Week 7.1 Flashcards
What are the three embryonic sources for eye development?
- surface ectoderm
- neuroectoderm
- mesenchyme
How does the lens placode form?
induction of the surface ectoderm by the underlying optic vesicle (neuroectoderm of forebrain)
What is anophthalmia?
the absence of an eye
Which genes play significant roles in anophthalmia and microphthalmia?
PAX6 and SOX2
What are hyaloid vessels?
those that supply blood to the developing retina and lens, ultimately giving rise to the central artery and vein of the retina
What is coloboma?
failure of the choroid fissure to close, leaving a key hole deformity in which the iris isn’t fully formed
What gene is implicated in those with coloboma?
PAX2
How does the optic lens form?
proliferation of cells on the posterior wall of the surface ectoderm-derived lens placode
What causes congenital cataracts?
failure of the lens to clear out properly
The external layer of the eye includes what?
the sclera and cornea
The middle layer of the eye includes what?
the choroid, ciliary body, and iris
How does the sclera develop?
from mesenchyme surrounding the optic cup
What is the iridopupillary membrane?
the anterior 1/5 of the choroid that separates the anterior and posterior chambers during development but should degenerate
A child presents with a sort of web like structure covering the pupil. What’s a likely diagnosis?
persistence of the iridopupillary membrane
What are the two layers of the developing retina?
pigment epithelium and neuroepithelium
The dilator and sphincter muscles of the pupils are derived from what embryonic tissue?
neuroectoderm of the optic cup
What is aniridia?
absence of the iris
The external ear develops from what?
the first and second bronchial arches
The external auditory meatus develops from what?
the first branchial cleft
The middle ear auricles develops from what?
- malleus and incus: 1st branchial arch
- stapes: 2nd branchial arch
The inner ear develops from what?
the otic vesicle from the surface ectoderm near the hindbrain
What part of the ear develops from the first branchial pouch?
the lining of the tympanic cavity
Auricular abnormalities are often due to what?
problems with neural crest migration (i.e. branchial arch syndromes)
The otic vesicle has what two portions?
the utricular and saccular portions
The saccular portion of the otic vesicle gives rise to what?
the saccule and cochlear duct
How do the semicircular canals form?
the utriclar portion of the otic vesicle flattens and then selective PCD leaves three rings
How does the perilymphatic space of the inner ear form?
from vacuolization of the cartilaginous otic capsule
The utricular portion of the otic vesicle gives rise to what?
- utricle
- semicircular canals
- endolymphatic duct and sac
The saccular portion of the otic vesicle gives rise to what?
- saccule
- cochlear duct
What is the danger of a cytomegalovirus infection during pregnancy?
congenital deafness
What is the danger of a rubella infection during pregnancy?
congenital deafness
The pinna is formed from what earlier structures?
the six hillocks of his
The 1st, 2nd, and 3rd hillocks of his give rise to what portions fo the pinna?
- 1st: tragus
- 2nd: crus of helix
- 3rd: helix
The external auditory meatus has what two segments?
- inner 2/3 are bony
- outer 1/3 is cartilagenous
What part of the external auditory meatus forms wax?
the outer 1/3
How does the tympanic membrane form?
- inner mucosal layer from endoderm (pouch)
- middle fibers layer from mesoderm (arch)
- outer epithelial layer form ectoderm (groove)
What is the pars tensa?
the majority of the tympanic membrane and constituted by three layers
What is the pars flaccida?
a minor region of the tympanic membrane formed by just two layers
Where is the pars flaccida?
the most superior portion of the tympanic membrane
What is a pneumatic otoscope used for?
to apply negative or positive pressure to the external auditory meatus in order to asses the flexibility of the tympanic membrane
What is a pre-auricular pit?
a cyst or sinus formed in front of the ear because the epithelium between two hillocks of his failed to resorb
What is microtia?
the most common dysmorphology of the outer ear
What is atresia?
the absence of an external auditory meatus
What is otitis external?
- aka swimmers ear
- inflammation of the ear due to constant wetness
How does the eustachian tube affect pathology of the middle ear?
it is responsible for ventilating and draining the middle ear, so failure can cause problems
What is serous otitis?
fluid behind the tympanic membrane
What is acute otitis?
a middle ear infection
What is cholesteatoma?
an accumulation of epithelium within the middle ear caused by atelectasis that will eventually erode the ossicles
What is treacher collins?
a first arch anomaly characterized by mid face and mandibular hypoplasia, cleft palate, microtia, and atresia
What are the features of Pierre Robin Sequence?
- micrognathia
- glossoptosis
- cleft palat
How are first arch anomalies treated?
initially just maintain breathing and feeding
What is mandibular distraction?
a treatment for pierre robin sequence in which the jaw is pulled and stretched forward
What is hemifacial microsomia?
a first and second arch anomaly characterized by malformed auricle, ossicular malformations, facial muscle asymmetry, and hyoid malformation
What is a double aortic arch anomaly?
a fourth arch anomaly in which the right dorsal aorta fails to regress
What are the symptoms of a double aortic arch?
- cyanosis
- wheezing
- stridor
- repeat lower airway infections
What is a pulmonary artery sling?
a sixth branchial arch anomaly characterized by respiratory and feeding difficulties
How will a first pouch anomaly likely present?
with recurrent ear infections due to eustachian tube dysfunction
What is a thyroglossal duct cyst?
a midline cyst caused by 3rd or 4th pouch anomalies
A lingual thyroid is an anomaly of what earlier structure?
the third or fourth pouch
What are two possible third or fourth pouch anomalies?
- thryglossal duct cyst
- lingual thyroid
What is DiGeorge syndrome?
deficiency of thyroid, thymus, and parathyroid glands
What are the features of DiGeorge syndrome?
- cardiac anomalies
- abnormal facies
- thymic aplasia
- cleft palatee
- hypocalcemia
What are type 1 and type 2 branchial cleft anomalies?
- type 1: sinus or cyst anterior to ear canal that is lateral to CN VII
- type 2: sinus or cyst at the angle of the mandible that ends in the ear canal and can be lateral or medial to CN VII
What is the most common branchial anomaly?
a second branchial cleft anomaly that presents as a painless cyst in the anterior triangle of the neck
