells, and parathyroid tumors)
What gene is responsible for testis-determining factor?
SRY gene on Y chromosome
Which cells are responsible for suppressing development of mullerian ducts in males? Which are responsible for stimulating the development of the mesonephric ducts in men?
Sertoli cells secrete mullerian inhibiting factor to inhibit paramesonephric ducts; Leydig cells secrete testosterone which stimulates mesonephric duct development
Discuss the roles of the Sertoli and Leydig cells in genital embryology
Under stimulation by TDF, the gene product of SRY on the Y chromosome, Sertoli Cells secrete MIF to inhibit mullerian ducts and Leydig cells secrete testosterone to stimulate mesonephric ducts? Note: conversion of test to DHT via 5 alpha reductase is responsible for EXTERNAL male genitalia
What is the gene product of the SRY gene on the Y chromosome?
TDF = Testis Determining Factor
Which cells secrete mullerian inhibiting factor?
Sertoli cells
How do mullerian defects present?
primary amenorrhea with anatomical defects and FULLY DEVELOPED SECONDARY SEX CHARACTERISTICS–which indicates functional ovaries
Where do the seminal vesicles, epididymis, ejaculatory duct, and ductus deferens come from?
The Wolffian duct (mesonephric duct)
What happens when there is incomplete fusion of the paramesonephric ducts?
bicornuate (bifid) uterus
How would a congenital 5 alpha reductase deficiency present in a boy?
male internal genitalia with ambiguous external genitalia, as the internal genitalia is determined by testosterone but the external is determined by DHT
How would a congenital lack of sertoli cells present in a boy?
They would develop both male and female INTERNAL genitalia due to the lack of mullerian inhibiting factor but they would develop male EXTERNAL genitalia as that is determined by DHT which is formed by 5 alpha reductase
What does hypospadias increase risk of? What does epispadias increase risk of?
Hypospadias = UTI’s; Epispadias is associated with bladder exstrophy and increases the risk of transitional cell carcinoma
Where does the prostate come from?
urogenital sinus
What does the urogenital sinus form in males? Females?
Males: prostate gland and Bulbourethral glands (Cowper’s glands); Females: Bartholin glands and Skene Glands
What occurs in boys when the genital tubercle is not placed correctly? When the urogenital folds close improperly?
Epispadias; Hypospadias
What is exstrophy of the bladder associated with developmentally? Long term?
epispadias; increased risk of transitional cell carcinoma
What is the fetal version of the gubernaculum testes? What is the female remnant of the processus vaginalis?
ovarian ligament and round ligament of the uterus; obliterated
