External & Middle Ear Embryology & Postnatal

Question 1

What is fetal age defined by?

Answer 1

The time of conception

Question 2

What is gestation age defined by?

Answer 2

Last Menstrual Period (LMP)

Question 3

Name the 3 prenatal development stages

Answer 3

1. Pre-embryonic (0-2/3 weeks)
2. Embryonic (3/4-8 weeks)
3. Fetal (9 weeks-birth)

Question 4

What is a morula?

Answer 4

12 or more blastomeres

Question 5

Gastrulation

Answer 5

The conversion of cells to a trilaminar disc with 3 germ layers

Question 6

Name the 3 layers of the trilaminar disc

Answer 6

Ectoderm, Mesoderm, Endoderm

Question 7

Neurulation

Answer 7

Mesoderm cells differentiate into chord-like structure

Question 8

The ectoderm forms what tissues:

Answer 8

• Surface epithelium

- Neural tissue

Question 9

The mesoderm forms what tissues:

Answer 9

• Muscle
• Bone
• Cartilage
• Connective tissues

Question 10

The endoderm forms what tissues:

Answer 10

-Epithelial linings

Question 11

What ear structures are formed from ectoderm?

Answer 11

-Parts of pinna
-Ear canal
Lateral layer of TM
Inner ear - cochlea, SCC, utricle, saccule
CN 8

Question 12

What ear structures are formed from mesoderm?

Answer 12

Parts of pinna
Middle layer of TM
Middle ear muscles
Middle ear bones

Question 13

What ear structures are formed from endoderm?

Answer 13

Inner layer of TM
Middle ear cavity
Eustachian tube

Question 14

Which pharyngeal arches form the outer and middle ears?

Answer 14

1st and 2nd

Question 15

Where are the clefts located & lined by what?

Answer 15

Outside of each pharyngeal arch. Lined by ectoderm

Question 16

Where are the pouches located & lined by what?

Answer 16

Inside of each arch. Lined by endoderm

Question 17

What week do the 6 auricular hillocks appear?
When is the pinna adult shaped?
When is it mature?

Answer 17

6th fetal wk
20th fetal wk
8-9 years of age

Question 18

Microtia

Answer 18

Micro ear / little ear

Question 19

Atresia

Answer 19

Absence or closure of ear canal

Question 20

Anotia

Answer 20

Absence of external ear & canal

Question 21

Where does the ear canal develop from?

When do sebaceous glands form?

Answer 21

1st pharyngeal cleft

2nd trimester

Question 22

Stenosis

Answer 22

Narrowing or lack of ear canal

Question 23

When does the TM develop?
When does the TM reach adult orientation?
When does the annulus develop?

Answer 23

9-10 fetal wks
3 years of age
2 years of age

Question 24

When do the ossicles: begin to develop?

Cartilage ossifies?

Answer 24

10 wks GA

17-31 wks GA

Question 25

The middle ear muscles are fully developed by when?

Answer 25

6 months of fetal life

Question 26

The middle ear resonant frequencies of: a chid 6-15 years of age is around ___ ? of an infant?

Answer 26

1000 Hz, 250 Hz

Question 27

What prenatal development stage do the outer and middle ear structures form? (But not mature)

Answer 27

Embryonic Stage

Question 28

Eustachian tube:
Where does the ET develop from?
When is it adult-like?

Answer 28

1st pharyngeal pouch

Matures 5-8 years of age

Question 29

Name two syndromes that have abnormalities of the 1st arch causing middle ear and mandibular issues

Answer 29

Treacher Collins

Pierre Robin