Pharyngeal arches, pouches and clefts

Question 1

How many pharyngeal arches are there?

Answer 1

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

Question 2

What are the components of the pharyngeal arches?

Answer 2

• Centre from paraxial mesoderm
• External covering of ectoderm
• Internal covering of endoderm
• 3 associated structures:
  1. Nerve (↑←)
  2. Artery (↑→)
  3. Cartilage (↓)

Question 3

What is the structure of the 1st pharyngeal arch?

Answer 3

Divided into the maxillary process and the mandibular process.

Question 4

What are the bones derived from the maxillary process of arch 1?

Answer 4

1. Pre-maxilla
2. Maxilla
3. Zygomatic bone
4. Petrous temporal bone

Question 5

What is the cartilage associated with arch 1?

Answer 5

Meckel’s cartilage

Question 6

What are the derivatives of Meckel’s cartilage?

Answer 6

• Malleus
• Incus
• Lingula (mandible)
• Sphenomandibular ligament

Question 7

What are the muscles associated with arch 1?

Answer 7

• Muscles of mastication
• Anterior belly of digastric
• Mylohyoid
• Tensor tympani
• Tensor veli palatini

Question 8

What is the nerve of arch 1?

Answer 8

[V₃]

Question 9

What are the derivatives of the arch 1 artery?

Answer 9

None - Degenerates

Question 10

What is the cartilage associated with arch 2?

Answer 10

Reichert’s cartilage

Question 11

What are the derivatives of Reichert’s cartilage?

Answer 11

• Stapes
• Styloid process (of temporal bone)
• Stylohyoid ligament
• Lesser horn of hyoid

Question 12

What are the muscles associsted with the 2nd arch?

Answer 12

1. Muscles of facial expression
2. Buccinator
3. Stapedius
4. Stylohyoid
5. Posterior belly of digastric

Question 13

What is the nerve of arch 2?

Answer 13

Facial nerve [VII]

Question 14

What are the derivatives of the arch 2 artery?

Answer 14

None - Degenerates

Question 15

What are the derivatives of the arch 3 cartilage?

Answer 15

• Greater horn of hyoid
• Body of hyoid

Question 16

What are the derivatives of the arch 3 artery?

Answer 16

Common & internal carotid arteries

Question 17

What are the muscles associated with arch 3?

Answer 17

Stylopharyngeus

Question 18

What is the nerve of arch 3?

Answer 18

Gossopharyngeal nerve [IX]

Question 19

What are the derivatives of the arch 4 & 6 cartilage?

Answer 19

Laryngeal cartilages

Question 20

What are the derivatives of the arch 4 artery?

Answer 20

• Right: Right subclavian artery
• Left: Arch of aorta

Question 21

What are the derivatives of the arch 6 artery?

Answer 21

• Right: Right pulmonary artery
• Left: Left pulmonary artery & ductus arteriosus

Question 22

What are the muscles associated with arch 4?

Answer 22

• Levator veli palatini
• Cricothyroid
• Pharyngeal constrictors

Question 23

What is the nerve of arch 4?

Answer 23

Superior laryngeal branch of vagus [X]

Question 24

What is the nerve of arch 6?

Answer 24

Recurrent laryngeal branch of vagus [X]

Question 25

How many pharyngeal pouches are there?

Answer 25

4

Question 26

What are the derivatives of the pouch 1?

Answer 26

• Eustachian tube
• Middle ear

Question 27

What are the derivatives of pouch 2?

Answer 27

• Palatine tonsils
• Tonsilar fossa

Question 28

What are the derivatives of pouch 3?

Answer 28

• Ventral wing: Thymns
• Dorsal wing: Inferior parathyroids

Question 29

What are the derivatives of pouch 4?

Answer 29

• Ventral wing: Ultimobranchial body (parafollicular cells of thyroid)
• Dorsal wing: Superior parathyroids

Question 30

How many pharyngeal clefts are there?

Answer 30

4

Question 31

What are the derivatives of cleft 1?

Answer 31

External auditory meatus

Question 32

What are the fates cleft 2-4?

Answer 32

Becomes the cervical sinus that eventually obliterates as the 2nd arch grows over the 3rd, 4th and 6th arches.

Question 33

What is the derivative of the 1st pharyngeal membrane?

Answer 33

Tympanic membrane