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week 1 > sievert H&N development > Flashcards

sievert H&N development Flashcards

1
Q

Three main types of primodia

A

placodes
somites
pharyngeal/branchial arches (branchial = pharyngeal… they’re synonyms)

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2
Q

location of branchial cleft and branchial pouch, respectively

A

Cleft on outside
Pouch on inside

both of these are invaginations in the inferior portion of pharyngeal/branchial arches

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3
Q

define a placode

A

ECTOdermal thickening (of the neural tube) that eventually only allows for the development of the ear or lens or olfaction

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4
Q

list the three placodes

A

olfactory (in forebrain)
lens (in outpouching of forebrain)
otic (around hindbrain)

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5
Q

What makes a somite preotic or postotic?

A

relative to the location of the otic placode.

preotic (upper to otic placode)
postotic (lower to otic placode)

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6
Q

where does the olfactory epithelium come form, and what does it do?

A
  • comes from the nasal/olfactory placode
  • fxn: comprises the true organs of smell, the ones w/all the receptors in the olfactory epithelium in the high superior border of nasal cavity.
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7
Q

etiology and fate of nasal/olfactory placode

A
  • Forebrain (telencephalon) has a bulge, this structure is called the olfactory bulb
  • This olfactory bulb induces the olfactory placode to start thickening.
  • The placode makes the primary olfactory epithelium.
  • Primary olfactory epithelium will end up growing up into the olfactory bulb
  • How? By have to penetrating through the cribriform plate of the ethmoid bone
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8
Q

how is the lens placode different than the other two placodes?

A

the other two make the sensory bodies of the nervous system BUT lens placode has NOTHING to do w/receptors… it only makes the lens

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9
Q

how are lens made?

A
  • First of all, an outpocketing of the diencephalic midbrain INDUCES the surface ectoderm to thicken, forming the lens placode
  • Lens placode thickens and invaginates and breaks off to make the lens.
  • The remaining part of the surface ectoderm, the part that didn’t beak off, becomes the cornea
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10
Q

how does the retina form?

A

the retina forms by an outpocketing of the diencephalon, and as the retina develops, it will be covering over the lens (basically lens placode invaginates into the developing retina)

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11
Q

what does the otic placode make, and how?

A

inner ear—membranous labyrinth, sensory neurons, and ganglion cells of CN 8

Otic placode is induced by the nervous system, specifically the hindbrain; the surface ectoderm ends up invaginating, forms otic vesicle, and then forms the future innr ear

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12
Q

how is the future middle ear made?

A

the endodermal lining of the pharynx (as part of the 1st branchial/pharyngeal pouch) makes a bilateral outpouch–this outpouch becomes the future middle ear cavity

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13
Q

how does the future external canal get made?

A

an additional invagination of surface ectoderm (branchial/pharyngeal groove)—not part of placode but is associated w/ cleft

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14
Q

from what does the tympanic membrane form?

A

mesenchyme situated between the middle and inner ear will eventually make the t-membrane

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15
Q

why is ear so susceptible to environmental effects?

A

coz it takes so long to develop and a long time to pick up said effects

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16
Q

How are CN ganglia similar to DRG?

A
  • no synapse

- pseudounipolar cells w/ peripheral and central processes

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17
Q

define somites

A

masses of mesoderm that form skeletal muscles

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18
Q

preotic somites define. include CN too

A

Preotic somites form muscles that move the eye (+levator palpebrae), not the muscles of the iris or the lens (innervated by CN 3 4 and 6, respectively )

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19
Q

postotic somites define. include CN too

A

Postotic somites form muscles of the tongue, CN 12

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20
Q

how do you classify muscles that came from somites?

A

general somatic efferents

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21
Q

how do you classify muscles that have fibers related to visceral structures, SM or cardiac?

A

general visceral efferents

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22
Q

define branchiomotor

A

muscles that came from branchial/pharyngeal arch mesenchyme… functionally the same as skeletal

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23
Q

define pharyngeal arch. when do they appear

A

Masses of mesenchyme tissue that flank the developing gut tube

appear around the 4th-5th week

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24
Q

describe the structure of each arch

A

outer half covering = ectoderm
inner half covering = endoderm
core region = mesenchyme

suspended within that mesenchyme, laterally we have a nerve, cartilage/bone in the middle, and an artery more medially.

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25
Q

describe the arch numbering

A

we have six arches present, two go away or merge.
arches 1-4
arch 5 gets overridden
arch 4 and 6 merge together

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26
Q

location of laryngeal orifice

A

right under the fourth arch

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27
Q

what role do neural crest ells play in the arches?

A

they migrate into these arches, forming their nerve component

fxn: to contribute to the skeletal components of face

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28
Q

list the four pharyngeal arch derivatives

A
  • muscle (probably from the -mesenchyme)
  • bone/cartilage (from the bone/cartilage component of arch)
  • skin (from the ectoderm of arch)
  • gut tube (from endoderm)
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29
Q

what formed the upper and lower jaws (maxilla and mandible, respectively?

what is the name for the ear upper jaw element and the early lower jaw element?

A

cartilage/bone of the first pharyngeal/branchial arch

maxillary process
mandibular process

30
Q

skeletal elements:

maxillary process forms the

A

maxilla
zygomatic bone
part of temporal bone

31
Q

skeletal elements:

mandibular process forms the

A

mandible
malleus
incus

32
Q

Skeletal elements:

second arch is also known as?

A

hyoid arch

33
Q

skeletal elements:

second/hyoid arch forms?

A

lesser horn of hyoid bone
styloid process
stapes

34
Q

skeletal elements:

origins of the ear bones

A

malleus + incus from first arch (mandibular process)

stapes from second arch

35
Q

skeletal elements:

what does the third arch make?

A

rest of hyoid bone

remember that lesser horn of hyoid formed by the second/hyoid arch

36
Q

skeletal elements:

what do the fourth and sixth arches form?

A

4th and 6th fuse. then they make the laryngeal cartilages

37
Q

pharyngeal arch muscles:

first arch?

A

muscles of mastication!!!! these are the only ones innervated by first arch

38
Q

pharyngeal arch muscles:

2nd arch?

A

muscles of fascial expression

39
Q

pharyngeal arch muscles:

third arch?

A

just the stylopharyngeus.

goes from styloid process to the pharynx

40
Q

pharyngeal arch muscles:

4th+6th arches?

A

muscles of palate, pharynx, and larynx

41
Q

when it comes to sensory innervation (maybe motor too, but i’m not sure yet), the nerves of EACH respective arch innervate what?

A

the endodermal lining of each respective arch

42
Q

what happens to the endodermal lining of the second arch?

A

its sensory lining gets overgrown by the first arch

43
Q

describe the sensory innervation of the tongue?

A

anterior 2/3rds: lined by ectoderm, first arch zone
posterior third: lined by endoderm (allegedly, waiting of sievert’s response), THIRD arch zone. is behind the sulcus terminalis.

44
Q

foramen cecum

A

see what sievert says!

45
Q

describe etiology of sensory innervation of the epiglottis

A

comes form fourth arch?

46
Q

what CN does the first arch and the cutaneous innervation of the anterior tongue?

A

5th cranial nerve

47
Q

what does the first pharyngeal cleft make?

A

external auditory meatus

48
Q

what do clefts 2 3 and 4 make?

A

they close ff tho make cervical sinuses/cysts, but you usually don’t see anything associated w/ it

49
Q

first pouch does what?

A

develops into auditory and primitive middle ear cavity

50
Q

second pouch develops what?

A

palatine tonsils

51
Q

third pouch develops to what?

A

thymus and inferior parathyroid glands

52
Q

talk about the migration of the thymus and its relationship to the parathyroid glands?

A

During dev, the thymus migrates from the back of the tongue, into the the foramen cecum area, down into the chest. As it does so, it pulls the inferior thyroid gland down with it until it’s below the superior. That’s why the superior pouch (third) gives rise for the inferior PT gland.

this is is weird coz embryologically, the inferior PT gland, thymus (inf PT connected to thymus), and superior PT gland

53
Q

fourth pouch gives rise to?

A

superior PT gland

54
Q

fifth pouch gives rise to?

A

parafollicular C cells

55
Q

CN 5 does what?

A

motor to muscles of mastication, but it’s main fxn is sensory

56
Q

list the cranial nerves to placodes

A

1, 2, and 8

57
Q

list cranial nerves to somites

A

3, 4, 6 (preotic, only somatomotor, extraocular eye muscles)

and
12 (postotic, only somatomotor, hypoglossal to tongue)

58
Q

list cranial nerve to branchial branches

A

V
VII
IX
and X

59
Q

CN 1:
full name
primoridium

A

olfactory n

olfactory placode

60
Q

CN 2:
full name
primoridium

A

optic nerve

optic vesicle

61
Q

CN 3:
full name
primoridium

A

oculomotor

preotic somite

62
Q

CN 4:
full name
primoridium

A

trochlear

preotic somite

63
Q

CN 5:
full name
primoridium

A

trigeminal

branchial arch 1

64
Q

CN 6:
full name
primoridium

A 
abducens
preotic somite (3 4 and 6 all extraocular eye)
65
Q

CN 7:
full name
primoridium

A

fascial

branchial arch 2

66
Q

CN 8:
full name
primoridium

A

vestibulocochlear

otic placode

67
Q

CN 9:
full name
primoridium

A

glossopharyngeal

branchial arch 3

68
Q

CN 10:
full name
primoridium

A

vagus

branchial arch 4, also branchial arch 6

69
Q

CN 11:
full name
primoridium

A

spinal accessory

probably branchial but dunno for sure

70
Q

CN 12:
full name
primoridium

A

hypoglossal

postotic somite

week 1 (12 decks)

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