Block 4 Embryo

Question 1

pharyngeal apparatus consists of

Answer 1

pharyngeal arches, pouches, clefts (grooves), and membranes

Question 2

each pharyngeal arch consists of

Answer 2

mesoderm (differentiates into muscles and arteries)

neural crest cells (differentiate into bone and connective tissue)

Question 3

List the cranial nerves associated w/ each pharyngeal arch

Answer 3

1: CN V (trigeminal)
2: CN VII (facial)
3: CN IX (glossopharyngeal)
4: CN X (superior laryngeal)
5: CN X (recurrent laryngeal)

Question 4

List the pharyngeal arches

Answer 4

1,2,3,4, and 6 (5 regresses)

Question 5

List the pharyngeal pouches and what they’re made of

Answer 5

1,2,3,4

evaginations of endoderm that line the foregut

Question 6

List the pharyngeal clefts/grooves and what they’re made of

Answer 6

1,2,3,4

invaginations of ectoderm located b/w each pharyngeal arch

Question 7

List the pharyngeal membranes & what they’re made of

Answer 7

1,2,3,4

consists of ectoderm, intervening mesoderm and neural crest, and endoderm located between each arch

Question 8

Fate of pharyngeal cleft/groove 1

Answer 8

develops into the external auditory meatus

Question 9

Describe development of the thyroid gland

Answer 9

in the midline of the floor of the pharynx, endodermal lining of the foregut forms the thyroid diverticulum

the thyroid diverticulum migrates caudally, passing ventral to the hyoid bone and laryngeal cartilages. during this migration, the thyroid remains connected to the tongue by the thyroglossal duct, which is later obliterated

Question 10

List arch 1 derivatives

Answer 10

mesoderm: muscles of mastication, mylohyoid, anterior belly of digastric, tensor veli palatini, tensor tympani
neural crest: maxilla, mandible, incus, malleus, zygomatic bone, squamous temporal bone, palatine bone, vomer, sphenomandibular ligament
CN V (trigeminal nerve)

Question 11

List arch 2 derivatives

Answer 11

mesoderm: muscles of facial expression, posterior belly of digastric, stylohyoid, stapedius
neural crest: stapes, styloid process, stylohyoid ligament, lesser horn and upper body of hyoid bone
CN VII (facial N)

Question 12

List arch 3 derivatives

Answer 12

mesoderm: stylopharyngeus, common carotid arteries, internal carotid arteries
neural crest: greater horn ad lower body of hyoid bone

Question 13

List arch 4 derivatives

Answer 13

mesoderm: muscles of soft palate (except tensor veli palatini), muscles of pharynx (except stylopharyngeus), cricothyroid, cricopharyngeus, laryngeal cartilages, right subclavian artery, arch of aorta
 neural crest: none 
CN X (superior laryngeal)

Question 14

List arch 6 derivatives

Answer 14

mesoderm: intrinsic muscles of larynx (except cricothyroid), upper muscles of esophagus, laryngeal cartilages, pulmonary arteries, ductus arteriosus
neural crest: none 
CN X (recurrent laryngeal nerve)

Question 15

Pouch 2 develops into

Answer 15

epithelial lining of palatine tonsil crypts

Question 16

Pouch 3 develops into

Answer 16

inferior parathyroid gland, thymus

Question 17

Pouch 4 develops into

Answer 17

superior parathyroid gland

Question 18

Groove 2-4 final state

Answer 18

obliterated

Question 19

Pharyngeal membrane 1 derivative

Answer 19

tympanic membrane

Question 20

Pharyngeal membrane 2-4 derivative

Answer 20

obliterated

Question 21

List the swellings that form the face

Answer 21

frontonasal prominence, maxillary prominence (pharyngeal arch 1), mandibular prominence (pharyngeal arch 1)

Question 22

Nasal Placodes

Answer 22

form nasal pits, then medial and lateral nasal prominence

Question 23

Nasolacrimal Groove

Answer 23

forms b/w maxillary prominence & lateral prominence; eventually forms nasolacrimal duct and lacrimal sac

Question 24

Intermaxillary palate

Answer 24

formed by fusion of nasal prominences at the midline; makes the primary palate

Question 25

Secondary Palate forms from

Answer 25

outgrowths of the maxillary prominences caulled palatine shelves (specifically, lateral)

Question 26

Describe the palate

Answer 26

primary and secondary palate fuse at the incisive foramen to form the definitive palate.

posterior part of the secondary plate eventually forms the soft palate & uvula and does not have bone

Question 27

First arch syndrome

result of
types

Answer 27

results from abnormal development of pharyngeal arch 1

treacher collins syndrome
pierre robin syndrome

Question 28

Treacher Collins Syndrome

Answer 28

mandibulofacial dysostosis

characterized by underdevelopment of the zygomatic bones, mandibular hypoplasia, lower eyelid colombras, malfomormed external ears

Question 29

Remnants of pharyngeal clefts 2-4

Answer 29

appear in the form of cervical cysts or fistulas found along the anterior border of the SCM

Question 30

Pharyngeal Fistula

Answer 30

occurs when pharyngeal pouch 2 & pharyngeal groove 2 persists, forming a patent opening b/w the tonsillar area to the external neck

found in the anterior border of the SCM

Question 31

Pharyngeal Cyst

Answer 31

occurs when parts of the pharyngeal grooves 2-4 that are normally obliterated persists, usually found by the angle of the mandible

Question 32

Ectopic Thymus, Parathyroid or Thyroid Tissue

Answer 32

result from abnormal migration of these glands

glandular tissue may be found anywhere along their path of migration

Question 33

Thyroglossal Duct Cyst

Answer 33

occurs when part of the thyroglossal duct persists and forms a cyst

most common in the midline near hyoid bone, but can also be at the base of the tongue (lingual cyst)

Question 34

Congenital Hypothyroidism

Answer 34

thyroid deficiency exists in the early fetal period; causes impaired skeletal growth and mental retardation

characterized by coarse facial features, sparse eyebrows, wide set eyes, broad nose

Question 35

Cleft lip results from (2)

Answer 35

maxillary prominence fails to fuse with medial nasal prominence

somitomeric mesoderm and neural crest fail to expand, resulting in persistent labial groove

Question 36

Cleft palate
involves
classification

Answer 36

involves neural crest cells

anterior or posterior, distinguished by incisive foramen

Question 37

anterior cleft palate

Answer 37

palatine shelves fail to fuse with the primary plate

Question 38

posterior cleft palate

Answer 38

palatine shelves fail to fuse with eachother and the nasal septum

Question 39

digeorge syndrome

Answer 39

pharyngeal pouches 3 & 4 fail to differentiate into the thymus and parathyroid glands

accompanied by facial anomalies resembling first arch syndrome

Question 40

Ankyloglossia

Answer 40

frenulum of the tongue extends to the tip of the tongue, preventing protrusion

Question 41

Cervical sinus

Answer 41

the common cavity for the pharyngeal clefts/grooves

Question 42

lateral cervical cyst

Answer 42

2nd pharyngeal arch fails to grow caudally over the 3rd and 4th arch; remnants of the 2-4th grooves remain in contact with the surface by a narrow drainage canal

Question 43

cranisynostosis

Answer 43

premature closure of the cranial sutures

Question 44

Describe the timeline for cranial suture closures

Answer 44

anterior fontanelle: closes by 9 to 18 months

sphenoidal and posterior: close during the first few months of life