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Flashcards in The Ear - HY Deck (46):
1

The otic placode ...?

Invaginates into the connective tissue (mesenchyme) adjacent to the rhombencephalon and becomes the OTIC VESICLE.

2

The otic vesicle divides into ...?

Utricular + Saccular portions.

3

The utricular portion of the otic vesicle gives rise to ...?

1. Utricle.
2. Semicircular ducts.
3. Vestibular ganglion of CN VIII.
4. Endolymphatic duct and sac.

4

The utricle:

1. Contains the sensory hair cells and otoliths of the macula utriculi.
2. Responds to LINEAR acceleration + GRAVITY.

5

The semicircular ducts:

1. Contain the sensory hair cells of the cristae ampullares.
2. Respond to ANGULAR acceleration.

6

The vestibular ganglion of VIII lies ...?

At the base of the internal auditory meatus.

7

The endolymphatic duct and sac is ...?

A membranous duct that connects the saccule to the utricle and terminates in a blind sac beneath the dura.

8

The endolymphatic sac ...?

Absorbs the endolymph.

9

The saccular portion of the otic vesicle gives rise to ...?

1. Saccule.
2. Cochlear duct (organ of Corti).

10

The saccule ...?

1. Contains the sensory hair cells and otoliths of the macula sacculi.
2. The saccule responds to LINEAR acceleration + GRAVITY.

11

The cochlear duct (Organ of Corti):

1. Involved in hearing.
2. Has pitch (tonopic) localization by which high-freq waves are detected at the base + low-freq --> at the apex.
3. Spiral ganglion of CN VIII lies in the modiolus of the bony labyrinth.

12

The membranous labyrinth consists of ...?

All the structures derived from the OTIC VESICLES.

13

The membranous labyrinth is initially ...?

Surrounded by neural crest cells that form a connective tissue (mesenchyme) covering.
--> This connective tissue becomes cartilaginous and then ossifies to become the BONY LABYRINTH of the temporal bone.

14

The connective tissue closest to the membranous labyrinth ...?

DEGENERATES, thus forming the perilymphatic space containing perilymph.
--> This sets up the interesting anatomic relationship by which the membranous labyrinth floats within the bony labyrinth by perilymph.

15

Perilymph, which is similar to composition to CSF, ...?

Communicates with the subarachnoid space via the perilymphatic duct.

16

Malleus develops from ...?

Cartilage of pharyngeal arch 1 (Meckel's cartilage) and is attached to tympanic membrane.

17

The malleus is moved by the ...?

Tensor tympani muscle, which is innervated by the V3.

18

The incus develops from ...?

The cartilage of pharyngeal arch 1 (Meckel's cartilage).

19

The incus ...?

Articulates with the malleus and stapes.

20

The stapes develops from ...?

The cartilage of pharyngeal arch 2 (Reichert's cartilage).

21

The stapes is moves by the ...?

Stapedius muscle, which is innervated by VII.

22

The stapes is attached to the ...?

Oval window of the vestibule.

23

Auditory tube and middle ear cavity develop from ...?

Pharyngeal pouch 1.

24

The tympanic membrane develops from ...?

Pharyngeal membrane 1.

25

The tympanic membrane separates the ...?

Middle ear from the external auditory meatus of the external ear.

26

The tympanic membrane is innervated by ...?

V3 and IX.

27

The external auditory meatus develops from the ...?

Pharyngeal groove 1.

28

The external auditory meatus becomes filled with ...?

Ectodermal cells, forming a temporary meatal plug that disappears before birth.

29

The external auditory meatus is innervated by ...?

V3 and IX.

30

The auricle (pinna) develops from ...?

6 auricular hillocks that surround pharyngeal groove 1.

31

The auricle is innervated by ...?

V3, VII, IX, X, C2, C3.

32

Minor auricular malformations ...?

Commonly found and raise only cosmetic issues.

33

However, minor auricular malformations may be associated with ...?

1. DOWN.
2. Patau (13).
3. Edwards (18).

34

Low-set slanted auricles may indicate ...?

Chromosomal abnormalities - Down, Patau, Edwards.

35

Auricular appendages are ...?

Skin tags that are commonly found ANTERIOR to the auricle (ie pretragal area) --> Cosmetic issues.

36

The embryologic basis of auricular appendages is ...?

The formation of accessory auricle hillocks.

37

Atresia of the external auditory meatus - Complete?

A complete atresia consists of a bony plate in the location of the tympanic membrane.

38

Atresia of the external auditory meatus - Partial atresia?

Consists of a soft tissue plug in the location of the tympanic membrane.

39

Atresia of the external auditory meatus results in ... and is usually associated with ... .

Conduction deafness, 1st arch syndrome.

40

A preauricular sinus is a ...?

Narrow tube or shallow pit that has a pinpoint external opening.

41

Congenital cholesteatoma (epidermoid cyst) is a ...?

Benign tumor found in the middle ear cavity that results in CONDUCTION DEAFNESS.

42

Embryological basis of congenital cholesteatoma?

Proliferation of ENDODERMAL cells lining the middle ear cavity.

43

Microtia is a ...?

Severely disorganized auricle that is associated with other malformations resulting in DEAFNESS.

44

Embryological basis of microtia ...?

Impaired proliferation or fusion of the auricular hillocks.

45

Congenital deafness ...?

The organ of Corti may be damaged by exposure to RUBELLA, especially during weeks 7 and 8 of development.

46

The internal ear develops in ...?

Week 4 - From a thickening of the surface ectoderm called the OTIC PLACODE.