2 Pharyngeal Arches

Question 1

Pharyngeal arches appear as pairs of bulges overlying the head and neck regions due to migration of ______.

Answer 1

Neural crest cells

Question 2

Each arch is lined externally by _____, internally by _____, and has a core of _____.

Answer 2

Ectoderm

Endoderm

Mesenchyme

Question 3

Each pharyngeal arch contains these 4 things:

Answer 3

1. Artery
2. Cranial n.
3. Muscle
4. Cartilage

Question 4

Cartilage from the 1st arch forms the ______ and ______.

Answer 4

Maxillary process

Mandibular process

Question 5

The maxillary process gives rise to:

Answer 5

1. Maxillary bones (including inferior nasal conchae)
2. Zygomatic bones
3. Vomer

Question 6

The mandibular process gives rise to:

Answer 6

1. Mandible

2. Squamous portion of temporal bone

Question 7

The ______ is the former site of 1st arch (meckel) cartilage

Answer 7

Mandibular canal

Question 8

The second arch cartilage gives rise to:

Answer 8

1. Lesser Cornu of hyoid bone
2. Stapes
3. Styloid process
4. Stylohyoid ligament

Question 9

3rd arch cartilage gives rise to the:

Answer 9

1. Body of hyoid

2. Greater cornu (horn) of hyoid

Question 10

4th and 6th arch cartilage give rise to:

Answer 10

1. Thyroid cartilage

2. Cricoid cartilage

Question 11

1st arch muscles give rise to:

Innervated by CN ___

Answer 11

1. MOM
2. Mylohyoid m
3. Anterior belly of digastric m.
4. “Two tiny tensors” (tensor tympani and tensor veil palatini mm.)

CN V (Trigeminal)

Question 12

2nd arch muscles give rise to:

Innervated by CN ___

Answer 12

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

CN VII (Facial)

Question 13

3rd arch muscle gives rise to:

Innervated by CN ___

Answer 13

Stylopharyngeus m.

CN IX (Glossopharyngeal)

Question 14

4th arch muscles give rise to:

Innervated by CN ___

Answer 14

1. Pharyngeal constrictor mm.
2. Levator veli palatini m.
3. Cricothyroid m.

CN X (Vagus)

Question 15

6th arch muscle gives rise to:

Innervated by CN ___

Answer 15

Intrinsic mm of the larynx

CN X

Question 16

Pouch 1 Derivatives:

Answer 16

1. Middle ear (Middle portion of tympanic cavity and mastoid antrum)
2. Pharyngotympanic tube (Eustachian tube)
3. Endoderm of tympanic membrane (eardrum)

Question 17

Pouch 2 derivatives:

Answer 17

Palatine tonsils

Question 18

Pouch 3 derivatives:

Answer 18

Dorsal buds -> inferior parathyroid glands

Ventral buds -> thymus (fuse at midline)

(These derivatives Migrate caudally -> common ectopic tissue)

Question 19

Pouch 4 derivatives:

Answer 19

Dorsal buds -> superior parathyroid glands

Ventral buds -> Ultimopharyngeal body -> parafollicular cells (C cells) -> calcitonin

Question 20

The 1st pharyngeal groove/cleft forms the:

Answer 20

1. External acoustic meatus

2. External surface of tympanic membrane

Question 21

2nd-4th pharyngeal grooves/clefts merge and form the _____

Answer 21

Cervical Sinus -> Cervical vesicle (eventually disappears)

Question 22

Remnants of a cervical sinus/vesicle or 2nd groove can form a _____ that often develops just below the _____.

Answer 22

Cervical (Branchial) Cyst (fluid filled)
(Cyst that leads to opening -> fistula)

Angle of the mandible

Question 23

The _____ develops between what will be the anterior 2/3 and posterior 1/3 of tongue

Answer 23

Foramen Cecum

Question 24

The median lingual swelling and 2 lateral lingual swellings develop at the level of the ____ arch to form the ______ of the tongue

Answer 24

1st

Anterior 2/3

Question 25

Posterior 1/3 of the tongue forms from elevations in the floor of the pharynx:

Answer 25

1. Copula (2nd arch level)

2. Hypopharyngeal eminence (3rd and 4th arch) -> overgrows copula (so innervated by CN IX)

Question 26

V-shaped line separating anterior 2/3 from posterior 1/3 of tongue

Answer 26

Terminal Sulcus

Question 27

Tongue Innervation Summary:

Answer 27

1. Anterior 2/3: from 1st arch-
CN V3 (general sensory)
CN VII (chorda tympani/taste)
2. Posterior 1/3: mainly from 3rd arch-
CN IX (sensory and taste)
3. Epiglottis: 4th arch- CN X (sensory and taste)