Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Med Neuro Block 2 > Development of the Eyes and Ears > Flashcards

Development of the Eyes and Ears Flashcards

1
Q

What are the four precursor tissues of the eye?

A
  1. Surface ectoderm
  2. Neural ectoderm
  3. Neural crest ectomesenchyme
  4. Head mesenchyme
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

The initial primordium of the eye is an outgrowth of what?

A

The developing brain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the first step of the development of the eye?

A
  1. Neural ectoderm (diencephalon) invaginates to become the optic sulcus
  2. Optic sulcus invaginates further to become the optic vesicle, which is induced to become the lens placode.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the second step in the development of the eye? What is the resulting structure?

A

The optic vesicle asymmetrically invaginates to become the optic cup.

The optic cup invaginates to become the lens vesicle that’s surrounded by the optic cup.

Result is 2-layered optic cup that is open inferiorly as the choroid (retinal) fissure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the third step in the development of the eyes?

A

Optic cup and lens continue to enfold to become spherical and form the lens vesicle.

Lens vesicle separates from the surface to form the corneal placode.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are primary and secondary anopthalmia? What does this usually present as clinically?

A

Absense of ocular structures.

  • primary is eyes only
  • secondary is eyes + forebrain

Clinically it’s usually seen as micropthalmia because true anopthalmia is very rare.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is cyclopia? What about synophthalmia?

A

Cyclopia: one eye

Synophthalmia: two eyeballs in the same orbit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What signaling center controls early development of the eyes? What genes are involved?

A

The presencephalic signaling center.

Pax 6 and sonic hedgehog (Shh) signaling is involved.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is the retina formed?

A

The optic vesicle asymmatrycally ingavinates to form the optic cup with an inner layer (mediated by pax6) and an outer layer (mediated by Otx and Mitf) that makes up the retina.

The layers have an intraretinal space between them.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The outer and inner layers of the optic cup contribute to the development of what?

A

The retina, iris, and ciliary body.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Most of the optic disk becomes what part of the retina? What is the other part?

A

The sensory retina: which is 9 out of the 10 layers the retina.

The last layer is the outer layer made of pigmented epithelium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What forms the iris and ciliary body? When does this occur?

A

The ventral edge of the optic cup becomes the iris and ciliary body; begins during fetal period.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does the optic nerve form?

A

The optic vesicle becomes the optic stalk via the narrowing of the connection to the diencephalon and Pax2.

Nerve fibers project from the optic stalk to form the optic nerve.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does the lens form?

A

The optic vesicle becomes the lens placode.

The lens placode invaginates to become the lens pit, which turns into the lens vesicle and separates from the surface ectoderm to become the lens.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What allows the lens to be transparent?

A

Alpha and beta crystallin proteins in all of the lens cells and fibers.

Gamma crystallin protein only in lens fibers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How can rubella impact lens development?

A

It has a teratogenic influence and causes congenital cataracts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How is the cornea formed?

A

The lens vesicle recieves inductive signals to become the corneal placode.

The corneal placode becomes three layers: the anterior corneal epithelium, the corneal stroma, and the corneal endothelium.

18
Q

What is each part of the cornea derived from?

A

Anterior corneal epithelium: surface ectoderm

Corneal endothelium: neural crest ectomesenchyme

Corneal stroma: head mesoderm and neural crest ectomesenchyme

Conjunctive: surface ectoderm

19
Q

How do the eyelids develop?

A

Upper from frontonasal prominence, lower from the maxillary prominence.

Fuse at week 8-9 and reopen at 5-7 months.

20
Q

What is the hyaloid system?

A

Vessels that sprout from the ophthalmic artery and initially supply the retina, lens, and vitreous.

Only the retinal branches remain in the adult.

21
Q

How do extraocular eye muscles develop?

A

From the head mesoderm of occipital somites.

22
Q

How do the aqueous chamber develop? What about the vitreous body?

A

Aqueous chambers: from clefts in mesenchyme ventral to the lens

Vitreous body: mesoderm derived structure primarily replaced by secondary at week 8

23
Q

What can be caused by abnormal development of the scleral angle?

A

Fluid accumulation resulting in congenital glaucoma.

24
Q

What is coloboma?

A

A notch in ocular structures; inferior to the iris is most common.

Occurs when retinal fissure doesn’t fully close.

25
Q

What is microphthalmia?

A

A reduction in globe volume.

Amount of deficiency depends on the time of insult.

26
Q

Most of the ear is located within what bone? What are the components of this bone?

A

Temporal:
1. Petromastoid portion: stuck in middle cranial fossa, location of inner ear

  1. Styloid portion
  2. Squamous portion: flat
  3. Tympanic portion: supports tympanic membrane and opens into middle ear.
27
Q

What forms the auricle? When does the auricle actually look like an ear?

A

6 auricular hillocks which are mesenchyme swellings that surround the 1st groove opening.

3 from 1st arch and 3 from second arch.

Looks like ear in week 8 but still isn’t in right location.

28
Q

What parts of the ear are thought to come from each arch?

A

Arch 1: tragus and part of helix (large ridge).

Arch 2: remainder of auricle

29
Q

What forms the cartilaginous portion of the external acoustic meatus? What about the osseous portion?

A

Cartilage portion: Dorsal part of the 1st pharyngeal groove.

Osseous: medial extension of 1st groove becomes meatal plug, which flattened medial end becomes the meatal plate ie the outer surface of the eardrum.

30
Q

What does the expansion of the first pharyngeal pouch form?

A

Called the tubotympanic recess, which forms the epithelial covering of the tympanic cavity mucosa as well as the auditory tube mucosa.

31
Q

What is the origin of the ossicles of the ear? What do they become covered by?

A

Pharyngeal arch 1: malleus and incus
Pharyngeal arch 2: stapes

Become covered by middle ear mucosa, which is derived frmo endoderm.

32
Q

What are the origins of the epidermic, stroma, and mucosal epithelium of the tympanic membrane?

A

Epidermis: from meatal plate derived from surface ectoderm

Stroma: from mesenchyme derived from neural crest

Mucosal epithelium: from pouch 1 lining

33
Q

What does the inner ear primordium form from?

A

The surface ectoderm is signaled by the hindbrain to become the otic placode.

Otic placode becomes the otic pit via signaling from pax2.

The otic pit separates to become the otic vesicles.

34
Q

What is the important signaling center for the development of the otic primordia?

A

The rhombencephalon.

35
Q

What does the otic vesicle differentiate into?

A

The membranous labyrinth: semicircular ducts, utricle, saccule, and cochlear duct.

The periotic mesenchyme which makes the otic capsule (osseous labyrinth-part of petromastoid portion of temporal bone): semicircular canals, vestibule, and cochlea.

36
Q

What is formed from the dorsal (vestibular) portion of the otic vesicle? What controls the development of this region?

A

The utricle and the semicircular ducts.

Wnt signaling from the hindbrain controls development of the dorsal portion.

37
Q

In three of the ampulla of the semicircular ducts, a ridge of epithelium forms called the _____ ______?

A

Crista ampullaris.

38
Q

What does the ventral (cochlear) portion of the otic vesicle form? What controls the development of this region?

A

The saccule and the cochlear duct.

Shh signaling from notochord controls development of the ventral portion.

39
Q

Each neurosensory area in the parts of the membranous labyrinth contain what?

A

Neurosensory epithelium with hair cells and gelatinous substance over the hair cells.

40
Q

What are the different types of congenital hearing loss?

A

Conduction

Sensorineural

Mixed

41
Q

What are the causes of congenital hearing loss?

A

Hereditary
Prenatal infection
Environmental
Unknown

42
Q

How does the auditory tube in infants differ from older children and adults?

A

It’s short, straight, shallow, and more horizontal.

Med Neuro Block 2 (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions