head and neck embryology Flashcards
What is the phase called when the single layered blastula becomes trilaminar gastrula
gastrulation
invaginating epiblast cells have 2 fates:
# 1. fill in between epiblast and hypoblast -\> mesoderm 2. replace hypoblast -\> endoderm
* remaining epiblast cells become ectoderm
growth of WHAT causes lateral folding of the trilaminar disc?
somites
longitudinal growth of the cranial and caudal ends of the neural plate and tube causes the trilaminar disc to what?
undergo craniocaudal folding
The oropharyngeal membrane, which is initially cranial to developing neural tube, is folded inside developing head which seperates what?
pharynx from oral cavity
What are pharyngeal arches? Name them
paired bulges along the wall of the developing pharynx
- 5 arches: 1, 2, 3, 4, and 6
mesoderm of the pharyngeal arches becomes what?
muscles of the head
neural crest cells in the pharyngeal arches contribute to form what?
skeleton of head and neck
Name the cranial nerve associated with each of the arches
- arch 1: Trigeminal
- arch 2: Facial
- arch 3: Glossopharyngeal
- arch 4 and 6: Vagus
1st pharyngeal arch has 2 processes and 1 cartilage associated with it. Name them
- maxillary process
- mandibular process
*nerve associated CN V*
- Cartilage: Meckel’s cartilage
meckel’s cartilage disappears except for 2 small pieces which ossify to form what?
malleus and incus of middle ear
Mesenchyme of 1 pharyngeal arch derived from neural crest cells form the bones of
mandible and lower face
Mesoderm derived mesenchyme of the 1 pharyngeal arch produces what
dermis of the face and muscles associated with mandible and ear
- CN V innervates all first derived structures: muscles of mastication; tensor tympani and Tensor veli palatini; skin of face
nerve of 2nd pharyngeal arch
facial n
cartilage of the 2nd pharyngeal arch becomes
- part of body and lesser horn of hyoid
- styloid process
- stylohyoid ligament
- stapes
Muscles of the 2nd pharyngeal arch become?
- stylohyoid and posterior digastric
- stapedius
- muscles of facial expression
3rd pharyngeal arch becomes what
- greater horn and inferior portion of the body of the hyoid bone
- stylopharyngeus
4th pharyngeal arch becomes what
- cartilages of larynx
- cricothyroid, pharyngeal muscles
- superior laryngeal nerve
6th pharyngeal arch becomes what
- intrinsic muscles of larynx (except cricothyroid
- recurrent/inferior laryngeal nerve
Between the pharyngeal arch swellings, how many external clefts and how many internal pouches develop
- 1 external pharyngeal cleft
- 4 internal pharyngal pouches
first pharyngeal pouch and cleft form between first and second arch. What does the cleft become? What does the pouch become?
- cleft -> external auditory canal
- pouch -> tympanic cavity and pharyngotympanic tube
what does 2nd pharyngeal pouch become
tonsils
What does 3rd pharyngeal pouch become
glands
What does 4th pharyngeal pouch become
contributes to C cells of thyroid gland
Bones of the face, mandible, and hyoid have what origin
neural crest cells
bones of the braincase have what origin
paraxial mesoderm
Nasal placodes consist of what 3 parts
- nasal pits
- medial nasal prominence
- lateral nasal prominence
nasal prominences fuse to form what
philtrum: intermaxillary segment
maxillary prominences form secondary plate and creates what
palatine shelves
fusion of palatine shelves and what completes the formation of the secondary palate
nasal septum
Several swellings from the floor of the developing pharynx contribute to the development of what?
tongue
Tissues of Tongue have innervation from which arches
1-4
innervation of tongue muscles come from what
occipital somites: some mesoderm migrates in to the tongue to produce the muscles and the somite innervation is preserved
