Embryology of Pharyngeal Arches

Question 1

What pharyngeal arch do the primordial jaws arise from?

Answer 1

1st PA

Question 2

PA1 receives NCC from what rhombomere?

Answer 2

R1-2

Question 3

PA2 receives NCC from what rhombomere?

Answer 3

R4

Question 4

PA 3/4 receive NCC from what rhombomere?

Answer 4

R6-7

Question 5

Rhombomeres arise from what part of the brain?

Answer 5

Hindbrain

Question 6

At what gestational age does the cervical sinus form? When does it disappear?

Answer 6

5th week to 7th week

Question 7

The normal formation of the cervical sinus is the result of what?

Answer 7

PA2 overgrowth of PA3/4 => Formation of an ectodermal depression

Question 8

What structures will a typical pharyngeal arch contain?

Answer 8

Artery - from truncus arteriosus

Cartilagenous rod - skeleton

Muscular component

Sensory/Motor nerves

Question 9

What does the dorsal part of Meckel’s cartilage form?

Answer 9

Malleus and Incus bones

Question 10

What does the ventral side of Meckel’s cartilage give rise to?

Answer 10

Primordium of mandible, will be overgrown by osteogenic cells

Question 11

What does the perichondrium of Meckel’s cartilage form?

Answer 11

Anterior ligament of Malleus bone and sphenomandibular L.

Question 12

What PA does Meckel’s cartilage arise from?

Answer 12

PA1

Question 13

What is the cartilage of PA2?

Answer 13

Riechert’s cartilage

Question 14

What arises from the ventral end of Riechert’s cartilage?

Answer 14

Lesser cornu/horn of Hyoid bone

Question 15

What arises from the perichondrium of the Riechert’s cartilage?

Answer 15

Stylohyoid L.

Question 16

What PA cartilage do the stapes and the styloid process of the temporal bone arise from?

Answer 16

Riechert’s cartilage from 2nd PA

Question 17

What does the 3rd PA cartilage give rise to?

Answer 17

Greater horn/Cornu of hyoid bone

Question 18

What does the hypopharyngeal eminence give rise to? What PAs does it arise from?

Answer 18

Body of hyoid bone

Arises from PA3 and PA4

Question 19

What PA do the laryngeal cartilages come from?

Answer 19

PA 4 and 6 (except epiglottis)

Question 20

What muscle does the 3rd PA give rise to?

Answer 20

Stylopharyngeus M.

Question 21

What muscles do the 4th PA give rise to?

Answer 21

Cricothyroid M.

Levator veli palatini M.

Pharyngeal constrictor ms.

Question 22

What PA gives rise to the intrinsic muscles of the larynx?

Answer 22

6th PA

Question 23

What type of cranial nerve supply muscles derived from the arches? Skin and mucous membranes?

Answer 23

Muscles - SVE

Skin and mucous membranes - SVA

Question 24

What initiates formation of double-layered pharyngeal membranes?

Answer 24

Pouch endoderm contacts ectoderm of pharyngeal grooves

Question 25

Around week 20, mesenchyme of the 2nd pharyngeal pouch will differentiate into what tissue?

Answer 25

Lymphoid tissue

Question 26

What is the direct embryonic origin of the inferior parathyroid gland?

Answer 26

Epithelium of Dorsal bulbar portion of 3rd PA

Question 27

What is the direct embryonic origin of the superior parathyroid gland?

Answer 27

Epithelium of dorsal bulbar portion of 4th PA

Question 28

In what week are the parathyroid glands formed?

Answer 28

Week 6

Question 29

What PA is a cervical/branchial cyst most likely to be a remnant of?

Answer 29

PA 2

Question 30

In what week are pharyngeal grooves 2-4 obliterated?

Answer 30

Week 7

Question 31

What is the direct embryological origin of the foramen cecum?

Answer 31

Thyroglossal duct

Question 32

What structure connects the fetal tongue to the developing thyroid gland?

Answer 32

Thyroglossal duct

Question 33

What week do thyroid follicles form?

Answer 33

Week 10

Question 34

A pt with a pyramidal lobe of the thyroid most likely had abnormal thyroid gland development in what week?

Answer 34

Week 7

Question 35

What week of thyroid development does colloid appear and TH synthesis begin?

Answer 35

Week 11

Question 36

What week do fetal TSH and thyroxine reach adult levels?

Answer 36

35 weeks?

Question 37

What is the direct embryonic origin of the ultimopharyngeal body?

Answer 37

Ventral part of the 4th pouch (NCC)

Question 38

What does the ultimopharyngeal body give rise to?

Answer 38

Parafollicular cells (fuses with thyroid gland and disseminates)

Question 39

Abnormal migration of NCC into the 1st pharyngeal arch can cause what facial features to be malformed?

Answer 39

Eyes, ears, mandible, palate

Question 40

Mutation in the what gene causes Treacher-Collin's sydrome? What does the mutation result in?

Answer 40

TCOF1 Cannot make TREACLE ptn, involved in ribosome biogenesis, leads to increased apoptosis of cranial NCCs

Question 41

What autosomal dominant disorder leads to malar hypoplasia, deformed external ears and down-slanting palpebral fissures?

Answer 41

Treacher Collins syndrome (Mandibulofacial dysostosis)

Question 42

What is the Pierre Robin Sequence?

Answer 42

1. Small mandible (Micrognathia) =\> 2. Posterior displacement of the tongue =\> Obstruction of full closure of palate =\> 3. Bilateral cleft palate

Question 43

Patients with Pierre Robin sequence likely had a defect in development of what embryonic structure?

Answer 43

1st PA

Question 44

Which lobe is more commonly absent in thyroid hemiagenesis?

Answer 44

L lobe

Question 45

A patient with agenesis of the thyroid and parathyroid glands, shortened philtrum of the upper lip, low-set ears, nasal cleft, and a heart murmur may have what disorder?

Answer 45

DiGeorge Syndrome