Pharyngeal Arches, Pouches and Cysts

Question 1

When do the pharyngeal arches begin developing?

Answer 1

4th week

Question 1

Most skeletal and connective tissues of head and neck are made of?

Answer 1

neural crest cells

Question 1

How are the pharyngeal arches numbered?

Answer 1

cranial > caudal

Question 2

Describe the pharyngeal system?

Answer 2

6 pairs of pharyngeal arches separated by endodermally lined pouches and ectodermally lined clefts (grooves)
> Four well-defined pairs visible externally
> Fifth and sixth rudimentary

Question 3

Each pharyngeal arch consists of?

Answer 3

nerve
artery
cartilage

Question 4

List the 3 components which make up the pharyngeal arches and what each component forms?

Answer 4

1. ectoderm > pharyngeal grooves
2. mesoderm > pharyngeal arches
3. endoderm > pharyngeal pouches

Question 5

How many pharyngeal arches develop in an embryo?

Answer 5

5
> 1, 2, 3, 4, and 6

Question 6

Which pharyngeal arch does not give rise to any derivatives?

Answer 6

5

Question 7

At what stage of development does the tongue develop?

Answer 7

4th week of intrauterine life

Question 8

From which pharyngeal arch does the anterior two-thirds of the tongue develop?

Answer 8

1st pharyngeal arch

Question 9

Which pharyngeal arches are responsible for the formation of the posterior third of the tongue?

Answer 9

3rd and 4th pharyngeal arches

Question 10

What is derived from the first pharyngeal arch?

Answer 10

1. Prominences
   - maxilla & mandible bones
   - zygomatic bone
2. Cartilage (meckel’s cartilage)
   - malleus & incus
   - anterior ligament of malleus
   - sphenomandibular ligament
3. Muscles (of mastication)
   - temporalis
   - masseter
   - pterygoids
   - mylohyoid
   - tensor tympani
4. Nerve
   - Mandibular branch of CV 5 (Trigeminal nerve)

Question 11

Which pharyngeal arches are responsible for the formation of the 3 bony ossicles of the ear?

Answer 11

1. malleus + incus > pharyngeal arch I
2. stapes > pharyngeal arch II

Question 12

What is derived from the first pharyngeal pouch?

Answer 12

1. Eustachian tube
2. tympanic membrane
3. Temporal bone

Question 13

What is derived from the first pharyngeal groove?

Answer 13

Develops into the external acoustic meatus
> The remaining grooves disappear and form cervical sinus
> May form and abnormal lateral cervical cyst or fistula

Question 14

What is derived from the second pharyngeal arch?

Answer 14

1. Reichert’s cartilage
   - stapes
   - the upper body & lesser cornu of hyoid bone
   - the styloid process of temporal bone
   - stylohyoid ligament.
2. Muscles
   - platysma
   - muscles of facial expression
   - stylohyoid
   - stapedius
3. Nerve
   - CV 7 (Facial nerve)
4. Artery
   - stapedial artery

Question 15

What is derived from the second pharyngeal pouch?

Answer 15

Lymphatic nodules - palatine tonsils

Question 16

What does the tubotympanic recess contribute to?

Answer 16

Eustachian tube

Question 17

What is derived from the third pharyngeal arch?

Answer 17

1. Cartilage
   - forms lower body of hyoid & greater cornu of hyoid bone.
2. Muscles
   - stylopharyngeus
   - superior & middle pharyngeal constrictors
3. Nerve
   - CN 9 (Glossopharyngeal nerve)
4. Artery
   - common carotid & proximal portions of the internal & external carotid.

Question 18

What is derived from the third branchial pouch?

Answer 18

1. Inferior parathyroids
2. Thymus gland

Question 18

What doe the fourth and sixth pharyngeal arches form together?

Answer 18

Fourth & sixth pharyngeal arch cartilages fuse to form the laryngeal cartilages

Question 19

What is derived from the fourth pharyngeal arch?

Answer 19

1. Muscles
   - cricothyroid
   - inferior pharyngeal constrictors
2. Nerve
   - Superior Laryngeal branch of Vagus nerve
3. Artery
   - Right Subclavian
   - Aortic arch

Question 20

What is derived from the fourth pharyngeal pouch?

Answer 20

1. superior parathyoid glands
2. parafollicular thyroid cells (ultimobranchial body)

Question 21

What is derived from the fifth pharyngeal arch?

Answer 21

has no derivatives
> is rudimentary if present

Question 22

What is derived from the sixth pharyngeal arch?

Answer 22

1. Muscles - remaining intrinsic laryngeal musculature 2. Nerve - Recurrent laryngeal nerve branch of Vagus nerve 3. Artery - Pulmonary Artery & ductus arteriosus

Question 23

Which cranial nerve innervates the first branch?

Answer 23

trigeminal nerve

Question 24

Which nerve innervates the second arch?

Answer 24

facial nerve

Question 25

Which nerve innervates the third arch?

Answer 25

glossopharyngeal nerve

Question 26

Which nerve innervates the fourth and sixth arches?

Answer 26

vagus nerve

Question 27

Which cranial nerves innervate muscles derived from preotic somites?

Answer 27

oculomotor trochlear abducents

Question 28

Which nerve innervates muscles derived from occipital somites?

Answer 28

hypoglossal nerve

Question 29

Describe branchial cysts?

Answer 29

Develop along anterior border of sternocleidomastoid Most found inferior to angle of mandible Often present in adulthood Remnants of cervical sinus and/or second pharyngeal groove

Question 30

Describe branchial vestiges?

Answer 30

Cartilaginous or bony remnants Usually anterior to inferior third of sternocleidomastoid

Question 31

Describe first arch syndrome?

Answer 31

results in various congenital anomalies of eyes, ear, mandible, palate - migration of neural crest cells into first pharyngeal arch implicated

Question 32

What are the 2 main manifestations of first arch syndrome?

Answer 32

1. Treacher Collins syndrome - Underdevelopment of zygomatic bones of face, defects of lower eyelids, external ear deformations 2. Pierre Robin syndrome - Hypoplasia of the mandible, cleft palate & eye and ear defects present

Question 33

What does first branchial arch syndrome look like on a person?

Answer 33

- The right corner of the mouth is extended in a cleftlike fashion - The right auricle is severely deformed and the external acoustic meatus is absent

Question 34

Describe the embryology of the thyroid gland?

Answer 34

Endoderm of the floor primitive pharynx between 1st & 2nd arches Descends as a bilobed diverticulum from foramen cecum around the 4th week to rest in the neck region by 7-8th wk.