head and neck embryology III Flashcards
what does surface ectoderm always give rise to?
epidermis
review of germ layers of pharyngeal arches
paired bars of mesenchyme
covered by surface ectoderm
contain core of ectomesenchyme derived from neural crest cells
pharyngeal pouches
areas of gut tube in pharyngeal portion that push out into the arches
pharyngeal clefts
grooves in between the arches
derivatives of 2nd pharyngeal pouch
epithelial lining of 2nd pharyngeal pouch proliferates into small buds
buds invade surrounding mesenchyme => primordia of palatine tonsils
tonsils invaded by lymphatic tissue later in development
part of pouch remains in adult as tonsillar fossa
derivatives of pharyngeal pouches (summary)
1: middle ear cavity, mastoid antrum, auditory tube
2: palatine tonsils, tonsillar fossa
3: inferior parathyroid, thymus
4: superior parathyroid
migration of inferior parathyroid
“hitch a ride” with thymus so end up below superior parathyroids
development of anterior tongue:
1: lateral lingual swellings and medial swelling (tuberculum impar) develop from floor of first pharyngeal arch
2: hypopharyngeal eminence (copula) develops from 3rd arch
3: lateral lingual swellings increase in size - overgrow tuberculum impar, merge with each other => anterior 2/3
4: hypopharyngeal eminence forms posterior part of tongue
arch derivatives (summary)
1st: anterior 2/3 of tongue, mucosa on body of tongue
2nd:
3rd: hypopharygeal eminence (copula), posterior part of tongue
4-6: epiglottis and extreme posterior part of tongue
development and innervation of mucosa of anterior 2/3 of tongue
derived from 1st arch so sensory innervation by mandibular branch of trigeminal nerve
development and innervation of posterior 1/3 of tongue
from hypopharyngeal eminence from 3rd arch so sensory innervation from glossopharyngeal nerve
development and innervation of epiglottis and extreme posterior part of tongue
derived from 4-6th arch
sensory innervation from superior laryngeal nerve
development and innervation of intrinsic muscles of tongue
occipital somites migrate into developing pharyngeal floor
innervated by hypoglossal nerve
derivatives of primoridia that compose tongue
tubercum impar and lateral lingual swellings - from 1st arch - innervated by CN V3 - derive mucosa of anterior 2/3 of tongue
from 2nd arch - CN VII (chorda tympani) - taste of anterior 2/3 of tongue
hypopharyngeal eminence - from 3rd and 4th arches - CN IX and CN X - make mucosa and taste of posterior 1/3 of tongue
occipital somites - CN XII - all intrinsic tongue muscles, all extrinsic except for palatoglossus
development of the thyroid gland
1: appears as diverticulum of foregut at foramen cecum
2: descends anterior to gut tube, hyoid bone and laryngeal cartilages to assume final position
development of nasal cavities
1: at 6th week, nasal placode invaginates to make nasal pit
2: oronasal membrane separates pits from primitive oral cavity
3: oronasal membrane ruptures, forming primitive choanae
4: when secondary palate formed, definitive choanae are at junction of nasal cavity and pharynx
5: paranasal sinuses develop as diverticula of lateral nasal wall - extend into maxilla, ethmoid, frontal, and sphenoid bones
6: reach maximum size during puberty - contribute to definitive shape of face
development of primary palate
from intermaxillary segment of frontonasal prominence
forms most anterior triangle of hard palate
development of secondary palate
develops from lateral palatine processes
initially vertically placed on either side of tongue
as tongue moves down in oral cavity palatal shelves swing up and fuse in midline with each other and also with primary palate
1st cleft derivative
external auditory meatus
2nd through 4th cleft derivatives
temporary cervical sinuses => obliterated when 2nd arch mesenchyme proliferates
cartilage derivatives of first arch
Meckel cartilage
Mandible
Malleus and incus
spheno-Mandibular ligament
muscle derivatives of first arch
Muscles of Mastication
- temporalis
- masseter
- lateral and medial pterygoids
Myohyoid
anterior belly of digastric
tensor tympani
tensor veli palatini
nerve derivatives of first arch
CN V2 and V3 (chew)
Treacher-Collins syndrome
1st arch neural crest fails to migrate => mandibular hypoplasia and facial abnormalities
cartilage derivatives of second arch
Reichert cartilage:
- Stapes
- Styloid
- lesser horn or hyoid
- stylohyoid ligament
muscle derivatives of second arch
Muscles of facial expression:
- Stapedius
- Stylohyoid
- platysma
- posterior belly of digastric
nerve to second arch
CN VII (facial expression)
Congenital pharyngocutaneous fistula
persistence of cleft and pouch (2nd?) => fistula between tonsillar area and lateral neck
cartilage derivatives of third arch
greater horn of hyoid
muscle derivatives of third arch
stylopharyngeus
nerves to third arch derivatives
CN IX (stylopharyngeus) swallowing
cartilage derivatives of 4th-6th arches
thryoid cricoid arytenoids corniculate cuneiform
muscle derivatives of fourth arch
most pharyngeal constrictors
cricothyroid
levator veli palatini
muscle derivatives of sixth arch
all intrinsic muscles of larynx except cricothyroid
nerve supply to fourth arch
CN X (superior laryngeal branch) - simply swallow
nerve supply to sixth arch
CN X (recurrent laryngeal branch) - speak
derivatives of first pouch
middle ear cavity
eustachian tube
mastoid air cells
contributes to endoderm lined structures of ear
derivatives of third pouch
dorsal wings develop into inferior parathyroids
ventral wings develop into thymus
end up below fourth pouch
fourth pouch derivatives
dorsal wings develop into superior parathyroids
MEN 2A association with pouches
parathyroid tumor from 3rd/4th pouches
parafollicular cells that cause medullary thyroid cancer are from neural crest cells associated with 4th/5th pouches
cleft lip
failure of fusion of maxillary and medial nasal processes (formation of primary palate)
cleft palate
failure of fusion of two lateral palatine processes or failure of fusion of lateral palatine processes with the nasal septum and or median palatine process (formation of secondary palate)
