Head and Neck development Flashcards
When does the bilateral pharyngeal apparatus start to form?
Four to five weeks post fert
Pharyngeal clefts
External aspect between arches (ectoderm)
Pharyngeal pouch
internal aspect between arches. There are four well defined arches, the fifth is reabsorbed. (endoderm)
Pharyngeal membranes
2 layered structures of ectoderm and endoderm
What is in the mesenchymal core of the arches?
Paraxial mesoderm, nc cells, and lateral plate mesoderm.
What does each pharyngeal arch contain?
A cartilaginous skeletal component(nc cell derived) connective tissue (nc cells) and muscle component (paraxial) a cranial nerve and a aortic arch artery
Intramembranous bone formation
Bone develops in WELL vascularized mesenchyme. No cartilage model. Makes flat bones of face and skull
Intra cartilaginous bone formation
Bone forms from pre-existing cartilage model, SOME bones of the pharyngeal apparatus are made this way
What are the two prominces of the 1st pharyngeal arch
Maxillary and Madibular
Describe the cartilagenous component of the maxillary promincence of the 1st arch
The cartilage is called the palatopterygoquadrate (HOLY FUCK THAT IS A WORD) and the cartilage regresses and leaves no adult remnant
Describe the cartilagenous component of the mandibular prominence of the 1st pharyngeal arch
It is called Meckel’s cartilage and it makes a large contribution to the face, it leaves SOME adult structures
What does meckel’s cartilage give rise to? and how?
Incus, malleus, by endochondral ossification
What does the perichondrium of Meckel’s cartilage form?
Anterior ligament of malleus, and Sphenomandibular ligament
What does intramembranous ossification form in the maxillary prominence of the 1st arch?
Squamous portions of temporal bone, maxillary bone, zygomatic bone, palatine bone
What does intramembranous ossification form in the mandibular prominence of the 1st arch
Mandible
What are the muscle components of the 1st pharyngeal arch?
the FOUR muscles of mastication, the Tensor veli palatini (sounds like martini lol) and tensor tympani. Anterior belly of the digastric. Mylohyoid.
What is the nerve component of the first pharyngeal arch
Mandibular branch of the TRIGEMINAL (nerve V) nerve supplies the muscles. Sensory supply to skin of face is through opthalmic, maxillary, and mandibular branches of CN V as well
What does Reichert’s cartilage of the second arch give rise to?
Stapes, the styloid process, stylohyoid ligament, lesser horn and upper body of hyoid bone
What muscles come form the 2nd arch?
Muscles of facial expression, stapedius, stylohyoid, posterior belly of the digastric
skeletal component of 3rd pharyngeal arch
Lower part of the BODY and greater horn of the hyoid
muscle component of 3rd arch
the ONLY one is the stylopharyngeus
Nerve component of 3rd arch
CN IX Glossopharyngeal nerve
nerve component of 2nd arch
Facial nerve VII
Skeleton of 4th and 6th arches
never as large as other arches, they merge together. They form laryngeal cartilage from lateral plate mesoderm, cartilage does not ossify
Muscles of arches 4 and 6
muscles of soft palate, pharynx, intrinsic muscles of larynx, muscles of upper esophagus. Myoblasts of 6th arch become intrinsic laryngeal muscles
Nerve component of arch 4 and 6
Vagus Nerve
where do pharyngeal arch muscles come from?
from cranial paraxial mesoderm and occipital somites
what is the fate of pharyngeal arch arteries
they are modified to form definitive arteries of the upper thorax neck and head
What is the diverticulum of pharyngeal pouches
it is a pouch or sace that branches out from a hollow organ.
First pouch expands towards
the first pharngeal cleft. The distal portion expands to form the epithelial lining of the tympanic cavity, proximal narrow portions forms teh auditory tube
Which pouch forms a stalk like extension?
the first, it eventually becomes the auditory tube
Which pouch has epithelial lining that proliferates and forms buds that extend into mesenchyme
The second one does
What type of tissue infiltrates the buds of the second pouch?
Lymphatic tissue
What does epithelial lining of 2nd pouch become?
the surface epithelium of the palatine tonsil
Where does palatine fossa come from?
part of the 2nd pouch
what are the 2 regions of the 3rd pouch?
dorsal and ventral
What does the dorsal region of 3rd pouch form?
the Inferior parathyroid gland
what does the ventral region of the 3rd pouch form?
stroma of the thymus
What are the two regions of the 4th pouch?
dorsal and ventral
what does dorsal region of 4th pouch form?
glandular cells of superior parathyroid glands
what does ventral region of 4th pouch form?
Ultimobranchial body (makes parafollicular cells of thymus) cells are derived from neural crest cells
What does the 1st cleft form?
epithelial lining for external auditory meatus
Pharyngeal membrane adult remnant is
the tympanic membrane
What part of the tonge does arch 1 make?
anterior 2/3
when does tongue development begin?
week 4 of development
where does second median swelling of the tonge come from?
from the 2nd 3rd and 4th arch
what forms the copula?
endoderm and underlying mesenchyme of second arch
what forms hypobranchial eminence?
endoderm and underlying mesenchyme of third and fourth arches
does the second arch have any contribution to the mucosa of adult tongue?
No the tissue of the 3rd overgrows it
what forms the most posterior part of the tonge?
tissue from 3rd and 4th arch endoderm, innervated by CNIX and X
where do the anterior and posterior parts of the tonge fuse?
at terminal sulcus
where do muscles of tonge come from?
from myotomes of occipital somites that migrate forward to developing tongue, the hypoglossal nerve follows them
when does development of the thyroid begin?
day 24
what does the thyroid first appear as?
a thickening of endoderm on the floor of the upper pharynx
what forms glandular cells of the thyroid?
the thyroid diverticulum
what starts forming at the foramen cecum of the developing tongue?
the thyroid gland
what is the thyroglossal duct?
the connection the thyroid has to the foramen secum as it grows and descends through the tissue of the neck
what happens to the thyroglossal duct?
it degenerates
what do follicular cells of thyroid produce?
colloid
what to parafollicular cells produce?
calcitonin
when does oropharyngeal membrane rupture?
day 26
how many facial prominences are there in early development?
five
what surrounds the stomodeum?
by frontal prominence cranially, laterally by 1st arch and caudally by cardiac bulge
how many primordia of the five come from first arch?
four, the bilateral maxillary prominences and bilateral mandibular prominences
What is the fifth prominence?
a single midline structure, it is the single frontonasal prominence, ventral to forebrain, it is the upper border of the stomatodeum
What forms the intermaxillary segment?
the merging of the inferior medial nasal prominces
what does the intermaxillary segment give rise to?
philtrum of upper lip, upper jaw compoent (where four incisor teeth will form) called premaxillary part of maxilla. And the primary palate
When does palate development start?
fifth week
Do the posterior parts of the lateral palatine process ossify?
no
where does skeletal muscle come from in soft palate?
from myotome cells that have migrated from arches
what is the nasopalatine canal? what does it become in an adult?
a small canal that persists between premaxillary part of maxilla and palatine process, it becomes the incisive fossa.
Why is the incisive fossa important?
It is considered to be the dividing landmark between anterior and posterior cleft deformitites
