Pharyngeal apparatus

• in 4-5 weeks surface elevations start appearing lateral to developing pharynx.

• Initially it consist of core of mesenchyme ( derived from paraxial & lateral plate mesoderm) is covered externally by ectoderm & internally by endoderm.

• During 4th week most of mesenchyme is derived from neural crest cells that migrate into pharangeal arches to contribute to skeletal element , while original mesenchyme give rise to musculature & vascular endothelium.

Pharyngeal arches

• Six paired swellings -lateral wall of primitive pharynx

• Fifth one disappears

• Develops in 4th week i.u

Components of pharyngeal apparatus

• Pharyngeal arches

• Pharyngeal clefts

• Pharyngeal pouches

• Pharyngeal membrane

Components of pharyngeal arch

• Core of mesoderm

• Cartilage

• Artery

• Nerve

Derivatives of first arch

• Nerve- Trigeminal nerve

• Muscles- muscles of mastication (…), anterior belly of diogastric, mylohyoid, tensor tympani, tensor palati

• Cartilage - meckel’s cartilage

ventral (malleus , incus) dorsal (mandible)

• ligaments- sphenomandibular, anterior ligament of malleus

Second pharyngeal arch

• All muscles of facial expression

• Facial nerve

Reicherts cartilage

ventral dorsal

(lesser cornu stapes

upper part of hyoid)

• Stylohyoid ligament

Derivatives of third arch

• Stylopharyngeus

• Glossopharyngeal nerve

Cartilage

ventral dorsal (disappears)(Greater cornu and lower part of hyoid bone)

PLANE OF CUT

Derivatives of fourth and sixth arch• Superior laryngeal

nerve(4th arch)• Recurrent laryngeal

nerve(6th arch)• 4th and 6th arch cartilage -

form cartilage of larynx (thyroid, cricoid, arytenoids and cuneiforms)

• Muscles- cricothyroid, levator palati, constrictors of pharynx, intrinsic muscles of larynx

Vagusnerve

MUSCLES OF BRANCHIAL ARCHES

First -TrigeminalVFourthVagusXSixthAccessoryXIInnervated by

Derivatives of pharyngeal pouch

Derivatives of pharyngeal pouch

• Pouch 1 – Tubotympanic recess - AuditoryTube, Tympanic cavity

• Pouch 2 – lining (crypts of Palatine Tonsils)

• Pouch 3- Inferior Parathyroid Glands & thymus

• Pouch 4 – superior ParathyroidGlands & C-Cells

Clinical

• Brachial cyst and fistula-

• congenital epithelial cyst

• lateral part of the neck

• due to failure of obliteration of the second branchial cleft (or failure of fusion of the second and third branchial arches)

BRANCHIAL ANOMALIES

• Tracher collinsyndrome

• Piere robin syndrome

• Di- georgesyndrome