1. Components
1.1. Arches
1.1.1. Shape
1.1.1.1. Horse-shoes
1.1.2. Number
1.1.2.1. 5
1.1.2.1.1. 1st
1.1.2.1.2. 2nd
1.1.2.1.3. 3rd
1.1.2.1.4. 4th
1.1.2.1.5. 6th
1.1.3. Location
1.1.3.1. Lateral wall of primitive pharynx
1.1.3.2. Floor (Ventral wall)
1.1.4. Components
1.1.4.1. Mesoderm core
1.1.4.1.1. Origin
1.1.4.2. Cartilaginous Rod
1.1.4.3. Artery
1.1.4.3.1. Course
1.1.4.3.2. Open into
1.1.4.4. Nerve
1.1.4.4.1. Pretrematic
1.1.4.4.2. Post trematic
1.2. Grooves
1.2.1. Number
1.2.1.1. 4
1.2.2. Derivatives
1.2.2.1. 1st
1.2.2.1.1. External auditory meatus
1.2.2.2. 2nd, 3rd and 4th
1.2.2.2.1. Cervical sinus
1.3. Pouches
1.3.1. Number
1.3.1.1. 4 pairs
1.3.1.1.1. 1st
1.3.1.1.2. 5th
1.3.1.1.3. 2nd
1.3.1.1.4. 3rd
1.3.1.1.5. 4th
1.3.2. Lining
1.3.2.1. Endoderm
1.4. Membranes
1.4.1. Layer
1.4.1.1. Ectoderm
1.4.1.2. Mesoderm
1.4.1.3. Endoderm
1.4.2. Number
1.4.2.1. 4
1.4.3. Derivatives
1.4.3.1. 1st
1.4.3.1.1. Tympanic membrane
2. Primordia for head and neck region
2.1. Mesoderm
2.1.1. Para-axial
2.1.2. Lateral plate
2.2. Ectoderm
2.2.1. Neural tube
2.2.2. Neural crest
2.2.3. Ectodermal placodes
2.3. Endoderm
2.3.1. Cephalic part of fore gut
3. Development
3.1. Week
3.1.1. 4th
3.2. Location
3.2.1. Lateral wall of primitive pharynx
3.2.2. Distal to the stomodeum
4. Clinical correlates
4.1. Branchial cyst
4.1.1. Cause
4.1.1.1. Failure of cervical sinus to obliterate
4.1.2. Location
4.1.2.1. Below and Behind angle of mandible
4.1.2.2. Anterior surface of sternocleidomastoid
4.1.2.2.1. Junction of upper 1/3rd and lower 2/3rd
4.2. Branchial fistula
4.2.1. Cause
4.2.1.1. Ruptured Branchial cyst
4.2.2. Internal Branchial fistula
4.2.2.1. Cause
4.2.2.1.1. Rupture of membrane between 2nd pouch and cleft
4.2.2.2. Course
4.2.3. External Branchial fistula
4.3. First arch syndrome
4.3.1. Cause
4.3.1.1. Lack of migration of neural crest cells into 1st pharyngeal arch
4.3.2. Most important
4.3.2.1. Treacher Collins
4.3.2.1.1. Mandibulofacial dysostosis
4.3.2.1.2. Manifestation
4.3.2.2. Pierre Robin
4.3.2.2.1. Cause
4.3.2.2.2. Manifestation
4.3.3. DiGeorge
4.3.3.1. Most severe
4.3.3.2. Cause
4.3.3.2.1. Microdeletion on long arm of chromosome 22
4.3.3.3. Manifestation
4.3.3.3.1. Fish mouth deformity (shortened philtrum)
4.3.3.3.2. Low set notched ears
4.3.3.3.3. Increased susceptibility to infections
4.3.3.3.4. Defect in cardiac outflow tract
4.3.3.4. aka 22q deletion syndrome