Embryology Flashcards
Preauricular sinus
improper fusion of 1st and 2nd branchial arches
Hillocks of Hiss
1-3 from first branchial arch, 4-6 from second branchial arch
Hillocks of Hiss - 1-3
1 - tragus, 2 - crus of helix, 3 - helix
Hillocks of Hiss - 4-6
4 - antihelix, 5 - antitragus, 6 - lobule
Jacobsons nerve
glossopharyngeal branch to ear
Arnold’s nerve
vagus branch to ear
Location of 1st Branchial Cleft Cyst Type I?
Work Classification
Type I
- Preauricular mass or sinus
- Duplication of EAC
- Ectoderm
- Sinus tract is anterior and medial to the EAC
- Preauricular region - Lateral to CN VII - Parallels EAC - Ends in EAC or middle ear
Location of 1st Branchial Cleft Cyst Type II?
Work Classification
Type II
- More common than Type I
- Presents at the angle of mandible or submandibular region
- Angle of mandible - Lateral or medial to CN VII - Ends in concha or bony-cartilaginous junction of EAC.
Location of 2nd Branchial Cleft Cyst?
95% of all branchial cleft anomalies arise from second cleft
- They are found along the anterior border of the SCM
- Pass through the carotid bifurcation
- Superficial to CN IX and XII
- Into the tonsillar fossa.
Location of 3rd Branchial Cleft Cyst?
Closely associated with thyroid gland
Usually on the left
- Lateral neck (similar or lower location than 2nd)
- Deep to carotids
- Deep CN IX, superficial to CN XII
- Superficial to superior laryngeal nerve
- Piercesthyrohyoid membrane
- Opens into apex of pyriform sinus
Location of 4th Branchial Cleft Cyst?
VERY rare
- Low in neck (anterior to SCM)
- Deep to common carotid
- Loops around aortic arch on the left
- (subclavian on the right)
- Deep to superior laryngeal nerve
- Superficial to recurrent laryngeal nerve
- Opens into pyriform sinus
1st branchial arch
Mandibular Arch
Skeletal components:
Meckel’s cartilage
Framework for mandible
Malleus head and neck
Incus body and short process
Muscles:
Muscles of mastication
Anterior digastric
Mylohyoid
Tensor tympani
Tensor veli palatini
**Nerve**: CN V (Trigeminal)
Artery:
Maxillary; external carotid
2nd branchial arch
Hyoid Arch
Skeletal components:
Reichert’s cartilage
Stapes
Malleus manubrium
Incus long process
Styloid process
Hyoid bone (lesser horn and upper body)
Muscles:
Facial expression, buccinator, platysma, stapedius, stylohyoid,
posterior digastric
**Nerve**: CN VII (Facial)
Artery:
Stapedial
3rd branchial arch
Skeletal components:
Hyoid (greater horn and lower body)
Muscles:
Stylopharyngeus
**Nerve**: CN IX (Glossopharyngeal)
Artery:
Common/Internal carotid
4th branchial arch
Skeletal components:
Thyroid, epiglottic, cuneiform cartilages
Muscles:
Cricothyroid, inferior constrictors
Nerve:
Superior laryngeal
Artery:
Subclavian, aortic arch
