Wu's embryo

Question 1

Tissue origin of pouches?

Answer 1

Endoderm

Question 2

Tissue origin of arches?

Answer 2

mesoderm

Question 3

Tissue origin of clefts/grooves/folds?

Answer 3

ectoderm

Question 4

**Bone and cartilage are derived from

Answer 4

Neural crest!

Question 5

Tympanic membrane is the first membrane

Answer 5

Connects the inner ear (a pouch) to the outer ear ( a fold)

Question 6

Each arch has an associated nerve and arterial arch

Answer 6

Question 7

What arch is innervated by the superior laryngeal branch of vagus nerve?

Answer 7

Pharyngeal arch 4; derivatives:

Question 8

Cricothyroid and posterior crycoartenoid

Question 9

What arch is innervated by the recurrent laryngeal branch of the vagus nerve?

Answer 9

Pharyngeal arch 6; derivatives:

Remember that the ductus arteriosis becomes the ligamentum arteriosum in teh adult

Question 10

What does cleft 1 become?

Answer 10

External auditory ematus

Question 11

What do clefts 2-4 become?

Answer 11

Nothing- they usually get obliterated. If they aren’t obliterated, you get cystic anomalies/remnants of the neck

Question 12

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?

Answer 12

• Cervical branchial cyst
• Thyroglossal duct/sinus
• Ectopic thyroid gland/ nodule

Question 13

Lateral mass in front of the SCM that enlarges with age- what is it?

Answer 13

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

Question 14

Midline mass on your neck tha tmoves with swallowing- what is it?

Answer 14

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

Question 15

Symptoms of hyperthyroidism and an off-midline mass represent what cystic anomaly of the neck?

Answer 15

Ectopic thyroid gland/nodule: extra thyroid tissue on gland/nodule or along the paht of hte thyroid gland

Question 16

Inner ear bones are associated with what nerve in what arch? What bone is the exception?

Answer 16

Mandibular n (V3) in the first arch.

EXCEPTION: Stapes is from arch 2, which is associated with the facial nerve (remember n to stapedius?)

Question 17

Hyoid bone is associated with what arches?

Answer 17

2 and 3

Question 18

Larynx is associated with what arches?

Answer 18

Arches 4 &6

Question 19

Treacher Collins Syndrome and Pierre Robin sequence are both problems with which pharyngeal arch?

Answer 19

The first arch. Both are bone problems, so the cause is a problem with NEURAL CREST!

Question 20

Treacher Collins Syndrome- what are the other symptoms What does it look like?

Answer 20

• 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)

Question 21

Pierre-Robin Sequence

Answer 21

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

Question 22

Pouch things are about organs because endoderm!

Answer 22

Arch 1 = middle ear

Question 23

DiGeorge Syndrome is caused by ___ and results in

Answer 23

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

Question 24

Normal functiosn of the 3rd and 4th pouch affected in DIgeorge syndrome

Answer 24

3rd pouch

• Dorsal wing -> inferior paraythyroid*
• Ventral wing -> thymus

4th pouch

• Dorsal wing -> superior parathyroid
• Ventral wing -> lil bit of thymus

Question 25

Symptoms of digeorge syndrome

Answer 25

No parathyroid -> low serum calcium

No thymus -> no T cells -> immunocompromised

Heart septa (neural crest) defective -> tetralogy of fallot

Question 26

Parathyroid hormone - what does it do and what pourches are responsible for it?

Answer 26

Parathyroid hormone raises calcium and depends on the 3rd and 4th pouch.

Question 27

What does calcitonin do and what pouch does it depend on?

Answer 27

Calcitonin tones down calcium and comes from the 5th pouch, which gives the ultimobranchial body -> parafollicular cells in thyroid that make calcitonin

Question 28

**The face is made of 5 pieces of neural crest

Answer 28

• 1st arch
  
  • 2 mandibular prominences
  • 2 maxillary prominences
• Cranial neural crest -> 1 frontal prominence

Question 29

Cleft lip

Answer 29

Failure of fusion of maxillary and medial nasal prominence

Most common: unilateral

Question 30

Cleft palate

Answer 30

Failure of fusionof maxillary processes

Question 31

Nasolacrimal groove (often an extension of cleft lip)

Answer 31

Failure of fill in the space between maxillary + medial/lateral nasal prominence