10.17.16 Embryology of Pharynx and Larynx

Question 1

What are the components of the pharyngeal (branchial) apparatus?

Answer 1

Pharyngeal grooves (Clefts), Arches, Pouches, and membranes (CAP)

Question 2

What does branchial mean?

Answer 2

Gill

Question 3

When do the pharyngeal arches begin to develop?

Answer 3

Early in the 4th week

Question 4

Briefly, what occurs as the pharyngeal arches begin to develop?

Answer 4

Neural crest cells migrate into the future head and neck regions

Question 5

Each pharyngeal arch has its own cartilage, nerve, vascular, and muscular components. How many pharyngeal arches are there?

Answer 5

6, but the 5th arch is rudimentary and the 6th arch becomes incorporated into the 4th

Question 6

What are the derivatives of the pharyngeal pouches?

Answer 6

1: Tympanic (middle ear cavity), auditory (eustachian) tube
2: Palatine tonsils, tonsillar fossa
3. Inferior parathyroid gland, thymus
4. Superior parathyroid gland, ultimobranchial body

Ear, Tonsils, Bottom To Top

Question 7

What is the fate of clefts 1-4?

Answer 7

1st: external auditory meatus

2nd, 3rd, and 4th: obliterated by overgrowth of the 2nd and 4th arch toward each other, forming a cervical sinus.

Question 8

What is caused by persistent overgrowth of the 2nd and 4th arches toward each other?

Answer 8

Branchial cyst or fistula found along the anterior border of sternocleidomastoid

Question 9

What is the fate of the membranes?

Answer 9

Only the 1st membrane persists and gives the tympanic membrane

Question 10

The thyroid gland develops as a down-growth from the floor of the ___ between the first and second pouches at the ___.

Answer 10

Primordial pharynx; foramen cecum

Question 11

The thyroid diverticulum grows in the ___ direction to its final position at the larynx.

Answer 11

Caudal

Question 12

The thyroglossal duct regresses except for its ___ part, which forms the ___ of the thyroid.

Answer 12

Distal; pyramidal lobe

Question 13

The parafollicular cells (C cells) in the thyroid gland are derived from the __, which are derived mainly from the ___.

Answer 13

Ultimo pharyngeal bodies; 4th pair of pharyngeal pouches

Question 14

What causes an ectopic thyroid gland?

Answer 14

Failure of the thyroid gland to descend completely from its site of origin in the tongue

Question 15

The thyroglossal duct may persist or remnants of it may give rise to thyroglossal duct cysts presented as ___.

Answer 15

Painless enlarging midline movable mass

Question 16

What are the two parts of the tongue?

Answer 16

Oral part (anterior 2/3), pharyngeal part (posterior 1/3)

Question 17

From what does the oral part of the tongue develop?

Answer 17

From fusion of 2 lateral lingual swellings and a median tongue bud (tuberculum impar)

Question 18

What innervates the tongue?

Answer 18

Anterior 2/3 - Sensory by V, taste by VII

Posterior 1/3 - IX

Question 19

From what does the pharyngeal part of the tongue develop?

Answer 19

From the copula (hypobranchial eminence)

Question 20

From what does the face develop?

Answer 20

From unpaired frontonasal and paired nasomedial, maxillary, and mandibular prominences

Question 21

What forms the forehead and dorsum and apex of the nose?

Answer 21

Frontonasal prominence

Question 22

What forms the alae (sides) of the nose?

Answer 22

Lateral nasal prominences

Question 23

What forms the nasal septum, ethmoid bone, and cribriform plate?

Answer 23

Medial nasal prominences

Question 24

What forms the upper cheek regions and upper lip?

Answer 24

Maxillary prominences

Question 25

What forms the chin, lower lip, and lower cheek regions?

Answer 25

Mandibular prominences

Question 26

From what does the palate arise?

Answer 26

The fusion of an unpaired median process (primary palate) and paired lateral palatine processes (secondary palate)

Question 27

What are two common craniofacial anomalies?

Answer 27

Cleft lip and cleft palate

Question 28

What causes cleft lip?

Answer 28

Failure of mesenchymal masses in the medial nasal and maxillary prominences to merge

Question 29

What causes cleft palate?

Answer 29

Failure of mesenchymal masses in the palatal processes to meet and fuse

Question 30

Is cleft lip caused by genetic, environmental, or combination factors?

Answer 30

Combination of genetic and environmental factors

Question 31

What are the muscular and skeletal derivatives of the mandibular arch (1)?

Answer 31

Muscles: Muscles of mastication (temporal, masseter, medial/lateral pterygoids), mylohyoid, digastric (anterior belly), tensor palatine, tensor tympani
Skeleton: Premaxilla, maxilla, zygomatic, part of temporal bone, Meckel’s cartilage, mandible malleus, incus, anterior ligament of malleus, sphenomandibular ligament

Question 32

What innervates the derivatives of the mandibular arch?

Answer 32

V (maxillary and mandibular divisions)

Question 33

What are the muscular and skeletal derivatives of the hyoid arch (2)?

Answer 33

Muscles: muscles of facial expression (buccinator, auricularis, frontalis, platysma, orbicularis oris, orbicularis oculi), digastric (posterior belly), stylohyoid, stapedius
Skeleton: stapes, styloid process, stylohyoid ligament, lesser horn and upper portion of body of hyoid bone

Question 34

What innervates the derivatives of the hyoid arch?

Answer 34

VII

Question 35

What are the muscular and skeletal derivatives of the third arch?

Answer 35

Muscles: stylopharyngeus
Skeleton: greater horn and lower portion of body of hyoid bone

Question 36

What innervates the derivatives of the third arch?

Answer 36

IX

Question 37

What are the muscular and skeletal derivatives of the 4-6 arches?

Answer 37

Muscles: cricothyroid, levator palatine, constrictors of pharynx, intrinsic muscles of larynx
Skeleton: laryngeal cartilages (thyroid, cricoid, arytenoid, corniculate, cuneiform)

Question 38

What innervates the derivatives of the 4-6 arches?

Answer 38

X - superior laryngeal branch (nerve to fourth arch - cricothyroid, levator palatine, constrictors of pharynx) and recurrent laryngeal branch (nerve to sixth arch - intrinsic muscles of larynx)