head and neck development Flashcards
three layers of embryo at day 17
ectoderm, mesoderm, endoderm going from the outside to the inside
prosencephalic organizing center and rhombencephalic organizing center
they are important signaling centers to tell how to form the brain and face and ear
olfactory plactodes and the frontonasal process (frontal) prominence
they are paired thickening of ectoderm and associatex with the telencephalon, forebrain frontonasal process (frontal) prominence- condensed mesenchyme
pharyngeal arches and grooves (clefts)
they are the ridges that form behind the frontonasal prominence
*mesenchyme condensations
*5 pairs
*usually 3 pairs are actually visible
*only the first arch has subdivisions
they make the outside of the pharynx
the grooves are the indentations between each of the arches there are usually only 2-3 that are visible. The floor of the groove is the pharyngeal membrane (closing plate) what ends the pharynx
pharyngeal pouches
they are little lateral dilations of the pharynx that are between the pharyngeal arches and on the opposite side of the pharyngeal grooves
interface between the groove and the pouch is the pharyngeal membrane
so groove is on the outside and pouches are on the inside
oral cavity
boundaries: Caudal- cardiac bulge
cranial-frontonasal prominence
lateral- first phayrngeal arch
posterior-oropharyngeal membrane
origin of the pharyngeal arch mesenchyme
paraxial mesoderm: head mesoderm or occipital somites
neural crest: ectoderm majority
pharyngeal arch basic components
core of condensed mesenchyme-becomes cartilage
loose mesenchyme-becomes connective tissue
head mesoderm-becomes skeletal muscle
a pharyngeal arch artery- aortic arch
a cranial nerve-becomes a cranial nerve
what the pharyngeal arches 1234and6 become
1- malleus and incus, anterior ligament of malleus and sphenomandibular ligament
2- stapes, styloid process and stylohyoid ligament
3-hyoid bone
4 and 6-thyrod and circoid cartilage
they also become bones and muscles in the skull and face 1- muscles of mastication 2- facial expression and sup strap 3-stylopharyngeus 4+6- pharyngeal/ larynx muscles
arches- cranial nerves
1- V 2-VII 3-IX 4-X sup laryngeal 6-X inf laryngeal (recurrent laryngeal)
first groove remains as the…
external autidory meatus
pharyngeal grooves incomplete
causes a hole that leaks in childhood or a really large lump
persistence of pharyngeal groove findings
1st cleft duplication
persistent cervical sinus (blind pouch)
cervical fistula- just an epitheleal tube that goes all the way to pharynx
cervical cyst
the openings are always lateral
derivatives of pharyngeal endoderm
thyroid gland, thymus gland, parathyroid gland, lining of middle ear, epithelia of palatine tonsil, epithelium of pharynx
fate of the pharyngeal pouches
1- middle ear cavity and inner tympanic mem
2- palatine tonsil
3+4= parathyroid glands
thymus and thyroid
chromosome 22q11.2, digeorge syndrome
mandible and ear issues
stromodeum
opening of the mouth
three parts of the developing face
frontonasal prominence, maxillary prominence, mandibular prominence
during 5-7 weeks what happens to the frontonasal prominence
there is a formation of the lateral and medial nasal prominences and the lateral nasal prominence merges with the maxillary prominence and frontonasal prominence. The two medial nasal prominences come together to form a intermaxillary segment- this forms the middle part of the upper lip, the incisor bridge of maxilla and the primary palate
choanal atresia
absence of nasal choanae- the hole that connects the primitive nostril to the nasopharynx
the human palate has two parts
primary- triangle
secondary-the actual palate
the tongue has to move down to get out of the way for the palate to fuse correctly
