Embryolog Pharyngeal Apparatus

Question 1

arch 1 nerve

Answer 1

trigeminal

Question 2

arch 2 nerve

Answer 2

facial

Question 3

arch 3 nerve

Answer 3

glossopharyngeal

Question 4

arch 4 nerve

Answer 4

vagus

Question 5

arch 5 nerve

Answer 5

mostly regresses so no nerve

Question 6

arch 6 nerve

Answer 6

vagus n

mainly the recurrent laryngeal branch

Question 7

what are pharyngeal clefts

Answer 7

external invaginations of ectoderm

4 clefts

Question 8

what are the pharyngeal arches

Answer 8

core of mesenchyme (neural crest and paraxial mesoderm)

the neural crest will give rise to CT components
paraxial mesoderm gives rise to muscles

each arch has its own nerve (cranial nerve) and blood supply (aortic arch artery)

there are 6 arches initially but the 5th arch regresses

Question 9

what are pharyngeal pouches

Answer 9

internal evaginations of pharyngeal endoderm

4 pouches

Question 10

what is the stomodeum

Answer 10

invagination of ectoderm which will form the oral cavity

Question 11

what are the skeletal derivatives of the first arch

Answer 11

bones of the face and CT of face

malleus and incus

Question 12

what are the muscle derivatives of arch 1

Answer 12

muscles of mastication (temporal is, masseter, medial and lateral pterygoids)

anterior belly of digastric
mylohyoid
tensor veli palantini
tensor tympani

Question 13

what is the orogpharygeal membrane development pattern

Answer 13

develops b/w the two processes of the first arch
composed of an outer layer of ectoderm and an inner layer of endoderm

ruptures by day 26 to allow communication b/w pharynx and oral cavity

Question 14

what are the skeletal derivatives of arch 2

Answer 14

stapes
styloid process of temporal bone

stylohyoid ligament
lesser horn and superior portion of body of hyoid

Question 15

what are the muscle derivatives of arch 2

Answer 15

muscles of facial expression

stylohyoid
posterior belly of digastric
stapedius (dampens noise in ear)

Question 16

what are the skeletal derivatives of arch 3

Answer 16

greater horn and inferior portion of body of hyoid bone

Question 17

what are the muscular derivatives of the arch 3

Answer 17

stylopharyngeus

Question 18

what are the skeletal derivatives of arch 4

Answer 18

with 6th arch forms all laryngeal cartilages

Question 19

what are the muscular derivates of arch 4

Answer 19

muscles of pharynx

cricothyroid

Question 20

what are the skeletal derives of arch 6

Answer 20

with 4th arch forms all laryngeal cartilages

Question 21

what are the mucsular derivates of arch 6

Answer 21

laryngeal muscles (except cricothyroid) 
skeletal muscle of esophagus

Question 22

what is the derivative of pouch 1

Answer 22

formation of middle ear and auditory tube

Question 23

what are the derivatives of pouch 2

Answer 23

forms stroma of palatine tonsil

tonsillar fossa

Question 24

what are the derivatives of pouch 3

Answer 24

dorsal portion–> inferior parathyroid glands

ventral portion –> thymus

the third pouch migrates and that is why it forms the INFERIOR PT glands

Question 25

what are the derivatives of the pouch 4

Answer 25

dorsal portion--> superior parathyroid glands ventral portion--> ultimobranchial body --> forms the parafollicular cells of thyroid (calcitonin and Ca regulation)

Question 26

what is the fate of first pharyngeal cleft

Answer 26

contributes to formation of external acoustic meatus and contributes to Tympanic membrane

Question 27

remnants of clefts 2-4 form what

Answer 27

form the cervical sinus which is later obliterated and if this is not obliterated there are clinical problems

Question 28

what is the thyroid derived from

Answer 28

median endodermal thickening of pharyngeal floor

Question 29

what is the development of the thyroid gland

Answer 29

the gland descends along the pharynx into the neck remaining connected to tongue via the thyroglossal duct which degenerates around week 7 superior opening of the thyroglossal duct remains as the foramen cecum

Question 30

what is the pyramidal lobe of thyroid

Answer 30

a remnant of the distal thyroglossal duct (looks like a little finger-like projection) 50 % individuals

Question 31

what are parafollicular cells derived from (C cells)

Answer 31

ultimobranchial body of the 4th pouch

Question 32

what does the 1st pharygeal arch contribute to tongue formation and what innervation

Answer 32

body (anterior 2/3) | GSA from trigeminal (ectodermal in origin)

Question 33

what does the 3rd arch contribute to tongue formation

Answer 33

posterior 1/3 or root of tongue GVA from glossopharyngeal

Question 34

what does the 4th arch contribute to tongue formation and what innervation

Answer 34

forms the epiglottic region of the tongue (GVA from vagus n)

Question 35

what is the muscle of the tongue derived from

Answer 35

paraxial mesoderm of occipital somites

Question 36

what is the cause of ectopic thyroid or parathyroid tissue

Answer 36

remnants of thyroid tissue can remain along the course of migration the parathyroids also undergo a migration and are highly variable in their location

Question 37

what is the cause of lateral cervical cysts

Answer 37

form when the cervical sinus fails to degenerate these cysts are found along the anterior LATERAL border of the SCM

Question 38

what is the cause of branchial fistulas

Answer 38

occurs when the second arch fails to outgrow the third and fourth arches the cervical sinus retains a connection with the surface (external fistula) in rare cases the lateral cervical cyst can open into the pharynx (internal fistula)

Question 39

what is the cause of thyroglossal cysts

Answer 39

remnant of thyroglossal duct always location on or near MIDLINE of the neck

Question 40

what are the problems with neural crest defects in the development of pharyngeal arches

Answer 40

severe craniofacial defects result from disruption of neural crest cell migration or differentiation treacher collins robin sequence digeorge anomaly goldnehar syndrome

Question 41

what are symptoms seen in treacher collins

Answer 41

malar hypoplasia micrognathia - undersized jaw malformed external ear impaired hearing

Question 42

what are the symptoms of robin sequence

Answer 42

micrognathia cleft palate glossoptosis - retraction of tongue

Question 43

what are the symptoms of Goldenhar syndrome

Answer 43

``` Underdeveloped facial bones -Ear anomalies -Eye anomalies -hemivertebrae -spina bifida ```

Question 44

what is DiGeorge Syndrome

Answer 44

``` Deletion of chromosome 22 cardiac abnormalities craniofacial defects thymic hypoplasia parathyroid dysfunction - hypocalcemia due to parathyroid insufficiencies ```