Head and Neck Development Flashcards
when does the pharyngeal apparatus begin to develop?
around 4-5 weeks post fertilization
symmetry of pharyngeal apparatus at 4-5 weeks and what is the sequence?
bi-lateral
1-6 (5 doesnt exist in humans) and is organized cranially to caudal with 1 being the largest
what do the neural crest cells invade in the pharyngeal arches?
the core of the mesoderm producing the ectomesenchyme
phayngeal apparatus (4 components) and describe them
- phayrngeal arch - 5 pairs (1,2,3,4,6) defined by the cleft and pouches
- groove/cleft - external aspect of ectoderm/epidermis
- pouch - INTERNAL structure formed by outpocketing of the endoderm
- membrane - 2 layered structure with ectoderm outside and endoderm inside
when will the pharngeal apparatus form adult structures?
by the end of the embryonic period
composition of the mesenchymal core of the pharyngeal arch
paraxial mesoderm (somitomeres=scleretome, myotome, dermatome)
neural crest cells
lateral plate mesoderm
what does each arch contain?
A cartilagenous component derived from neural crest cells
A connective tissue derived from neural crest cells
muscle component (paraxial mesoderm)
a cranial nerve
aortic arch artery
somitomeres
non-condensed somites or unsegmented. ALL UNSEGEMNTED IN HEAD AND NECK REGION (go into somites - condensed form in occipital region and down) which gives rise to the muscle in the area. from the paraxial mesoderm bu somitomere myoblast derived
prominence’s of arch one
- MAxillary - cartilage regresses
2. Mandibular which includes meckel’s cartilage
where does bone form in mandible?
AROUND meckel’s cartilage
T/F meckel’s cartilage gives rise to bone?
FALSE. bone here is neural crest cell derived (intramembranous ossification meaning no cartilage pre-curser) the bone develops around meckel’s cartilage. It provides a scaffolding
what develops from meckel’s cartilage? how does the development occur?
sphenomandibular ligament
anterior ligament of the malleus
incus and malleus is by endochondrial ossification
endochondreal ossification
cartilage is a precursor
bone development in the mandible
intramembranous (no cartilage precursor)
neural crest cell
intramembraneous ossification in the maxilla
- maxilla
- squamous portion of the temporal bone
- zygomatic bone
- palatine bone
intramembraneous ossification in the mandible produces?
mandible
muscle components of the first pharyngeal arch?
FOUR MUSCLES OF MASTICATION
tensor veli palatini and tensor tympani
ANTERIOR belly of the digastric
mylohyoid
nerve component of the first pharyngeal arch
muscle and sensory
CRANIAL NERVE 5- TRIGEMINAL NERVE mandibular branch supplies the muscles of the first arch
sensory supply is through the opthalamic, maxillary, and mandibular branches of CN V
cartilage of the second pharyngeal arch
Reichert’s Cartilage
Reichert’s cartilage gives rise to? How?
via endochondrial ossification as the cartilage is the precursor
- stapes
- styloid process
- styloid ligament
- lesser horn and upper body of the hyoid bone
what separates arch one from arch two
pharyngeal cleft
muscles from the second pharyngeal arch
MUSCLES OF FACIAL EXPRESSION
stylohyoid
stapedius
posterior belly of the digastric
cranial nerve of pharyngeal arch 2
facial nerve - cranial nerve 7
innervation of the anterior and posterior belly of the digastric
anterior - CN 5 - trigeminal
posterior -CN 7 - facial nerve
cartilage component of third pharyngeal arch
lesser body and greater horn of the hyoid bone
endochondrial ossification of the cartilage to form bone
muscle component of the third pharyngeal arch
stylopharyngeus
nerve supply of the third pharyngeal arch
CN IX - glossopharyngeal nerve
cartilage of pharyngeal arches 4 and 6 and characteristic (from where and what it forms)
laryngeal cartilage
NEVER OSSIFIES AND FORMS THE LARYNX
*DERIVED FROM LATERAL PLATE MESODERM
muscles associated with 4 and 6 arch
muscles of soft palate
muscles of the pharynx
intrinsic muscles of the larynx
skeletal muscles of the upper esophagus
describe the upper 1/3 of the esopohagus
striated skeletal muscle from arch 4 and 6
pouches and clefts are ______ to the arch they are associated with and made from ______
caudal and made from the diverticulum of the epithelium/ENDODERM of the pharynx
divertiuclum
pouch or sac that branches out from a hollow organ
when does the oral pharyngeal break down?
around day 26
first pouch
pouch expands towards the cleft
from endoderm creates the epithelial lining
distal portion = epithelial of tympanic cavity
proximal = epithelium of auditory/eustachian tube
extension of the first pouch is called
tubotympanic recess - projects to the cleft and forms a stalk like apparatus
mesenchyme
mesodermal embryonic tissue that usually develops into C.T, skeletal tissues, including blood and lymph
second pouch
endoderm forms the epithelial lining of the PALANTINE tonsile
it will later be infultrated by lymphatic mesenchyme
the initial buds - some remain and make a palatine/tonsillar fossa
third pouch regions
dorsal and ventral region
dorsal region of third pouch
inferior parathyroid gland and the chief cells that secrete the parathyroid hormone
ventral region of third pouch
STROMA of the thymus gland
parenchyma cell = thymocytes- maturation of t - cells and supporting cell = epithelial reticular cells
regions of the fourth pouch
dorsal and ventral
dorsal region of fourth pouch
epithelium of pouch forms the superior portion of the parathyroid gland and ends up on the posterior aspect of the thyroid
ventral region of the fourth pouch
ULTIMOBRACHIAL BODY - epithelium forms the parenchyma cells of the thyroid which are the PARAFOLLICULAR CELLS
parafollicular cells come from where?
ventral region of the fourth pouch - associated with the thyroid
thyroid and superior parathyroid associated with?
fourth pouch
thymus and inferior parathyroid associated with?
3rd pouch
pharyngeal membrane adult remnant?
tympanic membrane
first cleft forms
epithelial lining of the external acoustic meatus
what happens to clefts 2,3,4,6?
mesencyme of the second arch will overlap these clefts and they regress forming a transient structure called the cervical sinus
when does tongue development begin?
week 4 of development
producing tongue?
proliferation of the endoderm and mesenchyme of the pharyngeal floor which produce lateral swellings
lateral swellings from pharyngeal floor produce…
mucous membrane (epithelium and underlying connective tissue) of the tongue
pharyngeal arch one contribution to tongue
anterior 2/3 of tongue
copula
this is a second midline swelling that fuses/unites the second and third pharyngeal arches endoderm and underlying mesenchyme
T/F the second arch contributes to the mucus membrane of the tongue?
FALSE - does not. the third and fourth overgrow arch two
posterior (root of tongue) formed by?
the 3rd and 4th pharyngeal arch endoderm
CN IX - 3
CN X - 4
terminal sulcus
where the anterior and posterior tongue fuse
cranial nerve XII
hypoglossal nerve which innervates all of the intrinsic and extrinsic muscles of the tongue except the palatoglossus muscle
where do muscles of the tongue come from?
SOMITES- these are the condensed somites that migrate from the occipital region and form the myotomes. derived from the paraxial mesoderm
producing the scleretome
MYOTOME
development of the thyroid begins when
day 24 and is the first endocrine gland to develop
first sight of thyroid gland
seen as a thickening of endoderm on the floor of the upper pharynx (between the first and second arch)
what does the thyroid diverticulum form?
glnadular cells that produce/secret thyroidi hormone
final position of the thyroid gland
in front of the trachea
Function and fate of the thyroglossal duct?
the thyroid galnd will descend through the tissue of the neck and maintain contact to the foreman cecum via the thyroglossal duct and this duct will eventually degenerate
‘pit’ in the tongue
foramen cecum (from proximal portion of duct as it assumes anatomical position)
glandular cells of the thyroid and what they produce
follicular cells and they produce colloid
parafollicular cells
from the ultimobrachial body of the 4th pouch and these migrate to the thyroid gland and have an endocrine function
thyroglossal cyst?
occurs if the thyroglossal duct does not regress and could interfere with swallowing when born
summary of thyroid
- from the endoderm of the foreman cecum and then descends to assume position over the trachea (1/2 ring)
- the parathyroid assumes position on the posterior aspect
- the ultimobrachial body of pouch 4 contributes is parafollicular cells to the thyroid
when will the oralphayrngeal membrane rupture?
approx. day 26
how many prominence’s contribute to the development of the face? where and what are they?
FIVE
Four are from the first arch
Bilateral maxillary prominance is lateral to the stomatodeum
bilateral mandibular prominance is caudal to the stomatodeum
ONE single midline strucure is the single fronto-nasal prominance which is upper part of the stomatodeum
stomatodeum
pre-cursor of the mouth
it is between the brain and the pericardium
placode
thickening of ectoderm
nasal placodes aka
olfactory placodes
nasal placodes
bilateral oval thickenings of surface ectoderm appearing on the frontonasal prominance which marks the site of the future nasal cavities
nasal placodes invaginate to form…
nasal pits
medial (inner) and lateral (outer) nasal prominances
encircle the nasal pits and the placodes are within the nasal pits and form the primordial of the nasal
nasal lacrimal groove function and what it becomes
separates the lateral nasal prominence from the maxillary prominence and it becomes the nasolacrimal duct
nasolacrimal duct
upper end expands to form the lacrimal sac
it runs from the medial eye to the inferior meatus
how do the ectoderm (epidermis) of the lateral nasal prominence and amxillary prominence fuse?
nasolacrimal cord detaches
intermaxillary prominence
medial nasal prominence’s of frontobasal prominence become compressed in the midline and form this
creating mature face features?
differential growth of portions of the facial prominences, combining with fusion of several of them
direction of growth of maxillary prominence’s?
proliferate and grow towards eachother
intermaxillary segment gives rise to?
philtrum of the upper lip
upper jaw component (four incisor teeth- premaxilla)
the primary palate
primary palate is formed from?
intermaxillary segment - which is the fusion of the inferior medial nasal prominence’s
what prominence does the medial nasal come from?
fronto-nasal prominence- this is a single midline structure
cleft lip/palate?
fusion of the medial nasal prominences which forms the intermaxillary segment - if this fusion does not occur or something happens with this fusion because the intermaxillary segment gives rise to the philtrum of the lip, pre-maxilla (4 incisors) and the primary palate
range of development of the palate
starts at fifth week and does not finish until 12th week
primary palate
premaxillary component of maxilla
only small part of adult hard palate
secondary palate
forms bulk of the palate with the majority of hard and ALL OF SOFT PALATE
Where does the palate form?
roof of mouth and floor of nasal cavity- separates the oral cavity from the nasal cavity and nasopharynx
nasal septum
downgrowth of the frontonasal prominence
movement of tongue
from superior down
major events in development of secondary palate
- nasal septum - downgrowth from the fronto-nasal prominence
- two bi-lateral palantine from the maxillary prominance move down and horizontal
what must fuse for the palate to form
lateral palatine shelves with eachother, primary palate, and the nasal septum
primary palate contributions
intermaxillary segment of frontonasal prominence
secondary palate contributions
lateral palantine processes of the maxillary prominance
hard palate bone formatino
INTRAMEMBRANOUS - no cartilage precursor from neural crest cells
soft palate = posterior processes (bone/cartilage?)
NO OSSIFICATION no bone or cartilage - myotome cells that have migrated from the pharyngeal arches
landmark between the anterior and posterior cleft deformaties
nasopalantine canal- incisive fossa in the adult
fusion of hard palate occuring around?
week 9 - still going tho
