G56: Dev of Face and Pharynx

Question 1

Week 4

Answer 1

6 pharyngeal arches at rostal end

Question 2

arch 4-6 fuse and 5

Answer 2

is only seen transiently

Question 3

Pharyngeal arches/grooves are lined with

Answer 3

ectoderm (outer surface)

Question 4

Pharyngeal pouches are lined with

Answer 4

endoderm (inner wall of pharynx)

Question 5

Pharyngeal membrane

Answer 5

separates pouches and grooves; lined with an outer layer of ectoderm and inner layer of endoderm

Question 6

Paraxial mesoderm forms

Answer 6

CT, skeleton of posterior cranial vault and base, skeletal muscles of face

Question 7

AT week 4, neural crest cells invade to form

Answer 7

bones of face, thyroid and cricoid cartilage, middle ear, frontal cranial vault and base

Question 8

Each arch has

Answer 8

1. Mesenchymal core
2. aortic arch
3. cartilaginous rod for skeleton of arch
4. myoblasts for head and neck muscles
5. CN 5, 7, 9, 10

Question 9

Brachial motorfibers

Answer 9

refer to fibers that supply skeletal muscle derived from pharyngeal arches (not somites)

Question 10

Arch 1

Answer 10

Mandibular Arch; maxillary and mandibular processes - maxilla, zygomatic, temporal bone and mandible respectively

Question 11

Cartilage of Arch 1

Answer 11

Meckel’s cartilage: template for mandibular bone to form around, disappears and mandible forms in place

Question 12

Meckel’s cartilage that persists becomes

Answer 12

anterior ligament of malleus, sphenomandibular ligament, malleus, incus (endochondral ossification)

Question 13

Arch 1 muscle derivatives

Answer 13

muscles of MASTICATION, temporalis, masseter, pterygoids, tensor tympani, tensor veli palatini anterior belly of digastric, mylohyoid

Question 14

What nerve innervates all muscles of ARCH 1?

Answer 14

Trigeminal

Question 15

Treacher Collins Syndrome

Answer 15

underdevelopment of arch 1, underdeveloped zygomatic bones, mandibular hypoplasia, malformed external ears, inherited or teratogens
disrupts neural crest cell migration

Question 16

Arch 2

Answer 16

Hyoid Arch; hyoid bone

Question 17

Cartilage of Arch 2

Answer 17

Reichert’s Cartilage- upper part of hyoid bone, stylohyoid ligament, styloid process of temporal bone and stapes of middle ear

Question 18

Muscles of Arch 2

Answer 18

Muscles of FACIAL EXPRESSION; posterior belly of digastric, stapedius m, stylohyoid

Question 19

Cranial nerve associated with Arch2?

Answer 19

Facial n, sensory to tongue, motor to facial expression, visceral motor, general sensory to ear

Question 20

Arche 3

Answer 20

greater horn of hyoid bone; stylopharyngeus m

Question 21

Arch 4-6 derivatives

Answer 21

do not form bone, rather persist as cartilage (thyroid, cricoid, arytenoids, corniculate, cuneiform); Pharynx muscles: pharyngeal constrictor, crirocricoid m, levator veli palatine, intrinsic muscles of larynx

Question 22

Nerve of Arch 3

Answer 22

Glossopharyngeal

Question 23

Nerve of Arch 4-6

Answer 23

Vagus n

Question 24

Pharyngeal pouch 1

Answer 24

pharynx to middle ear (tubotympanic recess) which will become the auditory tube, middle ear cavity and mastoid antrum

Question 25

Pharyngeal pouch 2

Answer 25

forms tonsillar fossa; migrating mesoderm forms tonsils within fossa

Question 26

Pharyngeal pouch 3

Answer 26

Dorsal and ventral wings; Dorsal wing: inferior parathyroid gland, ventral wing: thymus

Question 27

Pharyngeal pouch 4

Answer 27

forms the superior parathyroid gland; ventral part of pouch 4: ultimobranchial bodies

Question 28

Ultimobranchial bodies of ventral pouch 4

Answer 28

are incorporated into thyroid gland to become parafollicular cells (Calcitonin secreting)

Question 29

Pharyngeal groove 1

Answer 29

external auditory meatus (ectoderm)

Question 30

Pharyngeal groove 2-5

Answer 30

overgrowth from arch, no persistent meatus. Grooves briefly form a small sinus (cervical sinus) but its obliterated

Question 31

Tympanic membrane

Answer 31

as arch 1 groove migrates inward and arch 1 pouch migrates outward they meet and form the tympanic membrane (endoderm internally and ectoderm externally)

Question 32

DiGeorge Syndrome

Answer 32

congenital absence of the thymus and parathyroid glands along with facial abnormalities. (pouch 3)

Question 33

Persistent Cervical sinus from groove 2-5

Answer 33

(Ectodermally lined cyst) forms a cyst or fistula along the border of sternocleidomastoid or into the pharynx (internal or external branchial fistula)

Question 34

Tongue week 5 dev

Answer 34

Arch 1: lateral lingual swellings, tuberculum impar (ant 2/3) CN 5 Arch 2-4: Copula (post 1/2 and epiglottis) CN9-10 Arch 2 mostly regresses CN7

Question 35

Intrinsic muscles of the tongue

Answer 35

come from the occipital region and migrate into tongue region and drag innervation with them

Question 36

Thyroid development

Answer 36

proliferation of endoderm on dorsum of tongue; foramen ceacum: thyroid diverticulum

Question 37

Thyroid diverticulum descends

Answer 37

inferiorly down neck, persistent thyroglossal duct or small part persists: pyramidal lobe, and ectopic glandular tissue

Question 38

Development of face (5 mesenchymal prominences)

Answer 38

5 mesenchymal prominences surrounding the stomodeum: Frontonasal, paired maxillary, and paried mandibular

Question 39

Frontonasal prominence derivatives

Answer 39

covers developing forebrain; frontal bones, bridge of nose, nasal septum, primary palate, upper incisors

Question 40

Maxillary prominence derivatives

Answer 40

Sup. arch 1: maxilla, upper cheeks, post-incisor maxillary teeth, secondary plate

Question 41

Mandibular prominences derivatives

Answer 41

Inf. arch 1: mandible, lower cheeks, mandibular teeth

Question 42

Frontonasal prominence development

Answer 42

nasal placodes (paired ectodermal thickening) -> nasal pits with medial and lateral nasal prominence surrounding it (mesenchyme), medial nasal prominence fuses at midline to give intermaxillary segment

Question 43

Maxillary prominence

Answer 43

gives rise to palatine processes that will fuse to form secondary palate

Question 44

Intermaxillary segment gives rise to

Answer 44

primary hard palate (from medial nasal prominence)

Question 45

Lateral nasal prominences

Answer 45

alae of the nose; separated from maxillary prominence by the nasolacrimal groove

Question 46

Nasolacrimal groove invaginates to form the

Answer 46

nasolacrimal duct, and the lateral nasal prominences fuse with maxillary prominences

Question 47

Mandibular prominences

Answer 47

fuse at midline to form the mandible

Question 48

Orofacial clefting anomalies

Answer 48

incomplete fusion of facial primordia, nasolacrimal duct

Question 49

Palatogenesis

Answer 49

Primary palate 4 incisors and incisor foramen, secondary palate is the rest

Question 50

Median palatal process (pre maxilla)

Answer 50

primary palate forms from the intermaxillary segment from frontonasal prominence

Question 51

Paired maxillary prominences

Answer 51

develop palatine processes, grow medial and fuse at midline to form SECONDARY PALATE (hard palate) Nasal septum (frontonasal) fuses with primary palate

Question 52

Orofacial clefting anomaly risk factors

Answer 52

genetics, syndromes, envrinoment (smoking, RA, maternal disease)

Question 53

Anterior cleft lip and anterior palate anomaly

Answer 53

mesenchyme deficiency in maxillary prominences and median nasal prominences only affecting the primary palate

Question 54

Posterior cleft palate anomaly

Answer 54

defective secondary palate, prevents lateral palatine processes from growing and fusing (palatine shelf defect)

Question 55

Complete Cleft lip and palate

Answer 55

both primary and secondary palate are deformed