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ENT > Intro/Embryology > Flashcards

Intro/Embryology Flashcards

1
Q

what happens during gastrulation (week 3)?

A

formation of trilaminar disc
invagination of epiblast cells through the primitive streak to form the definitive endoderm and mesoderm
mesoderm is then organised into 3 main groups
- paraxial
- intermediate
- lateral plate

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2
Q

what is the neural crest?

A

group of cells arising from ectoderm at the margins of the neural tube which eventually break off and move around the body to give rise to several structures

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3
Q

what 2 types of folding occur in development of embryo?

A

lateral folding

craniocaudal folding

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4
Q

what are pharyngeal arches?

A

remnants of fish gills (present in all vertebrates)

form much of the head and neck in human

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5
Q

what arches are present and when do they develop>

A 
all arches develop in week 4 and 5
arch 1 = day 22
2 + 3 = day 24
4 + 6 = day 29
(no 5th arch)
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6
Q

development occurs in which direction?

A

cranial to caudal

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7
Q

what are the 3 components of the pharyngeal apparatus?

A

core pharyngeal arch (mesenchymal tissue)
external pharyngeal cleft (ectoderm)
internal pharyngeal pouch (endoderm)

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8
Q

what separates the arches?

A

clefts and pouches

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9
Q

what is contained within each pharyngeal arch?

A 
core of mesenchyme derived from paraxial and lateral plate mesoderm
= forms musculature of the face
neural crest cells
= skeletal components of the face
cranial nerve component
= innervation (sensory or motor)
artery (aortic arch arteries)
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10
Q

what nerves supply the pharyngeal apparatus?

A

arch 1 = trigeminal nerve (V2 and V3 divisions)
arch 2 = facial nerve
arch 3 = glossopharyngeal nerve
arch 4 = superior laryngeal branch of vagus
arch 6 = recurrent laryngeal branch of vagus

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11
Q

what are the 2 portions of the 1st arch?

A 
maxillary process (cranial portion)
mandibular portion (caudal portion)
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12
Q

what does the maxillary process form?

A

maxilla
zygomatic bone
squamous portion of temporal bone

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13
Q

what does the mandibular portion form?

A

Meckels cartilage
incus and malleus (ear ossicles)
mandible

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14
Q

what muscles does the first arch give rise to?

A

all musculature supplied by CN V3

  • muscles of mastication
  • anterior belly of digastric
  • mylohyoid
  • tensor tympani
  • tensor veli palatini
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15
Q

what sensory nerves does the 1st arch give rise to?

A

V1
V2
V3

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16
Q

what is reichert’s cartilage?

A

cartilage of 2nd arch

all skeletal derivatives of 2nd arch develop from this

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17
Q

list the 5 skeletal derivatives of the 2nd arch?

A 
stapes (ear ossicle)
styloid process of temporal bone
stylohyoid ligament
lesser horn of hyoid
upper part of hyoid body
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18
Q

what muscles are derived from the 2nd arch?

A

all muscles supplied by CN VII

  • muscles of facial expression
  • posterior belly of digastric
  • stylohyoid
  • stapedius
  • auricular muscles
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19
Q

what skeletal components are derived from the 3rd arch?

A

greater horn of hyoid

lower part of hyoid bone

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20
Q

what muscles are derived from 3rd arch?

A

stylopharyngeus

longitudinal pharyngeal muscle

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21
Q

what nerve is associated with 3rd arch?

A

glossopharyngeal (CN IX)

22
Q

what skeletal components are derived form arch 4 and 6?

A

laryngeal cartilages

23
Q

what muscles are derived from arch 4?

A

cricothyroid
levator veli palatine
pharyngeal constrictor

24
Q

what muscle is derived from arch 6?

A

intrinsic laryngeal muscle

25
Q

what nerves supply arches 4 and 6?

A 
4 = superior laryngeal branch of vagus (pharyngeal plexus)
6 = recurrent laryngeal nerve
26
Q

what structure does the 1st cleft form?

A

external acoustic meatus

27
Q

what structure does 2nd - 4th cleft form?

A

cervical sinus (usually disappears)

28
Q

what is a branchial fistula?

A

congenital abnormality due to persistence of branchial apparatus remnants

29
Q

what does the 1st pharyngeal pouch form?

A

middle ear
tympanic membrane
eustachian tube

30
Q

what does the 2nd pharyngeal pouch form?

A

palatine tonsil

31
Q

what does the 3rd pouch form?

A

upper wing = inferior parathyroid gland

lower wing = thymus

32
Q

what does the 4th pouch?

A 
superior parathyroid gland
ultimobranchial body (thyroid gland/C-cells)
33
Q

what is the ultimobranchial body?

A

collection of C cells (produces calcitonin?)

34
Q

function of inner ear?

A

balance (semi-circular canals)

hearing (organ of corti)

35
Q

2 components of middle ear?

A

tympanic cavity

ossicles

36
Q

2 components of external ear?

A

external auditory meatus

auricle

37
Q

what is the otic placode?

A

thickening of the ectoderm on the outer surface of a developing embryo from which the ear develops

38
Q

what does the otic placode do?

A

otic placode invaginates in to form otic pit

otic pit encloses forming a otic vesicle

39
Q

what does the otic vesicle form?

A

inner ear

40
Q

what does the pars superior/utricular portion of the otic vesicle form?

A

semi-circular canals

41
Q

what does the pars-inferior/saccular portion of otic vesicle form?

A

cochlear

42
Q

when do the semi-circular canals form and how?

A

week 6
flattened outpocketings of utricular part of otic vesicles
central part of the walls appose each other and break down forming a central canal
- add picture

43
Q

what are ampullare in semi-circular canals?

A

bulges at each end of each semi-circular canal
dilates end = crus ampullare (X3)
non-dilated end = crus nonampullare (X2)
crista ampullaris found within the ampullare

44
Q

what is the crista ampullaris?

A

sensory cells for balance

vestibular fibres of CN VIII

45
Q

how does the cochlear duct develop?

A

grows in spiral between weeks 6-8

surrounding mesenchyme becomes cartilaginous

46
Q

what structures surround the cochlear duct?

A

lateral side = connected to bone via spiral ligament
medial = bony section = modiolus
space above = scala vastibuli
space below = scala tympani

47
Q

what is the organ of corti?

A

sensory organ in the cochlea

48
Q

otocyst?

A

another name for vesicle

49
Q

how do the ossicles form?

A

mesenchyme condenses forming ossicles

50
Q

how does the external ear develop?

A

dorsal part of 1st pharyngeal cleft
at month 3 - epithelial cells proliferate to form meatal plug
plug dissolves in month 7 and contributes to the eardrum

51
Q

what is the auricular hillocks?

A

group of 6 mesenchymal proliferations surrounding 1st pharyngeal cleft (3 from arch 1, 3 from arch 2)

52
Q

how does the auricular hillocks form the external ear?

A

hillocks fuse to form definitive auricle

external ears initially in the lower neck and then ascend due to the development of the mandible

ENT (21 decks)

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