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
Symptoms of digeorge syndrome
No parathyroid -> low serum calcium
No thymus -> no T cells -> immunocompromised
Heart septa (neural crest) defective -> tetralogy of fallot
Parathyroid hormone - what does it do and what pourches are responsible for it?
Parathyroid hormone raises calcium and depends on the 3rd and 4th pouch.
What does calcitonin do and what pouch does it depend on?
Calcitonin tones down calcium and comes from the 5th pouch, which gives the ultimobranchial body -> parafollicular cells in thyroid that make calcitonin
**The face is made of 5 pieces of neural crest
- 1st arch
- 2 mandibular prominences
- 2 maxillary prominences
- Cranial neural crest -> 1 frontal prominence
Cleft lip
Failure of fusion of maxillary and medial nasal prominence
Most common: unilateral
Cleft palate
Failure of fusionof maxillary processes
Nasolacrimal groove (often an extension of cleft lip)
Failure of fill in the space between maxillary + medial/lateral nasal prominence
