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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
what nerves supply arches 4 and 6?
``` 4 = superior laryngeal branch of vagus (pharyngeal plexus) 6 = recurrent laryngeal nerve ```
26
what structure does the 1st cleft form?
external acoustic meatus
27
what structure does 2nd - 4th cleft form?
cervical sinus (usually disappears)
28
what is a branchial fistula?
congenital abnormality due to persistence of branchial apparatus remnants
29
what does the 1st pharyngeal pouch form?
middle ear tympanic membrane eustachian tube
30
what does the 2nd pharyngeal pouch form?
palatine tonsil
31
what does the 3rd pouch form?
upper wing = inferior parathyroid gland | lower wing = thymus
32
what does the 4th pouch?
``` superior parathyroid gland ultimobranchial body (thyroid gland/C-cells) ```
33
what is the ultimobranchial body?
collection of C cells (produces calcitonin?)
34
function of inner ear?
balance (semi-circular canals) | hearing (organ of corti)
35
2 components of middle ear?
tympanic cavity | ossicles
36
2 components of external ear?
external auditory meatus | auricle
37
what is the otic placode?
thickening of the ectoderm on the outer surface of a developing embryo from which the ear develops
38
what does the otic placode do?
otic placode invaginates in to form otic pit | otic pit encloses forming a otic vesicle
39
what does the otic vesicle form?
inner ear
40
what does the pars superior/utricular portion of the otic vesicle form?
semi-circular canals
41
what does the pars-inferior/saccular portion of otic vesicle form?
cochlear
42
when do the semi-circular canals form and how?
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
what are ampullare in semi-circular canals?
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
what is the crista ampullaris?
sensory cells for balance | vestibular fibres of CN VIII
45
how does the cochlear duct develop?
grows in spiral between weeks 6-8 | surrounding mesenchyme becomes cartilaginous
46
what structures surround the cochlear duct?
lateral side = connected to bone via spiral ligament medial = bony section = modiolus space above = scala vastibuli space below = scala tympani
47
what is the organ of corti?
sensory organ in the cochlea
48
otocyst?
another name for vesicle
49
how do the ossicles form?
mesenchyme condenses forming ossicles
50
how does the external ear develop?
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
what is the auricular hillocks?
group of 6 mesenchymal proliferations surrounding 1st pharyngeal cleft (3 from arch 1, 3 from arch 2)
52
how does the auricular hillocks form the external ear?
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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