Embryology of Pharyngeal Arches Flashcards Preview

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Flashcards in Embryology of Pharyngeal Arches Deck (34)
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1
Q

• Pharyngeal/branchial arch

A

o Each has same basic structure
o Artery, nerve and cartilage
o Originally ectomesenchyme
o Formed from 1st 7 pairs of somitomeres
o Form everything in the head and neck
o Give rise to striated muscles of face, jaws and throat
o Send neural crest cells into the arches during 4th week
o Major source of cartilage, bone, ligament in facial and oral regions
o Ganglia of CN 5, 7, 9, and 10 partly derived from neural crest cells

2
Q

• Pharyngeal/branchial cleft/groove

A

o No mesoderm, only endo and ectoderm

1st groove only one that forms adult derivative: external acoustic meatus

3
Q

• Pharyngeal branchial membrane

A

o Formed by union of cleft and pouch

1st groove only one that forms adult derivative: tympanic membrane

4
Q

• Pharyngeal/branchial pouch

A

o Internal of the cleft
1st, 2nd, 3rd, and 4th & 6th form adult derivatives
-pharyngotympanic tube
-tonsillar sinus/fossa crypts
-inferior parathyroid & thymus
- superior parathyroid & parafollicular cells

5
Q

• Mandibular arch

A
o	1st arch (M arch)
o	Meckel’s cartilage
o	CN 5 (V2 & V3)- maxillary and mandibular division of trigeminal
o	Muscles of mastication
	Anterior belly of digastric
	Mylohyoid
o	Maxillary artery-arch 1
6
Q

Meckel’s cartilage

A
  • 1st arch
  • Maxilla & zygomatic bone, mandible (template) & squamous part of temporal
  • Malleus, incus, ½ of hyoid
  • Sphenomandibular ligament
  • Anterior ligament of Malleus
7
Q

Muscles of mastication:

A
  • tensor tympani,
  • tensor veli palatine,
  • masseter,
  • lateral medial pterygoids
  • Anterior belly of digastric
  • Mylohyoid
8
Q

1st Arch Pouch:

A

 Pharyngo-tympanic tube (eustacian or auditory tube)

• Opens up unto pharynx

9
Q

o Ist arch Groove:

A

 External Acoustic Meatus

10
Q

1st Arch Membrane

A

typmanic membrane

11
Q

• Hyoid arch

A
o	2nd arch (S arch)
o	Overgrows clefts of 2nd, 3rd, and 4th arches to form cervical sinus
o	Reichert’s cartilage
o	CN 7- facial nerve
o	Stapedial artery-arch 2
12
Q

o Reichert’s cartilage

A
- cartilage of 2nd arch
	Stapes, 
	styloid process
	upper body of Hyoid bone
	lesser cornu bone
	Stylohoid ligament
13
Q

o Muscles of 2nd arch

A

 Facial expression muscles
 Posterior belly of digastric
 Stylohyoid
 Stapedius muscle

14
Q

o Pouch:of 2nd arch

A

 Tonsillar sinus/fossa
• This is where palatine tonsil sits
 Surface epithelium of Tonsillar Crypts from endoderm

15
Q

• 3rd Arch

A
o	CN IX- Glossopharyngeal
o	Muscles
	Stylopharngeus
o	ligaments
	Lower hyoid
	Greater cornu (horn)
o	Pouch:
	Inferior parathyroid glands from Dorsal 
	Thymus 
•	Ventral: bilateral elongate and  hollow primordial come together and thymus descends
16
Q

Muscles and ligaments of 3rd arch

A
Muscles
	Stylopharngeus
o	ligaments
	Lower hyoid
	Greater cornu (horn)
17
Q

Pouch of 3rd arch

A

 Inferior parathyroid glands from Dorsal
 Thymus
• Ventral: bilateral elongate and hollow primordial come together and thymus descends

18
Q

• 4th & 6th Arches: Larynx Pharynx

A
o	Muscles of larynx and pharynx
	
o	Cartilage
	Laryngeal cartilages
•	Thyroid
•	Cricoid
•	Corniculate
•	Cuneiform
o	CN X – Vagus
	Superior Laryngeal to 4th arch
	Recurrent laryngeal to 6th arch
o	Pouch:
	Dorsal: Superior parathyroid glands
	Ventral: ultimobranchial body
•	Parafollicular (C) cells of the thyroid
19
Q

o Muscles of larynx and pharynx

A
  • 4th and 6th arch derivatives
    -Cricothyroid
     Levator veli palatine
     Constrictors of pharynx
     Intrinsic muscles of larynx
20
Q

laryngeal cartilage

A
- 4th and 6th arch derivatives
o     Thyroid
•	Cricoid
•	Corniculate
•	Cuneiform
21
Q

4th and 6th arch pouch

A

 Dorsal: Superior parathyroid glands
 Ventral: ultimobranchial body
• Parafollicular (C) cells of the thyroid

22
Q

• Aortic Arches

A

o As pharyngeal arches develop, aortic arches supply them
o 6 aortic arches develop
o 1st Aortic arch – maxillary arteries
o 2nd Aortic Arch –stapedial arteries
o 3rd aortic arch–carotid
 Proximal: common carotid
 Distal: internal carotid with dorsal aorta

23
Q

• Branchial abnormalities:

A
o	Usually results from persistence of 2nd groove and pouche
o	Opens into side of neck
o	10% of cases ar bilateral
o	Cyst- 
o	Sinus
o	Fistula-
24
Q

branchial cyst

A
  • mucosal lined, fluid filled cavity
  • Usually at angle of mandible where 2nd and 3rd come together or at the anterior border of the SCM muscle
  • Accumulate fluid and cellular debris
25
Q

branchial sinus

A
  • blind-ending pit with one opening
26
Q

branchial fistula

A

2 openings
 Often drain cervical cysts
 Open along the anterior border of SCM muscle
 ascends to pass between internal and external carotid arteries and opens into tonsillar fossa
 Treatment is excision

27
Q

• First Arch syndromes

A
o	Insufficient migration of neural crest cells
o	Deformed auricle
o	Perauricular appendage
o	Defect in cheek
o	Hypoplasia of mandible
o	macrostomia
o	Treacher Collins syndrome/mandibulofacial dysostosis
o	Pierre Robin Syndrome
28
Q

o Treacher Collins syndrome/mandibulofacial dysostosis

A
-1st arch syndrome
	TCOF1 gene on 5tq31-q34
•	Autosomal dominant
•	60% new mutation
•	> paternal age
•	Uses OMENS to differentiate diseases
	Malar hypoplasia
	Downslanting palpebral fissures
	Deformed external ears
	Defects of lower eyelids
29
Q

o Pierre Robin Syndrome

A
-1st arch syndrom
	Hypoplasia of mandible
	Celft palate
	Defects of eye, ear
- clenched fists
- SOX9, 50% cases (a sequence)
30
Q

• 3rd and 4th pouch syndromes

A

o DiGeorge syndrome

o Goldenhar syndrome

31
Q

o DiGeorge syndrome

A

-3rd and 4th arch syndrome
- Microdeletion of Chrom 22
 Absence of thymus
• Lots of infections
 Malformation of mouth (fish mouth)
 Nasal clefts
 Cardiac abnormalities
 hypoparathyroidism
• 1st and 2nd arch syndromes

32
Q

o Goldenhar syndrome

A

-3rd and 4th arch syndrome
-Hemifacial microsomia
• Half of the face usually around the eyes, ears, and the mouth (60%)
• Bilateral in the rest with 10-33% of those more severe on one side
• Majority of cases, right more affected than the left
 Oculo-auricular dysplasia
 Oculoauricular-vertebral spectrum
 Incomplete development of the ear, nose, soft palate and mandible and spinal column

33
Q

• Van Der Woude syndrome

A

o Autosomal dominant
o Most common clefting syndrome
o Cleft lip/palate with/without distinctive lip pits
o Tooth agenesis
o No other apparent structural abnormalities
o Pits in 88% and 64% they are the only manifestation
o 25% have no symptoms or minimal like missing teeth or lip pits
o Most common syndrome assoc. with cleft lip and palate
o IRF6 gene
- rare (1/30,000)
- (70% )VWS exonic mutation
- problems with wound healing

34
Q

• Dumbo rats

A

o 1st arch syndrome?
o MSX and Dlx homeobox genes expressed in the arches
o big ears, small lower mandible