embryology exam 3 text book questions Flashcards
which of the following molecules plays an important role in the determination of the dorsoventral axis of the developing limb?
A. Msx-1 B. Wnt-7a C. Hoxd-13 D. pax-1 E. FGF-8
B. Wnt-7a
What molecule is associated with myogenic cells migrating into the limb bud from the somites?
A. shh B. BMP-7 C. FGF-4 D. Pax-3 E. En-1
D. Pax-3
What is the principal function of the AER?
A. stimulating outgrowth of the limb bud
B. Setting up the anteroposterior axis of the limb bud
C. determining the specific characteristics of the ectodermal appendages of the limb
D. determining the pattern of neural ingrowth into the limb
E. attracting the subcutaneous plexus of capillaries in the limb bud
A. stimulating outgrowth of the limb bud
In the developing limb the sonic hedgehog (shh) gene product is produced in the:
A. progress zone B. region of interdigital cell death C. ZPA D. AER E. common muscle mass
C. ZPA
The connective tissue of the limb arises from the:
A. paraxial mesoderm B. neural crest C. intermediate mesoderm D. somitic mesoderm E. lateral mesoderm
E. lateral mesoderm
the formation of clubfoot (talipes equinovarus) is associated with:
A: a misplaced ZPA B. defective cellular migration from somites C. Thalidomide D. oligohydramnios E. a neural crest defect
D. oligohydramnios
an infant whose mother underwent chorionic villus sampling during pregnancy was born with the tips of two digits missing. what is the possible cause?
a tear of the amnion during chorionic villus sampling procedure could have resulted in an amniotic band wrapping around the digits and strangulating their blood supply, thereby causing the tips to degenerate and fall off
a woman who underwent amniocentesis during pregnancy gave birth to a child with a duplicated thumb. what is a possible cause?
this defect is unlikely to be related to the amniocentesis procedure because the morphology of the digits is well established by the time such a procedure is undertaken (15-16 weeks). the most likely cause is a genetic mutation
if the somites close to a limb-forming region are experimentally removed, the limbs will form without muscles. Why?
muscle-forming cells arise from somite
A child is born with webbed fingers (syndactylyl). what is the reason for this anomaly?
the immediate cause is likely the absence of programmed cell death in the interdigital mesoderm. the cause of the disturbance in cell death is currently not understood.
which of these cell and tissue types arise from cranial, but not trunk, neural crest cells?
A. sensory ganglia B. adrenal medulla C. melanocytes D. schwann cells E. none of the above
E. none of the above
which molecule is a poor substrate for migrating neural crest cells?
A. laminin B. chondroitin sulfate C. fibronectin D. type IV collagen E. hylauronic acid
B. chondroitin sulfate
neural crest cells arise from the:
A. somite B. dorsal non-neural ectoderm C. neural tube D. splanchnic mesoderm E. yolk sac and endoderm
C. neural tube
a six-month-old infant exhibits multiple congenital defects, including cleft palate, deafness, ocular hypertelorism, and a white forelock but otherwise dark hair on his head. The probable diagnosis is:
A. CHARGE association B. von Recklinghausen's disease C. HIrschsprung's disease D. Waardenburg's syndrome E. None of the above
D. waardenburg’s syndrom
what molecule is involved in the migration of neural crest cells from the neural tube?
A. Slug B. BMP-2 C. Mash 1 D. Norepinephrine E. Glial growth factor
A. slug
which is not a deriative of the neural crest?
A. sensory neurons B. motoneurons C. Schwann cells D. adrenal medulla E. dental papilla
B. motoneurons
what maintains the competecne of neural crest cells to diferentiate into autonomic neurons?
A. sonic hedgehog B. acetylcholine C. mash 1 D. glial growth factor E. transforming growth factor-beta
C. mash 1
if trunk neural crest cells are transplanted into the cranial region they can form all of the following types of cells except
A. pigment cells B. Schwann cells C. sensory neurons D. cartilage E. autonomic neurons
D. cartilage
how does the segmental distribution of the spinal ganglia occur?
Along the length of the spinal cord, migrating neural crest cells re funneled into the anterior sclerotomal region of the somites and are excluded from the posterior half. This results in the formation of a pair of ganglia for each vertebral segment and space between ganglia in the craniocaudal direction.
what are thee major differences between cranial and trunk neural crests?
Cranial crest cells can form skeletal elements; trunk crest cells cannot. Migrating cranial neural crest cells have more morphogenetic information encoded in them than trunk crest cells do. (for example, craniocaudal levels are specified in cranial crest, whereas they are not fixed in trunk crest cells.) cranial crest cells form large amounts of dermis and other connective tissues, whereas trunk crest cells do not.
neural crest-derived cells constitute a significant component of which tissue of the eye?
A. neural retina B. lens C. optic nerve D. cornia E. none of the above
D. cornea
the optic placode arises through an inductive message given off by the
A. telencephalon B. rhombencephalon C. infundibulum D. diencephalon E. mesencephalon
B. rhombencephalon
what molecule plays a roles in guidance of advancing retinal axons through the optic nerve?
A. pax-2 B. FGF-3 C. BMP-4 D. pax-6 E. BMP-7
A. pax-2
surface ectoderm is induced to become corneal epithelium by an inductive event originating in the:
A. optic cup B. chordamesoderm C. optic vesicle D. lens vesicle E. neural retina
D. lens vesicle
the second pharyngeal arch contributes to the:
A. cochlea and earlobe B. auditory tube and incus C. stapes and earlobe D. auditory tube and stapes E. otic vesicle and stapes
C. stapes and earlobe
during a routine physical examination, an infant was found to have a small segement missing from the lower part of one iris. What is the diagnosis, what is the basis for the conditions, and why may the infant be sensitive to bright light?
Colomboma of the iris is caused by failure of the choroid fissure to close during the sixth week of pregnancy. Because the area of the defect remains open when the rest of the iris constricts in bright light, excessive unwanted light can enter the eye through the defect.
why does a person sometimes get a runny nose while crying?
some of the secretions of the lacrimal glands enter nasolacrimal ducts, which carry the laccrimal fluid into the nasal cavity
what extracellular matrix molecule is often associated with migrations of mesenchymal cells, and where does such an event occur in the developing eye?
hyaluronic acid. migration of neural crest cells into the developing cornea occurs during a period when large amounts of hyaluronic acid have been secreted into the primary corneal stroma
why is the hearing of a newborn often not as acute as it is a few months later?
during the fetal period, the middle ear cavity is filled with a loose connective tissue that dampens the action of the middle ear ossicles. after birth, the connective tissue is resorbed
why are malformations or hypoplasia of the lower jaw commonly associated with abnormalities in the shape or position of the ears?
similar to the lower jaw, much of the external ear arises from tissue of the first arch bordering the first pharyngeal cleft
the facial nerve (cranial nerver VII) supplies muscles derived from which pharyngeal arch?
A. first B. second C. third D. fourth E. sixth
B. second
cleft lip results from lack of fusion of the
A. Nasomedial and nasolateral processes B. nasomedial and maxillary processes C. nasolateral and maxillary processes D. nasolateral and mandibular processes E. nasomedial and mandibular processes
B. nasomedial and maxillary processes
in cases of holoprosencephaly, defects of facial structures are typically secondary to defects of the
A. pharynx B. oral cavity C. forebrain D. eyes E. hindbrain
C. forebrain
Meckel’s cartilage is a prominent structure in the early formation of the
A. upper jaw B. hard palate C. nasal septum D. soft palate E. lower jaw
E. lower jaw
an early induction of tooth development consists of the ectoderm of the dental epithelium acting on the underlying neural crest mesenchyme. which of the following molecules is an important mediator of the inductive stimulus?
A. BMP-4 B. tenascin C. Hoxb-13 D. Msx-1 E. syndecan
A. BMP-4
a 15 year old boy with mild acne developed a tender boil along the anterior border of the sternocleidomastoid muscle. what embryological condition would be included in a differential diagnosis
one option is simply acne. another more significant possibility is a branchial cyst. branchial cysts are typically located along the anterior border of the sternocleidomastoid muscle. one possible reason for its late manifestation is the the same conditions that resulted in the boy’s acne caused a simultatneous reaction in the epidermis lining the cyst
the physician of the 15 year old boy described in the previous question determined that the boy had a congential cyst that needed to be removed surgically. what should the surgeon consider during removal of the cyst?
first, all epithelium lining the cyst must be removed or the remnants could reform into a new cyst and the symptoms could recur. the surgeon also must determine that the cyst is isolated and not connected to the pharynx via a sinus, which would result from an accompanying persistence of the corresponding pharyngeal pouch
why does a person sometimes get a runny nose while crying?
some of the secretions of the lacrimal glands enter the nasolacrimal ducts, which carry the lacrimal fluid into the nasal cavity
a woman who took an anticonvulsant drug during the tenth week of pregnancy gave birth to an infant with bilateral cleft lip and cleft palate. she sued the physician, blaming the facial malformations on the drug, and you are called in as an expert witness for the defense. what would be the basis for your case?
by 10 weeks, all the processes of fusion of facial primordia have already been completed. the cause of the defects could almost certainly be attributed to something that influence the embryo long before the time when the anticonculsant therapy was initiated, probably before the seventh week of pregnancy
a woman who averaged three mixed drinks a day during pregnancy gave birth to an infant who was mildly retarded and who had a small notch in an upturned upper lip and a reduced olfactory sensitivity. what is the basis for this constellation of defects?
these defects could be a manifestation of fetal alcohol syndrome. they could represent a mild form of holoprosencephaly, which in this case would relate to defective formation of the forebrain. the defects in olfaction and in the structure of the upper lip could be secondary effects of a primary defect in early formation of the prosencephalon
which condition is most closely associated with a distrubance of neural crest
A. anal atresia B. meckels' diverticulum C. omphalocele D. volvulus E. aganglionic megacolon
E
Meckel’s diverticulum is most commonly located in the
A. ileum B. ascending colon C. jejunum D. transverse colon E. duodenum
A
the primordium of which structure is locate dint eh septum transversum?
A. dorsal pancreas B. lung C. liver D. thymus E. spleen
C
the yolk stalk is most closely associated with which artery?
A. celiac B. umbilical C. superior mesenteric D. aorta E. inferior mesenteric
C
the dorsal pacreatic bud is initially induced rfom the gut endoderm by the
A. liver B. notochord C. lung bud D. yolk sac E. none of the above
B
splanchnic mesoderm acts as an inducer of all of the following tissues or organs except
A. teeth B. trachea C. liver D. lungs E. pancreas
A
during the first feeding, a newborn begins to choke. what conenital anomalies should be included in the differential diagnosis?
esophageal atresia or a tracheoesophageal fistula. in the former, the milk fills the blind esophageal pouch and then spills into the trachea via the laryngeal opening. in the latter, milk may pass directly from the esophagus into the trachea depending on the type of fistula
a newborn took the first feeding of milk without incident, but an hour later was crying in pain and vomited the milk with considerable force. examination revealed a hard mass near the midline in the upper region of the abdomen, what was the diagnosis?
congenital pyloric stenosis. projectile vomiting is a common symptom of this condition, and palpation of the knotted pyloric opening of the stomach confirmed the diagnosis
an infant was noted to extrude a small amount of mucus and fluid from the umbilicus when crying or straining. this should make the physician think of what congenital anomaly in the differential diagnosis?
the most likely diagnosis is a vitelline duct fistula connecting the midgut with the umbilicus. this allows some contents of the small intestines to escape through the umbilicus. another possibility is a urachal fistula which connects the urinary bladder to the umbiicus through a persistent allantoic duct. in this case however, the escaping fluid would be urine and would likely not e accompanied by mucus
a newborn was given a cursory physical examination and was taken home by the mother 1 day after delivery. several days later, the mother brought the infant to the clinic. the infant was in obvious sever discomfort with a swollen abdomen. physical examination revealed that an important congenital anomaly had been overlooked at the original examination. what was that anomaly?
imperforate anus. when examining a newborn, clinicians must ensure that there is an anal opening
