Embryology of the head and neck Flashcards
which weeks does the head and neck start to develop
what kind of stem cell tissue does the head and neck originate from to develop pharyngheal arches and clefts?
outpocketings in whih wall of the pharynx create pharyngeal pouches?
4th and 5th weeks
mesenchymal tissue
outpockets called pharyngeal pouches form in the pharyngeal pouches
initially, how many clefts are there?
which of these is the only one to give rise to a permanent structure in adults?
the other clefts are obliterated by what?
if not obliterated in adulthood, these clefts form what?
- 4 clefts initially
- 1st cleft
- clefts 2,3,4 are obliterated by the 2nd pharyngeal arch
- if not obliterated they will form cysts in adulthood along the ant border of sternocleidomastoid
how many pharyngeal arches are there originally?
which one regresses?
each arch has 4 things, what are they
in the adult, each pharyngeal arch is associated with a specific what?
6 arches originally
5th regresses
each arch has:
- arch associated cranial nerve
- muscular component
- branch of aorta
- skeletal and cartilaginous supporting element
in adults, each arch is associated with a specific head and neck structure
1st pharyngeal arch:
comprised of 2 parts, what are they? and what do they become?
artery:
CN:
sensory field:
muscles:
1st pharyngeal arch:
-
maxillary prominance- (dorsal portion)
- becomes the maxilla, zygomatic bone and part of the temporal bone
-
mandibular prominance- (ventral portion)
- becomes mandible
- Meckel’s cartilage- sphenomandibular ligament
artery: maxillary artery - terminal branch of ECA
CN: trigeminal
sensory field: that of CNV, skin of maxillla + nose + general sensation to ant 2/3 tongue
muscles: mastication + mylohyoid + ant. belly of digastric + tensor veil palatini + tensor tympani
2nd arch
2x arteries:
CN:
sensory field:
cartilage:
2x arteries: stapedial (regresses before birth) and hyoid (becomes corticotympanic in adults)
CN: facial nerve - innervtaes motor derivatives of 2nd arch (msucles of facial expression, plastysma, stepedius, stylohyoid, post belly digastric)
sensory field: posterior ear + taste to ant 2/3 via chorda tympani
cartilage: Reichod’s cartilage
3rd arch
artery:
CN:
sensory field:
cartilage:
muscle
3rd arch
artery: common carotid + some of inf. carotid
CN: glossopharyngeal
sensory field: taste + general sensation to post 1/3 of the tongue
cartilage: lower body + greater horn of hyoid
muscle: stylopharyngeus
4th arch
2x arteries:
CN:
sensory field:
cartilage:
muscle:
4th arch
2x arteries: left- aortic arch, proximal part of subclavian artery
CN: vagus
sensory field: superior laryngeal branch
cartilage: laryngeal cartilages
muscle: pharynx constrictors, levator palatini, cricothyroid
6th arch
2x arteries: left
CN
sensory field: widespread
2x arteries: left- ductus arteriosus right- proximal part of the pulmonary arteries
CN: vagus (recurrent laryngeal nerve)
sensory field: widespread- taste of epiglottis and pharynx, general sensation to larynx, oesophagus, EAM + ext ear, efferent limb of gag reflex, para symp innervation to viscera
pharyngeal pouches
seperate the pharyngeal arches of the inner endodermal surface
how many are found in adults?
derivatives of all the pouches?
4 in adults
derivatives of the branchial pouches:
1st- eustachian tube + middle ear cavity
2nd- lining of the palatine tonsils
3rd- dorsal- inf. parathyroid glands//// ventral- thymus
4th- dorsal- sup parathyroid glands//// ventral- C cells
development of the face and nose
which week does the external human face begin developing in?
palate?
distinction between the nasal and oral cavities?
external face- 4th- 6th week
palatal development- 6-8th week
distinction between oral and nasal cavities- 12 weeks
development of the face
week 3
week 4
structures in the face are derived from 2 sources, what are they?
development of the face
week 3- oropharyngeal membrane appears at the site of the future face. it is comprised of ecto+endoderm.
week 4- oropharyngeal membrane starts to breakdown to become the oral cavity. This is at the start of the digetsive tract
frontonasal prominence- formed from proliferation of mesenchymal neural crest cells ventral to the forebrain
mandibular + maxillary prominences- parts of the 1st pharyngeal arch, the space between the mox prominences is covered by the oropharyngeal membrane in this area called the stomatodeum a precursor to mouth and pituitary gland
nasal development (5)
- appearance of nasal placodes in both sides of the frontonasal prominence
- nasal placodes invaginate to form nasal pits within the medial and lateral nasal prominences
- maxillary prominences expand medially
- nasal prominences are “pushed” closer to the midline
- maxillary and nasal prominences fuse to form a continuous nasal structure
prominence and derivative
- frontonasal
- medial nasal
- lateral nasal
- maxillary (1st pharyngeal arch)
- mandibular (1st pharyngeal arch)
-
frontonasal
- forehead
- bridge of nose
- medial and lateral nasal prominences
-
medial nasal
- philtrum
- primary palate
- upper 4 inscissors and associated jaw
-
lateral nasal
- sides of the nose
-
maxillary (1st pharyngeal arch)
- cheeks
- lateral upper lip
- secondary palate
- lateral upper jaw
-
mandibular (1st pharyngeal arch)
- lower lip and jaw
development of the palate (5)
initially the nose and oral cavities are continuous but a series of steps works to leading to their seperation and establishment of the palate
- as the nose forms, fusion of the medial nasal prominence and its contralateral counterpart creates the intermaxillary segment- this forms the primary palate
- maxillary prominences expand medially to give rise to the palatal shelves
- max prominences continue to expand medially, fusing superior to the tongue
- the growing mandible increase the size of the oral cavity, allowing the tongue to develop out of the way of the growing palatal shelves
- palatal shelves fuse with each other in the horizontal plane. they also fuse with the nasal septum vertically to form the secondary palate
Development of the tongue
which week does it begin in?
which pharyngeal arch/arches does it derive from? what somite does it derive from?
stage 1 of tongue development - mucosa
tongue development starts in week 4
tongue is derived from the 1st to 4th arches (mucosa of tongue) and the occipital somite (musculature of the tongue)
stage 1 of tongue development
- lingual and medial swellings appear
- lateral lingual swellings x2- derived from 1st pharyngeal arch. contributes to mucosa of ant. 2/3 tongue
- medial swellings x3
- tuberculum impar- from 1st arch. mucosa of ant 2/3
- cupola (hypobranchial eminence) derived from 2nd, 3rd, 4th pharyngheal arches/ mucosa post 1/3
- epiglottal swelling- 4th pharynhgeal arch. forms the epiglottis
