Development of pharyngeal (branchial) apparatus

6 mesodermal thickenings on each side of primitive pharynx:

  1. Outer ectodermal covering (Externally – 5 grooves – Pharyngeal clefts)
  2. Mesodermal core
  3. Inner endodermal lining (Internally – 4 grooves – Pharyngeal pouches)
Image result for branchial apparatus
development of branchial apparatus

Basic structure of pharyngeal arch:

  1. Mesoderm – Cartilagenous bar (forms cartilage, ligaments and bones)
  2. Mesoderm – Striated muscle (special viceral muscle of head and neck)
  3. Aortic arch artery
  4. Own nerve (motor + posttrematic sensory)
  5. Next arch’s nerve (pretrematic sensory)

NB: 5th arch disappears

Derivatives of the arches:

Ectoderm, endoderm, mesoderm derivatives and shape of each pharyngeal arch:

derivatives of pharyngeal arches, from ectoderm, endoderm, mesoderm and shape


  1. Branchial cyst – along anterior border of sternocleidomastoid muscle due to failure of cervical sinus to obliterate
  2. Branchial sinus – Branchial cyst opens into skin by narrow canal
  3. Branchial fistula – Branchial cyst opens into lumen of pharynx
  4. Duplication of external auditory meatus – 1st branchial anomaly

Note: If left untreated, may become repeatedly infected and inflamed. Recurrent inflammation makes surgical resection more difficult. Excellent prognosis if lesion is completely resected.