Pharyngeal Arches

Question 1

Talk about pharyngeal arches
( when - how - how many )

Answer 1

• It is developed with the head and neck during 4 or 5 th week

• growth of mesenchyml cells ( mesoderm - neural crest) and it first starts in cranial region forming arches and clefts and pouches
• clefts separate the arches extrenally ( ectoderm)
• pouches separate the arches internally ( endoderm)
• there are 6 arches but the 5th is regress after forming due to degeneration of its blood supply
And there are 5 pouches and 4 clefts

Question 2

Talk about first arch
( arterial - cartilage components) - innervation- what it gives )

Answer 2

It is named mandiblur arch and has two portions
• maxillary portion ( dorsal ) that contain maxillary cartilage .
give rise to maxilla , zygomatic bone and squamous of temporal bone
• mandibuler portion ( ventral ) that contain meckels cartilage give arise to incus , mallius , sphenomandibuler ligament , anterior ligament of malleus , and mandible ir jaw line due to perichrondral ossification

• the artery become terminal portion of maxillary artery
• it is innervated by trigemenal nerve and pretrematic nerve ( facial nerve)

• derivatives
  • 10 skeletal
  Incus - malleus- maxilla- mandible- zygomatic bone - squamous of temporal bone- palatine bone - sphenoid bone spine - sphenomandibuler ligament and anterior malleus ligament

• 5 muscles
Musles of mastication - mylohyoid - anterior belly of digastric - tensor veli palatani - tensor tympani

Question 3

Talk about 2 arch
( arterial - cartilage components) ( innervation - what it gives )

Answer 3

It is named hyoid arch

• it is associated with 2 arteries
* stapedial artery : regressed before birth
* hyoid artery
• reicharts cartilage is the associated one that gives arise to 5 s * stapes * styloid process * stylohyoid ligament * small horn of hyoid * superior body of hyoid
• it is innervated by facial that supply motorly 5
( 2 p- 2s - m)
* platysma * Posterior belly of digastric * stylohyoid * stapedious *muscles of facial expression
And gives taste sensation to anterior 2/3 of tongue via chorda tympani

Question 4

Talk about 3 rd arch

Answer 4

• the artery will become CCA and proximal part of ICA
• the carilage associated gives arise to greater horn and inferior body of hyoid bone
• it is innervated by glossipharyngeal nerve ( 9) that innervates stylopharyngeas muscles made by 3 arch and gives taste and general sensation to posterior 1/3 of tongue

Question 5

Talk about 4 th arch
( nerve + muscles)

Answer 5

It is innerveted by superior laryngeal n from vagus that supplies 4
* cricothyroid muscle
* constrictors of pharynx
* levator palatani
* roots of tongue

Question 6

Talk about 6 th arch
( nerve + muscles)

Answer 6

It is innervated by recurrent laryngeal nerve from vagus and supplies
* 1 motor ( all intrinsic muscles of larynx except cricothyroid)
* 2 taste sensation ( epiglottis- pharynx)
* 6 general sensation ( pharynx-larynx- oesophages- external auditory meatas - parts of external ear - tympanic membrane

Question 7

Derivatives of 4 pouches

Answer 7

1- is at the same level of the 1st cleft so the cleft gives arise to external auditory meatus while the pouch gives eustachian ( auditory ) tube - middle ear cavity - tympanic membrane
2- palatinal tonsiller fossa
3- dorsal wing : inferior parathyroid glands
Ventral wing : thymus
4- dorsal wing : superior parathyroid glands
Ventral wing: redimentary thymus
Ultimobranchial body to form parafolliclur cells in thyroid

Question 8

Derivative of 2-3-4 clefts

Answer 8

They got obliterated by rapidly proliferation of 2nd arche forming temporary cervical sinus

If this is not obliterated then it persists into adulthood as branchial ( pharyngeal ) cyst
*that appears on the lateral wall of neck and at any point along anterior border of sm muscle
* it can swell and it is associated with upper respiratory tract infection
*It is two types ~ external branchial fistula : due to failure of growth of 2 nd arche to meet with 3 or 4
~ internal branchial fistula