Wu's embryo Flashcards
Tissue origin of pouches?
Endoderm
Tissue origin of arches?
mesoderm
Tissue origin of clefts/grooves/folds?
ectoderm
**Bone and cartilage are derived from
Neural crest!
Tympanic membrane is the first membrane
Connects the inner ear (a pouch) to the outer ear ( a fold)
Each arch has an associated nerve and arterial arch
What arch is innervated by the superior laryngeal branch of vagus nerve?
Pharyngeal arch 4; derivatives:
Cricothyroid and posterior crycoartenoid
What arch is innervated by the recurrent laryngeal branch of the vagus nerve?
Pharyngeal arch 6; derivatives:
Remember that the ductus arteriosis becomes the ligamentum arteriosum in teh adult
What does cleft 1 become?
External auditory ematus
What do clefts 2-4 become?
Nothing- they usually get obliterated. If they aren’t obliterated, you get cystic anomalies/remnants of the neck
Cystic anomalies of the neck arise from failure of clefts 2-4 to be obliterated; instead they are combined into a cervical sinus on the neck. What are the 3 types?
- Cervical branchial cyst
- Thyroglossal duct/sinus
- Ectopic thyroid gland/ nodule
Lateral mass in front of the SCM that enlarges with age- what is it?
Cervical branchial cyst: grooves connect together to form a gap in your neck; if connected to the outside, it’s a fistula.
Shown as lateral mass enlarges with age
Midline mass on your neck tha tmoves with swallowing- what is it?
Thyroglossal duct/sinus: tract between tongue and thyroid is not obliterated
- the typical remnant is the foramen cecum on the tongue
- usually asymptomatic, but may protrude tongue
Shown as a midline mass that moves withs wallowing
Symptoms of hyperthyroidism and an off-midline mass represent what cystic anomaly of the neck?
Ectopic thyroid gland/nodule: extra thyroid tissue on gland/nodule or along the paht of hte thyroid gland
Inner ear bones are associated with what nerve in what arch? What bone is the exception?
Mandibular n (V3) in the first arch.
EXCEPTION: Stapes is from arch 2, which is associated with the facial nerve (remember n to stapedius?)
Hyoid bone is associated with what arches?
2 and 3
Larynx is associated with what arches?
Arches 4 &6
Treacher Collins Syndrome and Pierre Robin sequence are both problems with which pharyngeal arch?
The first arch. Both are bone problems, so the cause is a problem with NEURAL CREST!
Treacher Collins Syndrome- what are the other symptoms What does it look like?
- Malar hypoplasia: Failure of the upper neural crest cells in the first pharyngeal arch to develop the zygomatic arch
- Down-slanting palpebral fissures: lateral eye slanted downwards because gravity
- Autosomal dominant
- Because it’s a first pharyngeal arch syndrome,
- Conductive hearing loss (malleus/incus)
- Small mandible
- Malformed/absent ears (auricular cartilage)
Pierre-Robin Sequence
Failure of the lower neural crest structures to form the mandible.
- U-shaped (bilateral cleft palate): tongue pushed back; doesn’t allow palate to close
- Upper airway obstruction
- Autosomal recessive
Pouch things are about organs because endoderm!
Arch 1 = middle ear
DiGeorge Syndrome is caused by ___ and results in
Cause: Deletion of one of the arms of chromosome 22 (thus, 22q11) -> neural crest issue -> endoderm of pouch can’t communicate with bad arch
Result: hypoplasia of 3rd and 4th pharyngeal pouch derivatives
Normal functiosn of the 3rd and 4th pouch affected in DIgeorge syndrome
3rd pouch
- Dorsal wing -> inferior paraythyroid*
- Ventral wing -> thymus
4th pouch
- Dorsal wing -> superior parathyroid
- Ventral wing -> lil bit of thymus
