Pharynx & larynx development defects

Question 1

Branchial sinus

Answer 1

• external (more common) opens onto skin on anterior border of SCM;
• internal (rare) opens into tonsillar fossa
• remnant fo 2nd pharyngeal groove and/or cervical sinus & ectoderm has not completely covered area
• communicating with surface

Question 2

Branchial fistula

Answer 2

internal & external sinuses communicate i.e. pharynx or posterior aspect of mouth communicates with exterior

Question 3

1st arch syndrome

Answer 3

since 1st arch is a major contributor to facial development, 1st arch problems result in congenital malformations of face, palate, and ear

Question 4

Pierre-Robin Sequence

Answer 4

• 2nd arch problem
• micrognathia & retrognathia:
• Glossoptosis: tongue pushed more posterior leading to problems with obstruction & feeding
• Cleft palate
• problems with feeding & respiratory distress

Question 5

Treacher Collins Syndrome

Answer 5

• 1st arch problem; failure of neural crest migration into it
• eyelid has not formed completely; drooping lateral part of lower eyelid
• micrognathia: small mandible but nl size tongue
• ~50% cleft palate
• underdeveloped zygoma
• conductive hearing loss
• malformed pinna
  *

Question 6

Di George anomaly

Answer 6

• Catch 22: deletion in long arm of chromosome 22
• faulty migration of neural crest cells
• exposure of retinoids, alcohol, and maternal diabetes mellitus
• cardiac anomalies
• abnormal face
• thymic hypoplasa/aplasia: 3rd arch derivates
• cleft palate
• hypocalcemia (parathyroid): 3rd & 4th arch derivative

Question 7

Derivatives of arches

Answer 7

• 1st arch:
  
  • skeletal (CN V three): mastication mm, MATT, malleus, incus
• 2nd arch:
  
  • skeletal (CN VII): facial expression mm, digastric post. belly, stylohyoid, stapedius, stapes, lesser horn of hyoid
• 3rd arch:
  
  • skeletal (CN IX): stylopharnygeus, greater horn of hyoid
• 4th & 6th arch
  
  • skeletal (CN X): Levator palatini, pharygeal mm., striated mm of esophagus, instrinsic laryngeal mm, thyroid & cricoid cartilage

Question 8

Pharygneal pouch derivatives

Answer 8

• 1st pouch: Eustachia tube, middle ear cavity, mastoid air cells
• 2nd pouch: palatine tonsil
• 3rd pouch: I. Parathyroid gland, thymus
• 4th pouch: S. Parathyroid gland, parafollicular cells of thyroid gland