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