"Gross Anatomy Development of the Face and Palate Jeffrey Amack" MARY Flashcards
Pharyngeal arches are prominent features of the developing head and neck. They are also called branchial arches because they resemble the gills of a fish. When do these arches develop?
Arches form in a rostral to caudal sequence: Arch 1 to 6 from week 4 onwards, Arch 1 and 2 appear at the time of closure of the cranial neuropore (Day 25).
The pharyngeal arches have grooves called:
Pharyngeal clefts on the exterior, and pharyngeal pouches on the interior.
The musculature of the face and neck derives from:
mesoderm
What developmental tissues are the progenitors of the pharyngeal arches?
Mesenchymal core - ectoderm on outside, endoderm on inside, mesoderm in the middle, plus neural crest cells that migrate into the arches
Each pharyngeal arch has certain elements associated with it:
A specific cranial nerve
An aortic arch artery
A cartilagenous rod derived from neural crest cells or lateral plate mesoderm (to form muscle)
What do neural crest cells give rise to?
Neural, skin, teeth, head, face, heart, endocrine, gastrointestinal tract
T/F: Neural crest cells do not follow distinct migration patterns. They travel indiscriminately as the embryo develops.
False. Neural crest cells migrate in three streams to the pharyngeal arches. Rhombomeres are patterned by a Hox code—NCCs take Hox expression with them. Differential hox expression allows NCCs to respond differently to signals from pouch endoderm.
The face is primarily derived from what pharyngeal arches?
1 and 2
Pharyngeal arches 3 and 4 contribute to form the:
neck (and 6)
Name the notable structures formed by pharyngeal arch #1.
Meckel's cartilage Malleus Incus Ligaments Mandible
Reichert’s cartilage, stapes, temporal bone styloid process and hyoid bone form from:
pharyngeal arch #2
Note that hyoid is also formed from arch #3.
Which pharyngeal arches primarily contribute to muscles that make up the face?
Mostly arches 1 and 2: 1 for muscles of mastication, 2 for muscles of facial expression.
Arches 3 and 4 contribute small muscles in the area of the larynx and pharynx.
T/F: Distinct cranial nerves innervate pharyngeal pouches.
True. Arch 1 - CN V and some other stuff Arch 2 - CN VII Arch 3 - CN IX Arch 4 - CN X and some other stuff
What are the characteristics of Pierre Robins Syndrome (Pierre Robins sequence)?
- malformation of first arch structures
- triad of micrognathia, cleft palate and glossoptosis (posteriorly placed tongue)
- difficulties breathing and feeding
Treacher Collins syndrome results from defects in what?
Pharyngeal arches 1 and 2 - leads to several craniofacial features ie downward slating eyes (hunchback of notre dame look)
What is the genetic defect in Treacher Collins syndrome?
TCOF1 gene, which leads to overactive p53 in the face during development ie. apoptosis of neural crest cells
T/F: Reducing p53 expression in mice can ameliorate the effects of a defective TCOF1 gene, as seen in Treacher Collins syndrome.
True
Pharyngeal cleft # ___ gives rise to the external auditory meatus.
1
How might a branchial fistula arise?
If the second pharyngeal arch fails to cover the 3rd and 4th
The first pharyngeal pouch forms:
Tympanic cavity and auditory (Eustachian) tube
What pharyngeal pouch forms the palatine tonsil?
Second
The third pharyngeal pouch becomes the:
inferior parathyroid gland
thymus
Remember this “T” for third, paraThyroid, thymus
What pharyngeal pouch forms the superior PTH gland and ultimobranchial body?
Fourth
On what side of the pharynx does the thyroid form?
Ventral
