Embryology Flashcards
Trilaminar Embryo: Layers
Ectoderm: neural tissue and surface epithelium
Mesoderm: most connective tissue of the body, muscle, bone, catiliage
Endoderm: lining epithelium of the gastrointestinal, urogenital, and respiratory tract
*all developed within 1-3 wks of development
Otic Vesicle Development
- evagination (folding out) and takes elongated shape
- -> divides into utricular-saccular area and a tubular extension –> endolymphatic duct - Week 4.5: portion of the otic vesicle connected to the endolymphatic duct can be recognized as the future vestibular portion of the labyrinth. Slender portion elongates from the saccular area as the future cochlea.
- End of Week 6: 3 arch-like out pockets are visible and will become the semicircular canals
Ossicle Development: Branchial Arches
1st arch: responsible for of the body structure of the malleus and incus
2nd arch: lenticular process of the incus, handle of the malleus, and stapes.
8.5 weeks: malleus and incus have cartilaginous adult like form. stapes continues to develop into the 15th week
15-16 weeks: ossification of the malleus and incus occurs
18 weeks: ossification of the stapes—> continues throughout life, even after ossification is complete
Abnormalities
Genetic, Environmental, Unknown
Genetic Abnormalites
Developes within the first 2 weeks of development
- chromosomal
- translocation of chromosome segments
Genetic Abnormalites
Developes within the first 2 weeks of development
- chromosomal
- translocation of chromosome segments
- singe gene mutation
Environmental Abnormalities
Teratogens= maternal effects (smoking, alcohol, drugs)
- bateria, virus, and parasites
- hyperthermia environmental contaminants, and radiation
External Ear Abnormalities
-low set or uneven ears= developmental abnormality of the head growth
-Thickened lobes= abnormal incus and stapes
-smaller cup ears w/o cartilage= mennonite absence of the incus and stapes
-absent superior crus=congenital ossicle fixation
Antonia— pharyngeal hillocks failing to form
External Ab: Antonia
- impacts external auditory meatus and middle ear bones
- Genetic associations: 1. Mandibulofacial dyostosis- treacher collins syndrome 2. hemifacial microsomia 3. Congenital aural atresia
External Ab: Treacher Collins
- Downward slanting eyes
- small jaw and chin
- alters development of facial bones and tissues
External Ear Ab: Auaral Atresia
No ear canal
External Ear Ab: Microtia
Small cup or over folded auricle.
- 40 + different associations (including syndromes0
- heairng and vison impairments
- -neurological abnormalities
- -clefting of the face and palate
- -musculoskeletal abnormalities
- may be caused by maternal drugs (thalidomidie, retinoic acid)
External Ear Ab: Aurical Fistulas and Sinuses
- harmless
- in 1/4 births
aurical appendages (tags) are common and not related to other developmental conditions
Stenosis (abnormal narrowing) of the EAC= uncommon postnatally due to chronic otitis extrna or acquired atresia`
FAS
- causes external ear abnormalities
- -lower/uneven ear position
- -“railroad track” ear= auricle ahas a curve at the top part of the ear
FASD
Fetal Alcohol Spectrum Disorders—effects that can occur in mothers who drank alcohol during pregnancy
Ex:
–physical, mental, behavioral, and leaning disabilities
–delayed auditory function, SNHL, and intermittent CHL (b/c of recurrent otitis media)
