External & Middle Ear Embryology & Postnatal Flashcards
What is fetal age defined by?
The time of conception
What is gestation age defined by?
Last Menstrual Period (LMP)
Name the 3 prenatal development stages
- Pre-embryonic (0-2/3 weeks)
- Embryonic (3/4-8 weeks)
- Fetal (9 weeks-birth)
What is a morula?
12 or more blastomeres
Gastrulation
The conversion of cells to a trilaminar disc with 3 germ layers
Name the 3 layers of the trilaminar disc
Ectoderm, Mesoderm, Endoderm
Neurulation
Mesoderm cells differentiate into chord-like structure
The ectoderm forms what tissues:
- Surface epithelium
- Neural tissue
The mesoderm forms what tissues:
- Muscle
- Bone
- Cartilage
- Connective tissues
The endoderm forms what tissues:
-Epithelial linings
What ear structures are formed from ectoderm?
-Parts of pinna
-Ear canal
Lateral layer of TM
Inner ear - cochlea, SCC, utricle, saccule
CN 8
What ear structures are formed from mesoderm?
Parts of pinna
Middle layer of TM
Middle ear muscles
Middle ear bones
What ear structures are formed from endoderm?
Inner layer of TM
Middle ear cavity
Eustachian tube
Which pharyngeal arches form the outer and middle ears?
1st and 2nd
Where are the clefts located & lined by what?
Outside of each pharyngeal arch. Lined by ectoderm
Where are the pouches located & lined by what?
Inside of each arch. Lined by endoderm
What week do the 6 auricular hillocks appear?
When is the pinna adult shaped?
When is it mature?
6th fetal wk
20th fetal wk
8-9 years of age
Microtia
Micro ear / little ear
Atresia
Absence or closure of ear canal
Anotia
Absence of external ear & canal
Where does the ear canal develop from?
When do sebaceous glands form?
1st pharyngeal cleft
2nd trimester
Stenosis
Narrowing or lack of ear canal
When does the TM develop?
When does the TM reach adult orientation?
When does the annulus develop?
9-10 fetal wks
3 years of age
2 years of age
When do the ossicles: begin to develop?
Cartilage ossifies?
10 wks GA
17-31 wks GA
The middle ear muscles are fully developed by when?
6 months of fetal life
The middle ear resonant frequencies of: a chid 6-15 years of age is around ___ ? of an infant?
1000 Hz, 250 Hz
What prenatal development stage do the outer and middle ear structures form? (But not mature)
Embryonic Stage
Eustachian tube:
Where does the ET develop from?
When is it adult-like?
1st pharyngeal pouch
Matures 5-8 years of age
Name two syndromes that have abnormalities of the 1st arch causing middle ear and mandibular issues
Treacher Collins
Pierre Robin
