Embryology of head and neck Flashcards
Paraxial mesoderm (somites and somitomeres) forms the majority of what 4 things?
Membranous and cartilaginous parts of the neurocranium
All voluntary muscles of the craniofacial region
Dermis and CTs in dorsal region of head
Meninges caudal to the prosencephalon (forebrain)
Mesenchyme for formation of the head region is derived from what 4 things?
neural crest cells
ectodermal placddes
paraxial mesoderm
lateral plate mesoderm
Lateral plate mesoderm forms what?
Laryngeal cartilages and CT in this region
Neural crest cells form what million things?
entire viscerocranium, part of neurocranium, bone, cartilage, tendons, dermis, pia mater, arachnoid mater, sensory neurons, glandular CT, dentin
Ectodermal placodes form what?
neurons of the 5th, 7th, 9th, 10th cranial sensory ganglia
When do the pharyngeal arches appear?
In the 4th and 5th weeks of development
Pharyngeal arches begin to develop as _____________ and migrate from ___________
neural crest cells
hindbrain
The pharyngeal arches support the lateral walls of the _________
primordial pharynx
which arch completely regresses and forms nothing?
5th
The pharyngeal arches have what 4 components?
1 Pharyngeal arch artery that arises from the truncus arteriosus and runs around the pharynx to enter the dorsal aorta
2 Cartilaginous rod that forms the skeleton
3 Muscular component
4 Cranial nerve that supplies the mucosa and muscles derived from the arch
Cartilage/bones and ligaments from 1st arch?
Meckel’s cartilage (provides template for mandible development)
Malleus and Incus (also from Meckel’s)
Anterior ligament of the malleus
Sphenomandibular ligaments
Cartilage/bones and ligaments by 2nd arch?
Reichert cartilage provides a template for:
Stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid, stylohyoid ligament
Cartilage/bones and ligaments by 3rd arch?
Greater cornu of hyoid
Lower part of body of hyoid
Bones/cartilage and ligaments of 4th and 6th?
Thyroid cartilage Cricoid cartilage Arytenoid cartilage Corniculate cartilage Cuneiform cartilage
Muscles and cranial nerves 1st arch
V2 & V3 Muscles of mastication Anterior belly of digastric Mylohyoid Tensor tympani Tensor veli palatini
Muscles and nerves of 2nd arch?
CN VII Mimetic Stapedius Posterior belly of digastric Stylohyoid
Muscles/nerves in 3rd arch?
CN IX
stylopharyngeus
Muscles/nerves from 4th arch?
Superior laryngeal branch of X
Muscles of soft palate (except tensor veli palatini)
Muscles of pharynx (except stylopharyngeus)
Cricothyroid and cricopharyngeus
Muscles/nerves from 6th arch?
Recurrent laryngeal nerve from X
Intrinsic muscles of larynx (except cricothyroid)
Striated muscles of esophagus
1st arch arteries?
disappear but remnants form
maxillary arteries
2nd arch arteries
disappear but remnants form
Hyoid and stapedial arteries
3rd arch arteries
common carotid arteries
1st part of internal carotid arteries
left 4th arch arteries
arch of aorta from left common carotid to left subclavian
right 4th arch arteries
right subclavian (proximal portion)
Remainder of internal carotid arteries?
dorsal aorta
external carotid arteries
sprout from 3rd aortic arch
Proximal arch of aorta and brachiocephalic artery?
aortic sac
Distal right subclavian and left subclavian
7th intersegmental arteries
There are ___ paired pharyngeal pouches that develop in a _________ sequence between the arches
4
craniocaudal
Pharyngeal membranes are formed by what?
Endoderm of pouches and ectoderm of pharyngeal grooves
The 1st pharyngeal pouch gives rise to what
Tubotympanic recess - tympanic cavity and mastoid antrum
Connection of tubotympanic and pharynx forms what?
Auditory tube
2nd pharyngeal pouch
palatine tonsil
portion will remain as tonsilar fossa
3rd pharyngeal pouch
Inferior parathyroid glands (solid dorsal portion) Thymus gland (hollow ventral portion)
4th pharyngeal pouch
Superior parathyroid gland (each bulbar dorsal portion) Ultimopharyngeal body (hollow ventral portion)
Fusion of the ultimopharyngeal body and thyroid gland gives rise to
parafollicular cells (C cells) of thyroid gland calcitonin producing
5th pharyngeal pouch
rudimentary and becomes part of 4th
There are ____ pharyngeal grooves that from during the _____________ weeks
4
4th and 5th
The pharyngeal grooves separate what? Are invaginations of what?
Pharyngeal arches externally
Ectoderm
Which is the only groove that persists? What does it give rise to?
Pharyngeal groove 1
external acoustic meatus
What happens to the other grooves?
lie in slit like depression known as the cervical sinus
Pharyngeal membranes form where? Which one survives and what does it become?
Found between pharyngeal arches
Pharyngeal membrane 1 becomes the tympanic membrane
Mandibulofacial dystostosis ?
Defective migration or proliferation of neural crest cells
caused by underdevelopment of 1st and 2nd pharyngeal arches
Treacher-Collins and Pierre Robin syndromes?
Congenital malformations of eyes, ears, mandible and palate
1st arch
DiGeorge syndrome
Caused by abnormalities of neural crest cell migration and proliferation while 3rd & 4th pharyngeal arches develop.
(1) minor craniofacial defects including micrognathia, low set ears, auricular abnormalities, and cleft palate
(2) total or partial agenesis of the derivatives of the 3rd & 4th pharyngeal pouches (thymus & parathyroid glands)
(3) cardiovascular defects.
This syndrome is associated with partial monosomy of chromosome 22 but is also seen with children of alcoholic women
Which glands are highly variable in number and location?
parathyroid (2-6)
A remnant of the thyroglossal duct may persist and form the
Thyroglossal duct cyst in the tongue or even the anterior portion of the neck usually just below the hyoid
infection = thyroglossal duct sinus
ankyloglossia
tongue tie
frenulum is too short but will stretch with time
Clefts of the anterior palate
Lateral palatine processes don’t meet and fuse with the primary palate
Clefts of posterior palate
lateral palatine processes don’t meet and fuse with each other and with the nasal septum
Clefts of the anterior and posterior parts of the palate
lateral palatine processes don’t meet with primary palate, each other, or nasal septum
Coloboma of the iris
Defect in the inferior sector of the iris or the pupillary margin gives the pupil a keyhole appearance
Failure of closure of the retinal fissure during the 6th week
