Anatomy & Embryology

Question 1

Describe the timing of the formation of the pharyngeal arches.

Answer 1

Develop in week 4 & 5;
arch 1 - day 22
arch 2&3 - day 24
arch 4&6 - day 29

Question 2

what are the 3 components of the pharyngeal apparatus?

Answer 2

core pharyngeal arch
external pharyngeal cleft
internal pharyngeal pouch

clefts and pouches separate arches

Question 3

Of the 3 components of the pharyngeal apparatus, which is mesenchymal/ectoderm/ endoderm?

Answer 3

arch = mesenchymal tissue
cleft = ectoderm
pouch = endoderm

Question 4

neural crest cells in each pharyngeal arch will become?

Answer 4

skeletal components of the face

Question 5

the core of mesenchyme in each pharyngeal arch will become?

Answer 5

musculature of the face

Question 6

Which cranial nerves are derived from each pharyngeal arch?

Answer 6

CN V (2&3) - arch 1
CN VII - arch 2
CN IX - arch 3
CN X - arch 4 & 6 (superior laryngeal & recurrent laryngeal branches respectively)

Question 7

What are the elements (skeletal & muscular) derived from the 1st arch?

Answer 7

maxillary process - maxilla, zygomatic, squamous portion of temporal bone
mandibular process - Meckel’s cartilage, incus & malleus, mandible

muscles of mastication, mylohyoid, tensor tympani, tensor vela palatine
sensory supply of skin to face; V1-3

Question 8

What are the elements (skeletal & muscular) derived from the 2nd arch?

Answer 8

cartilage of 2nd arch = Reichert’s cartilage

stapes, styloid process of temporal bone, stylohyoid ligament, lesser horn & upper body of hyoid bone

muscles of facial expression, stylohyoid, stapedius, auricular muscles

Question 9

What are the elements (skeletal & muscular) derived from the 3rd arch?

Answer 9

greater horn & lower part of hyoid bone

stylopharyngeus & longitudinal pharyngeal muscle

Question 10

What are the elements (skeletal & muscular) derived from the 4th & 6th arches?

Answer 10

laryngeal cartilages

4: cricothyroid, levator veli palatini, pharyngeal constrictors
6: intrinsic laryngeal

Question 11

Which pharyngeal cleft does the external acoustic meatus originate from?

Answer 11

1st cleft

Question 12

Which pharyngeal pouch does the middle ear, tympanic membrane & eustachian tube come from?

Answer 12

1st pouch

Question 13

Which pouch do the palatine tonsils come from?

Answer 13

2nd pouch

Question 14

What originates from the 3rd pouch?

Answer 14

inferior parathyroid gland & thymus

Question 15

What originates from the 4th pouch?

Answer 15

superior parathyroid gland & thyroid gland