Pharyngeal Arches

Question 1

How many clefts and pouches are found in a 5 week embryo?

Answer 1

4 clefts

4 pouches

Question 2

Arch 1 skeletal components:

Answer 2

Meckel's Cartilage
Maxilla
Mandible
Malleus
Incus

Question 3

Arch 2 skeletal components:

Answer 3

Ventral: Lesser horn and upper body of the hyoid
Dorsal: Styloid process and stapes

Question 4

Arch 3 skeletal components:

Answer 4

Greater horn

Lower body of hyoid

Question 5

Arch 4/6 skeletal components:

Answer 5

Both: Arytenoid Cartilage

4th: Thyroid cartilage
6th: Cricoid cartilage

Question 6

Arch 1 Muscle Derivatives:

Answer 6

Muscles of Mastication
Anterior belly of digastric
Mylohyoid
Tensors

Question 7

Arch 2 Muscle Derivatives:

Answer 7

Muscles of Facial Expression
Posterior belly of Digastric
Stylohyoid
Stapedius

Question 8

Arch 3 Muscle Derivatives:

Answer 8

Only Stylopharyngeus

Question 9

Arch 4 Muscle Derivatives:

Answer 9

Cricothyroid
Pharyngeal Constrictors
Levator Palatani

Question 10

Arch 6 Muscle Derivatives:

Answer 10

Intrinsic muscles of the larynx

Question 11

Arch 1 Nerves:

Answer 11

Trigeminal

Question 12

Arch 2 Nerves:

Answer 12

Facial

Question 13

Arch 3 Nerves:

Answer 13

Glossopharyngeal

Question 14

Arch 4 Nerves:

Answer 14

Vagus

Superior Laryngeal

Question 15

Arch 6 Nerves:

Answer 15

Recurrent Laryngeal

Question 16

Arch 1 Arteries:

Answer 16

Maxillary

Question 17

Arch 2 Arteries:

Answer 17

Stapedial

Question 18

Arch 3 Arteries:

Answer 18

Internal Carotid

Question 19

Arch 4 Arteries:

Answer 19

Aortic Arch

Right Subclavian

Question 20

Arch 6 Arteries:

Answer 20

Ductus Arteriosus

Roots of pulmonary arteries

Question 21

What does the 1st cleft and palate do?

Answer 21

Push together to form external auditory meatus and middle ear

Question 22

What forms where the 1st cleft and palate meet?

Answer 22

Tympanic membrane (only endo and ectoderm no mesoderm)

Question 23

What occurs with the 2nd pouch?

Answer 23

Epithelium dives into the mesoderm in the 5th week
Mesoderm reverses the process in the 7th week and infiltrates endodermal tissue leaving a space for lymph tissue to enter

Question 24

What does the 2nd pouch form?

Answer 24

Palatine tonsils

Question 25

What does the third pouch form?

Answer 25

Ventral wing: Thymus | Dorsal wing: Inferior Parathyroid glands

Question 26

What does the fourth pouch form?

Answer 26

Ventral wing: Ultimobranchial body which becomes the C cells of the thyroid Dorsal wing: Superior thyroid glands

Question 27

What is the foramen cecum?

Answer 27

Epithelial proliferation that the thyroid gland develops from (thyroid is endodermal) as the thyroid descends it maintains connection to the foramen cecum via the thyroglossal duct

Question 28

What is the pyramidal lobe a remnant of?

Answer 28

Thyroglossal duct

Question 29

What is the non-closure of the thyroglossal duct called?

Answer 29

Thyroglossal cyst

Question 30

What does the second cleft proliferate to do?

Answer 30

Mesoderm of 2nd cleft proliferates over to connect to cover the 4th cleft leaving a sinus

Question 31

What is it called if the 2nd cleft does not close over clefts 3 and 4?

Answer 31

Branchial fistula