Embryology Flashcards
(22 cards)
Branchial cleft
derived from ectoderm
Branchial arch
derived from mesoderm (muscles, arteries) and neural crest (bones, cartilage)
Branchial pouches
derived from endoderm
1st cleft
external auditory meatus
2nd- 4th cleft
temporary cervical sinuses, obliterated by proliferation of 2nd arch
What is the derivative of a branchial cleft cyst?
Persistent cervical sinus (2-4 branchial cleft)
appears in the lateral neck
1st arch
- Meckel cartilage: Mandible, Malleus, incus, sphenomandibular ligament
- CN V2,V3
- muscles of mastication, mylohyoid, belly of digastric, tensor tympani, tensor veil palatini
Treacher Collins syndrome
1st arch neural crest fails to migrate –> mandibular hypoplasia, fail abnormalities
2nd arch
- Reichert cartilage: stapes, styloid process, lesser horn of hyoid, stylohyoid ligament
- Muscles of facial expression, stapedius, stylohyoid, belly of digastric
- CN VII
Congenital pharyngocutaneous fistula
persistence of 2nd cleft and pouch –> fistula between internal tonsillar area and external neck
found along anterior border of sternocleidomastoid
3rd arch
- greater horn of hyoid cartilage
- stylopharyngeous m.
- CN XII
4th-6th arch
-cartilage: thyroid, cricoid, arytennoids, corniculate, cuneiform
-4th: muscle of pharyngeal constriction, cricothyroid, legato veil palatine
-6th: all intrinsic muscles of larynx except cricothyroid
4th arch: CN X (superior laryngeal branch)
6th arch: CN X (recurrent laryngeal branch)
1st pouch
“auditory tube”
: middle ear eustachian tube, mastoid cells
2nd pouch
“tonsillar fossa”
: epithelial lining of palatine tonsil
3rd pouch
“thymus and inferior parathyroid”
: dorsal wing = inferrior parathyroid; ventral wing = thymus
note 3rd pouch structures end up below 4th pouch
4th pouch
“superior parathyroids”
:Dorsal wings= superior parathyroid
Cleft lip
failure of fusion of maxillary and medial nasal processes (primary palate)
Cleft Palate
- failure of fusion of two lateral palatine processes
- failure of fusion of lateral palatine process with nasal septum and/or medial palatine process
(formation of secondary palate)
Genital tubercle–> M/F homolog
Male: glans penis, corpus cavernosum and spongiosum
Female: Gans clitoris, vestibular bulbs
Urogenital sinus–> M/F homolog
Male: bulbourethral glands of cowper, prostate gland
Female: greater vestibular glands of bartholin, urethral and pararurethral glands of skene
Urogenital folds –> M/F homolog
Male: ventral shaft of penis (penile urethra)
Female: labia minora
Labiosacral swelling –> M/F homolog
Male: scrotum
Female: labia majora
